Blew up again short rant

Went up to Lime Rock today and 5 laps into my first session the motor started to smoke. Looks like the same type of failure as last time. Had the motor rebuilt with new pistons and a bunch of other parts by a reputeable local builder that's done a few motors for me. He came and had a quick look and listen said pull it out and he'll try to figure out what caused it. timing is right on, fuel pressure & flow are good. Said it appears to be terminal in the lower end either piston/s or rings. Put about 30 laps on it at NJMP 2 weeks ago.
Just haven't got a clue what's causing the problem.

I'm pretty much out of patients with the car and considering just selling it. :banghead::banghead::banghead:

Could be that the track configurations is creating a low oil pressure situation... do you have an accusump?

Our Panoz hasn't moved since I snapped the crank in July so I feel your pain.

C4B
No accusump. I've been running this track (Lime Rock) for the last 10-12 years with other wet sump race cars no issues. A couple of other guys locally have GTS's on the same track and so far as I know they have not had this experience.

Sorry your still on the side lines. Saw your car 4 sale in a couple of spots and from the sound of it youv'e had no bites. I'm wondering if I would have any luck myself.

If you can e-mail me and let me know if you've had any action (stupid offers) I'm curoiuos. rfracer25(at)comcast.net

Sorry to hear about the grenade. Race cars can be very frustrating to get sorted and hard to know what went wrong. Your builder should stand behind the engine and if this is a GTRA you should be able to build a very durable small block Ford in the 3-400hp range easily. Just wondering if it had any break in dyno time. A good idea is to have the builder run it for 10 hours or so on an engine dyno to tune it and make sure there are no assembly failures.

The Accusump is a great idea for many reasons including pre-oiling. If you are running the Canton Road Race pan it may not be necessary unless Lime Rock has a long high speed sweeper (eg Willow Springs CA) then you can/will kill the engine. If this is a stock Ford pan w/o baffles or a drag race pan then oiling is a concern.

We run the Accusump on the GTSs with good reliability...I think most GTS cars have them after several crumped a few years ago at Willow.

Kevin
GTS/GTRA

Sorry to hear about the grenade. Race cars can be very frustrating to get sorted and hard to know what went wrong. Your builder should stand behind the engine and if this is a GTRA you should be able to build a very durable small block Ford in the 3-400hp range easily. Just wondering if it had any break in dyno time. A good idea is to have the builder run it for 10 hours or so on an engine dyno to tune it and make sure there are no assembly failures.

The Accusump is a great idea for many reasons including pre-oiling. If you are running the Canton Road Race pan it may not be necessary unless Lime Rock has a long high speed sweeper (eg Willow Springs CA) then you can/will kill the engine. If this is a stock Ford pan w/o baffles or a drag race pan then oiling is a concern.

We run the Accusump on the GTSs with good reliability...I think most GTS cars have them after several crumped a few years ago at Willow.

Kevin
GTS/GTRA


Kevin,
It's in a 351 GTS car. No real long sweepers at Lime Rock. The engine builder said take it out and get it to his shop and he'll try to figure out what caused it. He just rebuilt the motor finished late July. He's always been fair so I believe he'll treat me properly. We do have a Canton RR pan on it and I should add the accusump. (really cheap insurance). Last time I had a few detonated pistons which were not an oil problem. I have been racing for the last 34 years running everything from NASCAR open wheel modifieds to a GT-1 in the SCCA along with a stint in offshore boats. Blew an engine in the offshore boat once and have never had another failure in a race vehicle. Have never had this much heartburn in such a short period of time with anything I raced or tracked. Spent half the summer waiting for the motor to come back and did all the "while your in there" items like clutch, trans, flywheel etc. Been front to back on the car checking everything and replacing anything with a ?mark.

I know we all get po'd at our cars from time to time and I need to cool off a little. I'm tired of working on this car with only negative results to show for it.

Thanks for the Accusump suggestion and feedback. The forum is a great place for guidance and support.

Sorry to hear about the 2nd failure. Dont give up on the car just yet as when it is sorted you will be happy with it. Both the 351 and 302 are capable of performing very reliably in the chassis, so there is something wrong here.

I cant recall if you found a reason for the last failure?

If nothing conclusive was found during investigation/repair of the last engine, I would take a really good look at not just the engine but also all of the peripherals, i.e.

- Is the oil system plumbed correctly?
- Is the radiator partially blocked some where?
- Are there support wires inside the radiator hoses to prevent them from collapsing when hot?
- Is there a restriction in the oil system?
- Is the oil pickup the correct distance from the bottom of the pan?
- Is the dipstick marking providing the correct oil level?
- Are the senders for temperature and oil pressure reading correctly (verify with independent gauge)?
- Is the thermostat opening correctly?
- etc etc

Let us know what your engine builder finds/says when the engine is stripped as there may be some learnings for us on this.

Kel.

Sorry your still on the side lines. Saw your car 4 sale in a couple of spots and from the sound of it youv'e had no bites. I'm wondering if I would have any luck myself.

If you can e-mail me and let me know if you've had any action (stupid offers) I'm curoiuos. rfracer25(at)comcast.net
Yeah I posted it up on Racingjunk and NASAforums, but we're probably not selling it. I just threw it up to see what it'd do while my dad figured out what he was going to do. Have/had one serious buyer talking higher teens, but I'm 99% sure my dad's going to proceed with a 347 build.

Unlike yours, our failure was very very clear.... random undiagnosed issues would be very annoying.

Sorry to hear about the 2nd failure. Dont give up on the car just yet as when it is sorted you will be happy with it. Both the 351 and 302 are capable of performing very reliably in the chassis, so there is something wrong here.

I cant recall if you found a reason for the last failure?

If nothing conclusive was found during investigation/repair of the last engine, I would take a really good look at not just the engine but also all of the peripherals, i.e.

- Is the oil system plumbed correctly?
- Is the radiator partially blocked some where?
- Are there support wires inside the radiator hoses to prevent them from collapsing when hot?
- Is there a restriction in the oil system?
- Is the oil pickup the correct distance from the bottom of the pan?
- Is the dipstick marking providing the correct oil level?
- Are the senders for temperature and oil pressure reading correctly (verify with independent gauge)?
- Is the thermostat opening correctly?
- etc etc

Let us know what your engine builder finds/says when the engine is stripped as there may be some learnings for us on this.

Kel.

Kel,
We thought the problem was timing. I had a couple of badly detonated pistons.
The gauges all read in the normal range today
Water 210 Oil 220
Oil Press 60
We added jet extensions to the rear of the carb in case it was fuel starved. Also installed angled Brasswell floats. Running fat / rich jets breaking it in. nothing appears to be kinked or blocked in cooling or oil lines / hoses.
After a quick check of the motor today (leak down test and running it) the engine builder told me to pull it out and he would get into it.
He agrees that we missed something but we really have no idea. Fuel pressure and flow on the fuel pump appear to be right (checked during rebuild).
I'm going to try and get it out and to the shop Friday.

I'll post up when we get inside.
Thanks,
Rich

Kel,
We thought the problem was timing. I had a couple of badly detonated pistons.
The gauges all read in the normal range today
Water 210 Oil 220
Oil Press 60
We added jet extensions to the rear of the carb in case it was fuel starved. Also installed angled Brasswell floats. Running fat / rich jets breaking it in. nothing appears to be kinked or blocked in cooling or oil lines / hoses.
After a quick check of the motor today (leak down test and running it) the engine builder told me to pull it out and he would get into it.
He agrees that we missed something but we really have no idea. Fuel pressure and flow on the fuel pump appear to be right (checked during rebuild).
I'm going to try and get it out and to the shop Friday.

I'll post up when we get inside.
Thanks,
Rich

Rich,
was the new engine dyno'd in the chassis post fitment? If it is burnt pistons again then the likely suspects are the cooling system (localised overheating leading to detonation), fueling (lean condition causing detonation) or ignition (irregular timing). One thing I always do religiously now when dynoing Rich is fit a detonation sensor to the engine while it is being dyno'd. We take fuel and ignition past the optimal points during the runs to make sure that we have some safe detonation free margin at our choosen jet/timing settings when running dynamically on the track.

Did you note down the cylinders that let go last time as it will be interesting to see if it is the same ones or different holes this time.

Kel.

PS - If you dont find anything obvious on the strip down Rich, I would also have the distributor curve graphed on a distirbutor test rig (most good dyno shops or ignition shops should have one) to ensure that the curve suits your engine. Perhaps it is pulling in to much advance to soon.

Rich,
sounds like you have lots of experiance and a good builder, but some bad luck.

We run 2 GTSs in SCCA here in Norcal. The motors have been very reliable and are engine dyno'd to 445hp to be SCCA compliant. We upgraded the quality of the cranks (SCAT), rods, and forged pistons, but run the Edelbrock heads and spec manifold, cam, carb etc. The original Panoz engine internals were pretty junky and easily improved w/o "cheating" on HP.

Sounds like an early MIF (maintenance induced failure), but I'd really get them to run the new engine on an engine dyno first and tune it etc. We bring the headers and all externals to the builder and 5-10h of dyno time is put on them to make sure all is well before they are installed.

We "refresh" them every 100hrs.

In 4yrs of running the GTS I haven't had a single mechanical DNF (except for a tire puncture) and have won 2 4hr Endurance races. This can/should be a very reliable fun car....

Keep the Faith.

Kevin

Rich,
sounds like you have lots of experiance and a good builder, but some bad luck.

We run 2 GTSs in SCCA here in Norcal. The motors have been very reliable and are engine dyno'd to 445hp to be SCCA compliant. We upgraded the quality of the cranks (SCAT), rods, and forged pistons, but run the Edelbrock heads and spec manifold, cam, carb etc. The original Panoz engine internals were pretty junky and easily improved w/o "cheating" on HP.

Sounds like an early MIF (maintenance induced failure), but I'd really get them to run the new engine on an engine dyno first and tune it etc. We bring the headers and all externals to the builder and 5-10h of dyno time is put on them to make sure all is well before they are installed.

We "refresh" them every 100hrs.

In 4yrs of running the GTS I haven't had a single mechanical DNF (except for a tire puncture) and have won 2 4hr Endurance races. This can/should be a very reliable fun car....

Keep the Faith.

Kevin

Kevin,
Your note above is the very reason I decided to go with the Panoz. Just hasn't worked out that way for me. Dyno time may be part of the next package. I'm feeling pretty disgusted and discouraged right now fighting the urge to "dump" the car.

Thanks for words of encouragement,
Rich

Rich,
sounds like you have lots of experiance and a good builder, but some bad luck.

We run 2 GTSs in SCCA here in Norcal. The motors have been very reliable and are engine dyno'd to 445hp to be SCCA compliant. We upgraded the quality of the cranks (SCAT), rods, and forged pistons, but run the Edelbrock heads and spec manifold, cam, carb etc. The original Panoz engine internals were pretty junky and easily improved w/o "cheating" on HP.

Sounds like an early MIF (maintenance induced failure), but I'd really get them to run the new engine on an engine dyno first and tune it etc. We bring the headers and all externals to the builder and 5-10h of dyno time is put on them to make sure all is well before they are installed.

We "refresh" them every 100hrs.

In 4yrs of running the GTS I haven't had a single mechanical DNF (except for a tire puncture) and have won 2 4hr Endurance races. This can/should be a very reliable fun car....

Keep the Faith.

Kevin

Kevin, did you upgrade "from" or "to" Scat cranks? If "to", did you also use Scat rods? Assume you use a 4340 item?

Reason I ask Kevin, is that I am currently piecing together a 369 cube shortblock using a Dart block, Scat 4340 std weight crank, Scat H beam rods and CP pistons. Have had variable feedback about both Scat and Eagle in NZ so interested to hear of your experiences with Scat if that is what you are using.

Kel.

Rich, I have a few buddies here with 3 Panoz cars between them. They had some issues with maintenance on a few of the cars that led to problems. Then they started dabbling in building their own motors, swapping heads with new valvejobs, etc.... and still had problems. Motors coming apart, motors overheating.

One of the guys has a 347 crate motor from Ford in his cobra replica and I reminded him that he's run that snot out of that car on the track and never had a problem. So, they finally went the crate engine route and haven't had a problem with that setup so far. They did the $3495 306 setup from Ford with the GT40 aluminum heads.

I'm not saying the crate engine route is the best solution for everyone but from my experience it's a tough setup to beat in terms of reliability and value.

Good luck.

Basically Ford motors just suck ;) If you're frustrated put in the garage and put a cover on it and take up another hobby for a bit. After a couple months if you're still over the car then sell it.

We're probably putting a 347 in ours, but reusing our AFR 165s, Edelbrock Performer RPM manifold, and Pro-systems carb to choke it back to 330-340 rwhp which is all we can make for ST2.

Does the DSS engine come with a warranty?

Does the DSS engine come with a warranty?
Not when you buy it used it doesn't. I have a hard time justifying $3000 on a shorblock when I can get a complete Z06 LS6 crate motor for $3200 intake to oil pan. Plus the setup we're looking at uses a worked over stock block with a stud girdle. A good SBF shortblock with a Dart block priced out between $5000 and $6000 for good parts... pretty nuts IMO... no oil pan no nothing... shortblock only.

A few notes:

first REALLY sorry to hear!! I blew my first lSx motor before I even got it on track, turned out to be a misrouted oil line........

Second... ADD AN ACCUSUMP!(or dry sump if you're a high roller like KEL!) :-D

Third... add a stand alone knock sensor, they are just over a hundred bucks and will help tell you if you're detonating! One down side to a carb is the lack of all the checks and balances!

The Panoz cars pull some seriously hard G's and a good oil system is key!

Devin got 3-4 laps on his LS1 before it blew due to oil issues! it can suck bad!! Good luck

A few notes:

first REALLY sorry to hear!! I blew my first lSx motor before I even got it on track, turned out to be a misrouted oil line........

Second... ADD AN ACCUSUMP!(or dry sump if you're a high roller like KEL!) :-D

Third... add a stand alone knock sensor, they are just over a hundred bucks and will help tell you if you're detonating! One down side to a carb is the lack of all the checks and balances!

The Panoz cars pull some seriously hard G's and a good oil system is key!

Devin got 3-4 laps on his LS1 before it blew due to oil issues! it can suck bad!! Good luck

Nah, sorry Eric, I am no high roller. Strict budget on the car at the moment and small race program.

369 engine (996 GT3 Cup Car equaliser............) is well underway and shortblock kit arrives later in Oct. Dart block, Scat 4340 crank, Scat rods and CP pistons. Target for this combo using all my current gear but changing to a solid roller cam and single plane inlet, is around 450rwhp and 410'ish rwtq. No spare money for a dry sump so will most likely add an accusump until either the economy improves or I find the accusump isnt cutting the mustard.

Kel.

Lol.... Kel, hopefully you caught my intent at humor! I use the accusump and so far kits worked wonderfully!

Trust me - Accusump and the correct pan/pickup is key!

Not when you buy it used it doesn't. I have a hard time justifying $3000 on a shorblock when I can get a complete Z06 LS6 crate motor for $3200 intake to oil pan. Plus the setup we're looking at uses a worked over stock block with a stud girdle. A good SBF shortblock with a Dart block priced out between $5000 and $6000 for good parts... pretty nuts IMO... no oil pan no nothing... shortblock only.

Being Ford ain't easy. :banghead:

Are those LS6 engines still out there new? I thought they were out of production.

Being Ford ain't easy. :banghead:

Are those LS6 engines still out there new? I thought they were out of production.

Oh yeah you can buy new ls6 crate motors all day long. They still use them in things like the Hyundai genesis....

Oh yeah you can buy new ls6 crate motors all day long. They still use them in things like the Hyundai genesis....

No wonder Hyundai have one of the highest customer satisfaction rates in the USA!? Could never get my head around that one until now..........

or go with an LSx376 Crate from GM Performace....

I did -- bone stock 370+ RWHP - low compression numbers, so detonation concerns go away -- and ample upwards power growth potential.

Now, fingers crossed that the driveshaft holds up this weekend...

Not when you buy it used it doesn't. I have a hard time justifying $3000 on a shorblock when I can get a complete Z06 LS6 crate motor for $3200 intake to oil pan. Plus the setup we're looking at uses a worked over stock block with a stud girdle. A good SBF shortblock with a Dart block priced out between $5000 and $6000 for good parts... pretty nuts IMO... no oil pan no nothing... shortblock only.

Age old story Brian, you get what you pay for in the $3000 Vs $6000 option. If you go stock block and 347 with a girdle, you may get away with it for a season or 3. Just make sure you crack test the block first and then hand detail all sharp edges in the block. Also make sure that bearing clearances are rechecked once the studs/girdle are fiitted. Then again it may split the block within a few meetings and when it does, take out all of the internal gear and wreck your heads. This is why people spend $6000 on an aftermarket block.........to ensure the bottom end is up for the job and provides additional strength for future upgrading.

If you can convert your car to an LS1 for under $6000 and think that this will be more reliable in the long run then dont hesitate. Do it. My 10c worth. I would be wary though of short cutting now with a stock block 347 given that you clearly like to rev the car, as this will be more of an issue once you throw a stroker crank and more torque at a stock block.
and then go and turn it up rpm wise. I used a max of 5800 with the 347 and we short shifted when ever possible while still turning out the required lap times.

Kel.

Kel I won't be the main driver of the car anymore... that's what the silver Corvette is for. The car will be driven by my father and won't be subjected to the same stresses I put it through.

Kel I won't be the main driver of the car anymore... that's what the silver Corvette is for. The car will be driven by my father and won't be subjected to the same stresses I put it through.

That will help Brian.........!! But.........I still wouldnt trust a stock 5.0 block to last in a 347 road race application if it is going to see some miles. The power that a stock 5.0 block can handle is debated on many forums so I wont speculate on that. I have voted with my wallet by not investing any more in the stock block and getting a Dart block.

I think a sensible thing to do Brian is not to invest to much on internal parts if using a stock block. I.e. there is no use putting a 1000hp capable forged crank and H beam rods into a block that is marginal at 400 - 500hp.

Given this you could probably get away with say a stock block with a Scat 9000 series crank and I beam rodded setup for a lot less. Maybe even $1,500 - 2,000. I have looked at the $$ numbers and decided to wait until I had an aftermarket block prior to spending $$ on good internals as otherwise if the block lets go you have just potentially trashed the lot.

As an aside Brian, have a look at Keith Crafts website. He has a special on at the moment on a race spec stock blocked 347. 600hp and 500ftlbs of torque on the stock 5.0 block!! I see he says he uses aluminium main caps. Keith knows Ford engines as well as any builder out there so this is an interesting combo that I am interested to hear more about from him, especially durability wise............ Weight wise he says it is around 375lbs. Out of interest Brian, what does a fully built up LS1 weigh? Cant remember price, $8,000 odd? Would be a super competitive Panoz power plant if reliable.

Kel.

Eric1 .... Just lost a fresh re-build of my 302 ; it pulled 368 hp/355 t. on the dyno ... Had it installed ; ran enough to put it in & pull it out of the trailer ... Machine Shop is stand-up & leanning on the mechanic about the appearance of oil starvation & who is pleading no foul !!!
I've asked Josh / John Leverette @ Panoz for a oil line schematic ...
I feel I'm on the same road you traveled , can you share the painful details ??? Thanks / Paul W. :banghead:

Update:
Engine builder opened things up. #1 piston detonated & ruined. Appears to be detonation in every other hole as ring gap shrunk in all the other pistons. There was a little scuffing on the cylinder walls. Other than a little valve damage on #1 piston head area everything else looks ok. From a basic repair standpoint sounds like hone all bores, replace 1 piston, replace all rings, bearings etc. and replace valves on # 1.

Unfortunately my builder has no idea what's causing the failure. We were running timing 15 deg idle and 35 deg. full advance 3K rpm. The carb is jetted fat and plugs read rich.

He is looking at all the pieces and parts trying to find a cause. I'm going to send my 6AL-N box along with the distributor to MSD for testing and inspection.

Fuel quality is the last unknown which is now a month old.

Not sure where to go as he tries to sort this out.:confused:

Rich, isn't the timing a little high - mine is 12 / 28 on an engine with 9:1 ratios.

Update:
Engine builder opened things up. #1 piston detonated & ruined. Appears to be detonation in every other hole as ring gap shrunk in all the other pistons. There was a little scuffing on the cylinder walls. Other than a little valve damage on #1 piston head area everything else looks ok. From a basic repair standpoint sounds like hone all bores, replace 1 piston, replace all rings, bearings etc. and replace valves on # 1.

Unfortunately my builder has no idea what's causing the failure. We were running timing 15 deg idle and 35 deg. full advance 3K rpm. The carb is jetted fat and plugs read rich.

He is looking at all the pieces and parts trying to find a cause. I'm going to send my 6AL-N box along with the distributor to MSD for testing and inspection.

Fuel quality is the last unknown which is now a month old.

Not sure where to go as he tries to sort this out.:confused:

Rich, have the heads been cc'ed to check compression ratio? I would also check the dynamic compression ratio. There are some handy online calculators for doing this. Assume all stuff like head gasket orientation etc was OK? No signs of any vacuum leaks?

I run 14/34 or 15/35 timing on my current 347 which is 10.5 compression. I run it on our 98 octane pump gas which is probably the same as your 93? No probs to run on this octane detonation free. We really pushed the envelope on this gas in our last 6 hour as we used quite a bit of oil due to valve guide issues and still had no detonation problems.

Regards carb jetting, has this been baselined to maunfacturers specs then jetted up from there? I have had plugs read rich when the engine was actually experiencing a lean condition before. This can happen due to incomplete combustion in the lean condition fouling/wetting the plugs. Was an exhust sensor used to provide airfuel ratio info during tuning Rich? If not then that combined aith a knock sensor should be a must for post rebuild runs. I would also do the runs on a chassis dyno as opposed to an engine dyno so that all installation dynamics are accounted for in the dyno runs. Or you could do initial runs on an engine dyno and then re-run the car on a chassis dyno post installation. Personally I do all my tuning in a chassis dyno as I find it more convenient, less expensive and it accounts for all installation variables.

Kel.

12.0 to 1 compression 93 octane motor go boom!!

I thought my engine was factory GTS spec. Guess not. 60 cc Edelbrock heads and at or near "0" deck clearance equals lots of compression.

Still going to have the MSD box and distributor checked by the factory.

My builder is providing labor and any machine work at no charge. I'm buying 1 piston, rings, gaskets, 2 valves and some small parts plus the joy of putting the engine back in.

As Kel and others have suggested I'm going to break in and tune the motor on a chassis dyno while in the car. Cost locally for a half day is about $450.00 which should get me 6-8 pulls.
Hopefully on the road to recovery.

Still considering selling after it's back together.

Rich

Well that explains alot. To detonate you either have to have too much timing, compression, not enough fuel, or limited detination margin (ie. octane). Usually, we can't change these easily...

Stock GTS is 10.5:1 (I think) and runs on 110 Leaded.... ie very high detonation margins. Sounds like your builder should have been more specific on the octane required and messed up. Nice you are going to help with the learning cost...sometimes it is the easiest way to keep the relationship and peace.

Since our cars (GTS) lack knock sensors and any real way of hearing detonation (pinging) under full throttle noise, I think burning the good stuff is cheap insurance. Also, I think it is critical to run these race engines on a dyno to get the tuning right. Full load on a dyno would have shown detonation and problem prior to boom! BTW supply the fuel or verify what the dyno tuner will burn.

Kevin

So did you spec out a 12.0:1 compression motor? Or, did you just tell the builder to build you a motor to a certain power goal and he came up with that?

I mean the engine builder should know the compression and advise on fueling accordingly.

Actually I didn't spec anything. When the motor broke the first time he rebuilt it as I purchased it. Used the same heads with mostly new valves,valve job, valve springs, upgraded the push rods, replaced pistons with new (SRP) as were in when it broke, gaskets, rings, bearing blah blah blah etc.

We did not discuss compression or required fuel at the time. I didn't have the history on the car but thought I'd had an older bone stock 9.5:1 early GTS.

I should have pushed him for more information. The pistons are 0 clearance and the Edelbrock heads are 60cc. He ran a calculation yesterday after I spoke with him about the fuel because thing's just weren't adding up for me.

I'm sure if I pushed the issue he'd eat the whole thing. He's not a jerk and I have a long standing relationship with him. I can call and reach him almost anytime and he'll come to my shop to help me out and it's been that way for about 12 years now.

We both made a pretty big and costly mistake. I made the first before he ever got inside the motor the first time and was pretty dumb on round 2.

It's an expensive lesson both financially and physically with the work required to pull thing apart and put it together.

Even with a lot of experience I messed up.

Well that explains alot. To detonate you either have to have too much timing, compression, not enough fuel, or limited detination margin (ie. octane). Usually, we can't change these easily...

Stock GTS is 10.5:1 (I think) and runs on 110 Leaded.... ie very high detonation margins. Sounds like your builder should have been more specific on the octane required and messed up. Nice you are going to help with the learning cost...sometimes it is the easiest way to keep the relationship and peace.

Since our cars (GTS) lack knock sensors and any real way of hearing detonation (pinging) under full throttle noise, I think burning the good stuff is cheap insurance. Also, I think it is critical to run these race engines on a dyno to get the tuning right. Full load on a dyno would have shown detonation and problem prior to boom! BTW supply the fuel or verify what the dyno tuner will burn.

Kevin

Kevin,
I saw that 110 recommendation in the GTS manual and I think you are correct that the compression ratio is 10.5 to 1. I run a 10.5 302 with 36 degrees of total advance all in at 2200 RPM and have no problem with 93 unleaded pump gas on the track. No pinging until I set total advance north of 38 degrees. I am in favor of having a safety margin, but 110 is what 14 to 1 drag motors usually run.

Can someone explain to me why a 351 10.5 motor @ 34 degrees total advance and aluminum heads needs 110?

What I have believed is that using excessive octane for the compression ratio can cause incomplete burn, lower power and carbon build up in the cylinders (raising effective compression possibly enough to actually bring on detonation at some point and or require reduced total advance and retardation of the advance curve to avoid pinging). I'd really like to understand the relationships.

Mike

I suspect it has to do with reliability from Panoz on the new cars. 110 leaded seems to be available at every race track in the US. It is "overkill" with very good detonation margins in our mid performance engines. They might be fine with 100 or lower on cool days or less timing etc....but 110 will always be safe. Painful that it runs about $8/gal at our tracks in California, though. Our tracks seem to stock 110, 97, 93 so 110 is the only practical choice.

Aviation fuel (100 low lead) would also be fine as this is about 115 octane if you convert it to the R+M/2 scale we are used to at US pumps and runs about $4.5/gal.

To build a 450hp engine that runs reliably on 110 is pretty easy, but to build one that runs on 93 or 91 takes some serious engineering, electronics, and maybe boosting.

my .02

Kevin

12.0 to 1 compression 93 octane motor go boom!!

I thought my engine was factory GTS spec. Guess not. 60 cc Edelbrock heads and at or near "0" deck clearance equals lots of compression.

Still going to have the MSD box and distributor checked by the factory.

My builder is providing labor and any machine work at no charge. I'm buying 1 piston, rings, gaskets, 2 valves and some small parts plus the joy of putting the engine back in.

As Kel and others have suggested I'm going to break in and tune the motor on a chassis dyno while in the car. Cost locally for a half day is about $450.00 which should get me 6-8 pulls.
Hopefully on the road to recovery.

Still considering selling after it's back together.

Rich

Rich, you may want to check the calcs on compression. I also run 60cc chamber heads and flat top pistons on my current 347 for approx 10.7 compression. The 12:1 calculation seems to high if your 351 is say .030" overbore and has flat top pistons.

May be worth checking again just to make sure it is nailed.

Kel.

I have gone through it again with my builder Phil. According to the SRP catalog the flat top pistons I have with a 64cc head on a 351 with SVO block come up to 12.1:1 compression. The heads have been worked (shaved with valve jobs) over the years most recently when I had the engine rebuilt so the chambers are probably a bit tighter.

I have actually had him order new AFR heads to replace the stock GTS Edelbrock heads. Should result in 10.5:1 compression and ability to run pump gas / lower octane fuel but gain HP.

We are also changing the timing cover from the aftermarket part that came with it to a stock for cover due to the size of the water ports.

I think I'm on the right track.

FYI stock Edelbrock heads are now for sale for $350 including rockers as is. The valves in # 1 need to be replaced and valve job done in that hole, along with milling heads to clean them up. Sale price finished would be $600.

Rich,
Sent you a PM concerning your old heads.

Mike

Rich,
Sent you a PM concerning your old heads.

Mike

Mike,
Sent 3 responses and they are not showing up in my sent box. Please let me know if you did not receive any of them. you can e-mail directly rfracer25 at comcast.net.

Rich