Are stroker 347 SBF's more prone to piston slap?

Been an interesting year trying to assist my father with the Panoz. Here's the highlights:

1. I snapped the crank in the original 5.0 shortblock running the GRM UTCC at VIR in summer 2010.

2. Dad buys a used 347 shortblock and has it re-built my a very reputable shop in roadrace shop in his area (heart of NASCAR country too).

3. Car runs great in March at VIR... filling up the catch can though.

4. June at VIR it breaks a valve spring. For some reason the shop left the original springs in the heads when swapping them from the old 5.0 to the 347 (AFR 165s). Shop pulls the heads to check everything, replaces the springs, and re-adjusts the rocker arms etc etc.

5. October at VIR the car is running great but chucks the water pump pulley in the last session on Saturday. Mustang racers informed me it is common for the bolts to come loose and is something that needs to be checked often.

6. Shop goes through the car again and upgrades the accessory pulleys.

I was home over Thanksgiving and Dad wanted to show me the fancy new pulleys... While checking out the new parts I notice a fuel leak from the carb. In fixing the carb fuel leak I just can't get comfortable with the internal tapping noise coming from the engine. I don't know SBFs well enough to know what's normal for them. I.e. with my LS6 piston slap is common and the car sounds like it has a rod knock for a few minutes when started... would sound like an issue to someone who didn't know LSXs.

Here's a video checking everything with the VC's off... (I checked all of the rocker arms and all were good and pre-load was good on all of them)

http://www.youtube.com/watch?v=VxQLDHpGgeA&feature=feedu

On other forums I've heard everything from "YOU HAVE NO OIL PRESSURE" (if you rev it a little it'll fling oil all over. Pressure holds steady in the high 40s on the gauge), "It's bottom end, take the engine out, "It's nothing.... just some piston slap". While racing at Road Atlanta a couple weeknds ago I made a point to listen to various Ford powered cars in the paddock and most all made clatter/racket at idle.

Thoughts? At this point I think he's just going to drive it and if it blows up again we'll put a LSX in it.

~Brian

Brian,
I can't answer your question directly. I have just put a 331 in mine and broken it in on a dyno and some acceleration straight runs. Not done a track day yet. No unusual noises, but mine only has the 3.25 stroke. I know one of the longevity concerns with the 347 is the rod to stroke ratio with short skirt pistons. There is more tendency for the pistons to rock in the bore. It seems to me this would be an issue for piston skirt and cylinder wall wear. If the clearances opened up then piston slap can occur. This shouldn't be a rapid process.

Forged pistons grow a little with heat, but the cast hypereutectic don't as much. If the noise is reduced or gone when warmed up and the motor has forged pistons, then you might have the piston slap. Given the little use you have on it, I doubt it could have happened since the rebuild. I'd check to see if the pistons were replaced or checked carefully for taper and roundness top to bottom at right angles and if the cylinders were checked for taper at right angles. If the shop set the piston to cylinder clearance on the loose side, that might also be a factor.

My son Tom has run two 347's and neither one had piston slap or any like noises. One of these had at least 50 racing hours on it and was still quiet when he had it torn down for metal content in the oil. I've never heard of this being an issue on a fresh rebuild or low hour motor. Perhaps you can contact Kel directly or he'll chime in since he has a lot of SBF stroker experience.

Hope it is something minor that you can easily fix or can be ignored. Let us know how this turns out.

Mike

Rebuild 100% has new pistons. I remember my dad commented that he spent extra for some fancy lighter pistons. Also that the stroker kit was one that put the wrist pin in a better place in relation to the oil control rings.

I'm not one to try and gloss over noises i.e. I'm OCD and prefer to diagnose and fix, but at this point our options are:

1. Pay the sop to tear down the engine and inspect and show us what's wrong or that nothing is wrong (they don't think anything is amiss, but I think they're tired of fixing things on their dime)

2. Drive it until the noise gets worse/changes or it blows up!

Most all LSX's have piston slap. My race car has 122,000 miles on it and the engine still makes 360+ rwhp. I built the car summer 2010, raced it 3x that year and 8x this season and it's fine. The car is silent when first started, then starts slapping as it warms up, then once warm it gets quiet again... just how they do.

Brian, havent heard from you in a while and wondered what you were up to. The noise sounds more like a knock than a typical valvetrain tick and reasonably meaty. For this reason I dont think it is piston slap either as this noise is not so solid. Is the engine hot or cold in the video?

I am no expert on bearing knock noises but would do some googling around diagnosing knocks to see if there are any trick ways of diagnosing without pulling the engine. This is definitely something that you want to be confident that you do not have as racing on a big bearing clearance is likely to lead to short time failure and kill the crank etc. What were the bearing clearances when the engine was assembled?

Assume the "high 40's oil pressure" is with the engine hot? If so OK'ish, if cold then this is low in my experience (thus far) with 302 Ford's.

I am running 4.155" bore with .005" piston to bore clearance and do not have any noticeable top end piston related noise. Only thing that can be heard is the general valve train noise from the mechanical roller lifters and rockers which is more of a ticking noise and a lot "lighter" in tone that what your engine seems to have.

On another note we had to do some more dynoing last week due to exhaust changes (dual 3" to meet noise regs) and a head change to Edelbrock Victor Juniors. Now up over 466rwhp at 6400 and torque is way up as well.

Kel.

Brian,
I can't answer your question directly. I have just put a 331 in mine and broken it in on a dyno
Mike

Mike, what happened to the 331?

Kel.

Brian, havent heard from you in a while and wondered what you were up to. The noise sounds more like a knock than a typical valvetrain tick and reasonably meaty. For this reason I dont think it is piston slap either as this noise is not so solid. Is the engine hot or cold in the video?

I am no expert on bearing knock noises but would do some googling around diagnosing knocks to see if there are any trick ways of diagnosing without pulling the engine. This is definitely something that you want to be confident that you do not have as racing on a big bearing clearance is likely to lead to short time failure and kill the crank etc. What were the bearing clearances when the engine was assembled?

Assume the "high 40's oil pressure" is with the engine hot? If so OK'ish, if cold then this is low in my experience (thus far) with 302 Ford's.

I am running 4.155" bore with .005" piston to bore clearance and do not have any noticeable top end piston related noise. Only thing that can be heard is the general valve train noise from the mechanical roller lifters and rockers which is more of a ticking noise and a lot "lighter" in tone that what your engine seems to have.

On another note we had to do some more dynoing last week due to exhaust changes (dual 3" to meet noise regs) and a head change to Edelbrock Victor Juniors. Now up over 466rwhp at 6400 and torque is way up as well.

Kel.
Engine wasn't "hot" but it was a reasonably warm day and we'd started the car a few times messing with it so I'd say it was on the warm side vs. cold.

I don't know the specs on the tolerances etc. on the shortblock. That's why my father paid a shop... so he didn't have to worry about it :runaround:

The shop is adamant it's a "normal" noise... and I've got no good way to daignose a rod knock w/o being around the car and monitoring it for changes in tone or oil pressure etc. I'm not hands on with the car anymore as it "lives" four hours from me at my father's place. I see it when we hit the track together.

I guess at this point he should just drive it and watch oil pressure and listen for any changes and see what happens. It runs strong when parts are flinging off :tongue:

As for me... been running this Z06 hard all year. I've been instructing and running timetrials and then finally did comp school at VIR in October and have started wheel-to-wheel racing. I got my fourth race w/o incident done at Road Atlanta a couple of weekends ago so I get off "rookie"status. I had the track record for my class at VIR most of the year (lost it in october) and smashed the class record at Summit Point by 2.5 seconds. Ran a 1:17.8 vs. the previous 1:20.3 record.

Overall it's been a great year with the car. Getting ready to get back to it at VIR in February for the start of the 2012 season.

Mike, what happened to the 331?

Kel.
I think he means he just installed it and broke it in on the dyno.... i.e. not broken.

Engine wasn't "hot" but it was a reasonably warm day and we'd started the car a few times messing with it so I'd say it was on the warm side vs. cold.

I don't know the specs on the tolerances etc. on the shortblock. That's why my father paid a shop... so he didn't have to worry about it :runaround:

The shop is adamant it's a "normal" noise... and I've got no good way to daignose a rod knock w/o being around the car and monitoring it for changes in tone or oil pressure etc. I'm not hands on with the car anymore as it "lives" four hours from me at my father's place. I see it when we hit the track together.

I guess at this point he should just drive it and watch oil pressure and listen for any changes and see what happens. It runs strong when parts are flinging off :tongue:

As for me... been running this Z06 hard all year. I've been instructing and running timetrials and then finally did comp school at VIR in October and have started wheel-to-wheel racing. I got my fourth race w/o incident done at Road Atlanta a couple of weekends ago so I get off "rookie"status. I had the track record for my class at VIR most of the year (lost it in october) and smashed the class record at Summit Point by 2.5 seconds. Ran a 1:17.8 vs. the previous 1:20.3 record.

Overall it's been a great year with the car. Getting ready to get back to it at VIR in February for the start of the 2012 season.

Listened to the video clip again. Possible that it is top end as seems to clear with a few more rpm. Have you tried resetting the hyd lifter crush? I would do this and run again.

Enjoyed the racing vid. Car in front of you was loose coming off the apex of a few corners but shame to see him spear off.

Mike, what happened to the 331?

Kel.

Kel,
331 is fine, just ran it in on the chassis dyno and did some EFI tuning on a straight stretch with someone in the passenger seat on the lap top. I tried using the Ford GT-40 intake with 65mm throttle body, but I need to upgrade to 75mm TB and a Trick Flo intake as it is pulling vacuum at WOT. Stuff is now on hand but I think I'll run it as is the first time or two to get a feel for it before I swap the intake stuff. The motor is no monster and neither am I so it's a good fit. After the intake swap, I figuring it will be over 300 hp and over 330 torque at the wheels even with the shorty headers and stock exhaust. Given my skills, 3550 transmission and budget, it should be great fun. I was just getting tired of the stock mustang GT's pulling me on the long front straight at TWS. I built it to run forever since I just do track days to entertain myself even if everyone else is laughing! If I sell it it could easily get 350 at the rear wheels with a proper exhaust. I might even do that "one of these days."

Mike

Kel,
331 is fine, just ran it in on the chassis dyno and did some EFI tuning on a straight stretch with someone in the passenger seat on the lap top. I tried using the Ford GT-40 intake with 65mm throttle body, but I need to upgrade to 75mm TB and a Trick Flo intake as it is pulling vacuum at WOT. Stuff is now on hand but I think I'll run it as is the first time or two to get a feel for it before I swap the intake stuff. The motor is no monster and neither am I so it's a good fit. After the intake swap, I figuring it will be over 300 hp and over 330 torque at the wheels even with the shorty headers and stock exhaust. Given my skills, 3550 transmission and budget, it should be great fun. I was just getting tired of the stock mustang GT's pulling me on the long front straight at TWS. I built it to run forever since I just do track days to entertain myself even if everyone else is laughing! If I sell it it could easily get 350 at the rear wheels with a proper exhaust. I might even do that "one of these days."

Mike

Good to hear that the upgrade is coming along well Mike. I was very tempted to go 331 myself but we really need all the cubes we can get to try to run with GT3's........

On the exhaust topic Mike, we have yet to find the limit of the merged system on the car as we thought it may top out with the 369. Doesnt seem that way though as the power curve is still heading north at the same rate at our chosen cut off of 6400 even at 466 rwhp.

Dont worry about that 3550...........we have put a few hours on ours now with stroker combo's and it is hanging in there (touching wood as I write). Will be interesting to see how it goes with 450rwftbs of torque. I think a real help here with the 3550 is limiting standing starts as nearly all of the racing I am doing with the car is rolling start. The short first gear ratio in the 3550 is its achilles heal regards torque multiplication in standing start situations.

Have fun with the new combo Mike.

Kel.

Mike, Can you share the particulars of your engine build. I think I would like to build something similar.

Thanks

David

David,
Send me your email to mduke8 AT gmail.com and I'll send you all the part numbers, costs and specs. If I were doing this again, I'd probably buy a crate motor. It would probably have cost a little less and made a little more power. Not sure how much I'm losing with the stock exhaust, but some for sure. I think there might be 20+ at the wheels there because it has no X pipe and shorties. With it pulling 5 pounds of vacuum at WOT and this exhaust, there might be 20+ in the intake and TB as well. I have a 73mm mass air so that's not the intake restriction. Right now it is doing 280 hp at 5100 and 330 Tq. The cam is supposed to have peek hp at 5800-6000 and it fell off slightly 5100 to 6000 so obviously it is being choked as it is. It is a 10:1 motor with Trick Flo heads and a Comp Cams Extreme Energy hydraulic roller. This cam is their recommendation for road racing, 3000 lb. car, 6000 rpm peak power, 10:1, up to 347. Capable of high 300+ hp at flywheel with single plane and carb. Good compatibility with EFI.

Mike

When to the engine dyno on Monday with the refreshed 360 c.i. dart block, results
4000 rpm torq ft lbs 356
4684 rpm 469
plus 113

Max. 5800 rpm 491 ft lbs

7300 rpm 629 hp
7700 rpm 638 hp

Merry Christmas & Happy New Year

David,
If I were doing this again, I'd probably buy a crate motor. It would probably have cost a little less and made a little more power.

Mike
I put a Ford Racing 347 crate motor in my car and can't complain at all. I put 83 track hours on it and then decided to freshen it up. It needed nothing. Inspected everything, honed the cylinders and put in new rings and bearings etc. Broke it in on a chassis dyne yesterday and it put out 440 rwhp at 6000 rpm and 420 ft-lbs at 4800 rpm. It moves the car right along. Ford calls the engine 450 hp, but it is obviously doing better than that at the flywheel. It is such a reliable and easy engine, hydraulic roller cams, port matched Z Ford head. $8700 with intake, flywheel and damper. I bought it through Summit.

Craig

David,
Send me your email to mduke8 AT gmail.com and I'll send you all the part numbers, costs and specs. If I were doing this again, I'd probably buy a crate motor. It would probably have cost a little less and made a little more power. Not sure how much I'm losing with the stock exhaust, but some for sure. I think there might be 20+ at the wheels there because it has no X pipe and shorties. With it pulling 5 pounds of vacuum at WOT and this exhaust, there might be 20+ in the intake and TB as well. I have a 73mm mass air so that's not the intake restriction. Right now it is doing 280 hp at 5100 and 330 Tq. The cam is supposed to have peek hp at 5800-6000 and it fell off slightly 5100 to 6000 so obviously it is being choked as it is. It is a 10:1 motor with Trick Flo heads and a Comp Cams Extreme Energy hydraulic roller. This cam is their recommendation for road racing, 3000 lb. car, 6000 rpm peak power, 10:1, up to 347. Capable of high 300+ hp at flywheel with single plane and carb. Good compatibility with EFI.

Mike


Oh, I hear you. I spent the better part of 2011 doing some pretty comprehensive updates to my GTRA (Chassis #6), including a 331 stroker. In the end, it dynos at 380/380 at the wheels (on pump gas - the engine builder is optimistic that after fully breaking in, it's good for 400, but I'll believe that when I see it), through a TKO 600, and stock 9" rear end (3.73 as I recall). The work included the new engine and transmission, new dash/gauges, Kirkey seat and new harnesses, chassis reinforcements to the rear trailing arms, hard-wired cool-suit system, and a bunch of electrical work. A project that I *expected* to come in around $20-25k wound up costing $40k+, so with the cost of the car in the first place, I've got mid-50s in a car that I could maybe sell for low-30s. Needless to say, we're looking at a long-term relationship now. In terms of straight cost, I should have bought a new car (or at least got a good crate motor), but I'm pretty emotionally attached to the Panoz, and at this point, more of it's new than old.

Paul,
#6 has certainly come a long way since you bought it. Let me know when you'll be running it at Harris Hill or some place closer to me like MSR Houston or TWS. I'd like to see it, meet you and watch you run it.

Are you EFI or carb now?

Mike
College Station

I put a Ford Racing 347 crate motor in my car and can't complain at all. I put 83 track hours on it and then decided to freshen it up. It needed nothing. Inspected everything, honed the cylinders and put in new rings and bearings etc. Broke it in on a chassis dyne yesterday and it put out 440 rwhp at 6000 rpm and 420 ft-lbs at 4800 rpm. It moves the car right along. Ford calls the engine 450 hp, but it is obviously doing better than that at the flywheel. It is such a reliable and easy engine, hydraulic roller cams, port matched Z Ford head. $8700 with intake, flywheel and damper. I bought it through Summit.

Craig

Craig,
That is awesome. I really doubted Fords advertised hp rating on that motor, not any more! Which intake, carb, headers and exhaust?

Thanks,
Mike

Craig,
That is awesome. I really doubted Fords advertised hp rating on that motor, not any more! Which intake, carb, headers and exhaust?

Thanks,
Mike

It came with the Victor Jr. single plane intake, and I bought a Holly HP 650. (Since I'm only running to 6000 rpm a 650 works fine.) The headers are also from Ford, they are shorties made for the "Z" head install into a Fox bodied Mustang. The exhaust in 2.5 inches and includes a DynoMax Turbo Muffler, required to meet some of the sound limits on the west coast. I know that it sounds like I did everything wrong to make HP, but it all works, and have have no idea what the the engine would actually do on an engine dyno. I does drive like 440 RWHP, so I'm inclined to believe it.

Craig

I bought the stroker 392 ford crate motor and it did everything they claimed. Ran it for probably 25+ race hrs. and then sold it when our 427 drysumped motors got finished. The motor did everything I expected it to do.

Paul,
#6 has certainly come a long way since you bought it. Let me know when you'll be running it at Harris Hill or some place closer to me like MSR Houston or TWS. I'd like to see it, meet you and watch you run it.

Are you EFI or carb now?

Mike
College Station

Hi Mike:

I'm still harboring a lot of guilt for buying it when you were on your way to see it, but if you come unarmed, I'm sure we can work something out. Since I bought it, I've only driven it at Harris Hill, and I'm at a point now where I'd like to venture out to some different tracks, so maybe a trip to College Station/Houston will be in my future.

When we went for the build, we chose to go with EFI, principally to keep the car more plug and play, and maintain the throttle response, and ease of tuning that a road-racing motor would ideally have. I've been very happy with the results. The power level is enough to still hook up well coming out of corners, but get rowdy if you want to. I run on r-comps, so 380 to the wheels is enough to challenge them without being undriveable (I destroyed the rear suspension about 3 weeks after the rest of the build was complete, so that was another two months of non-running time to beef it up. I feel like at the moment, we have a good balance of power and chassis). From where we are now, the next obvious improvements in speed would come from less parachute-esque aerodynamic qualities, rather than extra horsepower.

Paul,
It was meant for you to get #6. I ended up getting a nice one also and made some great contacts in Florida and Georgia in the process. There are plenty of these great cars to go around as they remain one of the best kept track toy secrets.

I'll need to compare notes with you to figure out how to get a little more out of mine. Was your rear suspension problem in the four arms? What did you do to fix it?

Happy New Year,
Mike