GTRA 347 Conversion Sump Questions?

[NZGTRA17]

I am looking at various block & crank options at the moment for my GTRA and am interested to hear from anyone who has converted their GTRA from 302 cubes to 347.

Specifically;

1. Did the std Panoz supplied wet sump provide sufficient clearance for the additional crankshaft stroke?
2. Were any modifications required to the sump to get it to fit the 347 (i.e. trimming crank scraper or relieving the bottom of the sump)?
3. What rpm are you spinning your 347 to and have you had any oil surge or windage problems?
4. Did you modify the oiling system (i.e. adda an Accusump or other)?

Thanks, Kel.

[Blue Streak 21]

I've stroked my 302 into a 347. I purchased the block and rotating assembly from a local engine builder. He put in the oil pump, but I used the pan and pick up tube from the old 302 motor. Seems to be okay, as oil pressure is strong. I don't think the builder mentioned any clearance issues with the rotating assembly and the oiling system.

I spin the 347 up to 6000 RPM. The cam that was specially ground runs out of umph at around 5500 RPM. So no sense spinning it higher. I thnk the reason for the lower HP limit is that the EFI system doesn't breath well enough. Another mod I'm saving for next year. The 347 is making 350 ft lbs of torque at the wheels and about 315 HP. Nice improvement, especially coming out of the corners.

[NZGTRA17]

Originally Posted by Blue Streak 21

I've stroked my 302 into a 347. I purchased the block and rotating assembly from a local engine builder. He put in the oil pump, but I used the pan and pick up tube from the old 302 motor. Seems to be okay, as oil pressure is strong. I don't think the builder mentioned any clearance issues with the rotating assembly and the oiling system.

I spin the 347 up to 6000 RPM. The cam that was specially ground runs out of umph at around 5500 RPM. So no sense spinning it higher. I thnk the reason for the lower HP limit is that the EFI system doesn't breath well enough. Another mod I'm saving for next year. The 347 is making 350 ft lbs of torque at the wheels and about 315 HP. Nice improvement, especially coming out of the corners.

Thanks Jerry, feedback appreciated. Assume you used a std late model Ford 302 roller block with the 347 kit?

Kel.

[NZGTRA17]

Originally Posted by Blue Streak 21

I've stroked my 302 into a 347. I purchased the block and rotating assembly from a local engine builder. He put in the oil pump, but I used the pan and pick up tube from the old 302 motor. Seems to be okay, as oil pressure is strong. I don't think the builder mentioned any clearance issues with the rotating assembly and the oiling system.

I spin the 347 up to 6000 RPM. The cam that was specially ground runs out of umph at around 5500 RPM. So no sense spinning it higher. I thnk the reason for the lower HP limit is that the EFI system doesn't breath well enough. Another mod I'm saving for next year. The 347 is making 350 ft lbs of torque at the wheels and about 315 HP. Nice improvement, especially coming out of the corners.

Hi Jerry, checking in again to see if the 347 shortblock you are using is based on a standard 5.0 roller block (or an aftermarket block)?

How many race hours do you have on the 347 now? How is it holding up?

Thanks, Kel.

[Cobrafang]

I am no expert but my next motor will probably be a 331 cu versus a 347 cu. Regardless I am also going to go with a Boss Block from FORD. I just want the extra comfort that if I miss a shift or something like that it will hold together. Especially given the conditions we run our motors in, it just seems smarter even though there is a price difference.

I think the standard block is good for 400 hp and 6k. My dad knows more than me on this. I am sure he will chime in. He has all the internals waiting to build a really nice 347 motor.

Anyways my thoughts.

OBTW what do people think about the 331 cu FRPP crate motor that is said to make 500hp?

Thanks.

[NZGTRA17]

Originally Posted by Cobrafang

I am no expert but my next motor will probably be a 331 cu versus a 347 cu. Regardless I am also going to go with a Boss Block from FORD. I just want the extra comfort that if I miss a shift or something like that it will hold together. Especially given the conditions we run our motors in, it just seems smarter even though there is a price difference.

I think the standard block is good for 400 hp and 6k. My dad knows more than me on this. I am sure he will chime in. He has all the internals waiting to build a really nice 347 motor.

Anyways my thoughts.

OBTW what do people think about the 331 cu FRPP crate motor that is said to make 500hp?

Thanks.

Yes have looked at a lot of articles on 331 Vs 347. I am in the other camp, I am not convinced that all the negative hype around the 347 is for real. I like the prospect of pulling the rpm back with the 347 to increase engine life while still making the same or more power than a 331. The dyno software that I use for modelling combinations is telling me that the 347 has a decisive torque advantage over the 331. There are lots of articles that talk about the negative side of the 347 rod ratio but if you calculate this you will see that it is virtually the same as a 427 Ford combo. There are so many 427's and 347's running around now that I think this dispels the myth.

This is a table I put together looking at some of the engine combos for the Panoz and the mechanical pro's and con's.

CID Stroke Rod Length Rod Ratio RPM Mean Pist Speed Safe RPM Target RPM % of Safe RPM

302 3 5.090 1.69 6500 3237 8434 6500 77%

331 3.25 5.4 1.66 6500 3506 7785 6250 80%

347 3.4 5.4 1.588 6500 3668 7442 5800 78%

393 3.85 6.0 1.55 6500 4154 6572 5800 88%

427 4.0 6.25 1.56 6500 4316 6325 5800 93%

As you can see the rod ratio of a 347 is better than some of the more popular Ford stroker combos. The 'Safe RPM' is calculated from a formula provided by A Graham Bell in a book he wrote on performance 4 stroke engines. It is a guide only and in this case is based on a road race application with a forged crank, heavy duty rods and main bearing caps.

Would be interested to hear what your father has to say on this as well.

I am already on the 400hp mark with my 302 combo and this seems to be holding together fine so far. I am very careful to limit rpm though and my current combo is kept below 5800. Intention would be to do the same with a 347 until I have an aftermarket block.

I am not so sure about the Boss block. These are not well regarded over here as they are considered to have to short a bore wall. This is attracting negative comment from professional engine builders running 302 cube race engines and they do not recommend this block for stroker applications. I have not measured the bore wall length of a Boss compared to a Dart or World block but am told that the Boss is shorter at the bottom of the bore (?). Can anyone confirm this?

Kel.

[panozracing]

is there a reason nobody looks at the 351 stroker packages? Is it weight? Is it that you have 302 parts and I had 351 parts?

[NZGTRA17]

Originally Posted by panozracing

is there a reason nobody looks at the 351 stroker packages? Is it weight? Is it that you have 302 parts and I had 351 parts?

Bit of both for me really Brian. 351 based setup would probably add at least 50+ pounds to the car, it would raise the C of G and I would have to start from scratch.

If I had started out with a 351 based car, I would absolutely stick with that for sure. Starting out with the 302 though has made me look at ways of idealising that package instead.

I am not able to run slicks for endurance racing here either so having 550 ftlbs of torque would be wasted as I would not be able to get it all to the ground. This is another reason why I have looked at a big inch 302 base. I figure for my car to be an outright contender in endurance races here, 500hp and 460 - 480 ftlbs of torque will do the job. I beleive that I can reliably extract this from the likes of a 3.4" stroke x 4.155" bore Dart blocked 302 = 368 cubes. Modelling of this combo shows around 520 flywheel hp and 490ftlbs of torque all below 6200rpm.

Even at this torque/hp level I expect I will need to move up to say a 275 or 315 rear (DOT) tyre to last the required distances.

If I had an unlimited budget (and I dont, especially not now with a 6 day old baby in the house!!), I would go for an alloy blocked dry sumped 351 based engine and marry this to a sequentially shifted 5 speed Jerico. I would probably convert the rear end over to an independent set up as well. This combo would be unstoppable in our endurances series. Now to find a well heeled sponsor...............!!

Interested to hear others thoughts on their ideal setups.

Kel.

[PanozDuke]

Kel,
I do have all the internals for a 347. I bought the Probe pistons that do not cause the pin to intrude into the oil ring groove, H beam rods and a forged crank. I haven't built it, but planned on making 400-450 hp at 6000 using a 5.0 block with main stud girdle. The compression would be about 10:1 with a good hydrolic roller cam with about .550 lift. The motor was going to be used in a 69 Mustang for street and open track. Since my power and rpm limit goal was modest, I felt the 5.0 block would be fine. They seem to be OK up to 400 hp without a girdle as long as you don't power shift them or get them too hooked up from a standing launch. With the girdle, I felt it would be solid for my occasional track use. With the kind of power you are going to be making, I would not plan on the 5.0 block standing up to that long term. My knowledge of the new Boss block versus the others is nil. I believe at least one of them has to be notched for rod clearance. I would be surprized if the cylinder skirt length were an issue in the Boss block since it was built with the idea of making a 342 stroker. I could be wrong and it also might depend on the pistons you use. Since I haven't built the motor yet, I can only tell you what my experience led me to do in terms of the concept.

The 331 vs 347 debate I really don't know much about either. Since I had a way to avoid the oil control problem with the 347 and my rpm and power limits were reasonable, I wasn't worried about the rod to stroke ratio and it seemed OK. What I wanted was midrange torque and 347 beats 331 in my book. If I were looking for a pure road race motor with more power, I'd probably up the compression and keep the rev's down so it would live a good long life. I'd get the strongest block I could find. That is probably not the new Boss block and the costs of the others isn't that much more. I think they weigh more than the Boss.

About the 331 crate with 500 hp: my bet is that it is a drag race motor with not much in the midrange. I'd want to see the dyno numbers. I think you could get 500 out of 331 in a road race power profile, but it would be fragile and you'd be reving it over 6500. Not so good for long life. What you really want is midrange torque not max rpm hp. If you want 500 hp, do the 351 stroker with the best internals and an aftermarket block and keep it at 6000. Maximize the midrange. I have to agree that the stock 351 block is very marginal over 400 hp, even with good internals.

Mike

[Blue Streak 21]

Kel;
The 347 is doing great. I've got 7 hours on the motor now, and it's running strong. I dyno'ed the engine before the first race, and it makes 350 ft-lbs and 315 hp at the rear wheels. I figure that's 425 ft-lbs at the engine. The engine has 10:1 compression which can be run on pump gas. The torque is great for my home track due to the number of turns. It comes out of the turns like a hound from hell. I still run stock tire widths, and I can modulate the throttle well enough to keep the tire from spinning too badly. Can be a challenge, but what is racing without a challenge.
The block is a 5.0 l late model roller block with Canfield alum heads. Nothin' special, as I was going for reliability. I only spin it to 6000 rpm, so it's pretty tame. I used h-beam rods, and pistons with all ring grooves above the wrist pin. The cam provides .55" lift at the valve. The only thing I wish I had done was to go with a different EFI intake. THe Typhoon intake I'm using is a bit restrictive after 4000 rpm, so it limits HP. I'd use a BBS individual runner type if I had it to do over again. THat would help with the hp at higher rpm.
Jerry

[PanozDuke]

Jerry,
Thanks for that confirmation of the combination. Your results give me confidence in my goals. Are you using a stud girdle? Forged crank?

Kel,
You and I need the same sponsor! Congratulations on the new addition. Specifications?

Mike

[NZGTRA17]

Originally Posted by PanozDuke

Jerry,
Thanks for that confirmation of the combination. Your results give me confidence in my goals. Are you using a stud girdle? Forged crank?

Kel,
You and I need the same sponsor! Congratulations on the new addition. Specifications?

Mike

Cheers Mike, a wee boy, Ari. Havent measured him up for a race suit yet but already has his first toy car courtesy of a friend who crewed for me at the 6 hour enduro. Tried to get him to watch the V8 Supercars with me last weekend but he had other plans...............sleep.



As you can imagine there is not going to be much action in my workshop for a while!! Can do lots of planning in the interim, have a 7 1/4" tripple plate clutch and button flywheel already and just got a hydraulic clutch conversion (pedal, master cyl etc) in the post from Wirewheel. Plan at this stage is to fit the new clutch (should weigh less than 20 lbs Vs the 50 odd lb monster currently fitted) and an underdrive pulley set and go and do the odd race meeting over summer when babysitting arrangments allow!

If funds allow I may bolt a forged 347 rotating kit into my current block with the plan of carrying the rotating kit across into a stronger block when I can afford one. If I do bolt the 347 kit into the standard block I will again use the girdle, will do a ot of detailing on the block (chamfer and debur all holes, debur all main webs and possibly do some shotpeening of the main webs) and will run it to only 5600 or 5800 rpm.

By my calcs a 347 kit will bump rear wheel power in my combo to around 385 hp at the wheels and 375 ftlbs at the wheels. This is using same heads, carb, manifold, cam and exhaust that I have.

Also plan to improve the aeros. More work around the splitter/undertray and perhaps the addition of a diffuser.

Kel.

[Blue Streak 21]

Originally Posted by PanozDuke

Jerry,
Thanks for that confirmation of the combination. Your results give me confidence in my goals. Are you using a stud girdle? Forged crank?

Mike

All of your goals are defintely obtainable. With the right cam and intake, 450 HP and torque is very doable. For my engine, all internals are forged for reliability. It added a bit to the rotating assembly price, but nothing terrible. Since I was going to build it to last several seasons, I figured it was worth the extra $$$.

I'm not using stud gridles. My research showed that unless your normally reving well past 6000 on a regular basis, then the gridles were not needed. I'm shifting before 6000 because my motor doesn't breath well spinning that high. Maybe others here on the forum have different/better advice, but that's what I got from my engine builder.

Jerry

[PanozDuke]

Kel,
Great photo. I think he likes you. I also think you are going to be busy.

The idea of shot peening the main webs is great- hadn't thought of that, but it should be a help.

Keep us posted on both projects, Ari and the Crimson Kiwi.

Mike

[NZGTRA17]

Originally Posted by PanozDuke

Kel,
Great photo. I think he likes you. I also think you are going to be busy.

The idea of shot peening the main webs is great- hadn't thought of that, but it should be a help.

Keep us posted on both projects, Ari and the Crimson Kiwi.

Mike

Mike, I started thinking about the utility of shot peening when looking at the failure mode in the block below. I am thinking of shotpeening a band of approx 1" from the bottom of the no's 2,3 & 4 webs up. I have read a few engineering papers on the value of shotpeening cast iron and this varies significantly depending on the grade that you are working with. Seems that you could expect an improvement in fatigue life of 10 - 30%. I think that this in combo with removing all stress risers (sharp edges etc) will help.

There will certainly be need for care when shotpeening the webs though as they are not very thick. Shot size and peening pressure will need to be well considered. There is also a possibility that this process may affect the main bearing bore alignment.



I am going to talk to a local Ford specialist race shop to discuss where they normally see cracks originating in these blocks so I can work out whether the shotpeening idea is worthwhile. Next job will be to find a skilled operator that can be trusted to do the job and at a reasonable price.

I am not so trusting of these blocks though, that I wouldnt run a main girdle. I really think that any 347 application will benefit from a girdle and at less than $200 it seems a cheap way to add some strength to a marginal block arrangement. It is worth buying some girdle kits just to get the ARP main stud kit that comes with them (I think mine is a Probe kit and it came with ARP stud set up). This will also help to stabilise the bottom end of the engine.

Next job is to haul my engine out and strip it down to get the block crack tested to see how it has held up to the 6 hour beating that it got.

Kel.