LS3 GM Performance crate engine conversion P/N CT 525 for 89 951

I have a 951 used for racing and have grown weary of maintaining the modified engine per class requirements.

I like the GM Performance CT 525 crate engine (see here): GM Performance CT 525

AKA: 6.2L Gen IV Small Block V8

Here are a few questions:

1. Will the 968 trans-axle (with trans cooler) hold up to 600 hp/500tq, or what are the known limitations?

2. Has anyone modified gear ratios to more closely match the SBC (500-600hp) power band for track use? (Northeast tracks; usually no more than .25 - .4 mile straightaways), but more concerned with gear selection in turns.

3. How to strengthen gearbox to match the SBC (500-600hp) output for track use?

4. Any axle/u-joint recommendations?

5. What is the purpose of the transaxle reinforcement plate offered by 944 Hybrid?

6. Is there a 944 Hybrid engine mount kit that will accommodate this unit?

7. Has anyone set up this engine (or any LS3) in an 89 951 with dry sump?
(note that unlike corvette engines, the CT 525 is set up for circle track racing with wet sump pan which would be discarded & converted for this application).

8. Does the removable crossover tube help with dry sump clearance, and does anyone know the actual available clearance from top of the cross tube? I understand Lindsay Racing makes a crossover tube, is there anyone else?

9. Does the removable cross tube compromise rigidity, cause flex or create any other detriment?

10. It is possible to keep the engine low on the mounts with dry sump, or does dry sump introduce other issues?

11. Which Bell housing should I use?

12. I'd like to use a button-style racing flywheel/clutch - what is the smallest diameter flywheel for which I can expect to find a (quartermaster, etc. high torque-style) starter motor that will match the bell housing/flywheel?

13. Does anyone know if race headers are available (& where) for this engine as set up in an 89 951?

14. Has anyone built or had made an aluminum drives shaft tube, or is this not a good idea?

15. What is the weight difference between the LS3 SBC alu. head/block as compared to the Porsche 951 engine (base engine only, i.e., not including turbo plumbing, inter-cooler, etc.).

16. Last one... - Any opinions on dry sump-ing the LS3 for Road Racing applications? I am getting different opinions as to whether the engine can cope with high g-loads as relates to lubrication.

The car would move to a more competitive class with this change but the reliability could be worth it (at least engine-wise), - or am I just creating new problems?

- Many thanks for any feedback which will be greatly appreciated!

there is much info on oiling issues of the LS2/LS3 motors on the Corvette forums, including options for dry sump/Accusump/oil pumps/etc. Consensus is that LS2/3 motors have many issues with oil starvation in long left hand sweepers, with some motors dying within 2 laps. The LS6 motor is deemed by some as the hardiest of the variants

eclou wrote:there is much info on oiling issues of the LS2/LS3 motors on the Corvette forums, including options for dry sump/Accusump/oil pumps/etc. Consensus is that LS2/3 motors have many issues with oil starvation in long left hand sweepers, with some motors dying within 2 laps. The LS6 motor is deemed by some as the hardiest of the variants

Thanks for your feedback. - Are your observations on starvation in regard to wet or dry sump LS3 engines used on the track?

Thanks in advance for any further insight you can provide. Per your suggestion, I will also check out the vette forums.

eclou wrote:[You must be registered and logged in to see this link.]

After your first post I did take a look on the Vette/Camaro sites and found many, many similar posts to the one (which is a really good one) that you have included here.

I'm calling Bill Martin of GM Performance today to get his take. In any event, dry sump is the only way to go (with any track machine that run large rubber).

My existing 951 unit makes about 550hp/450tq at the crank is of course dry sump. I'm looking to change class, so I like the idea of a sbc.

Keeping the trans-axle in good shape is a concern & I hope some of you guys might know what's needed here too.

I also spoke to Bill Dailey (Dailey Performance) and Gary Armstrong (ARE) about their dry sump systems. One of my concerns is that the CT 525 was designed as a wet sump and may not have the correct seals to properly accommodate a negative pressure crankcase.

If that's correct, then going the crate route is not an option.

Many thanks again. I'll post back on this topic as soon as I have more information.

Check out this forum for the answer to most (if not all) of your swap questions. They have been asked before and been covered extensively.

The long story short on transaxles is that there isn't anything that will hold up to the power you're talking about for very long.

Porch wrote:The long story short on transaxles is that there isn't anything that will hold up to the power you're talking about for very long.

OK & thanks.

We have had good results (luck?) with the existing 968 trans-axle which was put in new & been rebuild once due to worn syncros (2nd gear) after 4 seasons. As such, no issues thus far with about 493 whp on the 951 engine. Perhaps light weight of the car helps (2,243 lbs.).

- Have many of you tried the GM Performance GM LS Series LS7 7.0L Engine, part no.: 19244098 ?

This is GM's Z06 engine. Another question I would have is how well this unit will withstand track-only use (about 20 hours/season).

Many thanks in advance & for replies thus far.

Lee.

The 968 trans has poor gearing for the v8--lots of shifting involved. The 951 transaxle is considered to be the best option in the Porsche world. Although it sounds like you have fairly short straights...

A stock LS7 would put you at around the max power level i would want in that light of a car (~450-475rwhp), but it's far from the cheapest way to get that much power. On the other hand it has a dry sump system already, and they're great motors.

Porch wrote:The 968 trans has poor gearing for the v8--lots of shifting involved. The 951 transaxle is considered to be the best option in the Porsche world. Although it sounds like you have fairly short straights...

A stock LS7 would put you at around the max power level i would want in that light of a car (~450-475rwhp), but it's far from the cheapest way to get that much power. On the other hand it has a dry sump system already, and they're great motors.

Thanks, - the longest straight I have is Mosport, Wat. Gen, & VIR. & yes, the 6 spd is probably not the best trans-axle for this setup.

- Would you happen to know if a stock LS7 Dry Sump can perform reliable at 1.6-1.7 sustained g loads?

..Here below are 3 views of an engine I am considering:

Can anyone comment as to:

1. Clearance of the dry sump pan per cross member requirements (Dry sump pan clearance on this engine is reported to be 1.5").

2. Is the alternator position OK? (will the steering shaft or other components be an issue?).

For sure many of you have much more experience than do I, so any feedback is greatly appreciated.

My apologies for redundancy if these issues have been discussed elsewhere, but I could not find any threads.

This engine is complete and prices out similarly to a fully dressed & prepped CT 525.

As for the LS7, it is not full dry sump. It is scavenge-assisted dry sump which is not ideal.

Thanks in advance.

Porch wrote:The 968 trans has poor gearing for the v8--lots of shifting involved. The 951 transaxle is considered to be the best option in the Porsche world. Although it sounds like you have fairly short straights...

A stock LS7 would put you at around the max power level i would want in that light of a car (~450-475rwhp), but it's far from the cheapest way to get that much power. On the other hand it has a dry sump system already, and they're great motors.

Well... there are guys in both PCA & NASA running 2600-2800 lb. 911s with 700-800 crank hp.

lbp wrote:
Would you happen to know if a stock LS7 Dry Sump can perform reliable at 1.6-1.7 sustained g loads?

Are you currently seeing 1.6-1.7 laterals? May I ask your suspension and tire setup?

You should talk to Katech: [You must be registered and logged in to see this link.]

DVC wrote:

lbp wrote:
Would you happen to know if a stock LS7 Dry Sump can perform reliable at 1.6-1.7 sustained g loads?

Are you currently seeing 1.6-1.7 laterals? May I ask your suspension and tire setup?

You should talk to Katech: [You must be registered and logged in to see this link.]

Hoosier Slick 320x18 R100 rear & 305x18 R80 front, Moton Pro, Wrightwood Charlie Arms (bump-corrected), Tarrett f/r, Kokehln Cross member (replaces torque tube) & sol. trans mount, sol. motor mount, IMSA-style cage, car is lowered about 1.5 in. 50/50 dist. (driver's position moved back 10 in.), etc. Wing makes about 400# (est.), Hypercoil 700/700 - may seem soft but is needed to keep the power down (mindful of the shock settings). We are also working on the front aero, etc. to develop a bit more down force although currently the nose is not too light. 996 Turbo brakes.

I spoke with a fellow who had a couple of DP KaTech (new) engines for sale last year at the bargain price of $10K each, but they seemed a bit exotic for a weekend warrior like me... I agree, - their sbc product may be very worth-while & will check on it. (thx)

When I go sbc, the car will no longer be legal for NASA GTS class(German Touring Series/Unlimited) & will move to SU (Super Unlimited). SU has quite a range of performance, however to be competitive requires a power to weight of around 4:1, hence my 600hp goal. I know personally of 3 liter 951's running in SCCA T1(?) with up to 700 hp here in the Northeast, so I am not entering unknown territory with regard to the base platform/drivetrain. Having said that, DT & ratios are a huge concern to me. For sure I will call Roger Browne in that regard.

I really don't know how many g's we pull, but have been told this is a reasonable range.

Regarding the LS7 (GM Crate), I have ruled it out for a number of reasons, but I'll post back after speaking with Katech. I note they use Daily Dry Sump, which is deployed on many of the the Daytona Prototype engines.

Thanks.

lbp wrote:
Well... there are guys in both PCA & NASA running 2600-2800 lb. 911s with 700-800 crank hp.

Yeah, but they have all their weight over the drive wheels. The v8 torque curve is going to be much different than the turbo curve and these cars don't hook, especially with instant torque.

I doubt anyone here can tell you about fitting the LS7. That engine alone costs more than many of our cars are worth. Buy it and find out!

Porch wrote:

lbp wrote:
Well... there are guys in both PCA & NASA running 2600-2800 lb. 911s with 700-800 crank hp.

Yeah, but they have all their weight over the drive wheels. The v8 torque curve is going to be much different than the turbo curve and these cars don't hook, especially with instant torque.

I doubt anyone here can tell you about fitting the LS7. That engine alone costs more than many of our cars are worth. Buy it and find out!

Having owned a few cars during my younger years, and now having an older guy's perspective, I understand what you mean. I'm not yet sure what I will do, but if the plan goes forward the 951 will get one more season & come out this Fall. SBC (whatever it is) proposed as a Winter project.

Based on your comments, perhaps I should look into a short stroke (302?) that makes its power up higher.. Might be better for the drive train too.

Actually though, what we are talking about here is not unlike a Cobra kit car that has a hi-perf V8 stuffed into that little AC Bristol... (drive train not-with-standing)

Thanks again for posting.

I spent a lot of time feathering the throttle trying to get traction at the track last week in mine and I only have 372rwhp. Running 275-40-17 Toyo RA1's and I just couldn't get the power down.

My friend behind me in his E36 M3 commented on it, where he said he backed off a bit to give me more space as the back end of my car was so lively.

lbp wrote:
Hoosier Slick 320x18 R100 rear & 305x18 R80 front, Moton Pro, Wrightwood Charlie Arms (bump-corrected), Tarrett f/r, Kokehln Cross member (replaces torque tube) & sol. trans mount, sol. motor mount, IMSA-style cage, car is lowered about 1.5 in. 50/50 dist. (driver's position moved back 10 in.), etc. Wing makes about 400# (est.), Hypercoil 700/700 - may seem soft but is needed to keep the power down (mindful of the shock settings). We are also working on the front aero, etc. to develop a bit more down force although currently the nose is not too light. 996 Turbo brakes.

That is an awesome setup. I would love to see some pictures of that car.

May I ask why you want to convert? It will be tough to get 4:1 with an LSx and you're not that far off with the turbo 4.

DVC wrote:

lbp wrote:
Hoosier Slick 320x18 R100 rear & 305x18 R80 front, Moton Pro, Wrightwood Charlie Arms (bump-corrected), Tarrett f/r, Kokehln Cross member (replaces torque tube) & sol. trans mount, sol. motor mount, IMSA-style cage, car is lowered about 1.5 in. 50/50 dist. (driver's position moved back 10 in.), etc. Wing makes about 400# (est.), Hypercoil 700/700 - may seem soft but is needed to keep the power down (mindful of the shock settings). We are also working on the front aero, etc. to develop a bit more down force although currently the nose is not too light. 996 Turbo brakes.

That is an awesome setup. I would love to see some pictures of that car.

[You must be registered and logged in to see this image.]

May I ask why you want to convert? It will be tough to get 4:1 with an LSx and you're not that far off with the turbo 4.

Well, many of the LSx track units I've looked into easily make 600+hp/500+tq.

race link:
NASA NE race at NJMP 4/17/11

I'm guessing those are flywheel numbers with no accessories. If i were to guess at the average rwhp of most "moderately" modified lsx, it would go like this:

ls1/6: 400
ls2/3: 450
ls7: 500

Of course there are plenty of cars making +/- 50hp, but for n/a i have not seen any making 600rwhp.

I googled "600 rwhp lsx" and this is a recipe for a 600rwhp lsx:
451 lsx block 12 to 1 compression built for a 300 shot
TFS 245 heads
custom cam motion cam
ported FAST 102 and NW TB
Halltech superbee
American Racing 1 7/8 headers, no cats, Z06 B&B Bullets
RPS BC2 clutch
"There is no traction below 70 anymore."

Keep in mind that headers will be an issue in the 944 as well.

Porch wrote:I'm guessing those are flywheel numbers with no accessories. If i were to guess at the average rwhp of most "moderately" modified lsx, it would go like this:

ls1/6: 400
ls2/3: 450
ls7: 500

Of course there are plenty of cars making +/- 50hp, but for n/a i have not seen any making 600rwhp.

I googled "600 rwhp lsx" and this is a recipe for a 600rwhp lsx:
451 lsx block 12 to 1 compression built for a 300 shot
TFS 245 heads
custom cam motion cam
ported FAST 102 and NW TB
Halltech superbee
American Racing 1 7/8 headers, no cats, Z06 B&B Bullets
RPS BC2 clutch
"There is no traction below 70 anymore."

Keep in mind that headers will be an issue in the 944 as well.

Thanks,

Here's another one from a reputable builder:
Schwanke Short Blocks

Again, that's 600/650 hp at the flywheel and probably without accessories. It will probably translate to about 475/525rwhp with all accessories. The stock LS3 heads included in that deal don't flow enough to support 600 n/a rwhp.

The major benefit to putting a v8 in your car will be reliability and cost. The engine you listed could probably be beat on all day every day for 100,000 miles with only regular oil changes. Compare that to a 944 Turbo motor...

Porch wrote:Again, that's 600/650 hp at the flywheel and probably without accessories. It will probably translate to about 475/525rwhp with all accessories. The stock LS3 heads included in that deal don't flow enough to support 600 n/a rwhp.

The major benefit to putting a v8 in your car will be reliability and cost. The engine you listed could probably be beat on all day every day for 100,000 miles with only regular oil changes. Compare that to a 944 Turbo motor...

Observations noted..

The only thing I can add is that we are currently making 493 whp and 550 chp on the 951. I was hoping to go a little more with sbc, maybe 10-13%. And yes, 600 whp would likely overwhelm the trans-axle.

Regarding trans-axle, keep in mind we do not dump clutch, pull hole shots or use other such techniques on the (RR) track.

docwyte wrote:I spent a lot of time feathering the throttle trying to get traction at the track last week in mine and I only have 372rwhp. Running 275-40-17 Toyo RA1's and I just couldn't get the power down.

My friend behind me in his E36 M3 commented on it, where he said he backed off a bit to give me more space as the back end of my car was so lively.

...Were your tire pressures, spring rate & shocks set up correctly? Do you have an adjustable sway bar? Suspension plays a big role. Too stiff in the rear will prevent the car from putting power down. If you still have the 944 torque tube, you will have little control over these parameters regardless of shock quality & settings or other component selections.

Still running torsion bars in the back. Tire pressures were proper, 39psi hot.

You can get more power from the SBC, but for the power levels you're talking about an LS7 would be the way to go.