64 fuelie chassis dyno

[Matt L.]

thought you all would like to hear i got my 64 dynoed the other night. it bested that night with 281hp and 292 torque. after the 1st couple runs we only got 270ish hp with very noticable topend rpm rich condition. after the mechanic leaned out the rich stop on the fuel injection 1/2 turn we gained 10 hp! we ran out of time to really dial it in. i am hoping for at least a safe tune of at least 300 hp. am i too optimistic with a factory rating of 375? my engine has been bored 60 over with the heads and block being decked to true them up. i think this engine would be more than capapable of some very good numbers.
take care,
matt

[Joe R.]

Re: 64 fuelie chassis dyno

thought you all would like to hear i got my 64 dynoed the other night. it bested that night with 281hp and 292 torque. after the 1st couple runs we only got 270ish hp with very noticable topend rpm rich condition. after the mechanic leaned out the rich stop on the fuel injection 1/2 turn we gained 10 hp! we ran out of time to really dial it in. i am hoping for at least a safe tune of at least 300 hp. am i too optimistic with a factory rating of 375? my engine has been bored 60 over with the heads and block being decked to true them up. i think this engine would be more than capapable of some very good numbers.
take care,
matt

Matt,

Your numbers sound pretty good to me. Keep in mind that the factory rating of 375 hp was based on SAE gross ratings with some marketing thrown in for good measure. Today's numbers are based on SAE net, which will give a lower number. SAE net requires that accessories are on the engine, where gross did not. Plus 375 is at the flywheel, not the rear wheels. Expect to lose around 20 % going through the drivetrain. Can you post your dyno results?

Did you do any head work? That's the best way to keep the bone stock look while freeing up those extra ponies and RPMs.

Hopefully Duke will chime in with the real scoop soon.

Joe

[Matt L.]

Re: 64 fuelie chassis dyno

Matt,

Your numbers sound pretty good to me! Keep in mind that the factory rating of 375 hp was based on SAE gross ratings with some marketing thrown in for good measure. Today's numbers are based on SAE net, which will give a lower number. SAE net requires that accessories are on the engine, where gross did not. Plus 375 is at the flywheel, not the rear wheels. Expect to lose around 20 % going through the drivetrain. Can you post your dyno results?

Did you do any head work? That's the best way to keep the bone stock look while freeing up those extra ponies and RPMs.

Hopefully Duke will chime in with the real scoop soon.

Joe

hi joe. yes i am aware of the flywheel numbers vs chassis numbers. i did however forget about the net and gross numbers. we didnt do any head work. we put the motor back to factory with the pop up pistons and solid cam. we did however have the timing backed down to compensate for unleaded premium fuel. i am planning for the next run to run some turbo blue or equal to turbo blue and will raise the timing. that alone should boost better numbers. i only have the sheet they gave me on the run. my airfuel mixture was 13.4 . hp peaked at 5300 and torque was consistently above 300ftlb from 3000 to 4600 with a best of 315ftlb around 4000.

[Matt L.]

Re: 64 fuelie chassis dyno

the 292 ftlb was the average torque. i looked at the wrong box on my 1st post.

[Duke W.]

Re: 64 fuelie chassis dyno

Peak Torque is primarily a function of compression ratio and displacement, and 327s are usually in the range of 250-280 lb ft, SAE corrected on a Dynojet chassis dyno depending on configuration. SHP/FI engines usually show lower peak torque and peak torque higher in the rev range than a good 327/300.

If you say your peak was 315 lb-ft, something doesn't jibe, but you gave no information on the type of dyno and correction factors used.

You need to give us more details - type of dyno, correction method(s) used, and more details about the engine.

Scanning and posting the sheet would be good. Also, if the test was done on a Dynojet, get the test file and use the (free download) Win Prep software to create a dyno sheet that you can post.

Some chassis dyno reports use an empirical correction factor to estimate flywheel torque/power from the rear wheel data. The correction is usually the reciprocal of the typical driveline/tire efficiency - 0.85 for manuals and 0.80 for automatics. Then there are several methods of correcting the raw data using various "standard" air density conditions. These details are necessary to make sense out of the data.

I suspect this may be the case here. Multiplying 315 lb-ft and 281 HP .85 and assuming SAE air density correction by .85 yields 267 and 239, which is much closer to what I would expect of a basically "stock" '64 327/375 HP FI engine, however peak, power at only 5300 is suspiciously low. I would expect it to be near 6000.

Unfortunately, most dyno test data is reported without full context, so comparisons are impossible.

The two "327 LT-1s" ('65 SHP engines with massaged heads and LT-1 cam) I system engineered a few years back were reasonably consistent. One was was tested on a lab dyno using STP correction. It made 338 lb-ft in the 4000- 4500 range and 356 HP at about 6500. This was true "SAE gross" data, and my empirically derived 0.89 SAE gross to net conversion factor for small block Corvettes with 2.5" pipes yields 301 lb-ft net torque and 318 net horsepower. The above data was with the production 2.5" manifolds. A set of dyno headers made about 6 percent more peak torque, but less than 2 percent more peak power.

Applying the 0.85 driveline efficiency yields and estimated 256 lb-ft and 270 HP, SAE corrected, at the rear wheels.

The second engine was tested on a Dynojet chassis dyno and made SAE corrected 264 lb-ft, and 278 HP.

Both engines achieved 80 percent peak torque at 2000.

George Jerome had his '65 327/375 FI engine tested on a lab dyno following an essentially OE rebuild and it made, SAE gross, about 321 lb-ft at 4700 and 332 HP at 5900. Well massaged heads would have increased the torque and power numbers to close to the advertised values.

Duke

[Matt L.]

Re: 64 fuelie chassis dyno

hi duke,
it was a dynocom chassis dyno. the test file is available to me. i just have to ask for it and download it.
we used an early style dontov solid cam. my builder recommended that one for drivability. i dont know exactly what the part # would be. the engine is 60 over with pop up pistons,decked heads and block. all balanced.
i would guess the power is on the lower rpm range 5,300, do to it running rich on the topend. we ran out of time in the evening to be able to adjust the rich stop on the unit. my builder only turned it 1/2 turn if that and we gained 10 hp. and it was still burning rich as we saw obviuos black smoke.
if anyone would like to check out the dyno shop's website...shelbycountyperformance.com they are located in botkins,ohio. nice guys. i paid for 3 runs and got 8 cause we were all curious as how to it would react to some of the small adjustments we made.
i really appreciate all the advice and help duke. all the technical data is something i need to learn and study.
take care,
matt

[James G.]

Re: 64 fuelie chassis dyno

The neat thing Matt is you got it running.......and now are having fun.This is a great time with a great car. You will learn a lot about power tuning Rochester Fuel Injection Corvettes, and you will keeep this knowledge going forward. So many of us old Gezzers worry about no one carrying the flag forward after we are gone. Duke will teach you right. Can't wait to see your car and meet you.