Latest dyno results

Big_G

Active Member
Some of you guys have seen my 383 supercharged build over the last few years. I knew there was more power left on the table with my combo, so another cam swap was in the works. To re-cap, I was at 555 rwhp using a Comp Cams solid roller: 230/236/114* installed on 110* intake LCA. Obviously Comp sales was guiding me a little too conservative. Called Dean @ Comp., and settled on a new grind: 244/248/114*/.615/.605 installed on 110* intake LCA. Improvement for sure! 625 rwhp and more to be netted. The dyno would not hold the 325 drag radials. Smoked them, (3 pulls) just about the horsepower peak @ 6,000+.
This is a stock Mexican 4 bolt block, with ARP studs. I will not push my luck any further...BTW, disregard the a/f plot..the sensor was defective.

dyno05081001.jpg

 
great info, thank you for posting!
most people forget that anything close to 600 REAR WHEEL hp is quite an accomplishment, and exceeding that is even rarer, and to have a fairly flat torque curve and usable low and mid rpm torque is a big bonus.
having a supercharger allows you to compensate for use of a bit more cam that an engine built without a supercharger would tolerate on a street car while still maintaining some decent low rpm driveability
 
grumpyvette said:
great info, thank you for posting!
most people forget that anything close to 600 REAR WHEEL hp is quite an accomplishment, and exceeding that is even rarer, and to have a fairly flat torque curve and usable low and mid rpm torque is a big bonus.
having a supercharger allows you to compensate for use of a bit more cam that an engine built without a supercharger would tolerate on a street car while still maintaining some decent low rpm driveability

I am extrapolating from the dyno plot a few things....the torque seems low at 3,000 to 3,500. I am assuming this is due to my 8.3:1 scr. Another thing comes to mind: Would advancing the cam an additional 4* (installed straight up with 4* built into the grind for a total of 8*) bring the torque and horsepower in a couple of hundred rpm's earlier...or is this the way the cam is best utilized? The cam is still making decent power (above 600 rwhp) out to 6,300+ rpm.
 
advancing the cam 4 more degrees should tend to move the whole torque curve a bit lower in the rpm range but its more likely to give minimal gains on the lower rpm band compared to the potential losses on the upper edge.
as a general rule if you need to advance or retard a cam from the strait up (split overlap)location in cam timing , more than about 6 degrees, MAX, you probably could use a different cam, to far greater effect than re-indexing the current cam will provide.
personally Id suggest, swapping to 1.6:1 ratio intake and 1.5:1 ratio exhaust rockers, first as a test to get some more info on how the change effects your power output. and measure your back-pressure in the header,collectors,at each rpm level, as those should give you more info on the cam,s effect on how the engines breathing, and potential areas to improve.
obviously you could also change blower drive ratios to build rotor rpms a bit faster as a second route to building low rpm torque faster.
 
grumpyvette said:
advancing the cam 4 more degrees should tend to move the whole torque curve a bit lower in the rpm range but its more likely to give minimal gains on the lower rpm band compared to the potential losses on the upper edge.
as a general rule if you need to advance or retard a cam from the strait up (split overlap)location in cam timing , more than about 6 degrees, MAX, you probably could use a different cam, to far greater effect than re-indexing the current cam will provide.
personally Id suggest, swapping to 1.6:1 ratio intake and 1.5:1 ratio exhaust rockers, first as a test to get some more info on how the change effects your power output. and measure your back-pressure in the header,collectors,at each rpm level, as those should give you more info on the cam,s effect on how the engines breathing, and potential areas to improve.
obviously you could also change blower drive ratios to build rotor rpms a bit faster as a second route to building low rpm torque faster.

I'm already at .619 intake lift...taxing the valve springs enough already. Also probably reaching the limits of the Edelbrock heads. In hindsight, I might have been better off with a static c/r of 9:1 or so. I can't pulley up the supercharger...it's maxed out in rpm's at 6,500. Of course, we wouldn't be having a torque problem if I was running turbos or a positive displacement blower. Thanks again.
 
personally I think your current combo is very effective and would be rather hesitant to change much,but
then the other alternative, you might want to think about, if your trying to boost the low rpm torque is to swap to a different cam,drop the cams duration slightly and tighten the cams lsa, that will boost the low rpm torque but also may cause the valve timing to increased overlap so the low rpm gains will be off-set with some reduction in average and peak hp, not necessarily a good idea.
then theres always an option of adding a nitrous kit ??????

the other alternative is to go the centrifugal supercharger/inter-cooler route, which don,t tend to fall in efficiency nearly as fast as the rpms build, but then you loose the instant off idle response of the roots design supercharger, but gain a good deal more upper and peak hp

http://www.paxtonauto.com/products.php?cid=4

http://www.vortechsuperchargers.com/
 
grumpyvette said:
personally I think your current combo is very effective and would be rather hesitant to change much,but
then the other alternative, you might want to think about, if your trying to boost the low rpm torque is to swap to a different cam,drop the cams duration slightly and tighten the cams lsa, that will boost the low rpm torque but also may cause the valve timing to increased overlap so the low rpm gains will be off-set with some reduction in average and peak hp, not necessarily a good idea.
then theres always an option of adding a nitrous kit ??????

the other alternative is to go the centrifugal supercharger/inter-cooler route, which don,t tend to fall in efficiency nearly as fast as the rpms build, but then you loose the instant off idle response of the roots design supercharger, but gain a good deal more upper and peak hp

http://www.paxtonauto.com/products.php?cid=4

http://www.vortechsuperchargers.com/
Well, I am already running an inter-cooled centrifugal, so that's that. I went with a 114* LSA just to get more mid-range, at the expense of greater peak numbers. I'll leave everything as-is for now. My back-up plan is that when I pull the heads I will mill some to gain compression, maybe to 9:1.
 
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