I thought I'd post these for anyone interested since several of you helped me out with dyno simulations last summer. I finally got the motor together and had it dynoed (engine dyno only, it's not back in the car yet).
The shop didn't have an FI controller, so we had to run it with an LT1 carb manifold (smaller ports than my heads, but this was really just for break-in and mechanical check) and a Demon 1000CFM carb.
Crank (not RWHP) numbers with NO accessories and open headers:
Torque 485.7 @ 5100RPM
HP 548.8 @ 5900RPM
(I'll try to upload a graph later)
It peaked a bit lower RPM than I was hoping, but the graph started getting a bit rough so there may be a valve control issue. Obviously the small ports on the intake weren't helping either. I'll have it in the car later this month so I'll have better numbers with the right manifold and proper tuning. Even still, I'm pretty happy since the projections were 500HP at best at the crank
Here's the graph -- It's not a very detailed sampling (100 RPM segments), but you can see it jumping around a bit just over 6K. Not sure if it's valve float or something to do with the port restriction from the wrong intake.
Last edited by MarkBychowski; 04-02-2008 at 12:30 PM.
Hi Cris,
Yes, corrected to 29.92, 60 degrees, dry air.
I'm actually not sure of the dyno model -- I didn't think to look for the name. It was a water brake dyno. The number F1200 shows on the printout, but not sure if that's a model or something else.
Great Numbers ! My new LT4 stroker is a 370 ci as well ! Your peaks will definitely be affected by the manifold as the motor will cylinder fill at lower rpms if the manifold you used has smaller ports.
What heads did you use? Are these the afr eliminator heads? Just curious what manifold you are using since I was told the LT1 manifold mated to these heads since they are not 'raised' runner.
Pryderei, yes they're AFR 210 Eliminators with competition porting. I'll be using them with a ported LT4 intake (777 gaskets). The 210s ports are higher than the standard LT1 intake gasket, but not sure how much. They are slightly shorter (about 1/8-3/16") than the 777 LT4 gasket, though. I had to blend the top of the ports on my heads in order to avoid having a ridge between the head and intake.
With the LT1 carb intake on the dyno, though, the intake port of the head was taller than the casting of the intake manifold -- we had to use a smaller intake gasket and offset it a bit just to get the thing to seal well enough to run. So if you're planning on running them with an LT1 intake, definitely mock it up first to make sure everything aligns correctly.
Also, something to check: the driver's side front oil drainback was completely blocked by the deck of the block. I had to grind the block to allow the oil to drain back properly (I found that before running it, thankfully). The other three drainbacks were fine.
Mark,
I still have your files saved, and I went back and ran the same combination but with open headers and a carb manifold & 1000cfm carb.
Most manifolds I've measured have had about 6 inch runners, and I used a diameter slightly less than the cyl-head intake diameter (like you stated).
I also ghosted the new graph on top of yours.
Will be nice to see what the final LT4 manifold does ... I think the 3 inch runners will peak much higher & maybe a bigger throttle body would help move up the peak numbers (I'll run that when I have some time).
Interesting anyway
Ok .. last graph for today
More equal comparision, like you ran the LT4 on the dyno the same way.
LT4 manifold, no MAF, no air cleaner, open headers, 1000 cfm throttle body.
vs
Carb manifold as before.
Thanks! That's actually pretty impressive that the figures track relatively close (the carb manifold graphs). Pretty depressing how much the torque curve suffers with the exhaust and the LT4 intake on there
I'm hoping the top end issues are related more to the intake than valve float, but I have a feeling I'm going to need to get some better springs or possibly a rev kit -- I'd rather keep it simple, though. Hopefully I don't need to go with Ti retainers.
Corvette Store
Dyno numbers on 370ci LT4 w/AFR heads
