Langadorf

I finally got the Vette out to the dyno (Speedworks in Lewisville, TX). Pulled a best of 353 RWHP and 381 FT-LBS. While I think this is good, I was hoping for closer to 400 RWHP with my setup. My setup is as follows:

383 LT1 (new style) w/ 11.7:1 compression
750 Holley DP
LT1 dual-plane intake
LT1 heads flowing 270i/200e w/ 2.2/1.6 valves
CC306 cam (230i/244e on a 112 LSA w/ lift of .544/.576)
hooker headers w/ no cats and dual flowmasters

I was able to get the timing up to 31 degrees without any detonation and the AFR was at 12.5 for the entire pull.

Do you think my dual-plane intake is the bottleneck? On all 3 pulls the power died off at 5700 RPM. If this is it, I'll probably get a Victor Jr. converted for an LT1 and see how it does.

Could there be anything else hindering me? I was planning on running race gas and adding a couple more degrees of timing, but the guys at the shop convinced me I wouldn't see more than a 5-10 HP increase. Do you agree?

Thanks for any ideas.

jmzlt1

Something is definitely wrong. I've seen people with 350's and your combo w/ fuel injection putting out 400rwhp. You should be at least 420 rwhp and tq. With a carb you actually should be able to squeeze out a tad more hp from the combo. Your timing seems a bit conservative, lt1's like timing because of the reverse flow heads. Hopefully someone else will chime in and give some insights.

Cmr0z28

flowmasters suck dude, i bet you could pick up a few horses by going with a straight-through muffler

MattysTA

Did you get a custom pcm tune for your set up? i think you could richen that afr up a little more maybe like 11.7:1 at wot

cef97ws6

Actually I don't think those numbers are bad at all with what you have. You are definately giving up some horsepower with the intake. But I think your real cork is the heads. A 383 at 11.7:1 will definately want more runner than a stock LT1 head will allow even ported. A set of AFR 210's and a nice solid roller cam and you should be close to the 500fwhp number. IMO

grygst76

go with a single plane team g and you will pick up all that was lost up high

joeSS97

You should be at 400rwhp or more,I think you need more cam.Cut out would help too.

Injuneer

He's running a carb, not EFI. He "tunes" with jets/metering rods in the carb.

Typical peak HP and torque are achieved at 12.8-13.2:1. The 12.5 might be a little rich. Did you try leaning it out a bit?

xxsaint69x

doesnt sound right at all.... 353rwhp out a 383

atljar

Dont listen to many of the above people about the heads, ECM "tune" (lol), more cam etc.

Injuneer makes a good point.. Did you try some different a/f ratios?

350 isnt great by anymeans, i would guess an EFI car set up like that would pull 380-390, BUT we are also using a totally different tranny. That th350 you have will rob some serious power to the ground.

Injuneer

Good call! I missed that in the initial post. Going from a T56 to the TH400, my rwHP (NA) dropped from 425rw with the T56 to 390rw with the TH400. I believe the TH350 is probably a little less of a power leach than the TH400, but it is still going to show up different than a 4L60E.

grygst76

Ok, A cam with high lift, heads with more then 180cc's and bigger valves, noone suspects the intake What is the jetting on the carbs primary and secondary? what size power valve?
I had what one would say a mild 327 with 750 doublepumper, XE284 cam, th350, ported 462 heads and a performer rpm intake, I made 375 on my first dyno. I switched over some stuff like msd ignition, fastburn heads and 780 doublepumper w/4 corner idle with fatter jetting weiand team g single plane intake and 2.5 power valve and then made 485 horsepower!!! Go with a victor Jr. or weiand team g that matches the cam rpm range and believe me in just the intake alone you should see a huge gain up top considering most dual planes are only good to 5000 and the better ones are raised runner dual planes.

VINCELEE123

yes, victor jr.
you cam is made to spin high, you intake isnt, your car is making more tq than hp, change the cam to match current intake, or victor jr.

Longerrunner=tq
shorter=hp

you cam isnt made for tq

Vince