Thread: horsepower

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I went and had my car dyno'd this past week and when the RPMs got to 4500 the horsepower stopped rising. the horsepower from 4500 to 5600 RPMs only went up 2 or 3. I have a stock bottom end, 350 Vortec heads, RPM Air-Gap, Comp Cams XE268, MSD ignition, B&M holeshot 3000 stall, dual 2 1/2" flowmaster. I don't undersatnd why the power would stop when everything is rated to 5900 or 6100 rpms. Any feedback would be great.

Without researching the specifications of your components and based upon the details you gave I would say your engine is breathing inadequately.

Stock Vortec heads can be improved on greatly, and you gave no mention of the induction system or if you are running stock exhaust manifolds or headers etc .............

Kitz

i knew i was forgeting something. i have 5/8" headers and a holly 750 with vac. secondaries. the intake is the edlebrock rpm air-gap. if i left anything else out, please let me know and i will tell you. thanx

Yup, what Kitz said. sounds like your heads just quit breathing......

Originally posted by TUBJUB
i knew i was forgeting something. i have 5/8" headers and a holly 750 with vac. secondaries. the intake is the edlebrock rpm air-gap. if i left anything else out, please let me know and i will tell you. thanx

One thing you did not talk about was your fuel pump.Like everyone has said maybe your heads quit breathing.Most of the un-touched Vortec heads are done at the 450 h.p. area from what I have seen.

i have heard 450 or 500 hp with porting, but mine dyno'd at 221 rwhp. and i ran a 13.2 1/4 mile with smoking tires and letting off to about half throttle. to me, those two numbers don't match up. I was also told that i might not have enough compression to use the cam that high. but honestly i don't know much about engines, im kinda new to all this.

the fuel pump is stock i believe. but i was also told that it would run lean if i wasn't getting enough fuel pressure. and it had an 0'2 sensor in there and it was running very close to perfect mixture

Originally posted by TUBJUB
I went and had my car dyno'd this past week and when the RPMs got to 4500 the horsepower stopped rising. the horsepower from 4500 to 5600 RPMs only went up 2 or 3. I have a stock bottom end, 350 Vortec heads, RPM Air-Gap, Comp Cams XE268, MSD ignition, B&M holeshot 3000 stall, dual 2 1/2" flowmaster. I don't undersatnd why the power would stop when everything is rated to 5900 or 6100 rpms. Any feedback would be great.

What was your total timing?

Did you use a complete cam and kit, including matched valve springs?

my total timing was somewhere around 32 - 34 degrees and I did use a complete cam kit with matched springs.

At the engine how much h.p. do you think you should have?

according to the engine build we used, along with several others that are the same but from different sources, it was said to have 390 - 427 hp at the flywheel. we got the build from super chevy magazine which was around 410 flywheel hp

What size is the engine?

350 ci, everything is exactly as the build said, except the 1.6 rockers (which i don't think will add 100 hp)

In a 350 engine I have never been able to go much over 360 h.p. with a cam this size or heads like this.The last 350 I built did 391 h.p. at 5,900 with a cam that was 234,244 at .050 and a set of bowl blended,gasket matched Dart Iron Eagle S/S heads.

Hay erik I just searched the web for some flow # on the dart iron eagles s/s and the vortec heads. And the vortec out flow the dart iron eagle s/s. here are the numbers Vortec int 239 exh 162 and the dart iron eagle s/s int 210 exh 139. so I don't think his heads are running out of steam at 4500 rpm with those numbers .
http://www.chevyhiperformance.com/te...98/index4.html


Here's the site I found the numbers on.