Increasing Exhaust Valve size (Head)

[Ormand]

Bryan, I agree with having more intake duration for a turbo engine. But it would be good to see some actual test results to confirm what we believe, and nobody ever does that for the turbo Buick. You can pick up a magazine at any news stand, and read dyno test results for Hondas, or small block chebbies, or Mustangs, where they swap parts and compare cams, or intakes, or air filters- whatever. When you said you had done the R&D years ago, I thought maybe you had some test results. GMHTP magazine did some back-to-back tests on intercoolers, but they kind of fudged the results, as I remember. Race Jace did those flow tests for the power plate, and that was good. But I've never seen any tests for cams in a turbo Buick.
As to John's theory about the bigger exhaust valve, it seems to me that at part throttle, before boost builds, the flow is going to be low. At low flow, small valves and ports, along with short duration, is needed to keep velocities up, to give good throttle response. So I'm not sure the bigger exhaust valve would provide any benefit.

 

[Bryan Weber]

I know what you mean about having dyno numbers but that gets difficult with cams because there are so many combinations and tune-ups. The only real dyno time for cam testing was back in the early 1990's at Lingenfelter's with Red Armstrong and Comp Cams. There were many pulls made and a total of 16 cams were tested. The information obtained from that session is what created the cams we offer for sale today with some very minimal changes over the years. It is impossible to say that any one cam is the best but it was easily determined at the time what these engines did not like (duration splits, centerlines, lobe separation, etc.). Some of the fastest Turbo Buicks in the country run our cams. Some very fast cars run other cams but that's part of their combination.
I don't intend to be evasive but when talking cams it is as specific as I can be in a general question. If The question were what would be the best cam for a given application with all other components and questions answered?, the answer would be much more specific. If you asked ten different people that question you would likely get several opinions.

As John said earlier the bigger exhuast valve would likely only have a noticable effect on the transition from vacuum to boost.

 

[SloGN]

I saw that there was a thread on increasing valves sizes so i dug this one back up.

 

[jsbuickpower]

Instead of installing a 1.77 intake valve why not install a larger exhaust valve?

Has anybody tried keeping the stock intake valve and going with a larger exhaust valve?

i will make this short as possible
i dont know alot about these engines but with sbc when building a nitrous engine(and motor meant to make more power with nitrous than with out)i tend to spend more time on the exhaust than the intake because you basically want to reduce exhaust pumping loses because so much more air is in the cylinder you may be making 300 hp on the power stroke but reabsorbing 150 on the exhaust stroke due to pumping loses meaning your only making 150 hp so you want to reduce the pumping loses on the exhaust stroke by increasing valve size and or opening the exhaust valve sooner you can still maintain the same overlap by just having a cam that just has more duration on the opening side of the exhaust lobe i know i didnt get into alot off detail but i think you can get the point it would kind of seem you would want to reduce the pumping loses with a turbo engine