Does anyone now the volume of the TPI plenum? I have searched this site and googled the web with no results. Just wondering because I have seen that 40 to 50% of engine displacement is about right. So with a 350 that would be between 140 and 175 cubic inches. Allen

aprox. 290 cubic inches could be as low as 250

Thanks. Allen

My estimate places the plenum volume at ~150 cubic inches. This is based on rough measurements of the plenum and reasonable assumptions.

Hi Brian

After this post I also did some rough measurements on my plenum and come up with 146 cubic inches. So I think 150 is quite reasonable. Reason I'm asking is that I just heavily modified my SLP runners and conservatively gained about 25 inches cubed of plenum area on each side for a total of 50. This would at the very least put me at 200 cubic inches of plenum area. That works out to 57% of my engine displacement.

When I get on the dyno I will have to see what improvement that made. Problem is I also further ported my plenum where it meets the throttle body so that will help some. Allen

Allen,

Thanks for the conversation. I'm actualluy becoming a TPI nut after buying a setup to use on my '73 4WD Suburban. I put a post on this message bored titled something like "real-world TPI." If you have a chance, please read it and let me know your thoughts.

Also, I'd like to hear more about your setup and your dyno results. What effect does the extra plenum area have? MY gut says it should reduce throttle response, maybe low end, but boost the top end. Your thoughts?

Warm Regards,
Brian

err.. board

Opps I ment to put a one in front. Wa a late post

Regarding plenum volume to engine size I have seen some widely scattered figures. Anywere from 40% minimum to 100% the volume of the engine as being the best. Most of the posts I have read in the past say that the TPI plenum volume is smaller than what it should be.

I don't know if your familiar with the Accel Superram but it has a good size plenum and makes very good horsepower over a wide rpm range. There are other factors that reduce bottom end and throttle response.

Reducing the length of the runners will cut down on the low end power but will increase the top end. What I have done is make the upper 1/3 of the SLP runners one large chamber by connecting the first and last openings into one large oval. I also did the same to the TPI plenum by connecting the 1st and 4th openings into one large oval. The two center openings are now gone along with the center post and bolt hole. I added a lug at the top to relocate the upper center bolt.

Back to the runners they start out with one big oval at the top 1/3 and then split into two siamesed runners to the Edelbrock TPI manifold for the lower 2/3. So my total runner length is now around 11-12 inches. Being only the length of the intake manifold and what runner length is in the Trickflow heads. Allen