Thread:

Tunnel ram plenum volume

Originally Posted by bowtiebro

is there any kind of formula to calculate the needed plenum volume in a tunnel ram im going to build a new upper for my t-ram to change my carb arangement and might change the volume of the plenum to better suit my engines rpm range what i have is a old edelbrock tr2 and if you have ever seen one you will know why im interested in modifing it

Easier to learn this: E=MC² and "what it is women really want".
Or send the thing to Steel. (with some cash)

You think the rod length thread was contorversial? You think it had more to it than you originally thought going in?
I don't even know the engine size or RPM range or use of the boat, and the first thing I would ask is why do you think it needs a plenum volume tweek as opposed to a runner length/runner volume tweek?

Who knows. Maybe all the engine really wants is a longer rod

Originally Posted by bowtiebro

No rod length remarks haha im using the tram for its "aperance" the engine its goin on only needs a 4150 single plane its a lake rod the higher you put the carbs the bigger your dick appears to be im sure you understand, i agree runner volume is way more important but im tring to increase drivabilty/useable rpm power and im not willing to start hogging out or welding up this piece do to its nostalgic value Any usefull guidelines would be opreciated such as smaller volume better for low rpm or smaller for high rpm

Just messing with you bowtie. But I like your attitude and response

Steel is the guru on the plenum and runner volumes. It would be impossible for him to tell you exactly what you need and how to do it. But he might be able to tell you if you need to stuff the box and roughly how much volume you need to take up. You can do it with something as simple as epoxy coated wood. (At least I have).

I assure you, Steel is more than a little bit familiar with the TR2. He slept with one instead of a teddy bear like normal 5 year olds. He is a very strange individual. But harmless.

Originally Posted by bowtiebro

No rod length remarks haha im using the tram for its "aperance" the engine its goin on only needs a 4150 single plane its a lake rod the higher you put the carbs the bigger your dick appears to be im sure you understand, i agree runner volume is way more important but im tring to increase drivabilty/useable rpm power and im not willing to start hogging out or welding up this piece do to its nostalgic value Any usefull guidelines would be opreciated such as smaller volume better for low rpm or smaller for high rpm

Well this isn't scientific but here is what I found playing with an Edelbrock Victor 2R base and a custom top plate with a pair of Holley 750 double pumpers. Less plenum volume made my engine more responsive and gave it better part throttle and tube/ski pulling manners. Adding a spacer my have gave it a slight edge on max power but it lost some manners in the areas I mentioned before. So for what its worth IMO I'd run larger carbs on a smaller plenum if this is a recreation or true dual purpose boat. If your racing and looking for every last tenth I think the incresed plenum vloume helps peak power.

For what it's worth the tunnel ram set up was worth almost 2/10th on a 1000' course compared to my old Wieand Team G with a flowed 850 Holley double pumper.

I'm sure Loren would be glad to hook you up, and on my 565 a spacer cured a mid range hesitation, and by that I mean if I matted the pedal at say 25 to 3000. From a stop there was no issue, only from part throttle.

Originally Posted by Bubbletop409

I'm sure Loren would be glad to hook you up, and on my 565 a spacer cured a mid range hesitation, and by that I mean if I matted the pedal at say 25 to 3000. From a stop there was no issue, only from part throttle.

Thanks Larry. I guess our set ups must be different enough to require a plenum volume change. If I remember we're about 100cid different and you have 2 x 600s on a 565 and I had 2 x 750s on a 467. I might retest the spacer once my new engine is together. Glad yours is still working out for you.

Not only working well, but that billet top sure adds to the bling factor. With my small carbs and large displacement the air velocity going through will chill the top to the point of frost forming between the two carb pads. Before the spacer, the manifold would be cold to the touch even at the head junction. The spacer seems to insulate the bottom part of the manifold somewhat now, but with no ill effects.

Back in the day, I worked many combinations of setups on that TR-2X tunnel Ram and this is what I found out. The 750 6109 carburetors with a little modification work the best. If you take them out of the box and put them on a .060 over bored 454 with about 10 to 1 CR and a rumpity rump cam shaft using the best pump gas, you will need to jet them up for Max RPM. Once you do that, it will be too rich for driving around and pulling skiers. So ....... because they use Power Valves in the Primary Metering Blocks, you need to drill out the Power Restrictor hole under the Power Valve .015" bigger. That will put more fuel in when the vacuum drops below 6.5 inches, (6.5 power valve). To test when that happens, I drilled a hole into the vacuum chamber and installed a small brass tube so I could attach a vacuum gauge and watch. With the same engine listed above in a flatbottom with 18% gears and a 11 1/2 X 15 2 blade prop, the chamber had 10 inches of vacuum up to 5,000 RPM. When I would go to full throttle, it dropped to 0 and I had it rich enough to run up to almost 7,000, (with a light chop on the water). If you put the 6109 750 Holleys on a newer tunnel ram, you do not have to modify them. I am assuming it has to do with the size of the Plenum. It might be too big or too tall.