long time lurker, first time poster.. have a few questions

im building a 383 and i have been racking my brain for the last few weeks about if i should siamese my intake or not, i know it adds HP up high and allows the tpi to breathe passed the 4500 rpm "wall", but thats not really the kind of build im after... after reading the TPI shoot out that super rod did and im not so sure i want to anymore, i cant justify losing low end torque for a few extra hp... the 383 build will be very similar to the test engine they used in the shootout but with a smaller cam

its going into a 98 s10, regular cab short bed that weighs less than 3000 lbs, the engine will have the LS1 "0411" PCM conversion, will have a T56 6 speed trans

im not after a quarter mile monster, i doubt it will see any more than 2 runs in its lifetime, only to "see what it can do"... this will be an around town weekend warrior/tire shredder

ive never driven a tpi car before so i really dont know what to look for and what combos behave like on the street, any suggestions?

 

You might loose torque " on paper " but you are not going to notice it especially with the bottom end of a 383.
Anything you can do to enhance the top end breathing of a TPI is to benefit
Stock TPI 350 has awesome bottom end to the point where traction is limited so a loose of torque down low can be a benefit

 

I did the siamesing and the top end pickup was noticeable, the low end felt like a little throttle responce. But then I added an airfoil and I picked all that throttle responce back up. So my advise is; if you don't want to grind on your tpi but would like more power just get an airfoil.

 

I wouldn't siamese the intake/base unless it was a temporary quick fix, cheap, stop gap,, until I could get something else. You'll end up with the worst flowing short runner intake on the planet. Once you get past about the 1/2 point on the RUNNERS,, you get well into diminishing returns on the stock type TPI intake. Take advantage of the TPI runner length and the midrange torque boost they provide or sell what you have and save up for a StealthRam.

 

not really interested in a stealth ram or any other of those manifolds, i want a stock or stock appearing tpi intake like a large tube, like i said, this build wont see race time or sustained high rpms

i actaully have 2 units, i could mess around with 1 of them and if i didnt like it could always switch back over to the other one, i am thinking of buying big mouth runners though

 

siamese looks dumb

 

Siamesing will change the shape of your VE, and so will require extra tuning work, but really shouldn't cause you a big loss of usable power at WOT. Your efficiency at part throttle cruise may be affected in a way you don't like though.

As was stated earlier by BadSS I think, the stock base and runners will work on a 383, but if you're after power you need to swap to larger base and larger runners. Your base will be restricted for WOT.

 

Mav, have you seen this article? Compares different intakes on a 383. Shows stock TPI against many of the aftermarket TPI options. Stock unit will work, just leaving power on the table with it. Have you seen a FIRST TPI unit? Looks like stock but flows the best for TPI.

http://www.compcams.com/Community/Ar...?ID=1737510521

 

yes i have, its been in my favorites folder for about a year now, i mentioned it in my first post, my 383 will have similar parts that their test engine had

i am familiar with first and would love one of their units, ill have to look it up again but i remember them being a bit pricey, maybe ill slowly put money aside for one

 

OMG thank you so much. I've been contemplating whether or nut to upgrade to a 383 and that article just sold me. I'm keeping the stock TPI layout but going with the bigmouth base and runners now. (want the car to look stock)

 

Sorry about that Mav, must have been day dreaming.

I think you are putting too much thought into this. Stock TPI with 383 will be plenty powerful. You have another set so give it a whirl. It's nice to know that If you ever want some more power, you can always throw on a different intake. You can enjoy your truck now and search around for intake deals. We recently did a group purchase for FIRST where they were $875. First still may be open to it. It seems that Comp Cam xfi268 or xfi280 work well with TPI setups. Something similar should work for yah on street. Keep us updated. I want to see a 383 TPI in your S10 when you are done

 

i probably am putting too much thought into it.. i tend to do that with just about everything... endlessly research and over analyze stuff trying to decide whats best for what im trying to do, only to end up with an unfinished project... it drives me nuts

i gave it some more thought today, and read the tpi shootout yet again, and i think im going to stick with the stock plenum and stock intake (heavily ported of course) and get some big mouth runners, that should be plenty for what im doing. like i said earlier, i dont need to rev to the moon and i dont need to be quarter mile king, my only concern is to look cool, sound good, and to shred tire at will

 

That'll do it. Work on the transition angles at the runner and heads and port the entire length of the base (you'll need a 6" shank burr). You might want to consider getting a set of SLP or cast runners and taking the divider down to the half way point. That'll still shread tires at will and if you're comfortable with a grinder and put the time in the grinding,, siamesing the runners will extend the top end a few hundred RPM. That'll really help for those highway kicks.

 

yeah im pretty comfortable with a die grinder and have all the bits i would need, i work in a performance shop so we do a bit of port work and whathaveyou, we also have a cnc machine and bridgeport mill that i get to play with, so any porting i need to do is well within my means

i will think about the cast runners, i have a bit of time yet before i need to have the engine together as im still building the truck, but if i can find a good used set i may just pick them up

thanks for all the help guys, just made this a lot easier for me