Alright after much thought and worry I've decided to use my LPE 24216 cam with the stock stamped rockers on my TPI car. This car is stock, and by stock I mean 200,000 miles dented oil pan, stock from throttle boy back and down. It will be even more stock when I install the factory rockers back on. So my question now is, I've gone as fast as a 13.5 in this car; it has a 3000rpm stall and 3.27 gears. I just shaved possibly over 100 pounds off the nose of the car, plus another 80 or so pounds of rotating mass (weld draglites all around) and it no longer has to turn its own power steering pump (went with a rack). My best MPH to date was 100, but that was with no water for the water pump to move (busted a hose) it averages 97 to 98 mph. I spray this car HARD, 200 shots are mandatory anymore though I'll probably only need a 175 shot or so from here on out. My question no is as the title states, Do you think I'll safely gain speed if I siamese the base while it's off the car? I'm gaining over 10 degrees of camshaft duration here but are these stock 87 TPI heads going to hinder me from any more top end flow? Anyways the poll is up, thanks again guys; I should have some results back for you as soon as the track opens in Febuary.

 

You'll get a bit more top end ability if you siamese everything.

I'd say go for it.

 

The big number that I shold've emphasized more is 97mph average trap speed; can stock heads trap higher than this with a big stall, 3.27's, and probably 3200 pound with me in it weight?

 

I think they can handle it - the intake/plenum/runners themselves will limit the heads.

 

I went 103.8 mph in good air with my stock L98 longblock with HSR with stock L98 cam with 1.6 rockers in a 3450 lb or so race weight. 2800 stall/3.42 gears.

summer time was 99-100 mph.

I also touched 100 with my stock TPI setup, this was in cool air. most of the summer/fall it was 96-98.



i'd be weary about the cam install. i went to throw one in my L98 at 158K miles and discovered a loose timing chain and a bad front cam bearing. SO i decided to build a 383 but if it looks good, then go for it.

And yes, Siamese the base alittle. It will raise your powerband to higher rpms which in itself will improve your et's and trap. that cam will want to peak near 5200-5300rpms i would think, so definately siamese the TPI to get more rpms out of it. Dont have to go too far, a few inches will do.

 

Why not get an aftermarket intake? Edelbrock sells them for the lowest price.

The pinch area on TPI intakes is where the injectors are. Concentrate on porting that area without going thru, and you'll gain more flow. My Edelbrock intake flows 310 CFM after doing this porting. Stock it was 260 CFM.

 

This base is already mega ported, I'm not spending another penny on this motor, I have a Vortec 350 and a Vortec Stealth Ram ready to go, it's just to see how far I can push this setup before I remove it.

 

i was unaware that any TPI based flowed more than 230cfm? stock bases are like 200 right? The HSR and miniram flow like 275-280 cfm and have much better/shorter runners

thats pretty good flow.

 

I think he's saying his stock Edelbrock high flow was 260.

 

wasnt there a guy or two on here who siamesed the base and blew the motor from 1 cylinder going lean from it?

 

aftermarket base or not, i have not heard any good flow numbers from there except from stealthram.com which has some data

http://stealthram.com/flowcomparison.html

 

There's a rumor that it blew the number 7 cylinder on a car because it went lean but if you really consider this, number 5 and 7 are going to act exactly the same no matter how long the runners are, it pulls from it in the base, or the plenum either way. I do believe that it turned out to be a bad valve guide that killed the particular engine that broke; I do still worry about that particular distribution problem on the nitrous.

 

Here are a couple of tidbits. The First Injection TPI intake manifold will flow over 300 cfm right out of the box. Open up who knows but I bet it would be pretty high.

I won't give the exact figures because the people that own them may not want it known. But I will say that with a little welding the Edelbrock TPI intake manifold can be opened up to flow over 300 cfm. This is with a reasonable cross sectional area.

 

either way, the more air you can get thru that TPI the better off you are. Even tho stock heads may not flow more than 200cfm, the stock style TPI stuff chokes it enough to not get full potential.

I believe the benefits of siamesing is more to get higher rpm flow potential rather than just peak flow numbers. Just because you have flow numbers doesnt mean it will still make good high rpm power. I am waiting to see results with teh First TPI setup that is claiming to support 5500-6000 rpms. It flows more than the HSR out the box, but the runner length still prevents high rpm wave tuning.

i think with more rpms, you'll run faster ETs due to the wider powerband. you can keep the motor in the power rpm range longer

 

The CFM numbers are really secondary to what I'm going for with the siamesing; the heads can only flow around 200cfm so there's no real point in trying to get more flow from my base without touching the heads. What I'm debating is if I should keep my resonant tuning and let her rip out of the hole, or if I should go ahead and siamese, change the resonant tuning and hope for some more power up top. I know for a fact I'll lose power at 3500 to 4500 or so but I'm wondering if I'll ahceive enough top end to make up for it. It's strange to me I've read EVERY thread on siamesing the bases and even porting them but I went my own route on porting my base, and there's very little real track info on siamesing stock bases. I've done so many tricks to my stock TPI plenum I would LOVE to have it flow tested and see what it does; right now I"m just wondering about siamesing for the big change in resonance it gives. This mod's been around since 2001; you'de really think alot more people would've done it and reported results.

 

i think TPI torque thing is overrated. my car actually 60 footed QUICKER with the HSR addition. And i lost peak torque for sure but gained a flatter torque curve with more torque at higher rpms.

I think you'll notice the same effect with siamesing and it will help you go faster down the track.

Heads may only flow 200cfm, and stock TPI setups are said to be around 200cfm as well. I gained hp by adding a HSR that flowed 275 so go figure? I think it was more from the fact that TPI just cant flow that CFM as rpms go up and you move past the wave harmonics that tpi is tuned for. It showed as i made similar power up to 4000rpms but then the HSR took over all the way to 5000.

So based on my gains that i've seen with my car, i'd say siamesing to move wave tuning effects to higher rpms will be very beneficial over stock length TPI runners reguardless of how much cfm they flow from your port job. give it a port job and siamese it and you'll see great gains

 

Siamese the crap out of it. More air is better if you're trying to maximize your setup...

 

See this magazine article I recently posted:
https://www.thirdgen.org/waiting_to_...ance-july-2000

It lists the Accel intake flow numbers, as well as stock TPI. But I take my data back. My Edelbrock base flowed 260 after port-matching, not stock out of the box.

 

sweet, thanks for the link! those numbers with extrude honing are pretty stout for a TPI setup.

 

MPH should be up with the siamesed base. I think your ET gains or losses will be dependent on shift recovery. The higher you spin the engine before shifting and the higher your RPMs are after completing the 1-2 and 2-3 shifts the better your ET will be with the siamesed base compared to ported stock. You'll get more benefit from the siamesed base running the TH350 in your profile versus the original 700R4 due the closer spacing between 1st and 2nd gear, reducing the RPM loss after the shift, on the TH350.