IMHO no matter what you do to the TPI system (exclude Stealth Ram and MiniRam) the TPI can not flow enough air like a Carb can. So far on the TGO board I haven't seen nor heard anyone make over 400 to the wheels. Why is that? So far I've seen on the Dyno 393whp on a 355cu. But not a 383cu. Now I have seen 406cu make 403whp but it may be possible that it was still being restricted due to the manifold flowing 320cfm. More than likely the manifold needs to flow atleast 350cfms to take advantage of the cubes.

The TPI was made for a 305cu. What's y'all opinion on this? Also I don't think the AFR 195 are needed for a TPI. The AFR 195 are better suited for bigger cubes rather than a 350 unless you're going to rev the motor 7000+. With the TPI you will not take the full advantage the the heads.

 

I find little wrong with your thinking. TPI or carbs., it's not too often to see 400 rwhp on a streetable 350/383 ci. vehicle. That figures to be about 500 fwhp. Cubic inches is everything, unless you're using forced induction!

 

The bigger the cubes the more air it needs. So the question is do you think a TPI can support the air for the bigger cubes?

 

My opinion?...Low rpm torque..yes. High rpm power...no. Keep in mind I run about 7 k on my 383.

 

"Now I have seen 406cu make 403whp"

On that motor the exhaust was the big restriction.

"do you think a TPI can support the air for the bigger cubes"

The First intake system certainly can. Properly set up I think it can support 600hp at the motor. I believe this year we will see over 400rwhp on the dyno and that will be from a motor smaller than a 383. Remember my high stall auto was at 396rwhp at only 5500 rpm. If that had been a T5 the rwhp would have been well past the 400hp mark.

My definition of TPI is welded up and hogged out for increased air flow using aftermarket parts. Stock no way.

 

Yea but you don't have a TPI.

 

LOL...but I work on them almost every day. Does that count?

 

You have a 369cu. This is about 383 and bigger.

 

I think with smog legal cams you are leaving a few ponies on the table, along with a small restriction in the exhaust.

But I believe a 383 TPI fully ported will support 400whp...just need a well matched combination of parts and good air to dyno in The First setup seems a likely place to start...if you throw enough compression at it with a big cam I think you will find 400whp capable but its gotta be a great setup. You are rpm limited with long tube runners even tho the largest First ones can flow decent airflow.
Lower flowing manifolds like HSR out of the box or mildly ported have supported 400whp before but those setups turn some rpm. Not sure what a box stock 1205 miniram flows or a mild ported LT1 intake flows but they are good over 400whp as well. Higher rpms makes for more total air flow through the motor and thus more power potential. If you can turn rpms, I assume you will need a large flowing intake and head combination to make good power at the lower rpms.

IF you consider siamesed setups and cut/welded runner combos that do support higher rpms, then it should be well over 400whp capable but its not really a TPI anymore

 

Well since you work on them, have you made or seen one make over 400whp? If so how without power adders?

 

Even if it did make over 400whp, no more than 410whp. But with a Carb it more than likely be around 440whp+. The way I look at it you will not get the max out of it because the air flow will still not be enough. I should have not included the FIRST SYSYEM.

 

IF a TPI made 400 and a carb made 440, it would be because of the shorter runner intake design of the carb and able to produce more rpm. I dont think a carb setup would make hp peaks in the 5000-5500 rpm range and still produce 400+whp.

 

No, they usually pull the tpi and go to either a Mini-ram or Holley SR. One 406 with all the large tpi parts did make right at 400 rwhp, though.

 

Giving that, any engine that makes 400 rwhp at 5,500 rpm is making 382 lb/ft rwtq. For any 350 ci. engine, that is quite a feat...about 450 lb/ft at the crank, about 100 lb/ft over a stock engine.

 

Thats what I'm saying... that much hp at that low rpm is going to be difficult to make.

I know of a 383 that was built kinda following the rpm range of EMC which is not past 6500. It made peak around 6400 but was 4 hp shy of that peak by 6100 so top end was leveling out. The heads were only 190cc after porting...GM vortec castings with 2.02 valve. 230/234 hydraulic roller with very aggressive lobes.

At 5500 it was still making 523hp and 499lbft on the engine dyno. I'm wondering if you restricted the top end with TPI to about that rpm range, would it still make that power if you have alot of intake flow? I'd assume the TPI intake would need to be slightly siamesed perhaps to support that rpm range but the FIRST should beable to hold a 5500 rpm peak.
My theory is that the long runners of the TPI manifold do not help the intake ramming events (wave reflections/harmonics) for the higher rpm ranges and thats why it doesnt pull to higher rpms, but if the runners help the intake ramming at 5000-5500 and flows well enough, it should beable to keep power production up.

It makes me wonder if that motor would beable to produce a similar power curve with TPI but only make 520-530hp by 5500 and fall off, when the cam/heads really want to go to 6400+. 520hp by 5500-5600 should be 400whp

 

Orr89RocZ....We both know those EM challenge engines make great power...but they would't last a month on the street. Their whole purpose is to make really big numbers for a very short time. The cams are stupid aggressive, with very high ramp acceleration and valve spring rates. The V-E numbers are high, and that is where it ends. For the average hot-rodder, you would need very deep pockets to reproduce the lofty EM numbers. In the real world, intake runner length and cross-section can be optimized for maximum power and torque, but again, a compromise. Too big, and your runner tuning goes sky high. Too small, and you kill horsepower, which we all know is a function of rpm. Think of the I-R systems like Inglese and Crower. They make sick horsepower numbers through tuning of the intake runners, but the power band is extremely narrow. Not ideal for the street. The LT-1 based intake style seems to be the best option for most applications, giving a fairly broad torque curve with a respectable upper rpm range. Besides, intake tract tuning math is above my pay grade...lol

 

Well i guess the question was can 400whp be made... no one mentioned if it had to live on the street for a while I'd be curious to see what the big tube TPI setups could do in a limited application motor like EMC style stuff.

In any case, 400whp out of a street 350-383 is alot of power any way you look at it.

 

The bottom line is how much cfm the intake system can flow. How much fuel air through the intake will determine how much horsepower can be made providing the mechanicals are there to take advantage.

The cubic inch of the motor will determine at what rpm range peak power will happen. The bigger the motor the lower in the rpm range the peak power will come. The smaller motor will have to rev higher to take advantage of the flow and have a higher peak power rpm.

I have decided to start a thread on my long tube runner project as I am exploring this right now in what I will call an engineering exercise.

 

Are these comments TPI specific?

 

You lost me there..(easy to do). I thought the cam profile dictated where the relative power (torque) occurred. Unless John's question comes into play. Then a restrictive intake tract will affect different C.I. engines, whether carbureted or tpi equipped. An exercise worth exploring would be which engine, 350 or 383, would get faster down the 1320 using the same hardware (tpi set-up).

 

that's what I was thinking...

 

"providing the mechanicals are there to take advantage"

This would include the camshaft.

 

I think that would depend ultimately on gearing and tire size...if you could optimize those two to fit each motors power band. I believe the theory goes if you have 300cfm to play with (from your head/intake combined flow, and I know cfm isnt everything but bear with me) then a 283 ci motor will have same power potential as a 406 ci motor but the 283 will have to spin MUCH higher to do so.

If you are familar with pipemax, you can use it to simulate engine data and calculate recommended cross sectional area for your heads and optimal intake runner length for whichever harmonic/reflection you want to tune for. Its interesting to note that the 2nd and 3rd harmonics/reflections use much longer runners and make most peak torque. 4th harmonic is common because it gives a runner length that most cars can fit under the hood

I modeled a 305 LB9 and for 2nd harmonic thats 22.1 inches. 3rd harmonic is 15.45". 4th is around 12" and similar to some single plane intakes which reduce torque peak. Doesnt give optimal length for peak hp tho but i've heard the 2nd harmonic is stronger than the 3rd, and the 3rd is stronger than the 4th.
TPI is in the ~18" range I believe so its closer to the 3rd harmonic. But we all know the short runner miniram/superram/stealth ram are known to swap on these motors and make more hp at higher rpm peaks with the sacrifice of peak torque...but they make broader torque curve and thus run faster. So if you kept runner length long for the stronger 1st and 2nd harmonics, the only thing that will help power and rpm range is if the runner is larger to flow more. This seems to be the thinking I've read. It makes sense to me.

So TPI runner length may be ok for 383's but need to really flow alot to use the 2-3 harmonics effectively.


Pipemax is a fun tool but for some reason it did not accurately model my 383...using the cam, compression, head data I have, it says my cam couldnt produce peak hp above 5500 rpm and would be choked or something.... I made dyno proven peak at 6250 and it carried to 6500+. I dont know...

 

"So TPI runner length may be ok for 383's but need to really flow alot to use the 2-3 harmonics effectively"

Exactly.

 

One thing for sure I guess is that a 350 will out torque 383 and larger with the same cam and heads but it will peak about the same hp but at a higher RPM. So is it really worth spending the extra money for a 383TPI?

 

I think a 383 and larger will work far more better with a Stealth Ram and Mini Ram. I think a Super Ram is a happy medium for street performance. Plenty of torque and decent RPM range up to 6000.

 

"I think a Super Ram is a happy medium for street performance"

I agree if done correctly. The Super Ram will be my fall back position if for some reason my long tube runner project does not work out. I will have to make my own runners though to fit my manifold.