A&TZ28

What do u guys think of a 402/408 TPI with LTR's? I think that would be a great combo, since it seems like keeping the bore around 4 inches doesnt make the motor require as much airflow as opposed to a 4.125/4.155 bore. the powerband should be similar to a 383 but with more torque i would think. it also seems a healthy aftermarket LTR setup will support 1.1 hp/cu in. so i myself have been building a large cu. in. LTR setup motor on paper. I think it would be a blast to have a motor that can make 425-450hp and i would think at around 550 lb.ft. of torque and would never have to see anything above 5000 RPM and loaf along the hwy around 1500 RPM (depending on trans/gearing) while barely sipping gas. yet still power our heavy cars into the 11's. besides everyone and their mom has done the 383 to death. I know some will say that the tpi chokes a 350 but thats how it works. For a street car i feel its better to run the car off of grunt than high rpm hp. I know some will also talk about not being able to hook with the excessive torque down bottom but honestly i have driven quite a few BBC cars with more bottom end grunt than that on the street and it wasnt unbearable at all. just requires a little change in driving habits. What do u guys think? thanks

danziger

I had a LTR 383 in a 1990 Corvette and it was ridiculous...the car was sideways more often than it was pointed straight. Not the fastest combo in the world, but certainly a giggle-inducing tire destroyer.

1989GTATransAm

iTrader: (3)

Doable. The First system would work the best. Even better if it was opened up some. Ken is working on some 2" runners which would fit your motor even better. What heads would you be using?

Orr89RocZ

iTrader: (20)

I like this idea for a few reasons. The 4" stroke 4" bore setup or even a 3.875" stroke 4" bore setup doesnt like alot of rpms. You have rod ratio problems, piston velocity problems, etc. So keeping the rpms lower helps. TPI is a lower rpm setup. The 2 go well together.

The long stroke with the long TPI runner will make an incredible amount of torque. That will be a blast on the street for sure. Response will be incredible.

Only downside is they still require some air flow if you want to get up over 4500 rpms. The FIRST TPI with its big tube runners will be the best bet here. I agree with 1989GTA above.

For heads a good 195-210 cc head for 400" will suffice. You dont need alot of cross section to turn 5K rpms on those motors, so a faster velocity port could do well here. Get as much air flow in as you can. Lower seat duration on the cam, high lift and a tighter LSA should make an insane torque curve. Likely over 400lbft from idle to 4000 rpms+ if done right. I could even see 500lbft at the tires on a 408 if done right.
With 408" you can cam up, 230 deg or so and be perfect with TPI.

vetteoz

iTrader: (13)

Super Rod got 500ft/lb at the crank with a stock TPI on a 383

http://xtremecarzone.com.au/index.php?showtopic=386

dhirocz

iTrader: (2)

Engine: tuned port injection, 427 cubic inches
FIRST TPI intake, mildly ported
30# SVO injectors @ 50 psi
Bowtie block and dart pro1 230cc heads
0411 pcm swap
Custom LS1 firing order cam

What I've found is that the first is sized fairly well to 427 cubes.

88fastgta

iTrader: (9)

had i had the FIRST tpi before my dad and i built the engine block i would have gotten a junkyard 400 block and made a 406 first tpi.... would be a killer street car.....

1989GTATransAm

iTrader: (3)

"dart pro1 230cc heads"

I think that is helping your situation out quite a bit. I would say in the last month or so my thoughts on cylinder heads has changed a lot. Need I say airspeed, airspeed, airspeed.

Orr89RocZ

iTrader: (20)

Yep. It is something that is often overlooked. But on this application, not turning alot of rpm, I think you can get away with a faster port head. AFR 220 would work well but I'd be inclined to try Dr J's airwolf 220 or 235's, or Speier's profiler 227cc heads as well. Dart 230's are decent heads but for the money, I'd want something abit more custom hand-crafted like the above heads, or a out of the box type head that AFR is best known for. The Pro 1's require alittle finishing port work to perform best, so I'd prefer to start with something already done and the prices are all competitive.

dhirocz

iTrader: (2)

Well put. I had to compromise though, that engine aint cheap. The heads I can port and prep myself, considering there wasn't as much needed as say an iron L98 head. The port sizes were fairly close to begin with as well. Not optimal, but still does the job well.

BlackenedBird

iTrader: (5)

AFR is a good choice, but not the 220?

I've never heard of "Dr J's airwolf 220 or 235's, or Speier's profiler 227cc heads". Granted, I've never been big in big engines, but I've also never seen their names anywhere before.

Orr89RocZ

iTrader: (20)

No, the AFR 220 is a great head. I'd use it but I believe its cross sectional area is a tad smaller than the other guys heads near similar size in cc. AFR is a faster airspeed style head which works great on street engines with lower rpm ranges. Something like a 427-434 may do alittle better with alittle larger head, and the AFR 227-235's start requiring some special parts like offset rockers or lifters due to 60/40 valve spacing. The 220 is the largest head that still uses stock valvetrain equipment. I believe Dr J's 235 uses stock style valvetrain stuff, but I know Chad Speier has heads in 220, 235 and 245cc that use stock valvetrain components. No special shaft rockers or anything needed. I have his 245cc heads.

1989GTATransAm

iTrader: (3)

"I have his 245cc heads"

I am giving his 220 heads a serious look. Something I would have never considered two months ago. The learning process never stops.

TTOP350

iTrader: (8)

The LS7 427 runs a 259cc runner.
Im running 235 afrs on my 4??ci motor and I think they are a tad small...

Orr89RocZ

iTrader: (20)

Its hard to overhead a 4.125"+ bore 400"+ motor

TTOP350

iTrader: (8)

Where is the "like" button?? lol

dhirocz

iTrader: (2)

The whole point of having the extra cubes over the 402/408 is simply to reduce the effects of shrouding the valves in this situation. I run a 2.08 valve. The 2.02 wouldn't quite cut it IMHO, and the 2.08 starts getting rather close to the cylinder wall.

I think 230 degrees is a little large for a 408/427 if staying LTR. A 224/230 with 30# injectors seems to work well. I can see it working well with a siamesed type runner and/or if you were trying to shift the torque peak a little. With TPI engines, when it comes to parts selection, err on the small side; when it comes to the intake tract, err on the efficient side with the proper CSA and tuned length for velocity. Still, when you go that big, it gets rather hard to go overkill. The FIRST would do well here.

Orr89RocZ

iTrader: (20)

Speier racing just developed a large CSA head designed for small bores, 4.030-4.060" bores. Great for the big strokers 396-408 but works great for high rpm 383's too. Its based on a 2.055" valve. I like valve size as said above, seems to cut down on valve shrouding. 2.08 is the largest I'd run on a 4" based bore, but there are plenty of heads getting it done with 2.00-2.05" valves so its all in the port shape.

They may be slight over kill for a LTR based 396-408, but could work with a big FIRST setup. Problem with the big stroke 4" bore based setup is compression, need abig dish to keep compression down, but with thin piston like that its hard to get much of a dish without compromising ring location. So a larger CC chamber head would work to keep compression down, or you just cam it up and thats what i'd do.

Longer runner intakes tend to like wider LSA's according to one cam grinder I talked to, who I used on my 383 and now my new turbo build. With wider lsa, you now need to go higher on intake duration to get the IVC event later to help bleed compression down. Its all a compromise but I dont think you are going too large with 230 deg on a 400" motor. My 401 with a 233 cam seemed to only pull to mid 5000 rpm range with 195 cc heads. Larger heads would maybe hold on abit longer, say 6000 rpm but with a big TPI intake, that larger cam will pull to 5000 and hold onto power longer before dropping off. A good thing with TPI since its known to fall off very quickly. Just my thoughts

A&TZ28

Sorry for the long delay guys been kinda busy with work lately. Very interesting responses tho. Im thinking of bringing the cubes down to 396 and running something like the AFR 180 comp port since they have proven to make around 475 hp on a flat tappet low compression 406. I know it was a magazine engine (the impersonator CHP) with no accessories but i still think that head has the cfm potential (270/275 at .500 ish lift) and enough CSA for 475+ hp around 5700 rpm on a 406. Granted the LTR setup will only be around 48-5200 rpm at peak hp. If a head that small can feed that engine that spins a little higher than a LTR setup. why go bigger than that? And i also think that the cam duration should be no more than 224 with a wide lsa. What do u guys think?

87rattler

Awesome engine build.

I've been thinking, what to do to keep up with today's cars? I thought an LS was the way to go, seeing the FIRST intake builds has put the TPI on top of my future engine build.

Orr89RocZ

iTrader: (20)

I'd still go atleast a 195. Base 195 is cheaper than the comp port 180 by a good margin I dont think there will be a significant difference between the 2. Air velocity will be high in the smaller head at peak rpms..which may be a good thing with a small motor. Use a fast valve motion cam lobe and it could be a very torque setup. I just dont see it making big hp with 180's and 224 cam. That setup wouldnt do much over 350whp if allowed to rev up over TPI rpm range. I think the 195's with a little larger cam would make abit more hp at peak rpms even tho the TPI is gonna limit things abit.

I dont know, may be discuss it with a good cam grinder to see what they'd recommend for a big cube low rpm motor with long runner intake.

A&TZ28

thank for the advice Orr89RocZ. your 401 seems unique. tell me a little about it.