I'm trying to build an older 350 with tbi and need some help getting 400 hp out of it. It'll be .030 over at 9 to 9.5-1 compression, completely rollerized, have full 2.5" dual exhaust with headers and high flow cats, retrofit LS1 beehive springs, a modified 454 throttle body that'll flow about 700 cfm, a high rise manifold, custom eprom chip for a 350 ecm, some porting to the stock heads, rhoads roller lifters and bolt to a th200 4r. I will use the stock #80 injectors and raise the fuel pressure to 20 psi to support up to 400 hp. I'm not sure on the best cam yet, would an LT1 cam or comp's xtreme energy cam do the job?. I'm not sure if I should delete all the tranny functions and buy a tc lockup kit or stick with the computer and just delete the speed limiter. I have a budget of $3000 and it has to be strong enough to be a daily driver. I want to avoid a new set of heads and crank if possible, but I don't have a lot of experience building engines (3rd one I've built) and need to know what would work well with this setup. I've heard extrude honing is an easy way to get 20% extra flow out of stock parts, but there's conflicting stories on how costly it is. Does anyone have experience or know how expensive it actually is? How much more lift would 1.6/1 rockers give me over 1.5/1? I plan to put a 150 shot of nitrous through it at the dragstrip as well, how well do you think the stock crank would hold up?

 

I can only answer the last two questions for you, lift is easy to calculate from 1.5 to 1.6 rockers its just 1.6Xlift/1.5
If you know how to play with nitrous a 150 shot is safe enough unless your parts have gone through a ton of stress already.

 

Crank's in a '76 block, you tell me. (Although I'm not sure it's a '76 crank)

 

I believe you can take it into a shop and have them pressure check the block and inspect all the parts, that may be a good idea before you try hitting the juice on a 30 year old motor.

 

Man im not trying to be a D!CK and im not expert but i hope you mean 400 on the juice. if not i highly doubt that engines gonna produce any place near that w/ stock heads and an lt1 cam. thats almost a stock block w/ the exception of some of the smaller things you mentioned. im not saying it to be impossible its just unlikely from what ive seen unless you plan many other little things here and there. you sound like you started off w/ good ideas. the duals and 454 tbi. that will cover the air and fuel at the beggining and the breathing out part but then you hit a big bind in the middle w/ a cam thats popular in 305s making no place close to that and some stock heads. and if your using the same block the crank is in it may not be a roller block so i would check that cause to swap one over isnt all that cheap. i belive youd be best suited w/ a 383 before you spent the money to make a non roller a roller block. just my two cents though its all in eye of the beholder.

 

well, i agree with justlearning that there is no way your going to make 400hp on motor alone with that setup and i would definately not recomend putting a 150 shot into an untouched 76 bottom end, but my biggest concern is the joke of a transmission that you plan on using, the th200 has a hard enough time handling the 2.8L nevermind a 400 horse 5.7

 

So I guess I should go with comp's extreme energy cam then, right? With 1.6:1 rockers, the ex. energy cam, some porting and a single plane race manifold it should flow enough, right? I can get a set of bare vortec heads from a friend pretty cheap, would they give me the flow I need with some porting? The block's hydraulic, a friend of mine used it as a race engine for a while then stripped it and decided to go bigger. I want to stick to a 350, so how can I get 400 hp naturally aspirated? I don't care how driveable it is or if the mileage sucks, and I want a lumpey idle so what's the biggest cam I can put in it without machining the block? Most people don't realize the difference between the th200 and the th200 4r. Although I think they share the same case the 4r is a much stronger tranny, which is why gm put them in the grand nationals and turbo buicks. The 4r I'm building should handle 500 hp without a problem.

 

with ported vortecs and a port matched vortec manifold along with roller cam and roller rocker (cam will have to be fairly lumpy) you should see around 400hp. I'm not very good at choosing cams but, remember the vortecs are going to need some serious machining to fit a fairly high lift cam in the same motor.

 

ahh good catch, i apologise for my incorrectness

 

It's too bad the th200 4r gets such a bad rep from the th200 because it's a great tranny when you iron out the bugs, but finding performance parts for it can be hard sometimes. I've been wondering how a crossfire inj. system with two 350 tbi's would perform. I'd have to mill out ports for the 2 barrel tbi's to flow properly, but the manifold is fairly large and capable of flowing alot more than what 2 single barrel throttles could supply. It would make a great sleeper look and could possibly flow enough for 400-500 hp. And it would be cheap.

 

Anyone have an opinion on crossfire manifolds? The intake ports are small (1 1/8" by 1 1/2"), but I could easily port them out to 1 1/6" by 2". Anyone have experience with these manifolds?

 

You'd be better off searching one of the old school vette forums for info on those manifolds. I haven't heard of anyone running them on here.

 

CHP ran a couple of nice articles in 2005 about how to build a budget SBC.

"Squeezer Mouse", March 2005: 350 sbc .030" over, Holly SysteMax Power Package (comes with fully assembled 68cc aluminum performance heads, Lunati cam, lifters, intake, pushrods, etc), 1.5 roller rockers, 750 cfm carb. The Lunati cam had .490/.490 lift with 235/240 duration, 112 lsa. Engine ran at 9.5:1 compression. Peak dyno numbers were 415 hp @ 5600 and 432 ft-lbs @ 4200. Claimed they spend about $3000, but $900 of that was the fully assembled short block bottom end.

"King Vortec", July 2005: This article covered the buildup of a 350 sbc .030" over, comparing the performance of several versions of Vortec heads. All heads tested with same 750 cfm carb, vortec intak, and Crane Cam with .509/.528 lift, 222/230 durations, 112 lsa. Of the four Vortec heads they tested, the OE modified heads for $655 from Scoggin-Dickey (modified for up to .600" lift) looked like the best bang for the buck. It ran 391 hp @ 5400 rpm and 431 ft-lb @ 4000.

So yes, the ingredients to build a ~400hp 350 sbc (naturally aspirated) are pretty simple and you can do it pretty cheaply. BUT, can you do it with TBI and LT1 cam ?? Based on what I've read on this forum, only the guys willing and dedicated to learning diy tuning have done it (without nitrous). With TBI you'll definately need a larger fuel pump, 80-90# injectors, bigger TBI (from 454 or the Holley Projection 670) and a better cam than a LT1. If I were you, I'd starte with the LT1 cam (theyr'e a dime a dozen from the 4th gen guys and easy to tune) and 1.5 rockers first to learn the tuning, then move to a more radical cam later.

 

You cannot enlarge the runners in a crossfire manifold easily as there is a water jacket running under the runners. Anything is possible, but it would require LOTS of cutting and welding.

 

I've checked a few corvette sites and they all said it's possible, but I'd either need a lot of patience with a die grinder or a lot of cash to port it out enough. I think I'm going to go with the 1.6 rockers and a slightly milder cam for durability and modify the heads myself to make them fit. I could easily increase the manifold's volume by putting a spacer between the lower and upper halves, but enlarging the runners will be the difficult part. That brings me back to the extrude honing idea. Sand blasting removes material and would simulate actual airflow better than a liquid would, so wouldn't it be possible to "extrude hone" the runners with a sand blaster?

 

It is NOT possible to port a crossfire manifold to have runners 2" tall for their entire length.
Whoever told you that is wrong.
I own, and have cut up several of them.

 

At the port it can be cut out to 2" by 1 1/6". It looks like the runners are thick enough to remove a 1/16" from the walls without a problem, but I don't know how much space there is between the water jacket and the runners. How much do you think I could safely take off before it became structurally weak?

 

Listen to Ben........

 

Also forgot..........check out member Dominic Sorresso's ride as he has that manifold (I think) and it's running low 13's.

 

ahh, thanks! This post made me think of that pic, but I didn't have time to search for it top prove a point..
You can see from that you can only significantly enlarge the runners for the 1/2" before thay meet the head.. That leaves 7" of choking ~1sqin runner..

Dominics setup runs well. The extrude hone process costs ~$600.

 

That pic proves what I said before. I could remove a 1/16" from the runners and enlarge the ports out to 2" tall to get the results I need. $600 for extrude honing? Yikes! Thanks, the pic explained alot.

 

Has anyone fully siamesed the runners before? The only problem I can think of is that cylinders 5 and 7 are open at the same time right next to each other so they might not fill as well as the others, but they wouldn't run lean so that shouldn't be a problem. If anyone can think of a reason I shouldn't siamese the runners let me know because I'm almoast ready to bolt it all together.