Tom400CFI

If you want a 400 CID "LT1" (if that's what you're getting at), the fastest, easiest way to that is a SBC 400, Miniram, and an "option converted" HEI distributor...then run it all off the LT1 ECM/harness.

MatthewMiller

Yes, except I'm fantasizing about throwing my current 3.875" crank into a .030-over 400 block to get a 421 vs my current 396. But same idea.

Guessing that was supposed to be "optical converted" or "opti converted." Okay, that makes perfect sense. I see a couple writeups for making your own, and maybe the "dual-sync" aftermarket options would work? Just more time and money, but it's doable. Nothing I'm going to be worrying about any time soon, but I'll file that away in the back of my mind for the future.

Tom400CFI

Yes...OPTI Converted. God Damn spell check. It's like cars with doors that lock themselves for you. Great....until you can't get out.

That is roughly my plan for my '92; a Gen 1 SBC 400/miniram, a Tom-converted Opti/HEI. Nothing special...but it will have that nice PULL in each gear that the stock 350 doesn't.

MatthewMiller

Please tell me you're going to create a thread on that Tom-conversion!

Tom400CFI

Yeah, I'm sure that I will. It may be years...even decades away though. First, I need to build the 400. For that, I need disposable $$. With a family, that may never happen. :-/

My buddy has an '88 fox. He's "going to build a 347". I have two 400's in my garage -one bare, virgin block, the other a medium used short block. I'm "going to build me a 400"....some day. I joke with my buddy that we're in a drag race. We're racing to see who has their engine built/running first. We're both losing.

-Tom


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MatthewMiller

I totally understand that!

candipogo

i have a 64 roadster. custom or mod. call it what you will. i have a pro built 400 stroked to 421. it's about all any sane person would want on the street and still be able to just cruise. the xtra c.i. and the torque are wonderful. yes, i have a tbi fuel injection set up on the engine.
phil

pologreen1

Yes, there is no real reason to have a destroyed street engine. Take a stock c4 especially stick, throw cubes in it and have fun.

brianfiske

Thank you for all the feed back. Based on the input I will be going the 383 route. I may also bold on some long tube headers this season and explore the miniram set up prior to my build so I can get a some added performance (although limited I know) in the mean time.

84 4+3

Now that's interesting.

My input, rpm limitations back in the day were due to the materials of the stock cranks.... as in nodular. My current 383 is in a truck and fuel cutoff is programmed to 6300 with 6000 rpm shift points. However it has a cast crank and I'm terrified everytime it spins that high. do whatever you want. It's a freaking street car. If done right you'll never kill it anyway in either configuration.

C409

….. Ahhh ! … but even the LS blocks are available in a variety of displacements … LS1=350 , LS3=372-ish , LS7=427 …..

MatthewMiller

And you can now buy an LS with stock block dimensions (i.e. not a tall-deck block) up to at least 468 that will live at any rpm you want. And if you have the cash, there is no good reason not to do that. No matter how well an engine breathes, more cubes is always better.

vetteLT193

If I was going with a new 350 block I'd go 377. If I was rebuilding what I had 383.

the377stroker

the 377 has many good things goin for it less friction on the piston wall side loading less friction on the crank internally balanced less valve shrouding and higher rpm horsepower if there built the same as 383 vs 377 the 383 might get it by a few feet off the line but at the end of a 1/4 the 377 will be ahead if there both built the same i know ive tried them both and they are more efficent there less friction all the way around especially if u use a longer connecting rod less wear on the engine to any one want to argue cause i know ive done them both and a 400 has a bad connecting rod set up from the get go i dont like the rod and stroke set up and the 350 crank has less drag hopefully this will help any doubters

the377stroker

the 377 has many good things goin for it less friction on the piston wall side loading less friction on the crank internally balanced less valve shrouding and higher rpm horsepower if there built the same as 383 vs 377 the 383 might get it by a few feet off the line but at the end of a 1/4 the 377 will be ahead if there both built the same i know ive tried them both and they are more efficent there less friction all the way around especially if u use a longer connecting rod less wear on the engine to any one want to argue cause i know ive done them both and a 400 has a bad connecting rod set up from the get go i dont like the rod and stroke set up and the 350 crank has less drag hopefully this will help any doubters

Gale Banks 80'

This is the exact build I recently did. I bought a Vortec Truck 4 Bolt Main from my Machinist, and he said Boring it is a waste of time and just honed it. In the past buying stock bore pistons used to be difficult but that is no longer the case. So, it runs just like a 383 should minus 5 CI.

Gale Banks 80'

Would it be safe to say that for a modern Street engine build with the accessibility of aftermarket Cylinder Heads, Cranks and Rods and much lighter Forged Pistons has eliminated a lot of the 1970's rules on how not to build one of these engines as far as RPM restrictions and other do nots do's? And after all these years of debate there is no one combination that is clearly better than another. And that every combination above does have some advantage over the rest for a certain application.

MatthewMiller

The only thing that's really safe to say is that displacement is king. The only reason anyone would even contemplate destroking a 400 block to make a 377 is if there were a set of class rules that limited displacement to 377. Otherwise, if you already have a 400 block, then destroking it is just dumb. You will always make more power with more longevity and more efficiency by going for the most displacement you can squeeze from a block. I've already gone over the reasons why. These days there are plenty of 468 LSs and 480 LTs being put on road courses for sustained high-RPM operation with no troubles. As with any engine, you have to understand the right way to build them, but the valvetrain is more of a concern for high-RPM durability than the rotating mass.

Gale Banks 80'

I do agree, After all the autocross club I compete in has very few C4's. However the really fast guy is running a 468 CI Small Block or some crazy displacement close to that. And getting a ride in his car and then jumping back in mine makes my 383-377 combo AFR Superam fell like the L98 I took out !

AZSP33D

Define what you would want to do exactly, and then determine what formula is appropriate.

NASCAR back in the 1980’s used a destroked formula as they were limited to 355. They also used a crank with 400 SBC sized mains, it’s overlap between main journals and rod journals meant a much more stable crankshaft.

Today, you can build a high HP/RPM/PSI monster where it’s common to use the 400 SBC size mains with shorter stroke, and it can be certainly more reliable at a similar displacement compared to a stroker. Lots of ways to skin a cat, and also if you’re tire/torque limited, the destroked larger bore may be a better formula.

I’ve queued up a destroked budget LS project for a similar reason, it will be 8K+ RPM engine for a Porsche 944 Turbo where the transaxle is torque limited. I think in most cases RPM limitations are more expensive than torque limitations, but certainly not on this case.

On the C4 the torque limit is higher, but eventually you could get there without too much trouble, where a destroked version of the power curve is preferred with regard to crank/clutch/trans/DS/Diff/axle combination… although all of those can be built up also.