Try2pass

I have a LS3 in my '80 vette but always wanted a 427. Can we rebuild it into a 427 or not? I think they are redone into a 416 but I want a 427. Is that possible and how would we go about it?

lil john

yes you can simply add a 4.100 crank with rebored block *or* 4.125 resleeve bore with a 4.00 crank.

Custom piston are needed for the stock block 4.1 + crank get with Brian Nutter 4 pistons.

you can expect 500 rwhp with stock heads and simple bolt ons...550 and running with bigger engines or crazier timing events....

If resleeving might as well do a 4.185 x 4.125 bore and crank = 454 off the top of the head


Get with ERL or Steve @ RED.... and your done both do re-sleeves.

KCS

iTrader: (20)

Wiseco actually makes shelf pistons for 4.100 and 4.125 strokes, no custom pistons necessary.

BOLO

iTrader: (40)

If I were to do a 427 out of an LS3 block, I would have it resleeved to a 4.125" bore and run a 4.000" stroke, as mentioned by lil john.

Tuskyz28

Plus one for a resleeved block. Safer all the way around!!

NAVYBLUE210

Plus 2 for the re-sleeved block, RED or erl.
Better!

1989GTA

I have a tale of two LS3 based 427 motors. A friend of mine had one built up using Wiseco pistons. He had his rear seal leaking with excessive blowby. He had to use an elaborate crankcase venting system to cure the problem. Outside of that no other problems.

Tale number two. I had a LS3 based 427 built up using JE asymmetrical pistons and have had no problems at all. Based on my friends problem I did vent the oil cap with a filter just in case but it has remained dry. Oil consumption is fine.

So IMHO the success of a LS3 427 build will depend on which pistons you choose.

KCS

iTrader: (20)

Did the same people build and machine the two engines? I know of plenty 4.100 and 4.125 stroke combos with Wiseco pistons without any issues. There are a few details to address in the block with the longer stroke cranks that will cause problems if overlooked though, which I think a lot of problems ca be attributed.

FLYZNTN

Agreed. Too many unknowns to imply that the Wiseco pistons are inferior to a set of JE pistons.

OP. Yes, you can do a 427 with an stock bore LS3 block. There are several people on this forum who run a 4.1" or 4.125" stroke crank with a bore of 4.06, 4.065 or 4.070 and like KCS says, "plenty with no issues."

That said, if you are going to add a power adder than you might want to reconsider doing a 427 where the stroke is longer then the bore IMO.

Try2pass

So should I go with the LS7 heads or my LS3 heads? Rods? Would this engine (LS3 made into a 427) be as good as a LS7 for reliability and power?

lil john

Do you want to spend the extra 3 grand + for a extra 25 hp(heads,intake, rockers arms..etc). Yes it can be built just as good. Get the stock heads ported and save the $ on something else. Trust me.

This is how it adds up !st: Resleeve block 4.125 and a 4 in crank and 6.125 rods

or

4.100 crank and rebored LS3 block to 4.070 with 6.125 rods.

Your choice.

Try2pass

Which company is RED or ERL? Why do I read about rebuilding to a 416 but have never read to rebuild to 427? I don't want more than 427 or less than 427. I want the 427 because of it's history in corvettes. Is there a company that would sell me a "kit" that would have everything we need to rebuild it by any chance?

flintwrench69

iTrader: (11)

I wanted to go 427 too so i could say I have a 427 & the extra torque of course. Everyone says it will live longer with the 4 inch stroke so just gonna do the 416 or 418. Whatever a 4.070 bore comes out to.

Try2pass

4.07 bore with the 4.00 stroke is 416 ci. 4.125 bore with the 4.00 stroke is 427. Why not go the 4.125 bore and have your 427?

lil john

Why not do a 4.185 bore and 4.125 stroke and tell every1 its a 427 when it's really a 454. The price would be about the same and who will ever know. My friend tells every1 he has a 383 when it's really a 434 sbc.

SHovV

iTrader: (1)

If you wanted to use LS7 heads you need a minimum bore of 4.125. Or you could get "small bore" aftermarket LS7 heads.

Tuskyz28

4.100" bore is minium bore for the LS7 head. Calspeed performance have did that a couple of times.

FLYZNTN

RED stands for Race Engine Development. They specialize in re-sleeving blocks.

ERL also re-sleeves blocks.

There are others but these two are the heavy hitters in that market.

Now back to your 427:

If you want an LS7 spec 427 (4.125" bore x 4"stroke) with LS7 heads using your LS3 block then you will need to re-sleeve the block. If you go this route then I would suggest selling the LS3 block and then purchase a 5.3 truck block from RED or ERL. 5.3 truck blocks are the best candidate for resleeving.

The jump from 416\427 (LS3 bore) to 427 (LS7 bore) incurs an additional +-2500 dollar expense not including LS7 heads. If you do re-sleeve that opens up many options for added displacement because the ductile iron sleeve material allows for aggressive cylinder boring.

If you are just doing this so that you can honestly say "I have a 427" then I'd suggest going with the LS3 bore (4.070 bore x 4.1 stroke) and ported LS3 heads. I think you'd be happy (As long as you don't add a blower) and it will save you about $5000 (Resleeving + LS7 Heads). That said, if money is not an object, then by all means, resleeve.

Tuskyz28

I would do a set of LS7 heads over a set of LS3 heads on anything over a 4.125 bore if I was go run a GM head.

FLYZNTN

Absolutely.