What is the maximum bore and stroke a stock L98 be machined to? I know 383's are common, however, can a 406, or slightly larger, work in my stock block? So, I can order the correct rotating assembly to fit in the stock 1990 6-speed L98 block...

Thanks!

 

4.060 is max over bore on a stock L98. Some blocks will not have enough cyl wall thickness for use in a high HP engine at that bore. It will need to be sonic checked first. 4.030 is the most common overbore and most all blocks can survive at it.

You can stuff a 4" stroke crank in a L98 block. At .060 over this would build a 414 inch engine. It's lot of grinding, your almost certain to break thru the lower bulkhead into the water jacket and you will need to pour the block solid to the bottom of the freeze plugs. These engines use a 1" compression height piston (with a 6" rod) and there are not many shelf stocking options.

Next smaller crank is a 3.875" stroke which commonly builds a 396/398/401 inch engine. Same applies. It's alot of grinding and with some rods your going to have to pour the block. This engine with the common 6" rod uses a 1.060 compression height piston and there are about 3-4 shelf stocking options from ICON, Probe and SRP.

Next is the ever popular 3.75" stroke crank which makes the 383/385/388 inch engines. Some grinding but not terrible and you rarley need to pour the blocks. There are too many opinons to specify here on shelf stocking pistons for 5.7, 5.85 and 6 rods which are all availiable in great quanity from any piston mfgr you can name.
Will

 

Thanks Will, I kept getting mis-info from other places trying to sell me a block, saying mine was useless in anything above a 383.

 

FWIW, I needed very little clearancing on my 3.875 stroke with 6" rods. The caveat is that they're I beams. Pics of the crank & rods are in my photos. IIRC, I only needed to graze the pan rail and notch the cylinders in a couple places, and use a .990 base circle cam.

 

+1 ^ 3.875 stroke with 30 or 60 over will get you a stout 396 or 398. Use a nice set of 6 inch stroker rods like crower and very minimal grinding on the block is required. No low filing should be necessary.

My 396

 

Is that an L98 block? There seems to be difference in opinions whether they were 2 bolt or 4 bolt from the factory.

 

That block is from a 3/4 ton or 1 ton truck. L98's were 2 bolt mains.

 

 

You can always do it the hard way
'

 

Whoa! Would the oil pan even fit over that??

You get the LM1 ron?

 

WTH:

This must be the same guy

 

Since we want to turn this thread into the worst fabrication you've ever seen done on a SBC.....

That dude has some mad engine machining skillz. Seems he's been building a SOHC conversion for the SBC as well......












Will

 

wow ! wonder where he got 40' of double row timing chain?

All that and a 2 bbl intake !

 

Thats probally (2) 530 Motorcycle chains and he was going to modify that intake for dual 90mm throttle bodies....