Brettinator

GM LT1 4-Bolt mains were used in which cars or as replacement engines?

When I bought my 97 Z28 I had the dealer do a Carfax (all was fine) and also a dealer sheet of work ever done to the car. Two months after this car was purchased by the original owner the engine was replaced with a brand new engine (no details on why, etc). Well I don't like rumors but was told when GM did warranty replacements they would often use the LT1 4-bolt main as the replacement, yeah whatever, I have my doubts because that just doesnt make sense from a GM logistical repair standpoint. But My friend has a 96 Z28 she bought new, it flooded a year later and GM replaced her engine with a 4-bolt main LT1. She threw a valve into a piston, tore the engine down and to her surprise it was a 4-bolt vs 2-bolt.

I DO realize it adds NO more power, but obviously it's a little more durable and with my plans for a 396 stroker I was excited (although it's my understanding the SPLAYED 4-bolt mains are actually a little stronger than stock 4-bolt main castings).

Still I'm just curious as to any of this rumor being factual and would the Block ID tell me for sure what engine is in this car in that level of detail (4bolt main vs 2)???

Brettinator

someone has to know something regarding this? At least does the engine block ID give you any engine details? Like 4 bolt main, etc? Anyone?

BUBBA

I doubt that GM cared whether they replaced the 2-bolt with a 4-bolt. Once production ceased on the Lt1, whatever inventory was left would be dumped, i.e, sent to dealerships for replacements, etc.

When my 97 bit the dust, I found a dealership that just happened to have one shortblock left in their warehouse, and it happended to be a 4-bolt.JMHO

Z28SORR

No. The dealer will put in what ever they get from the warehouse. If you get lucky it may be a 4-bolt, but it may not be either.

rskrause

The generally accepted word on this was that all replacement shortblocks, iow all those that weren't put in a car, were 4-bolt blocks. Every replacement I have seen has has the 4-bolt mains. This must be related to some aspect of GM's system for engine production, but I have idea how that's organized.

Rich Krause

Brettinator

well that just makes my day then

Injuneer

You can't assume that the splayed conversion will be any stronger than the stock straight 4-bolt orientation. Nor can you even say that it will be as strong as the stock orientation. The block was designed to accept straight 4-bolt mains. That's where they put the "meat"... not necessarily off to the sides. When you drill into an area that is already "weak", you may do more damage than you will ever recover in other benefits.

Brettinator

Makes sense, like my post said it was just my understanding based on what I've heard/read others say. I'd much rather have a factory 4-bolt main.

Got-LT1

Same here. According to carfax mine has a new engine, When I do a rebuild I'll let you all know if I have a 4 bolt.