I performed a compression test on my 383, cylinders 5 and 7 only have 100lbs of compression while the other 6 are around 120. So i did a leak down test on those two cylinders and it showed that it was the rings. The question is do i get a new block? or can i just buy 4.00 pistons and have it bored into a 400? I cant find any pistons other than the 3.905 or 4.00. Will the block handle that big of a bore? Or is it a cheaper route to resleeve the original block? or just find a good used one? Thank you for all the help

 

GM High Tech: Cylinder honing is simply a term that refers to the precise removal of material from cylinder walls. This stands in opposition to boring, where a large amount of material is removed rather inaccurately. Honing gets the cylinder to the exact size needed and puts the correct surface finish into the metal of the wall. As mentioned earlier, with the aluminum-block Gen III, only a small amount of material can be removed from the cast iron cylinder liners. Simply put, they can't be bored--only honed.

 

Ok i know they only shaved off a little bit to do the 3.905. But it is not possible to go further on the sleeves to do a 4.00 piston?

 

i'd say call texas-speed or any engine builder tomorrow for the best answer

 

No, 3.908 is the largest piston you will find for the ls1. I have seen 3.910, but can't remember where. If we could go 4" we wouldn't have 383's we would all be rocking 402's.

Those compression numbers look low all around. When you did the leak down did you set each cylinder to tdc?

 

Do you know where those 3.908s were? I did it at top dead center, it was done right. That was at 7200 ft, but elevation will not affect it that bad.

 

you know you CAN order custom pistons

 

Arent those really expensive??

 

Well I dont know for sure, but ive heard that you can use a 5.3 iron block with your stroker internals. That would be something i would look in to.

 

Mahle powerpack I'd just search for some vendors. I think they might have made the 3.910's also, but I can't seem to find them anymore. They might be discontinued. I run the 3.903's, but if you plan on huge forced induction or nitrous numbers I'd probably use a wiseco, etc

 

I just want to restore my compression, i didnt think just doing a slight hone and slapping new rings, using my 3.905 pistons i already have would work?? so i was just gonna get a slightly bigger piston

 

It's hard to say. Did the engine ever run well? The problem is will it clean up with only 0.003" oversized pistons or not as strokers can be hard on cylinder walls even set up right. Hard to tell until it's in the hone tank. If you do find a 3.910" 383 piston make sure they hone with a torque plate and check the bore for size as it's honed (in multiple spots)

You might need a block or you might not. Nobody can say for sure untill things are measured. You could use a 5.3 block as the others have said as it might be cheaper then a ls1 and reuse all your old stuff with new rings.

 

The thing has used oil ever since it was built. But it is getting worst. I thought a 5.3 was a 346 with a smaller bore and same crank to get a 327? Or is it just a destroked 346?

 

Only dfference is bore. It can be opened up to 5.7 size though, but would require a bore then hone. Using most of the old parts will save some money.

What brand pistons are in the engine now? It's your call. My car does use some oil when beat on hard, but just tooling around it doesn't seem to use much at all. It made the number in my sig like this though. Lots of stroke on a short sleave block tends to make the piston rock at BDC as the skirts are coming out of the bottom of the bore. Pistons are short also with the oil control ring in the pin boss.

 

The ls1 and 5.3 are very similar in size. Ive heard that the 5.3 can be bored and stroked as much as an ls1. See thread below.

https://ls1tech.com/forums/generatio...-5-3-bore.html

 

take it apart and have it checked by a local machine shop. if the bores is the problem and a simple hone job/new rings can't fix it find another 5.7 aluminum block and just hone it to fit.

 

It has really short mahle pistons in it, it was a callies compstar package with the powerpack mahle pistons and rings. It uses some oil just cruising around but when i really get on it it drinks it, i raced a yota sc truck 5 times in 45 minutes and it used a full quart during that time. The leak down test showed that 5,7 are the ones leaking they are the only ones with oil on the spark plugs. The rest of the cylinders are just weak on compression. Is there any years of ls1s that i should not get?? Thanks for all the help guys

 

I heard the 98 fbody ls1 has smaller sleeves than the rest. Im not 100% sure.

 

Everyone seems to think the later 01' and up blocks can go a full .010" over (I'd still use a .012" over piston if you could find it off the shelf). Basically I'd check the block and if it's in decent shape hone and rings (I doubt it's in going to look that good though. Otherwise just get a used block and do some machine work on it with your old parts. Remember a 5.3 aluminum block (if you stumble on one for cheap) can be bored to 5.7 also.

 

So a 5.3 aluminum block can handle the 3.905 pistons? I researched the blocks a little bit, i think it will be around 500 so that isnt to bad