11 replies to this topic

[Apdiliars250]

I have measured my 1380 block and its too worn to use ideally.
So my question is what would the best size to go for my turbo build? I have a original 1275 block to use and it looks like it has never had a skim.
Would it be worth using the pistons med sell for forced induction or just cast omegas they sell?

Thanks

Edited by Apdiliars250, 05 December 2022 - 05:21 PM.

[nicklouse]

Talk to MED about resleeving it back to 1275. That would be the best option rather than using a new(old) block.

[Apdiliars250]

Talk to MED about resleeving it back to 1275. That would be the best option rather than using a new(old) block.

I have just seen they do sleeving for 1380s

[nicklouse]

 

Talk to MED about resleeving it back to 1275. That would be the best option rather than using a new(old) block.

I have just seen they do sleeving for 1380s

 

Yep. Will be better suited for the application.

[Java_Green]

With the sleeves, you come to the same question as I am looking for an answer to. What is a suitable choice of pistons with forced induction, "factory" deck height and preferably STD dimension (70.60mm)?

[mini13]

I think 1380s can be be an issue to Sleeve, it may not be possible if they haven't been offset Bored.

Best thing would be get it measured properly if you arn't able to do it, if the bores are round and straight it may be best to stay at 1380. Despite what people will say Ive not had issues running 1380 turbo's, I'm rebuilding my 1380 currently that has about 15k miles on it ( to swap to a K head) and I was not able to measure any bore wear.

 

 

In terms of clearance the normal way is to get the block bored & honed to the pistons to get the correct clearance, although modern pistons are normally pretty good dimensionally, so swapping in another set should not be a problem.

Do you have the pistons from it? they may be usable for a turbo build, I have used dished out cast pistons in the past.

[Apdiliars250]

I have had it measured properly by a engine building company. They said it is too worn I can't remember how much but.Also they said it has not been offset bored. I would of thought it would of been because the engine was done by minisport. I bought cast omegas for this engine because its on the final bore size.

I have a 1275 block what needs a re bore so it's probably better to use that









I think 1380s can be be an issue to Sleeve, it may not be possible if they haven't been offset Bored.

Best thing would be get it measured properly if you arn't able to do it, if the bores are round and straight it may be best to stay at 1380. Despite what people will say Ive not had issues running 1380 turbo's, I'm rebuilding my 1380 currently that has about 15k miles on it ( to swap to a K head) and I was not able to measure any bore wear.


In terms of clearance the normal way is to get the block bored & honed to the pistons to get the correct clearance, although modern pistons are normally pretty good dimensionally, so swapping in another set should not be a problem.

Do you have the pistons from it? they may be usable for a turbo build, I have used dished out cast pistons in the past.

Edited by Apdiliars250, 06 December 2022 - 01:16 PM.

[mini13]

that's not great news.
 

thinking about it the block might still be sleevable, but you ma not be able to bore it as much, sleeved blocks normally only go to +40 IIRC, so maybe you could only do +20 on a non offset sleeved block, thats really a question for someone that bores a lot of blocks though.

[Steve220]

Whichever block you use, I would go for the smallest bore you can get away with. MED/Omega sell most of their start bore size pistons as +0.20 (1293cc). I'm using their cast 10cc dish pistons in my turbo build at around 180bhp. You only need forged if you're looking to break 200bhp or rev it to the moon (which you won't as a boosted engine).

 

https://www.med-engi...ast-pistons-020

[Apdiliars250]

Med say there sleeves can be bored +60 not sure how much offset bore or not would affect the bore sizes. I will have to ask them.
I might get my worn 1275 block checked and go to the next over size for that because it would work out cheaper. Then look in to sleeving the 1380 later on.
Piston wise I might go for the med forced induction ones. They are probably a bit over kill for what power I'm going to MAKE. shame they don't do them in a smaller dish size like 15cc.

[mini13]

Yeah that sounds like a plan, 15cc turbo pistons used to be available, but they have dried up in recent years, presumably form people assuming they need a mega low compression ratio to run boost, which really isnt the case especially with modern ignition systems.

getting 10cc cast pistons dished out would be a viable option, and should be a fair bit cheaper than forged ones.

[Steve220]

I've asked MED on numerous occasions to make a 10, 12 and 15cc dish option on their forged pistons, but they're just not interested. Someone there Still believes that having an almost 7:1 CR is key for boosted engines unless you deck the block by almost 40thou to bring the CR back up - then you need to start shimming rocker posts.