Its as Danny says, my block has been decked to accommodate a 1.8mm HG with no change to the compression ratio. I would re deck the block from 1.8mm to 2.0mm. Sadly I can't go the other way so a 1.2mm or 1.5mm are no use.
Arias Pistons - Bore size
- Thread starter campbellju
- Start date
Found on the SR20 forum, might be nonsense?:
The GTiR blocks were designed to be used in BTCC and JTCC where they bored them to 88mm and used a 82mm crank which was 1995cc's.
I know the GTiR blocks were cast with the liners thick enough to reliably do a 88mm bore. I would imagine the std blocks all use the same liners and 88mm would be ok as well.
I have done 2 87.5mm turbo builds before. both about 475whp
The GTiR blocks were designed to be used in BTCC and JTCC where they bored them to 88mm and used a 82mm crank which was 1995cc's.
I know the GTiR blocks were cast with the liners thick enough to reliably do a 88mm bore. I would imagine the std blocks all use the same liners and 88mm would be ok as well.
I have done 2 87.5mm turbo builds before. both about 475whp
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Active Member
I don't think it's nonsense , the 54c block was indeed the above and they used to rev it to 8500 rpm on a gtir head too.
Thanks Danny. I'll see where I'm up to with my engine builder and have a good think about what to do.
Update on this ridiculously slow build. The engine builder sourced some upsized rings as mentiond. He trialled them into the bore and you could see they overlapped and would need to be ground down. He said he could do this and had done it before but not on a highly tuned engine so couldn't guarantee anything. I just said we'll have to hold until I can find out more. :x
Unless someone tells me otherwise, it seems you can get away with this strategy but at best you lose HP as the rings are pushing out more and at worst you lose compression or they break.
So back to the drawing board. I've looked into Tomei 87.5mm pistons with the existing block but even without a new block it will cost significantly more than just starting again.
So current options are get another block and new pistons/rings, get a cheap 2nd hand engine or just flick a match in the tank and walk away Hollywood style :twisted:
Unless someone tells me otherwise, it seems you can get away with this strategy but at best you lose HP as the rings are pushing out more and at worst you lose compression or they break.
So back to the drawing board. I've looked into Tomei 87.5mm pistons with the existing block but even without a new block it will cost significantly more than just starting again.
So current options are get another block and new pistons/rings, get a cheap 2nd hand engine or just flick a match in the tank and walk away Hollywood style :twisted:
This.
Seriously though; at this stage, a cheap running engine might be a better starting point. You know it's working before you do anything to it... but it may not take all your ancillary parts; you can always pull it apart and refurbish it. Or you can use it for a while and put some work into it later.
Any chance of on-selling the block and/or pistons you've got to recoup some of the costs?
If I was unscrupulous I could recoup some costs but I wouldn't want to give someone else the hassle.
Blooming heck Stu, that's a very kind offer! I've just got in from work and need to sort things out. Can I give you a call over the weekend if convenient?
Pretty inconvenient then :lol::lol:
We can talk after the 10th once you're back. 8)
We can talk after the 10th once you're back. 8)
I've got my 87.5mm supertech pistons delivered from the states. The alloy is similar to 4032 so I expect I can run sightly tighter tolerances than with the Arias pistons.
The spec sheet with the pistons says a minimum piston to wall clearance of 0.0027" but this sounds tight?
I think my HKS pistons used 0.003" or 0.0035". They worked fine. I understand the Supertech pistons use the same alloy as that used in the Mahle pistons so they might give a reasonable guide. Anyone any feedback on high silicone pistons cylinder wall clearance?
The spec sheet with the pistons says a minimum piston to wall clearance of 0.0027" but this sounds tight?
I think my HKS pistons used 0.003" or 0.0035". They worked fine. I understand the Supertech pistons use the same alloy as that used in the Mahle pistons so they might give a reasonable guide. Anyone any feedback on high silicone pistons cylinder wall clearance?