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Thread: The rebuild

  1. #1
    Junior Member
    3rd Gen
    Join Date
    Jun 2016

    The rebuild

    ok so you guys have seen a fair bit of me lately, but due to the rebuild I have had a lot of questions

    one particular one which is stopping me from putting it back together is a piston questions.

    Now from what i see i have two options.. i have scrapped the idea of boring to 87.5 (yes pistons are easy to find, but no i don't wanna run the risk it it failing)

    i havnt scrapped the idea of boring all together though. i have been going through the helms manual and read countless threads on sites all over the place

    situation is, I have the rebuild kit and that rebuild kit has pistons and rings (NPR)
    i have had the cylinders honed a little and they are sitting at around 87.06ish mm

    so first choice is, do one final measurement of the cylinders and it there all still under service limit, then ill start putting it back together with the NPR pistons and rings

    second choice is- I have found OEM 87.25mm type s pistons, i have shops around that can do the cylinder work and hopefully they will be able to listen to my suggestions (as pointed out in the helms) for the very slight bore work

    so should i throw it back together now with the pistons i have or buy the OEM oversized pistons and find some rings and then throw it back together (after some cylinder work)

    i have been racking my brain for weeks and this FRM liner is really making things interesting

  2. #2
    Regular Member tassie_bb1's Avatar
    4th Gen
    Join Date
    Dec 2013
    Yes, the FRM makes it interesting. IMO go with the type S pistons, 87.25 is only 0.25 over stock which should be fine and gives you a little boost to your compression. Anything more than a 87.50 bore and you'd need to start looking at sleeving though.

    I've been looking into some of these off the shelf rebuild kits myself lately and have heard varying reports of their reliability, I wouldn't chance it with their pistons.
    Symmons Plains - 1:12.280

  3. #3
    4th Gen
    Join Date
    Dec 2008
    I believe that NPR supply OEM parts for a a lot of cars. Ive seen mostly a lot of good reports on them and a few bad. basically do your research and assemble the motor correctly and you shouldnt have many issues. What sort of power figures are you going for? what other parts are you using? any aftermarket gear?

    other things to consider, especially if you are wanting to go down the type s route, Are your block and head flat? are the bores ok? (if any of these is true, I would advise to check valve to piston clearances with some clay or whatever it is they use haha)

    To determine what size pistons you need, you will need to check the sizes of the bores. consult helms to see what the tolerances are. Send the if its within the tolerances, dont worry about boring. just remember that if you want to do a relatively stock rebuild in the future, you will want to try not bore it as much as possible otherwise as stated above, youll need to sleeve it. in saying that, if its too close to the tolerance, bore it and get matching pistons so you can get some longevity. I would highly suggest honing the bores as well.

    Is this the first time the motor has been rebuilt? Studs can only be used twice. So if its the first time, it will be the last time you use the studs again. If you choose to go with ARP studs, You will most likely need to have the crank tunnels bored to allow the studs to be installed without crushing the caps around the crank and seizing the whole rotating assembley.

    FRM liners are a pain in the ass but as long as they are within service limit and you have them honed, you will be fine with using the NPR's (providing the motor is assembled correctly)

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