Stock bore?

[georgie2577]

First I'd like to say hi to all the DSM'ers on this site. Truly an awesome resource!.. Thanks for all the great information.

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I have a 91 gsx.

Small 16g
Apexi N1 3inch turboback
Joe P MBC
Autometer Boost guage

I was doing pretty good with these mods until my boost spiked to 20 psi and I messed up the engine (detonation). I've been doing alot of research on this site to help me get to where I am right now. I noticed the white smoke out of the dipstick and oil cap so I researched it on this site and found to check the PCV valve and it turned out ok. Next step was to check the compression.

1- 159 psi
2- 159 psi
3- 84 psi
4- 168 psi

It seems to me that I blew the rings on that cyl 3 which is a great reason to pull the head! I would like to know if it would be a bad idea if I stayed with the stock piston and ring size and just had some OEM stuff put back in. I'm only looking to run 12's at the fastest. One of the biggest motivations to staing with the OEM parts is because I'm not financially capable of upgrading to the good stuff and having the engine pulled out. I'm going to be doing the work myself and I'm gonna have to stayed as cheap as possible on this rebuild. :/ Any comments would be appreciated.

Thanks friends.

g30

 

[GTM]

Originally posted by georgie2577

...
Next step was to check the compression. ...
3- 84 psi
...
It seems to me that I blew the rings on that cyl 3 which is a great reason to pull the head! I would like to know if it would be a bad idea if I stayed with the stock piston and ring size
...

You obviously are going to take a close look at that #3 cylinder before buying any parts. If you don't have a bore gage you can use the pistons and feeler gages to get some idea where each cylinder is. Use the #3 piston right side up and then upsided down in each cylinder then take the smallest diameter and use that piston to check everything again. This will tell you if you can replace just that #3 piston or the whole set. Don't take your measurments at the very top of the bore but 1/4" down. If you are really on a budget and the bores are good you can get your existing pistons shot peened and / or knurled which will expand the skirt to compensate for wear. You will need to carefully check ring gap and have access to "first rebuild" rings which are only a couple thou. larger rather than a full rebuild at .010" over. This means each ring has to be gapped for each cylinder so you will place a ring in a cylinder press it down with a piston so it's square in the cylinder to take your measurments again at the top and the bottom of each cylr. You then lay these out in size gap from largest to smallest. You then take your cylinder measurments which you took earlier and match each ring from smallest to the largest so you get the best possible combination to keep them all balanced.

Okay?

Cheers,
GTM

 

[georgie2577]

Hey thanks for the information! I've got access to a full machine shop but the only problem is my buddy doesnt speak english. All spanish. sheesh. Translating the tech terms is a nightmare. How do you say bore gauge in spanish? hehh

Fact of business, Its hard to find a good machine shop here in the valley that knows whats goin on.. :/ ohh well..

 

[GTM]

Originally posted by georgie2577

...
I've got access to a full machine shop but the only problem is my buddy doesnt speak english. All spanish. sheesh. Translating the tech terms is a nightmare. How do you say bore gauge in spanish? hehh

Fact of business, Its hard to find a good machine shop here in the valley that knows whats goin on.. :/ ohh well..

Automotive machine shops are not the same as a machine shop. The racers edge will come from a full machine shop that has all the knowledge and tricks of the trade.

Bore gage= picture taken of the tool. However, is he more comfortable with mm or inch calculations for this is not the time to be having trouble with math.

As for finding one, best I can suggest is going around to the different shops and ask who does their work. If there is a local track which is active this time of year you can ask the mechanics who does their machine work.

You can find bore gages, mikes, and verniers on eBay at reasonable prices if you are going to really get involved.

Cheers,
GTM