"Boring" Question

T

TStiles

Senior Member
I'm in the midst of a conversation with a guy regarding cylinder bore on an 8BA rebuild using stock crank, cam, etc. The plan is to go .020 over original (the block has never been bored).

He states that it would be advisable to bore an extra 1 thousandth because the clearance might save the day for pistons in the case of an overheat situation.

Wisdom of the Barners would be appreciated on this.

Thanks,
Tim
 
Boil the block to clean out sand and rust and other crud. Use rebuilt water pumps, clean out the radiator so you don't overheat in the first place.
 
Yup, Ken, me too... Read manufacturers instructions, they'll have info that will work for their product...
Karl
 
id go .060 or get avalible off shelf piston- boring is done smaller than size then honed to final size according to piston measerments- you must have pistons before proper boring to instructions
 
Frank is right-measerment of bores should shoud be done first - to see what they are - they might not clean up at .020
 
Ring gap will not make a significant difference. We discussed that last month. I personally would not want the piston any looser in the bore than it has to be. I have read about people over heating but I have not seen many post about siezing the motor due to it. I am sure by 10k or so you will have worn another thou in the bore and you will be where you want to be.
 
That's why I use Egge pistond and fit them tight. Besides a bigger engine, with more compression is more fun to drive.
 
I have been boring blocks here in the shop for years as mentioned earlier clean up is chancy at .020.

Instead of using cast pistons, call some one like Arias and get some of their low expansion alloy forged pistons. From our experience with many sets in both tour cars and vintage racing cars they are the only way to go and really don't cost much more. Their quality of is unbelievable.

I just took a set out of a racing engine that had seen over 3000 miles of hard use on the road and the track and they look like they are brand new. They don't even have any scuff marks on them.

They would work perfect in a flathead that might turn into an occasional tea kettle as the will not expand as much as cast pistons.
 
$525 a set, not much more than Egge?? and what clearance do you start with? These are exelent racing pistons, but a little over kill for a grocery getter.
 
I just purchased cast .020 pistons from Patricks. I was informed that at that relatively small overbore higher end pistons where not available.
 
I would do mucho measuring and checking before determining a .020 bore increase would be acceptable for clean-up of worn bores. While I do not agree with the "automatic" +.125 concept I do believe in being "safe" with an overbore size decision. I think .020 is risky.
 
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