bearings clearence
#1
bearings clearence
i have this block that was perfectl fine except one rod was slightly bent witha leaky headgasket...got it apart and got the block cleaned up and im looking for another stock rod thats in good shape so i dont need to get all my rods resized...i got the crank and some standard bearings and put tit ogether plasticgauged it and came up with about .34 on most of the mains and i think the stock specks are .020-.030
i know its close but what are you guys opinion? should i have the crank turned then oversize bearings? id rather not the cars just goana be a cam only car with little nitrous, not really a street car but will see some mileage driving to the track and such
i know its close but what are you guys opinion? should i have the crank turned then oversize bearings? id rather not the cars just goana be a cam only car with little nitrous, not really a street car but will see some mileage driving to the track and such
#2
If you are looking to reduce clearances a bit, you can either get another set of .001 over bearings and use half/half to get the clearance you want or you can buy a nice set of coated bearings which tighten up the clearances a few thou.
#3
I t would be fine IMO but you really can't rely on plastigauge......
Like he said you can mix em up and get them right. OR do the coated ones
But if all others are .0030 and one is .0034 I would fix it, but saying its .0034 with plastigauge doesen't say much
Like he said you can mix em up and get them right. OR do the coated ones
But if all others are .0030 and one is .0034 I would fix it, but saying its .0034 with plastigauge doesen't say much
#4
There's a problem if you are getting .0034" clearance - stock these motors run .0012" - .0024" so you have a worn crank. Plastigauge is not the right way to measure clearances.
You need to take your components in to the machine shop and have the measured properly, especially if you are going to race/spray it.
You need to take your components in to the machine shop and have the measured properly, especially if you are going to race/spray it.
#5
whats wrong with plasticgauge???
and the thing is this motor was running pefrectly fine when it came outa a 94z with 170k on it...we pulled it to refresh it and put it back together...i would think with new bearings it woulda tightened it up more...how else could i get it checked thats "mmore reliable"
and the thing is this motor was running pefrectly fine when it came outa a 94z with 170k on it...we pulled it to refresh it and put it back together...i would think with new bearings it woulda tightened it up more...how else could i get it checked thats "mmore reliable"
#7
I read an article in Hot Rod or Car Craft Magazine, where they compared plasti-gauge to a micrometer. Plasti-gauge almost always gave a reading of twice the clearance that was ACTUALLY there.
So divide by 2. It has the opposite side pulled up against the journal.
David
So divide by 2. It has the opposite side pulled up against the journal.
David
Last edited by FASTFATBOY; 04-06-2008 at 06:30 AM.
#10
whoops well the motor in my car now has within spec on plaster gauge it has 35 psi at idle and 80+ at wot its got 15k on it now
it was i think .0022-.0024 on all the rods
think the mains were .0018-0020 and 0024 on #5
if yall are sayin half of this that means the mine were way too tight....
anyways i read some threads about getting undersized or oversized bearings by 0001 and using one half of it to tighten them up some....so would i need -.0001 or + to tighten it up
the crank and rods and mains all came outa the motor fine...im goana get a mic i recheck but if i still need to tighten them up can i just get oversized bearings
it was i think .0022-.0024 on all the rods
think the mains were .0018-0020 and 0024 on #5
if yall are sayin half of this that means the mine were way too tight....
anyways i read some threads about getting undersized or oversized bearings by 0001 and using one half of it to tighten them up some....so would i need -.0001 or + to tighten it up
the crank and rods and mains all came outa the motor fine...im goana get a mic i recheck but if i still need to tighten them up can i just get oversized bearings
Last edited by Daniel6718; 04-07-2008 at 02:22 AM.
#11
It seems odd, but what you want are called undersize bearings, because they are thinner than a standard bearing. If you need to mix bearing sizes, put the more undersized half on the bottom (in the cap). I disagree about Plastigage - it is accurate but not as precise as using instruments. It has an advantage in that you are measuring the clearance of the assembled part. Also, while the ultimate precision is less than using mikes, it is easier to achieve. IOW, mikes are hard to use correctly, Plastigage is easy. Have you calibrated your instruments recently?
Rich
Rich
#12
JUst repeating what I had read. I was mistaken, I am getting old, the clearance was 1/2 of what the Mic said it had.
Here ya go
http://www.carcraft.com/techfaq/116_...ter/index.html
http://www.carcraft.com/techfaq/116_.../photo_04.html
David
Last edited by FASTFATBOY; 04-07-2008 at 06:35 AM.
#13
A problem that I had when building my current motor pertaining to plasti-gage, was the rods twisting when I torqued them down, which seemed to give me a "tighter than actual" measurement. I was using an X bearing, which is .001 OVERsized and gives you an extra thousandth of clearance and was still getting ~.018 on the rods. I finally took the feeler gauges that I had used to check side clearance, put them between the rods to hold them straight, and PRESTO... .0022 rod clearance!
Probably the same problem they are having on that rod journal in the link you supplied.
Probably the same problem they are having on that rod journal in the link you supplied.
#14
A problem that I had when building my current motor pertaining to plasti-gage, was the rods twisting when I torqued them down, which seemed to give me a "tighter than actual" measurement. I was using an X bearing, which is .001 OVERsized and gives you an extra thousandth of clearance and was still getting ~.018 on the rods. I finally took the feeler gauges that I had used to check side clearance, put them between the rods to hold them straight, and PRESTO... .0022 rod clearance!
Probably the same problem they are having on that rod journal in the link you supplied.
Probably the same problem they are having on that rod journal in the link you supplied.