Cylinder Bore Diameter

rickbtbird

Registered User
I have an 89 used block that I picked up for next to nothing. I was going to attempt a rebuild as a learning experience project. The bores measure 3.813" There's doesn't appear to more then .0005 of an inch in taper but I'm doing this with an inside mic.
The book I have is for the 95 which says that the bore diameter should be 3.81. Is it scrap or what?
 
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I have an 89 used block that I picked up for next to nothing. I was going to attempt a rebuild as a learning experience project. The bores measure 3.813" There's doesn't appear to more then .0005 of an inch in taper but I'm doing this with an inside mic.
The book I have is for the 95 which says that the bore diameter should be 3.810. Is it scrap or what?

idk if its scrap for sure but if i wouldnt thing so....get it bored .30 .60 over which is more then .03 over 3.810

also i would think that 3.810 would be good to say because if it was bigger in 94-95 then it wouldnt be a 3.8L lol
 
idk if its scrap for sure but if i wouldnt thing so....get it bored .30 .60 over which is more then .03 over 3.810

also i would think that 3.810 would be good to say because if it was bigger in 94-95 then it wouldnt be a 3.8L lol

Oh I'm aware that boring out the block would be an option, if that's the way you want to go and invest the money in it in that respect. I'd rather investigate a legitimate way from doing that. What other options do I have?
 
Is there still a clean hone(hatch pattern) finish on the bores?

Also check piston tops to see if they are stock or overbored.

If Dave chimes in hes rebuilt enough fo these to give an opinion
 
Just because the cross-hatch is visible, in a high mileage motor, doesn't mean it's serving a function. It's like laminating paper. You can still read it, but you can't touch the paper. Not to mention the purpose of a cross-hatch is to retain oil, but mainly for seating new rings

The bore tapering is a small part of the equation. The cylinders become out of round. You will need to overbore it and get a set of pistons to match the bore.
 
Thats why I mentioned a clean hone..On a supposedly low miliage motor they should be very visible and clean. On a higher miliage motor they generally appear worn and glazed or faded.

Rick you can probably get away with a hone and a rering but personally I would get myself some replacement .20 over ones for prosperity sakes and get a good rebore with torque plates. Be better then new
 
Thats why I mentioned a clean hone..On a supposedly low miliage motor they should be very visible and clean. On a higher miliage motor they generally appear worn and glazed or faded.

Rick you can probably get away with a hone and a rering but personally I would get myself some replacement .20 over ones for prosperity sakes and get a good rebore with torque plates. Be better then new

Don't you mean .020 over. I don't know if I ever heard of .200 over but what do I know anyway.. LOL.
.200 is two hundred thousands or 200/1000
.300 is three hundred thousands or 300/1000
.020 is 20 thousands or 20/1000
.030 is 30 thousands or 30/1000
.003 is three thousands or 3/1000
.002 is two thousands or 2/1000
Anyway the specs in the book say the bore should be at 3.81. I could have sworn that there was a standard in the machining industry. Unless otherwise specified, typically when a value is written without the trailing zero there's a larger tolerance involved. If it were written at 3.810 then the tolerance is suppose to be smaller. I haven't machined anything in 15 years and my old age is catching up with me. Back in the day I could rattle this stuff off like I invented it.
 
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Bore 1 is 3.812 to 3.813 taper and out of round is no more then .001
Bore 2 is 3.812 to 3.813 taper and out of round is no more then .001
Bore 3 is 3.812 to 3.813 taper and out of round is no more then .001
Bore 4 is 3.811 to 3.812 taper and out of round is no more then .001
Bore 5 is 3.811 to 3.812 taper and out of round is no more then .001
Bore 6 is 3.812 to 3.813 taper and out of round is no more then .001

Cross hatch is almost gone on all cylinders
 
ah ha damons secret is out 200 over bore!

did you off set grind your crank 30 k .

go 20 over these sc blocks can really destort ive been able to rering a few but some are so out of round they resemble eggs
 
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