Block Sizes - ZR-1 Net Registry Forums

Bob G · 11-22-2008

Does Anyone Know The Exact Size Of The Main Bearing Bores In The Block For Line Honing ?
Thanks Bob

A26B · 11-22-2008

Bob,
This is the best info I have. It is taken from OEM engine drawings for the 375hp engine. I cannot say if there were revisions later, but you should be able to tell by reassembling the lower crankcase to the cylinder case and measuring the bores. If undamaged journal bores fall in this tolerance range, I would feel comfortable with the dimensions given here.
Jerry

lbszr · 11-23-2008

Quote:

Originally Posted by A26B

Bob,
This is the best info I have. It is taken from OEM engine drawings for the 375hp engine. I cannot say if there were revisions later, but you should be able to tell by reassembling the lower crankcase to the cylinder case and measuring the bores. If undamaged journal bores fall in this tolerance range, I would feel comfortable with the dimensions given here.
Jerry

Mine measured 2.9428 1,2,3,4 and 2.9417 on 5 so my .003 more could be measuring technique or stretch or they didn't hit the mark.

A26B · 11-23-2008

I thought the tolerance in the drawing was pretty generous (0.01mm). Would have thought it would have been tighter than that.

74.56mm = 2.9354"
74.66mm = 2.9394"
0.01mm = 0.0040"

Since you're calling out dimensions in ten-thousandths, I think it's safe to assume your technique it pretty darned good and used something better than dial calipers.

How did your bearing wear pattern look?

lbszr · 11-23-2008

Quote:

Originally Posted by A26B

I thought the tolerance in the drawing was pretty generous (0.01mm). Would have thought it would have been tighter than that.

74.56mm = 2.9354"
74.66mm = 2.9394"
0.01mm = 0.0040"

Since you're calling out dimensions in ten-thousandths, I think it's safe to assume your technique it pretty darned good and used something better than dial calipers.

How did your bearing wear pattern look?

If I remember right, #1 showed the most wear on the top half which gm manual said that was normal and all the others showed signs on the lower half but all were minimal and plastigaged good within limits, the other halfs basically showed no wear.

I used a inside micrometer but didn't trust it so then measured the inside micrometer with outside micrometer, don't have a bore micrometer.

11-22-2008	#2
A26B Join Date: Dec 2003 Location: Arcadia,OK Posts: 3,394	Re: Block Sizes Bob, This is the best info I have. It is taken from OEM engine drawings for the 375hp engine. I cannot say if there were revisions later, but you should be able to tell by reassembling the lower crankcase to the cylinder case and measuring the bores. If undamaged journal bores fall in this tolerance range, I would feel comfortable with the dimensions given here. Jerry __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1*, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed.

11-23-2008	#4
A26B Join Date: Dec 2003 Location: Arcadia,OK Posts: 3,394	Re: Block Sizes I thought the tolerance in the drawing was pretty generous (0.01mm). Would have thought it would have been tighter than that. 74.56mm = 2.9354" 74.66mm = 2.9394" 0.01mm = 0.0040" Since you're calling out dimensions in ten-thousandths, I think it's safe to assume your technique it pretty darned good and used something better than dial calipers. How did your bearing wear pattern look? __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed. Last edited by A26B; 11-23-2008 at 01:03 PM.*

11-22-2008	#1
Bob G Join Date: Dec 2005 Location: Huntley IL Posts: 170	Block Sizes Does Anyone Know The Exact Size Of The Main Bearing Bores In The Block For Line Honing ? Thanks Bob