HG and cyclinder bore question

[trufanatic]

I am purchasing my build parts, before i make a F-up, i need the following two questions answered.

1. Cometic MLS gasket or hks 1.4mm gasket------hp goal is around 600,which is better

2. whats the stock pistons bore size

3. whats the skinny on King's performance rod and main bearings.

Lol, i know i only said 2.

 

[IJ.]

1) Cometic can get away with a rougher surface finish.

2) 83mm/3.267"

3) My shop showed me some failed Aluminium Kings bearings that have turned me off using any of their products fullstop.

 

[trufanatic]

1) Cometic can get away with a rougher surface finish.

2) 83mm/3.267"

3) My shop showed me some failed Aluminium Kings bearings that have turned me off using any of their products fullstop.

thanks

 

[Nick M]

The piston diameter and the cylinder bore size are not the same thing.

 

[trufanatic]

The piston diameter and the cylinder bore size are not the same thing.

i know, stock piston size is 83-83.5mm. correct me if im wrong.

 

[arz]

Stock piston is designed for a 83mm bore. 83.5mm is considered .020 inches "over"

.020 inches is actually .508 mm but its kinda hard to measure .008 on a piston skirt. My JE forged pistons were as much as .006 inches different when measured at the bottom of the skirt vs. 1 inch down from the top of the piston (which is generally considered the proper location to measure the diameter of a piston).

Most machine shops wont even start to machine until they have all the pistons in hand.

 

[Bishop92t]

I would stay away from King bearings. I've actually had good luck with the stock bearings if properly installed and machined. Couple of friends have had good luck with Clevite as well.

 

[brad92t]

yay i love resurecting threads for fun.

anyway, i am trying to understand what i am about to get into.. looking at cometic MHGs i see stock 83mm and then oversized 84 and 86mm bores...

i want to bore only .5mm over (.020") but can i do this with these choices of gasket bore sizes? i guess i would just step to the 84mm gasket with an 83.5mm bore.. or do i have to bore 1mm (.040") ??

thanks

 

[jdub]

yay i love resurecting threads for fun.

anyway, i am trying to understand what i am about to get into.. looking at cometic MHGs i see stock 83mm and then oversized 84 and 86mm bores...

i want to bore only .5mm over (.020") but can i do this with these choices of gasket bore sizes? i guess i would just step to the 84mm gasket with an 83.5mm bore.. or do i have to bore 1mm (.040") ??

thanks

Cometic will custom make a gasket...add together the total material removed from both the block and head, add to 1.0mm and you've got the thickness. Specify a 83.5mm dia bore and you're good to go

 

[brad92t]

Cometic will custom make a gasket...add together the total material removed from both the block and head, add to 1.0mm and you've got the thickness. Specify a 83.5mm dia bore and you're good to go

oh i was just going from the sizes listed as available on HPF and 935 websites.. i guess i can just call wherever i decide to order from and tell them what i want? or do i have to go to cometic direct? either way they are made to order and i have to wait i guess...

thanks

 

[jdub]

oh i was just going from the sizes listed as available on HPF and 935 websites.. i guess i can just call wherever i decide to order from and tell them what i want? or do i have to go to cometic direct? either way they are made to order and i have to wait i guess...

thanks

Those are the std sizes...check out this link:
http://www.cometic.com/catalogs/AutoCat04.pdf

Page 2 is the custom order form...took mine about a week :icon_bigg
I had the machine shop order it..I knew the guy and I got the "dealer" cost.