Larry --
I'm not an expert on engine rebuilds, but I have read in books and on
the list that a total variation of less than 10% in cylinder
compression is OK. You've got a variation of 5 lbs either way from
150, which is 3.3% each way or 6.6% total - I think you're OK. You
may also find that the compression evens out a little and maybe even
increases slightly as the rings bed in. Check compression again
after you've driven for a couple thousand miles and see.
150 lbs for a GT6 motor with domed pistons sounds about right, but
200 lbs seems *awfully* high for a street motor. Perhaps it wasn't
working just fine, and that's why it blew up!
Dan
At 7:51 -0700 03/02/02, <lstein6@earthlink.net> wrote:
>hey guys,
> before i blew up my 72 gt6 engine i used to have 200 lbs compression in all
>6 cylinders (really). i don't know how the previous owner got the compression
>so high, but it worked. well that is until it blew up. anyway, now that i
>have the engine rebuilt, with the same high dome pistons (new replacements)
>and a high performace cam etc. i have run the engine a total of 20 minutes on
>the engine stand. yes, i had all the safety gear, radiator etc. hooked up.
>here is my question. i have removed all the plugs and ran a compression test.
>now i have 145 to 155 lbs in each cylinder. they are not all exact as in 150
>for all 6. is 145-155 normal ? okay to have a difference of 10 lbs between
>different cylinders ? the cylinder head is the same one, just completely
>rebuilt with new seats, valves etc. the block is the same one just cleaned,
>honed, machined, the crank is the same one, just polished. are there
>different head gaskets with different thicknesses that can account for the
>previous compression ? the old pistons were the high dome stamped .030, so
>the new ones are the high dome done .040 what do you think ? if i have a
>problem i want to fix it before i put the engine back in the car. or is this
>fine and just move on ahead ?
>thanks for all the great help you guys share !
>larry@ehc.org
--
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Dan Buettner - Des Moines, Iowa - mailto:danb@thelittlemacshop.com
1957 TR3, TS15098L 'O' - with a nice shiny rear axle installed!
Front suspension & steering back together too - now for the brakes.
1977 Spitfire, FM64159U 'O' - in storage.
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