i have a stock a12 in my 120y
i plane to do the following:
put a 32/36 webber or 180 holley on it
get the cam regrinded
extactors
50mm pipe (about 2 inch)

now i have worked out that if i shave 1 mm of the deck i will get a comp ratio of 10:1 (thanks to http://www.johnmaherracing.co.uk/enginecalc.htm)

now i don't wont to pull my motor apart
so if i get someone to shave 1mm of my head, will that bump the comp ratio up to 10:1?

thanks for all the help
dave

ps: is the stock comp ratio 9:1 and is the deck heght 0.15
becase if its not it puts all me c

i recently shaved my head, and it lowered my compression ratio .... uh, wait a minute, i thought you were talking about haircuts

seriously, haven't you answered your own question?

yea that helps

Quote:

Now I may be underestimating your knowledge here, but you do know that you will have to pull the engine out of the car and take the head off to perform this.

i was thinking of just taking the head off and leaving the bottom end in there

but i might have to take the motor out to get the cam in/out

i'll c what happins

i had a look at the car
i think i can take the head off and take the cam out with the bottom end of the motor still in the car

so...

is the stock comp ratio 9:1?

is the deck heght 0.15?

and if i shave 1 mm of head will it have the same affect as shaving 1mm off the deck

The maximum you can take off a A15 head is 120 thou (3mm), thats with a cam regrind and nothing off the block. But then again a different grind may not allow that. Our reground CAMs are still adding lift however.

rob.

If you can figure out how to replace the cam while the engine is still in the car, then please let us all know how it's done.

The problem that others have is with the tappets [cam followers] They need to be lifted clear of the cam to allow it to be removed or installed, & that's the hard part. It's also a good idea to have them radius ground, or replaced with new, before the new cam goes in, so they need to come out anyway.

Most people just pull the engine & mount it on an engine stand. Removing the head will be easier there & then you rotate the engine upside down to do the cam.
Removing small Datsun engines is surprisingly easy & it makes the rest of the job a breeze.

To deck the block will mean a total teardown of the engine & you need to be carefull that the pistons don't protrude & hit the head in the finished product. Head shaving is the lesser of those two evils.

Good luck with the job.

ok thanks

well when i get the cam regrinded they will makeup some lifters for me
so i'll just say to them that the head will b sitting 1 mm closer, so i'll get them to make them a littel bit shorter

will that work?

and will taking 1 mm of the head b the same as taking 1 mm of the deck?

thanks
dave

I once coverered the lifters in thick grease & stuck them up so the cam could come out while the engine was still in the car, I then removed them got them ground & stuck them up with grease again so the new cam could be installed, it did work but i would pull the engine next time as the sump front cover radiator, grill, rockers & pushrods had to come off anyway.
Trev
Aus