970s piston height

[ricardo]

Gray, I don't know if this is just semantics, but if you have rockers 1 and 2 rocking, you're not on the firing stroke on no. 1. Instead you're firing on the 4th. That means you are 180 out. Does the engine backfire through the carbs?

Maybe this is just semantics... when you point the rotor to no. 1, you must have both rockers loose, ie, you can swing them with your hands.

[Spider]

I'm sure you'll get it running, that's only a matter of time (and fiddling!) really.

The engine has new pistons and rings

Ah, in that case, don't get too upset over the compression pressures seen, though I would expect to see them a bit higher. Check it again after you start to bed it in.

[Andrew1967]

Gray, I don't know if this is just semantics, but if you have rockers 1 and 2 rocking, you're not on the firing stroke on no. 1. Instead you're firing on the 4th. That means you are 180 out. Does the engine backfire through the carbs?

Maybe this is just semantics... when you point the rotor to no. 1, you must have both rockers loose, ie, you can swing them with your hands.

That is what I was thinking as well Ricardo.

[Gray]

Sorry my poor description !! When I said rocking I was meaning loose i.e. you can wobble them by hand and not as in opening and closing on the cam doh!

[Andrew1967]

Well that's that easy fix out of the window

[CooperTune]

I missed the chance to reply to the piston to deck info. While the thread has moved on I'll go back just for the fun of it. When building a race engine it's nice to have the crank stroke checked by someone with the ability to do so. They are not always right. Once you have that info you can find TDC #1 and lock the crank. Using the lightly polished piston pin I like to place each piston on the same rod and check all in the #1 bore using a strip of brass shim stock around the crown to stop piston flop. This gives me a idea if the piston compression distance is the same for each piston. Next its each rod checked using one piston all in the same bore. Now we know the center to center length for each rod. Now we can match pistons and rods to get same length. Rods can be adjusted for length by careful reconditioning if required. Now you take one piston/rod assembly and check it in each cyl. Looking for taper in the block. With careful set up you can cut a little more off one end than the other. These engines seem to respond to compression. I measure twice and cut once as they say. Deck of .005 to zero is fine with me. I like to put the combustion chamber in the head. Steve (CTR)