Head and valve to piston clearances? What's good?

powerfeind

i didn't know that there was a difference between head gaskets at all!

otherwise i may be of some use to you. the minimum clearance between head and piston is .040" or 1mm. mine is .046" (1.15mm) standard which is top stuff!

the piston to valve minimum is 1mm but on a big valve engine i would go for 1.5mm inlet and about 1.8 exhaust.

you will find that none of this matters however because the '01' and the '53' proved to have over 5mm in both sets of pockets. way more than enough! that means that the '55' will be the same for certain. but that's only certain in MY engine and not yours!

however by getting the timing a tooth out i somehow had valve bounce twice!?!? because i had the valve seats 'kissed' the valves had sunk .75mm into the head and the spring tension is some .75mm less or as lineweaver told me: about 13 lbs pressure. my dealer says the valve bounce is the valve timing being wrong but i've never heard of anything like it before! sounds crazy!!!!!

so i have had some shims made up which i collected this morning and we'll see if that makes a difference this sunday. i'll be putting one shim under each valve spring (metal) seat.

i cannot see how the other two cams will come a lot closer.

Taffy

Anyone knows what are the stock: valve to piston and cylinder head to piston clearances? 550 '07 engine.

very big. 3+mm

regards

Taffy

I personally prefer somewhat larger clearance to the exhaust valves, like minimum 2,5mm. With a missed gear and maybe not so high spring pressures, it´s really easy for the piston to catch up with the exhaust valves and pay them a visit. With rocker arms some attention may also be spent on the radial clearance in deeper pockets as well (around 1,5mm and above is usually ok).

Thanks for the response.