Mazda Motorsport SUB question
Thread Starter
Joined: Apr 2014
Posts: 18,643
Total Cats: 1,870
From: Beaverton, USA
Yeah, if I needed to I could run them. But I got half and half. In the same labeled bag. And the bag I got from a distributor had the same issues. So something weird is going on. We'll see what they can ship me.
Please forgive my really noob question. I read something on another forum which confused me (completely different car so not sure if applicable).
Is there such thing as lash changing after torquing a head down?
Is there such thing as lash changing after torquing a head down?
Thread Starter
Joined: Apr 2014
Posts: 18,643
Total Cats: 1,870
From: Beaverton, USA
I've heard different answers to that question. Both from people I trust know what they are doing. I'm going to measure mine in the next few weeks and see if anything changed. I forgot to measure after I installed the head.
I just finished my head and put it back on the block yesterday. I'll recheck valve lash this weekend cause this was asked in a different thread.
If I remember correctly I think the head I did on the bench openned up around 0.5 to 1.5 thou on the most outward lifters. I'll guess it would vary per head as well depending on how straight it is.
The last rebuild I measured all lifters with the head bolted down to the block on a used but good gasket. I targeted 8-10 thou on intakes and 10-12 thou on exhaust but ended up slightly looser on a few. I'm not sure if the feeler guages I used weren't clean or the seats had oil on them but some of my exhausts measured up to 14 thou.
I think the inacuracies in measuring and steps in shim sizing means the install error is more than an untorqued head anyway. It all depends on how fussy you are and how long you want to spend tweaking shims.
btw order on the tighter spec rather than looser. I found most of my tolerances were more open than my calcs. It is better to be too large rather than too small as it is easier to sand them down to size.
I use 400 or 800 grit wet and dry stuck to a sheet of glass with a bit of oil. It only takes a short time to drop a thou or two. Max I'd take it is around 4 thou otherwise you can start tapering the shim. Just make sure you rotate the shim as you sand.
I just checked my head after installing. New gasket and torqued to nominal torque value. Clearance matched the values I'd written down using the same feeler gauges (.001" increments) as go/no-go.
If there's a difference it's in the "feel" so maybe a couple tenths.
If there's a difference it's in the "feel" so maybe a couple tenths.
What ended up happening with the lash caps you were going to use? Did you get some replacements for the wrong sized caps? If so from which distributor?






