1quickTransAm

iTrader: (4)

Can some of you guys double check my decision on push rod length? I am building my first engine (383 LT1).

I disassembled a lifter and stuffed the internals to make is "solid" at max length and used an adjustable length push-rod checker. I then twisted the poly lock to finger fight to set zero lash. With the checker set to 7.10" here were the travel patterns on the #2 and #8 intake and exhaust valves.







This length (7.10") seemed like the most centered on all the valves. So since this was with a "solid" lifter, I know I need to add my pre-load measurement to that. What should that be? Is the rotation of the poly lock past zero lash what determines the lifter pre-load or are those two separate things?

I plan on turning the poly locks to 3/4 turn past zero lash. Threads are 7/16-20 so that means that 3/4 past zero lash would lower the rocker 0.0375". Does that mean by lifter pre-load would be ~.0375" and therefore I need a 7.15" push rod? (7.1375" rounded up to common 7.15" length).

hrcslam

Yes on all accounts.

That is a great location on the valve tip. But have you tried going .050" longer for a smaller sweep area closer to the exhaust? You want the smallest sweep you can get, then the most centered you can get. If you can get both, great. But that typically isn't the case. You want small sweep more than you want center sweep. Of course this is within reason. If you are sweeping small, but close to the edge it's not good. Just remember, the more sweep it gets (regardless of location) the more side loading it will put on the valves, and the sooner your guides will wear out.

1quickTransAm

iTrader: (4)

Thanks for the help and guidance. I was only really focusing on being centered but luckily I took a few pictures with other lengths. The sweep doesn't seem to be all that different. 7.15" might have had a tiny bit less sweep but certainly isn't as centered. Here are how some lengths looked (again, this is the solid lifter length w/o preload).

7.05" on #2 intake:




7.10" on #2 intake:




7.15" on #2 intake:

1quickTransAm

iTrader: (4)

Looking at those images do you think I should go .05" longer (so the 7.15" image plus preload so 7.20" Rod)?

BALLSS

7.200 is stock length. most often with a decked block and heads you wind u with a shorter PR. narrow and centered pattern is what you want

another way of checking (and easier) is to get one of these
http://www.summitracing.com/parts/pr...FU6UfgodSSsALg

you can use a feeler gauge to determine what +/- length you need from 7.200. Or Set the adjustable PR length check tool so it meets the Proform tool while it rests on valve tip. measure the adj PR tool length and get that PR. I pre-measure my adjustable PR rod to 7.150 then 7.100 and see which length is best as aftermarket PR's come in .050 length increments.

1quickTransAm

iTrader: (4)

Huh... I've never seen someone use that tool before. I feel like the patterns on the top of my valves looks pretty good, but I'll keep that tool in mind for next time.

BALLSS

I did it with a PR length checker just like standard method and then checked that against this tool. spot on.

your 7.100 pattern looks good. what I wound up using on my build, although each one is different so you do need to check PR length

shorter PR moves pattern closer to intake manifold, longer moves it to exhaust manifold side of valve tip

1quickTransAm

iTrader: (4)

I was concerned that maybe the sweep was too long with the 7.10" PR so I'm glad to hear you think it looks good. I'll double check tonight before ordering.

BALLSS

from the pics the 7.150 looks a little to the exhaust side. The 7.100 looks more centered. the 7.050 is to short