Does this contact pattern look right?
http://memimage.cardomain.net/member_images/9/web/2373000-2373999/2373747_24_full.jpg

I'm also curious if having a small base circle cam impacts how I set the lash?

I'm asking all the questions because Edelbrock claims that I should be running stock pushrods + .1". The above pictures reflect just over an 8.0" pushrod length :confused:

Details:
383
Edelbrock RPM heads
Harland Sharp Rockers (1.5)
Comp Cams XE-274H - SMALL BASE CIRCLE
Block - decked true (I can still read the suffix code stamp).
GMPP head gasket (.028" thick compressed)

EDIT: I used a solid lifter for setting the lash...

Maybe a tiny bit long. A tiny bit shorter would bring the mark into the center bit more, I believe. You may be fine though. You can pick up an adjustable pushrod checker at Jegs or Summit for CHEAP.
I believe a cam lobe spec (lets use 228/235dur .530 lift as an example) will be the same for a small base circle, as it would be for a normal diameter cam.... it s the core thats smaller. So I think the lash procedure will be the same. Somebody please correct me if I'm wrong.

Agreed. I can see what you are saying.

Does the contact pattern look wide enough? I expected more travel - but perhaps that is a function of max lift?

I'm stil a little puzzled why the pushrod length is about .2" longer than stock and not .1" like Edelbrock recommended. Perhaps this is a function of the Harland Sharp rocker arms?

-Eric

You want the roller centered at max lift for the least amount of lateral pressure under maximum load..... it the travel is at absolute center... it will increase lateral load at max lift, and be centered at about half-loading.

Although the mark on the bottom appears to be rotated slightly.... check your guide-plates. You may have to go to a split-plate to take the rotation out of it. Assuming there is clearance to the intake runner, of course. Very minor issue.

What you have looks pretty doggone good to me! ;)

I re edited my post after you posted so you can go back and read if you want. Anyway, your pretty close as it is. The valve lash procedure should be the same with your cam.

You want the roller centered at max lift for the least amount of lateral pressure under maximum load..... it the travel is at absolute center... it will increase lateral load at max lift, and be centered at about half-loading.

OK, I think I understand. I want the rocker arm roller tip centered on the valve stem when I am at max lift. Simply having the travel path centered may actually NOT place the tip at center on the valve stem at max lift - which increases the pressure under max load - which is not as good. Right?


Although the mark on the bottom appears to be rotated slightly.... check your guide-plates. You may have to go to a split-plate to take the rotation out of it. Assuming there is clearance to the intake runner, of course. Very minor issue.

Actually, I bumped the guideplate towards the exhaust side to get more clearance on the intake pushrod - it was pretty darn close to the head! I'll play with it some more to try and get it straight(er). Good eye.


I believe a cam lobe spec (lets use 228/235dur .530 lift as an example) will be the same for a small base circle, as it would be for a normal diameter cam.... it s the core thats smaller. So I think the lash procedure will be the same. Somebody please correct me if I'm wrong.

I wasn't sure since the lash is set when the lifter is on the base circle of the cam (isn't it?) With the smaller base circle, I didn't know if that changed anything. That additional .1" length has me a little concerned...

Thanks for the comments so far!
-Eric

Yup, side loading is what chews-up valve guides quick. You can get pretty close to the intake runner... I have actually had a few that showed very slight wear marks where they brushed against the runner with no issues. Leave a couple thousandts and you should be good.
It's kind of a balancing act...

There are other professionals that are more qualified to comment... but you look OK as far as pushrod length to me.

Lash is the same....

Agreed. I can see what you are saying.

Does the contact pattern look wide enough? I expected more travel - but perhaps that is a function of max lift?

I'm stil a little puzzled why the pushrod length is about .2" longer than stock and not .1" like Edelbrock recommended. Perhaps this is a function of the Harland Sharp rocker arms?

-Eric

Big mouse, I'm getting ready to do the same on my 383 w/ edelbrock rpm heads. I'm going to use a set of checking springs. I wanted to use a pair of solid lifters, but I noticed that all the ones I looked at, the plunger in the solid lifter sat about .130 below the rim of the lifter from what the hydralics sat at.

Here is some more info:

http://www.nastyz28.com/forum/showthread.php?t=85727

http://www.nastyz28.com/forum/showthread.php?t=84411

Thanks Rustover - I appreciate the heads-up on the solid lifters. I wish I had found Doechsle sticky before I put my heads on... I saw it yesterday for the first time.

I did recheck mine last night. I shortened them to the stock +.1" and the pattern basically reveresed on the valve tip - it was slightly off center towards the intake manifold side instead of the header side. Doing this put the tip of the roller rocker closer to the center of the valve stem - like what K5JMP was talking about. If I'm understanding correctly, this is what I am shooting for.

I'll double check everything with my actual lifters. :cool:

when you are checking with a solid lifter you have to make sure the pushrod seat is the same height as the hyd lifter. This is an issue with some mfg's. The hylift Johnson solid tappet has a pushrod seat .120 deeper in the lifter than a stock Delphi GM hyd. Just pay attention to that. When the geometry is correct , the pattern on the valve tip will me the narrowest possible. As the geometry gets worse the pattern will get wider. Keep in mind you are trying to piece together parts that are made by different manufacturers with their tolerances. If lets say the head company is trying to get a little better head flow by shifting the guide angle over 1/2 degree and the rocker arm mfg. is making a rocker that is too short , then the contact pattern may be offset on the valve tip even when the geometry is perfect. That's why you shouldnt shoot for just getting the pattern in the center. In your pictures you have a nice narrow pattern on the tip but its offset from the center. lets just say for the sake of this conversation that you did the measuring method that is in my article and the closed measurement is the same as the open measurement and this is the contact location on the valve. By taking the measurements you know that the geometry is correct, but the contact pattern is offset due to variences in rockers, guide angles, valve heights etc. Now lets say a buddy convinces you that the pattern is supposed to be in the center of the valve. So you go and shorten up the pushrod .200 and get the pattern back to the middle of the valve, I guarantee you the pattern will be wider, because the geometry will be off. The closed measurement will not be the same as the open measurement.

Thanks for popping in guys... I understand the concept, but have a hard time verbalizing it....:screwup:
IMHO... you just got advice from a couple of VERY knowledgable guys there.

Hey Dennis... I love the solid roller you sold me!!! Sounds sweet and pulls like snot!! Wonder what I will have when I actually get it tuned-out:eek: Thanks man!!!:D :cool:

Your very welcome. Just remember to tell a friend. :bowtie: Thank you for the Kind words. Dennis

Doechsle (and all:cool: ) - wow - thanks for the comments. I had to read your post & sticky 3 times, but it I get it now. :brightide

So, let's say I wanted to measure the pushrod length using my actual Hyrdaulic lifters. What changes in the process (vs. using a solid lifter)?

I read the sticky & I really didn't see anything called out about that little detail.

What am I missing?

P.S. Sorry for the dumb questions - but I'm learning a bunch. I apprecaite the help!

Eric

Whoops - I just saw ZS10's comments in the sticky. I think that answers my question...

Thanks guys!