Running into a slight dilemma while checking pushrod lengths on my 383. I've got both check springs and the proform plastic tool available to me. I'm getting different lengths is the issue.

I've never used the proform plastic tool before but I thought I'd give it a try and maybe I'll learn a new method for checking pushrod lengths. With everything setup, it tells me I need 7.2" pushrods.

When using check springs and marking the valve top, I get 7.1" pushrods as being the better choice. I'm not sure which method to trust.

Both lengths actually work. However, the 7.1" leaves a witness mark through the middle third of the valve stem top. The 7.2" moves it just to the outside towards the exhaust. It's the same width witness mark with either length.

The block has been decked so the pistons are 0.015-0.018 in the hole and the heads have been milled to a minimum of 57cc chambers according to Ai. I don't see how I wouldn't need shorter pushrods given the work that's been done. Just not sure which method to trust really since the plastic checking tool is new to me.

In case it matters my methods are as follows. Snug the head down with the head gaskets I'm using in place. Set the valve lash at 1/2 turn past zero. Rotate engine over a few times. Check witness marks. Adjust pushrod length. repeat and compare witness marks.

I did notice that the exhaust lifter doesn't compress as I check it. However, the intake valve does compress the lifter when I rotate the engine. I was kind of surprised since the check springs were supposed to keep that from happening. I let the lifters soak in oil overnight.

So which method would you trust, or does anyone have any other suggestions.

Thanks

 

I would use the witness mark method. 7.100" is what I wound up with on my 383 H/C build

with a 7.100 PR installed, does the Proform tool sit flush on both PR & valve tip...or is there a .100 gap between tool & PR tip?

 

There's a good gap between the pushrod and proform tool.

See anything wrong with my methods possibly? It's the way I've done it in the past. I'm just surprised the proform tool didn't even come close to agreeing. Assuming I am using the tool correctly of course.

Ah, the joys of trying to learn a new method.

Thanks

 

I have the Proform also and it matches what I got when I did my PR length check per your method

are you sure the lifter has come all the way up when you used the Proform tool?

I would follow the standard method you used show 7.100 length

 

When you ask if the lifter has come all the way up, are you asking about the plunger? Since, I'm using check springs the plunger doesn't compress on the exhaust side. I've done my primary measuring with the exhaust valve and just have double checked on the intake.

Thanks

 

yes I was asking about the lifter plunger. Didn't know if you were using just the same valve to test length. If you have tried a few and they are all the same that is good

 

I prefer to use checker pushrods and springs as it test the valve geometry in action as it will work.

 

I use the marker way

 

So I went back out there tonight and rechecked everything. I still like 7.100 the best. I get a wide sweep on the valve tip, almost 1/8", from the rocker right through the middle of the valve. I'm not used to seeing it that wide, but I don't think there's anything I can do about that.

I did notice that the plunger on the lifter is getting pushed in a little as I roll the engine over. It's not much but I'm surprised it's occurring at all given I have check springs in place. How does that affect things?

Thanks

 

If the intake is off, why not get an oil pump pimer, prime motor and check pushrod length since lifters would be pumped up

 

I'm not ready to put the pan on and fill the engine with oil is the problem. Otherwise, that's a good idea.

The amount that the lifter plunger was pushed in won't be a problem if it's supposed to not compress any while the engine is running.

Thanks

 

are these new lifters?

 

Yes, brand new. Soaked in oil for 24 hours before putting them in the engine. Sat in the engine for a couple days while figuring out the length. I should have my 7.100 push rods tomorrow.

Sorry I didn't reply to this sooner.

Thanks

 

http://www.hotrod.com/articles/ctrp-...rain-geometry/

You mentioned you had a nice wide sweep. The above seems to suggest that you want a narrow sweep. It even goes as far to say that the sweep doesn't have to centered, as long as it's not within 0.020" of the edge of the valve tip. According to the above, being off center has virtually no effect on valve guide wear or valvetrain harmonics.

Same thing is mentioned here...
http://www.enginelabs.com/engine-tec...ting-it-right/

From above...
"According to Massingill, it’s better to have a narrower sweep that’s a little off-center (most of the time to the exhaust side) than a wider sweep, even if it’s perfectly centered. The width of the sweep is a little more important than the location. If you’re getting a narrow sweep, the side loads on the valve stem are reduced as compared with a wide sweep."

Something to think about.