Thread: Push rods too short?

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Hey All,

New to the site, but not new to twisting wrench's - I've been searching threads on an issue that we've been having with a fresh build on a 383 chev SB so I thought I would turn to you professionals - so thank you in advance as this may get lengthy...



So here goes-

The recipe:

1987 4 bolt Main 388 Stroker
Eagle balanced 3.75 cast steel crank
Eagle 5.7 Con Rods
Keith Black 9.9:1 hypereutectic pistons
Comp 270 .480 intake .498 Exhaust degreed 108
Stock Hyd lifters
Eldelbrock Alum E-Street 64cc heads
Eldelbrock RPM Air Gap intake
Roller Rockers 1.5's


So here is the issue - and yes, I left out pushrod length, that I will divulge in a moment as I think it's the culprit, but want your opinion...

Issue:

excessive knock in cylinder one, exhaust lifter

sounds like excessive lifter noise

can adjust value (tighten) by 1/8th turn, noise goes away for 30 seconds or so and then gradually comes back to where it was

if I adjust out the noise by tightening adjuster until it's gone, hangs the valve open and we get next to zero compression.

This by the way, only takes about 3/4 turn from zero lash to hang valve open.

checking the pushrod length, it currently has 7.74's and upon some research, the head instructions call for 7.90's so we are .106 short...

Quite a bit at almost a quarter inch by definition...

Nice lumpy cam drowned out by taptaptaptap. and not quiet like the sowing machine I see referenced. please shoot me.:guns:

Previous to rushrod investigation, lifter replaced thinking it was done so that eliminates that, we have good oil flow out the top of the pushrod so I would say that eliminates ovalized lifter bore I would say, plus - this engine has less than 500 miles on it since the build / line bore from the machine shop. So I would HOPE that is good.

I have 7.9's on order but won't arrive until Monday due to a shipping delay-

Think I am on the right track?

As a side note, number 2 will dry foul the plug after a while - running normal heat range, I have no idea if that is a hint or not - leaning towards a possible valve misadjust - for the record - adjustment is 1/2 turn past zero lash on all with the exception of number one exhaust that is adjusted all the way just shy of compression loss and still has the noise.

Thanks for the direction, I could really use it-

any questions please ask, I tried to cover it all info wise but am sure that I left something out that could help-

I'd have to suggest investing in a pushrod length checker and the adjustable pushrod to check it with rather then just buying more pushrods and getting the length close.

You stated stock hydraulic lifters---hopefully this means the new one's that came with the cam when you bought it?

sounds like in your future you will be looking at new push rods .lifters .cam. you need two checking valve springs and a testing pushrods thats adjustable for length .a fixed lifter or sold lifter so you do not get bleed down with you lifters in testing . test valve springs need to be very lite or you are never going to arrive at the right push rod over all size

Hey Dave-

Thanks for the reply!

They are the lifters that came with it, the only one that was replaced was the #1 exhaust due to the suspicion that it was faulty, it was switched out with a stock chevy lifter since that is what was in it - I've been told that the lifters that come with the cam are the same as the stock small blockchevy lifters with an Comp Cam label on 'em that is more $ with the branding. is this accurate as far as you know?

The reason that I am replacing all of the pushrods is due to the fact that the edelbrock heads actually call for that part # (#9629 - 5/16 7.9 Long) It says "+.100 longer than stock hardened pushrods for use with stamped steel rocker arms or with 64cc heads." Which this head is that...

thoughts?

do you have a small base circle cam because of the stroker????????


if its #1 ex that's bleeding down could maybe indicate that the galley plug is leaking and/or missing in the oil galley

Jeez Pat, I hope that is not the case - Just went thru that - 'll need therapy and almost do I swear...

Jerry, I have looked on everything that came with the cam and I can't find that anywhere - however researching the cam online I've seen that it's a small base circle - Comp 12-243-3 part number.

I appreciate the input, this is going to drive me nuts, that is a good direction on the galley plug-

The engine was built by local well known and experienced builder - BowTie Performance in Turner, Oregon - Ron.

I have about 2 inches of paperwork on it, so I am happy to research the direction, thanks again.

If you would like to call and chat about it, PM me and I can jet you my number-

Originally Posted by jerry clayton

do you have a small base circle cam because of the stroker????????


if its #1 ex that's bleeding down could maybe indicate that the galley plug is leaking and/or missing in the oil galley

seen this done on a chevy oil psi will be way low as well loud lifters

Originally Posted by jerry clayton

do you have a small base circle cam because of the stroker????????


if its #1 ex that's bleeding down could maybe indicate that the galley plug is leaking and/or missing in the oil galley

could be oil band in lifter body drop past lifter bore and open oil feed

Last time I had a lifter tick which would come back shortly after it was adjusted out, and on a lumpy cam too; the rocker arm studs were pulling out.

his head s have screw in studs

The Oil Pressure is 60lbs and has been strong consistently - The only lifter noise, which is very prominent is from the #1.

The Rocker Studs are threaded, and holding steady at the 40lbs they were torqued at -

On the lifter bore, I considered that - but since we are getting good flow out the top of the pushrod that says that it's not bypassing, correct?

Was I correct on the theory on the lifter being a lifter?

out the top of the push rod is where they will bleed off----------

Originally Posted by JustaChevyGuy

The Oil Pressure is 60lbs and has been strong consistently - The only lifter noise, which is very prominent is from the #1.

The Rocker Studs are threaded, and holding steady at the 40lbs they were torqued at -

On the lifter bore, I considered that - but since we are getting good flow out the top of the pushrod that says that it's not bypassing, correct?

Was I correct on the theory on the lifter being a lifter?

in short no . cam could be wearing away thats why it comes back . the oil band in the lifter can bleed off seen it not realy the bore but lack of bore and chevy block casting can be off making a leak for oil to leak out lifter

It comes back in like 40 seconds, increase preload and it dissipates, once I get it to stay gone, the valve is not closing and compression drops...

Originally Posted by JustaChevyGuy

It comes back in like 40 seconds, increase preload and it dissipates, once I get it to stay gone, the valve is not closing and compression drops...

sounds like cam how far is the rocker or poly nut down on that rocker should be level with all others and if so check that valves are coming up a pocket machine rule helps set it across valve retainers