Need Push Rod input from Big Block Experts

[Detroit Iron]

I basically want to know if the push rods I'm using are causing my problem.

The 383 (original engine) in my '64 Polara has a sputter that I can't seem to tune out. I've tried multiple carburetors, distributors, ignition boxes, timing settings etc. and still sputter persists. It shows itself on mild acceleration and cruising speeds.

The reason I am looking at push rods at this point is this. When I was building my engine nine years ago, my buddy said he had a brand new set of push rods for a 383, so I used them. They didn't come with a part number and they felt right when I torqued the rocker shafts on, so I went with it.

I recently did some research and found a stock length rod should be 8.645" long. I pulled a rod today and it is labeled 8.600", so I'm looking at a .045 difference. Is that a problem with hydraulic lifters? I also just learned stock should be a non-oiling rod, and the rods in the car are oiling. Is this a problem?

Sealed Power replacements are 8.645, and Melling replacements are 6.635. Could .035-.045 make enough of a difference to make this car sputter?

Here are the engine details:

Original '64 383 bored .030 over
Keith Black Hypereutectic pistons
Lunati 60300 very mild cam
Lunati 71977 recommended lifters
Edelbrock E-street Heads
Rockers are stamped Comp Cams

 

[Lefty71]

I would say your problem lies elsewhere. Although I agree there is a chance that a longer pushrod would be used if they were measured and custom made. However, being a hydraulic, you are still very much in the ballpark, especially if the motor was blueprinted, and likely decked as well as the heads.

 

[Detroit Iron]

I would say your problem lies elsewhere. Although I agree there is a chance that a longer pushrod would be used if they were measured and custom made. However, being a hydraulic, you are still very much in the ballpark, especially if the motor was blueprinted, and likely decked as well as the heads.

Thanks for the input. The engine was not blueprinted, nor was the block decked.

 

[GrabberOrange69]

Do a compression check on all cylinders. You might have a burned valve, or valve not seating.

 

[turbine68rt]

I realize it's a bit late, but it's my understanding that whenever a new cam and lifters are used, the lifter preload should be verified for .020"-.040", possibly different specs per cam manufacturer. I know that when I installed a stock grind Comp cam and lifter set, along with a new stock rocker/shaft assembly it produced way too much preload and had to order specific length shorter rods to get close to the .030" I was after. Everything worked out great once that was established.

 

[Paul Secoy]

I could see too long causing an issue with hanging valves off the seat when the lifter is pumped up, but being short would only likely clatter, but run fine otherwise.

 

[Pistol Pete]

If you really want to be certain...

https://www.jegs.com/i/COMP-Cams/249/7703-1/10002/-1

 

[Ranger16]

I also just learned stock should be a non-oiling rod, and the rods in the car are oiling.

Really? Pardon my ignorance, but I thought all hydraulic lifter push rods where oiling, meaning oil passes through the push rod to lube the rocker arm pocket. How else would it get lubricated? Can someone elaborate?

 

[dadsbee]

Stock the rocker shaft gets oil flow via the bolt holes that are countersunk (#2 and #4) and take the longer bolts. Then out into each stamped rocker and then the rod tip is oiled via the little holes in the socket.

 

[Detroit Iron]

Really? Pardon my ignorance, but I thought all hydraulic lifter push rods where oiling, meaning oil passes through the push rod to lube the rocker arm pocket. How else would it get lubricated? Can someone elaborate?

Yeah, that's what I thought too. Don't take what I said as gospel. I got that information from looking up push rods on Rock Auto. The Sealed Power and Melling part numbers they listed said "non-oiling".

But the rods in my 383 now are oiling (hollow). When I pulled one out, it was full of oil.

 

[mopar 3 B]

What style lifter does it have? Lifter design changed sometime in the mid 60's. The push rod shown would be for the later style lifter.

 

[Wietse]

What type push rod is it? (can't see on the pictures)
If this is a ball/ball type then an oiling hole is required according me to lubricate the upper end, well...when using aftermarket (roller)rockers with cup type adjusters you do.
Does the Comp Cams stamped rockers have an oiling hole as well?
When the push rod is installed, with the lifter at camshaft base circle, is there any preload visible?
Is the little inner piston off the circlip/retainer? Probably is otherwise you would have a noisy valve train you would have noticed.

A sputter at mild acceleration and cruising speeds seems more likely to come from ignition/carburation side.
These 2 driving condition are the ones with high manifold vacuum, which could be more likely the problem.
Vacuum advance in use? Adjustable or not?
Any specs on compression ratio?

 

[miller]

Really? Pardon my ignorance, but I thought all hydraulic lifter push rods where oiling, meaning oil passes through the push rod to lube the rocker arm pocket. How else would it get lubricated? Can someone elaborate?

Stock BB Mopar ball to ball pushrods are solid. As mentioned, the rocker arms, and upper ball of the pushrods, get oiled via the rocker arm shafts.
Tappets, and lower ball on the pushrods, get oil from the oil ports, from front to rear of the block. If you pull a tappet out, you can see the oil ports, cut into the tappet bores.

I'd suggest doing a vacuum check, at the base of the carb, and see what you have.

 

[Paul Secoy]

I'd be inclined to think it's lean at part throttle. My brother chased that issue one whole summer, it was pretty frustrating.

 

[wyrmrider]

wet pushrods are better in addition to the splash lube
lifter ball cup did change- high wear in the early ones- always use the later (and oiling) lifters and matching pushrods Chrysler changed for a good reason
unfortunately lots of catalogs list the early lifter and pushrod for the early years
this most likely not a pushrod issue
do the tests and let us know
REad their website comp shows nothing good on how to set pushrod length or rocker arm geometry for a mopar actually even wrong for a sbc

 

[33 IMP]

Do a compression check on all cylinders. You might have a burned valve, or valve not seating.

Agree. OP stated he has tried just about every ignition and fuel fix. That sounds like a mechanical problem to me. Leakdown or compression check will either confirm the problem, or, if good , direct further inquiries elsewhere.