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Old 04-14-2006, 03:33 PM
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Big Block Chevy Pushrod length

What is the length of pushrods on a Big BLock Chevy?
I bought an engine in a car that has Procomp 1.7 roller rockers and a Comp hydraulic flat tappet cam. I was in the process of replacing the 305 duration cam with something with better vacume at idle. I discovered the end of one of the pushrods and the rocker chewed to pieces with fragments of metal all over the lifter valley.
I would like to know the correct length for the pushrods as I think the reason it failed was the rod was too long and caused a severe angle with the valve fully open.
This complete engine teardown will be my first on a Chevy since 1978. It should raise enough questions to power several interesting threads.

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Old 04-14-2006, 03:59 PM
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When building your valve train from parts other than stock,you should use an adjustable checking pushrod to determine correct heights,valve clearances and rocker angles,then order the pushrods to the length you need.

Different combinations need different lengths.
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Old 04-14-2006, 04:13 PM
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What are the stock lengths? We have to have a starting place.
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Old 04-14-2006, 04:23 PM
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stock lengths are 8.280 and 9.250 but if your pieces have been machined its best to check with a set of adjustables as stated by prior post. its the only sure way.
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Old 04-14-2006, 06:45 PM
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Quote:
Originally Posted by scanman
stock lengths are 8.280 and 9.250 but if your pieces have been machined its best to check with a set of adjustables as stated by prior post. its the only sure way.
Thanks, that gives me a couple of sizes of adjustable pushrods. The stock size should work since the lifters have the same dimension as stock. The only difference is in the 1.7 vs 1.6 rockers.

The pushrods that were in the engine and failed were 8.5 and 9.5 inches. There is obvious wear marks on the rockers where the pushrods were hitting the body of the rockers when the valve opened fully. There was a side load on the rod that simply broke it off.

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Old 04-14-2006, 06:59 PM
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Uh stock rocker ratio for a BBC is 1.7 and the only reason to not use a stock length pushrod (intake or exhaust) is because of changes in installed height of the valves so you can correct the geometry... (possibly a different base size cam also)


Also with the chewed up end of the pushrod what comes to mind are these stock pushrods...? (ball type end...?) also what size diameter are they...?
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Old 04-14-2006, 09:32 PM
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Quote:
Originally Posted by Bumpstick
Uh stock rocker ratio for a BBC is 1.7 and the only reason to not use a stock length pushrod (intake or exhaust) is because of changes in installed height of the valves so you can correct the geometry... (possibly a different base size cam also)


Also with the chewed up end of the pushrod what comes to mind are these stock pushrods...? (ball type end...?) also what size diameter are they...?
It appears they are 3/8". They are tapered on both ends with one end having a pressed in tip. The his tip was the end that failed. It appears the rod (where the tip was pressed in) was hitting against the rocker right next to the socket. I can see this because all the exhaust pushrods and rockers are marked and would have failed eventually.

The last BBC I owned was in 1973 in a 67 Camero. In the last 20 years it has been all Ford so I really don't know what I'm looking at. I can order a set of stock lenght pushrods and maybe find 1 rocker to match the set. The hardest part is tearing down the engine and scrubbing all the metal bits out of it.
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Old 04-15-2006, 06:44 AM
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Sounds like a cheap set of pushrods were installed...? For performace apps the welded ends are whats really needed... I`m not real sure on the Procomp rocker are you sure they are not Proform...? Either way they kinda sound like a cheaper offshore brand... I`m sold on Crane or what I run now which is the Comp Pro Magnums (steel full roller rocker)... With a BBC the valve train has to be right or things such as your problems occur...
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Old 04-15-2006, 07:28 AM
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Quote:
Originally Posted by Bumpstick
Sounds like a cheap set of pushrods were installed...? For performace apps the welded ends are whats really needed... I`m not real sure on the Procomp rocker are you sure they are not Proform...? Either way they kinda sound like a cheaper offshore brand... I`m sold on Crane or what I run now which is the Comp Pro Magnums (steel full roller rocker)... With a BBC the valve train has to be right or things such as your problems occur...
I agree on the pushrods. I would have never installed them. The Rockers look fine and must be really tough. The one that is chewed up stayed together even though the open jagged end of the pushrod was in contact with the socket area.
I was able to find Procomp in Canada. http://www.procompelectronics.com/
It appears they sell a line of knock offs. They even have a version of your crane stainless steel rockers. It all looks like pretty high quality stuff. I guess it is made in Austraila or South Africa because they have parts for Holdens which is their Chevy.
I don't mind using high quality knockoffs. If I did, I would stay away from Walmart.
My engine really does not see the high side of 4,000 RPM. It is in a T Bucket which is like driving a 4 wheel motorcycle. Stock rockers and pushrods would work fine cruising around the street though I have been known to smoke a ricer when necessary. I think a full throttle 1/4 mile or even 1/8 mile run would be pretty scary. I've been 160 in a quarter in my Fox Mustang but it had a cage and all safety equipment. I don't think I want to go there in my T even though it probably could be pretty quick.
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Old 04-15-2006, 07:47 AM
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Well you might contact them directly and see about a single replacement...? Their stuff looks pretty good but without it being in the hand to really look at it then its hard to say...? If you can get a replacement rocker then do so and buy a good set of pushrods and with a cleanout as you mentioned... (would pull a main bearing cap or two and possibly a rod cap to check for bearing damage...?)
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Old 04-15-2006, 08:54 AM
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Quote:
Originally Posted by Bumpstick
Well you might contact them directly and see about a single replacement...? Their stuff looks pretty good but without it being in the hand to really look at it then its hard to say...? If you can get a replacement rocker then do so and buy a good set of pushrods and with a cleanout as you mentioned... (would pull a main bearing cap or two and possibly a rod cap to check for bearing damage...?)
The I got an e-mail answer last night from Viktorija Nikolovska the office manager. They will sell me 1 rocker. The time of day I got the e-mail makes me think that their office must be in Australia or somewhere else where the time zone is vastly different than ours.

I will order a set of Crane street rod pushrods from Star Performance which is much cheaper and has better service than Summit and Jeggs.

I am really dreading it but it must be completely torn down so I can run brushes through all the oil galleries and passages. If I don't do it right, I will never be able to go on a long cruise in it again. All I have to do is miss one chunk.
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Old 04-15-2006, 10:19 AM
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If going that far I would just have it boiled...? Also I buy from these people and have had good luck...
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Old 04-15-2006, 12:03 PM
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Quote:
Originally Posted by Bumpstick
If going that far I would just have it boiled...? Also I buy from these people and have had good luck...
Thanks for the lead. I'll check with them on my shopping list. They handle procomp products http://www.competitionproducts.com/p...?number=PC2301


I just came in for a lunch break. So far I've got it down to the point that all the lifters and bores are clean without a scratch. The cam journals and bearings are likewise OK. If I have it vatted they will have to install new bearings. I think I may use degreaser and a garden hose and high pressure air to clean it if there is no sign of damage.
Now to run over to Northern or Harbor Freight and buy another engine stand.

Last edited by Choctaw Bob; 04-15-2006 at 12:06 PM. Reason: another thought
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Old 04-16-2006, 11:54 AM
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Quote:
Originally Posted by Bumpstick
If going that far I would just have it boiled...? Also I buy from these people and have had good luck...
Hey Bumpstick, I got the heads off the engine and I have found something that puzzles me. The block is a 69 396 and the heads are 73-85 Oval port 454s. The water passeges don't match well between the heads and the block. Also the felpro gasket doesn't match either heads or block very well. How does the water flow from the block to the heads to the intake? Are these water passage issues a common problem with these engines? I know with a small block Ford, some holes drilled in the right places can really help. I know that with fords, later models had more restrictive water flow so it would run at 225 or so for emissions. This engine ran around 225 - 235 with no thermostat and a 3 core aluminum T-Bucket radiator which should be plenty.

I would really like this engine to run at 160 with a thermostat just like my 67 BB Camero did.
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