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Weird pushrod length SBC?

General engine tech -- Drag Racing to Circle Track

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mikes
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Weird pushrod length SBC?

Post by mikes » Sun Sep 08, 2019 12:58 pm

I'm far from a professional engine builder so please forgive my ignorance. I'm building a 383 using a late model 350 factory roller, one piece rear seal block with the taller lifter bores. This is a mild street build using an Isky standard base circle hydraulic flat tappet cam and world product S/R torquer heads. When I check for pushrod length, much to my surprise I come up with 7.420?? A stock length pushrod puts the roller almost off the edge of the valve. I've used these blocks before but never had this issue? What I do know, these heads were used on a circle track engine and have a at least a .100 longer valve but I'm sure this isn't my issue as longer valves usually dictate longer pushrods? There are no signs of angle milling and I also have to use flat guide plates as the raised one are too tall for this combination. Am I over looking something here? I'm feeling pretty stupid right now on such a simple build! Thanks for the help!

Walter R. Malik
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Re: Weird pushrod length SBC?

Post by Walter R. Malik » Sun Sep 08, 2019 3:01 pm

mikes wrote:
Sun Sep 08, 2019 12:58 pm
I'm far from a professional engine builder so please forgive my ignorance. I'm building a 383 using a late model 350 factory roller, one piece rear seal block with the taller lifter bores. This is a mild street build using an Isky standard base circle hydraulic flat tappet cam and world product S/R torquer heads. When I check for pushrod length, much to my surprise I come up with 7.420?? A stock length pushrod puts the roller almost off the edge of the valve. I've used these blocks before but never had this issue? What I do know, these heads were used on a circle track engine and have a at least a .100 longer valve but I'm sure this isn't my issue as longer valves usually dictate longer pushrods? There are no signs of angle milling and I also have to use flat guide plates as the raised one are too tall for this combination. Am I over looking something here? I'm feeling pretty stupid right now on such a simple build! Thanks for the help!
That is near hydraulic roller length.
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Re: Weird pushrod length SBC?

Post by BillK » Sun Sep 08, 2019 3:46 pm

What lifter are you using to check with ?

That being said if the heads were used on a circle track engine and you have no idea what has been done to them you simply need to go with what you have. Circle track guys are known for doing some crazy stuff to heads and then making them "look" like nothing has been done :)

Still, that is awful short ????
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midnightbluS10
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Re: Weird pushrod length SBC?

Post by midnightbluS10 » Sun Sep 08, 2019 4:12 pm

I've seen it on builds using retro roller lifter upgrade and .100" longer valves 7.42 - 7.45 is usually what they come to rather than the usual 7.200"
JC -

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Re: Weird pushrod length SBC?

Post by mikes » Sun Sep 08, 2019 4:34 pm

Gentlemen, thanks for the replies! Lifters are Comp 812's. I just don't understand why with a regular hydraulic lifter that my pushrod is so short? I can see the retro roller stuff being taller needing the shorter pushrod but a conventional lifter? This is where I'm confused. I guess it is what it is, math don't lie. Maybe it is something crazy in the heads but I sure cant tell.

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Re: Weird pushrod length SBC?

Post by Walter R. Malik » Sun Sep 08, 2019 6:09 pm

mikes wrote:
Sun Sep 08, 2019 4:34 pm
Gentlemen, thanks for the replies! Lifters are Comp 812's. I just don't understand why with a regular hydraulic lifter that my pushrod is so short? I can see the retro roller stuff being taller needing the shorter pushrod but a conventional lifter? This is where I'm confused. I guess it is what it is, math don't lie. Maybe it is something crazy in the heads but I sure cant tell.
Are the rocker arms correct for the application...?
Ford or Pontiac rockers are a little longer than Chevrolet's but, will fit.
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Re: Weird pushrod length SBC?

Post by BillK » Sun Sep 08, 2019 6:31 pm

mikes wrote:
Sun Sep 08, 2019 4:34 pm
Maybe it is something crazy in the heads but I sure cant tell.
It has to be. I have used those blocks for flat tappet builds and not had an issue.
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Re: Weird pushrod length SBC?

Post by mikes » Sun Sep 08, 2019 8:02 pm

Rockers are standard 1.5 ratio Harland Sharp for 7/16 stud. I do have two other sets to compare, Crower steel 1.5 and Scorpion 1.6 ratio. I'll check those quick just for giggles.

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Re: Weird pushrod length SBC?

Post by mikes » Sun Sep 08, 2019 9:38 pm

Well this gets crazier by the minute. My Crower rocker, using a 3/8 stud, needs a 7.600 pushrod. Maybe like Walter mentioned, I have an incorrect set of Harland Sharp rockers. The installed height is 1.920 IN and 1.950 EX. EX valve is a Ferrea 1100pq and according to catalog, looks like + .050 long. I need to pull the other spring to see what intake valve is. Maybe spring seats were cut but either way, this is getting ugly. I struggled getting my spring pressures where I wanted and ended up using spring locators and shims to get a 1.860 installed height with 1.470 double springs allowing 115/120 seat and 300 open pressure . At this point, I'd love to figure out what's going on with the heads but I'll have more time invested than its worth. I can honestly say I've never struggled so much. Something is off and I don't have the experience to figure out what. Might be time to buy new heads.

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Re: Weird pushrod length SBC?

Post by Dave Koehler » Mon Sep 09, 2019 7:00 pm

Try not to panic.
Rocker mfgs do not subscribe to any standard as to where the pushrod pocket goes.
Found that out the hard way many moons ago and now so are you.
Maybe this is simplified but just get the pushrod length you need and not what you expect.
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Re: Weird pushrod length SBC?

Post by mikes » Tue Sep 10, 2019 6:34 am

Thanks guys, I’m going to continue pursuing Solutions and will eventually get this buttoned up. Every day is a learning experience for me but I never figured a stock replacement style head would cause so much trouble. It just seems like way too much effort for a 400 hp engine.

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Re: Weird pushrod length SBC?

Post by Dave Koehler » Tue Sep 10, 2019 7:25 am

mikes wrote:
Tue Sep 10, 2019 6:34 am
It just seems like way too much effort for a 400 hp engine.
I'm going to pretend you didn't say that.
Dave Koehler - Koehler Injection
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Re: Weird pushrod length SBC?

Post by mikes » Tue Sep 10, 2019 12:10 pm

The “too much effort” or “400 hp” or both lol

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Re: Weird pushrod length SBC?

Post by mikes » Wed Sep 11, 2019 7:03 am

Latest update.....and with some embarrassment. :roll: Tried going back to square one, looked all over for a stock sbc retainer and lock only to find a set of later model heads with all rotaters on intake and exhaust. Took all shims and spring locaters off, installed the factory parts and holy sheet, exhaust is now 1.750, intake is 1.720? I never realized that I was using retainers and possibly locks that would yield + .200 installed height? Well this allows me a better spring/retainer package, all I need to deal with is the pushrod length. I will let that measure out to whatever gets me the best sweep and move on! =D> Thanks for everyone's help and suggestions. This was quite the learning experience.

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Re: Weird pushrod length SBC?

Post by tenxal » Wed Sep 11, 2019 8:30 am

mikes wrote:
Wed Sep 11, 2019 7:03 am
.....all I need to deal with is the pushrod length. I will let that measure out to whatever gets me the best sweep and move on!
Be aware that adjusting push rod length for the best 'sweep' will often cost you lift. With a mild cam, you don't need a perfect 'sweep' at the expense of lift and power.

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