pushrods

banjo · Post by **banjo** » Thu Jul 10, 2008 11:10 am

I am building my new motor, and I want to step up to a 3/8ths pushrods. It is a SBC 406, AFR 210 heads. Currently run a comp cams 5/16 .080 push rods. Going from a flat tappet to a solid roller, with 300 seat and about 600 open. Max rpm should be around 7000 rpms. My pushrods slightly rub in some places. I haven't purchased my lifters, would it be a bad thing to do to get offset lifters to gain the needed clearance. I already have jesel rockers, I wish I would have got offset ones. What does everyone recommend for pushrods and what are the opinions on the offset lifters. Do I need more than a 3/8s pushrods

Thanks

axegrinder · Post by **axegrinder** » Thu Jul 10, 2008 11:27 am

With the rpm that low I would go with Manton 3/8 .140 wall. Probably more than you need but it wont hurt anything and it leaves you "room to grow". I would not buy cheap off the shelf .080 wall, get atleast .120 wall. Jesel will sell just the rocker bodies in almost any offset, but they are kind of high priced. I have never run offset lifters and no offset on the rocker but I dont see what it could hurt.

jeffmckc · Post by **jeffmckc** » Thu Jul 10, 2008 11:44 am

You can run a offset lifter with a standard shaft rocker.

Warp Speed · Post by **Warp Speed** » Thu Jul 10, 2008 12:24 pm

I would not recomend an offset lifter as the twist load it puts on the tappet typiclay ends in failure with any high rpm's (8500+) especialy with 300lb seat preasure.
With that being said, why so much spring presure??
The last standard valve layout small bock I did I used manton series 5 pushrods, 3/8x.145 wall on the intake and 7/16x.168 on the exhaust. And that was with about 50lb less seat pressure (245lb) and 625lbs at .800 lift.

banjo · Post by **banjo** » Thu Jul 10, 2008 2:20 pm

Sorry, After rechecking my spring info, I mispoke on the closed pressure, it is 240, I don't know what I was thinking,

So am I correct in saying I will need an addition .030 clearance to step up from a 5/16 to a 3/8 push rod?

Why do you run the bigger pushrods on the exhaust or is that what clearances would allow?

What is a good source on the Manton pushrods?

Post by **jmarkaudio** » Thu Jul 10, 2008 2:27 pm

My SB2 has offset lifters and rockers @7800, you won't hurt anything on yours. Just keep the offset to the minimum you need for clearance. As far as Manton, call and ask for Terry @ Manton. Anyone can buy direct. Be sure of your lengths to get the geometry correct.

jeffmckc · Post by **jeffmckc** » Thu Jul 10, 2008 3:04 pm

You are opening the valve against pressure on exhaust,,,,, Think big block chevy push rods run at angles all the time it does not hurt.

Warp Speed · Post by **Warp Speed** » Thu Jul 10, 2008 3:07 pm

banjo wrote: Why do you run the bigger pushrods on the exhaust or is that what clearances would allow?

Yes, there was more room so 7/16 would fit, but the real reason is that the exhasut valve has to open under cylinder preasure, so this coupled with the seat pressure of the spring works the exhaust side pretty hard.
1/2 in would have been better, but wouldn't fit unless I went to an offset lifter...and you have already heard how I feel about those!

Warp Speed · Post by **Warp Speed** » Thu Jul 10, 2008 3:13 pm

jmarkaudio wrote:My SB2 has offset lifters and rockers @7800

I would limit it to 8000rpm max (unfortunatly that is about were an SB2 really starts to run good) if you are using a cam with any kind of valve speed. That is the reason we got away from the offset lifters on our Busch SB2 engines long ago. Would rather deal with an offset rocker and more pushrod angle than the offset lifter route.
IMHO

Post by **jmarkaudio** » Thu Jul 10, 2008 8:00 pm

Warp Speed wrote:
jmarkaudio wrote:My SB2 has offset lifters and rockers @7800

I would limit it to 8000rpm max (unfortunatly that is about were an SB2 really starts to run good) if you are using a cam with any kind of valve speed. That is the reason we got away from the offset lifters on our Busch SB2 engines long ago. Would rather deal with an offset rocker and more pushrod angle than the offset lifter route.
IMHO

Mine is a 447 with reworked cup heads. Peak HP is at 7500, shift at 7700, traps about 7800. This was built to keep the RPM's down, and valvetrain maintenance to a minimum. My point is Banjo is planning to keep his R's to 7000. While offset lifters may not be the best way to gain the clearance, he won't be hurting anything at the RPM he wants to run with the small amount of offset he will need.

Warp Speed · Post by **Warp Speed** » Thu Jul 10, 2008 10:07 pm

jmarkaudio wrote: Mine is a 447 with reworked cup heads. Peak HP is at 7500, shift at 7700, traps about 7800. This was built to keep the RPM's down, and valvetrain maintenance to a minimum. My point is Banjo is planning to keep his R's to 7000. While offset lifters may not be the best way to gain the clearance, he won't be hurting anything at the RPM he wants to run with the small amount of offset he will need.

My bad Mark,
I guess I read right over the Banjo's 7000rpm limit. I have just seen too much nice stuff get tore up due to offset lifters even at that rpm. Of course it's not crank speed but tappet speed (and spring pressure) that gets them into trouble. Many people run them with success (your proof) but I hate them!
Why do you have to run an offset lifter in your SB2 package? Are you using an standard 23/18 degree block?
We use a pretty good size pushrod in our stuff with a standard, non-offset lifter.

banjo · Post by **banjo** » Fri Jul 11, 2008 12:54 am

I planned on getting the severe duty crowler cutaway lifters with the oiling. They have .180 offset, is that extreme?

Post by **jmarkaudio** » Fri Jul 11, 2008 10:29 am

Mine is a standard block, we wanted to keep the ability to go a different route on heads. The 9.5 AL block we are putting together does have SB2 lifter angles.
The 66292 Crower lifters list a .175 offset. More than you need, but it looks like all the lifters are offset in that range.

banjo · Post by **banjo** » Fri Jul 18, 2008 8:38 am

Would a tapered pushrod work to get me the additional clearance? What is the purpose of a tapered pushrod if not for clearance? I see manton has some 3/8-5/16 tappered pushrods. How far does the taper typically go down?

Thanks

axegrinder · Post by **axegrinder** » Fri Jul 18, 2008 10:56 am

The tapered Mantons that I have seen go down not quite half way.