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Discussion Starter · #1 ·
I am curious to know what the best options for a road race type valvetrain is for a high revving 302 or 351 stroker small block Ford is. The 8000 rpm stock block thread got me thinking of this. Ideally this would mean not having to adjust the valvetrain all the time after running the car hard. Kind of like the GT350, which is a totally different beast, but you can beat on it and not worry about adjusting the valvetrain afterwards.
 

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I'm far from being an engine builder, but from what I understand, you'd want lightweight components throughout the entire engine build.
Titanium pieces come to mind.
Also, zero balance.
I was reading through that thread as well.
It's fun to think about an easy 8000rpm engine build, but it's definitely not for the average person.
 
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Thick wall pushrods to go along with those shaft rockers also. You can never have too strong of a pushrod at high RPM. It's all about column strength. Trend and Smith Brothers build some of the best money can buy.
 

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Discussion Starter · #8 ·
I run Jesel shaft mount rockers on a AFR 220 Renegade head and spin 8k+ no problem. I also run a Jesel belt drive to help with valve train stability.
I'm sure you built your engine right the FIRST time, because yours sounds stout.
 

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All this talk about pushrods, no mention of cam, lifters used, or springs. Pretty pointless. Putting the cart before the horse, and the wrong cart in fact.

The length of a 302 deck pushrod is extremely short, probably the shortest in the industry. Going to a 3/8 pushrod is going backwards in most cases if RPM / weight is the goal. I have used a 5/16 in 9.5 deck solid roller applications with no issues. In an 8.2 deck they are best so long as you are not talking about huge open pressures. Of course you can get them in thick wall, and restrictor, too. 11/32 is available too, which gives you more strength and much lower weight than a 3/8.
 

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All this talk about pushrods, no mention of cam, lifters used, or springs. Pretty pointless. Putting the cart before the horse, and the wrong cart in fact.

The length of a 302 deck pushrod is extremely short, probably the shortest in the industry. Going to a 3/8 pushrod is going backwards in most cases if RPM / weight is the goal. I have used a 5/16 in 9.5 deck solid roller applications with no issues. In an 8.2 deck they are best so long as you are not talking about huge open pressures. Of course you can get them in thick wall, and restrictor, too. 11/32 is available too, which gives you more strength and much lower weight than a 3/8.
8k rpm pretty much dictates a solid roller, so no need to mention it. 8k rpm pretty much dictates high spring pressures to control the valve.
I did not buy Titanium valves and even then it is a $1k bill to replace all 16 valves.
Valvetrain stability makes the springs last longer, as well as the rocker arms and pushrods lasting longer.
You don't need a belt drive for the cam, but the springs will last about twice as long if you do. When a set of valve springs cost over $500 the belt drive pays for itself in short order.
Can 8k rpm be done without all that stuff? Sure but it won't make as much HP at max rpm and replacing worn parts will cost more in the long run.
I ran 4 seasons without having to replace a single valvetrain component. I perform a valve adjust once a year. When I had my engine out for a re-fresh, the valvesprings were checked. 4 of them were down 25 lbs of pressure @ open. I could have continued to use them, but the cost if one failed at rpm would have far exceeded the near $600 to replace them.
So by all means, go cheap on your 8k rpm build. Talk to me in 4 years and let me know how that worked out for you. No doubt, some one will make it work, but they will be the outlier not the norm.
 

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8k rpm pretty much dictates a solid roller, so no need to mention it. 8k rpm pretty much dictates high spring pressures to control the valve.
I did not buy Titanium valves and even then it is a $1k bill to replace all 16 valves.
Valvetrain stability makes the springs last longer, as well as the rocker arms and pushrods lasting longer.
You don't need a belt drive for the cam, but the springs will last about twice as long if you do. When a set of valve springs cost over $500 the belt drive pays for itself in short order.
Can 8k rpm be done without all that stuff? Sure but it won't make as much HP at max rpm and replacing worn parts will cost more in the long run.
I ran 4 seasons without having to replace a single valvetrain component. I perform a valve adjust once a year. When I had my engine out for a re-fresh, the valvesprings were checked. 4 of them were down 25 lbs of pressure @ open. I could have continued to use them, but the cost if one failed at rpm would have far exceeded the near $600 to replace them.
So by all means, go cheap on your 8k rpm build. Talk to me in 4 years and let me know how that worked out for you. No doubt, some one will make it work, but they will be the outlier not the norm.
I build 2 to four engines a year. My current engine build is a hemi head SBF with an 8-71 blower. I dont do cheap anything.

You are not telling me anything, you are just babbling. Lots of superstockers running flat tappet cams over 8000 with 5/16 pushrods.

Recommending a 3/8 pushrod on a 8.2 deck engine without knowing what cam, valvetrain, etc is just amateur hour at its best.
 

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I build 2 to four engines a year. My current engine build is a hemi head SBF with an 8-71 blower. I dont do cheap anything.

You are not telling me anything, you are just babbling. Lots of superstockers running flat tappet cams over 8000 with 5/16 pushrods.

Recommending a 3/8 pushrod on a 8.2 deck engine without knowing what cam, valvetrain, etc is just amateur hour at its best.
I was just responding to your babbling since you did not name specifics in your own assertion of what is acceptable. Lol.
 

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1990 Ford Mustang LX 351M powered!! Project Cherry Bomb!!
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It seems to me that it's just basically physics. Use strong parts yes, but if you can use lighter parts and control the motion better that's the formula. If your spring pressure isn't that high, you can use a 5/16 pushrod as it's a lighter component. Ti valves are much lighter and stronger yes, but if you can use SS valves and control them with your springs by using Ti retainers and keepers to reduce weight then use em. If you need to use a shaft mount rocker to reduce deflection and control harmonics, which is another thing that's key, then by all means that's a great foundation to use. Smokey Yunick once said that it's all basically high school physics. Same here... Use the same principles and you'll get the results you're searching for..
 

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I'm not spinning to 8 grand but I'm running to 7200-7300. Comp gold rockers, Stock 205 11R springs with titanium hardware, Howard's linked lifters, .120 wall pushrods. I don't have stud girdle either. I've had many say they're good and some say hogwash. Eventually I would like to go to a shaft setup.
 

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Here's some "proven" facts to ponder.....

Mass on the lifter side of the rocker arm fulcrum is negligible.

Mass on the valve side of the rocker arm fulcrum is critical.

As for push rod diameter... I run the largest that fits the engine without doing stupid things to make it fit...

/carry on....
 

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I don't agree with Jessel's theory on rocker design, I prefer a rocker design that is perpendicular to the pushrod and valve at half lift. Pretty sure most pro level class engines with rockers will use the half lift design as well. Mark's Probe shafts were designed as such, Crower, and T&D Machine as well.

A thick walled double tapered pushrod helps with stiffness, and resistance to harmonic issues compared to a constant diameter pushrod. The more radical the combination, the more specialized and expensive parts are required. 8k really isn't all that high in the grand scheme of racing engines.
Here's some "proven" facts to ponder.....

Mass on the lifter side of the rocker arm fulcrum is negligible.

Mass on the valve side of the rocker arm fulcrum is critical.

As for push rod diameter... I run the largest that fits the engine without doing stupid things to make it fit...

/carry on....
It is my understanding that a tapered rod is beneficial in controlling harmonic forces that affect high speed stability in pushrods, just curious if you are using a double tapered pushrod in high RPM builds, or if you think that's unnecessary?

Jay
 

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Jesel is the benchmark others follow. If it hadn't been for their shaft system, Pro Stock and NASCAR would still be fighting with valve spring longevity. Might want to review the Danny Jesel concept on valvetrain before discounting it. Valve action is the key to how the rocker configuration works, not just the swipe. T&D also uses the same philosophy as Jesel.

It's easy to read about other concepts and with certain rocker arm designs, they seem to work but I've had the best results with Jesel shafts.

As for tapered push rods, never saw the need for them. Didn't use them on the Hot Street engine (9800 RPM) nor were they used on that high RPM Drag Week 427 Higgins build. Valvetrain was as stable as the rock of Gibraltar.

Like anything in this world, lots of opinions but very few truths.

:cool:
 
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