[1968junkerjim]

My cam is 51-433-9 hyd roller 236/242@50 520/540lift have 400 #16heads with crane 99838 spring 1.700 install height my machine shop says I can’t shim them. I’ll be out of the pocket the seat pressure is only 100 they say they’re find as long as I don’t rev over 5000 rpm do you guys agree? This will mostly be a street motor with some burn outs few time at local track .

[Steve C.]

COMP Cams Xtreme Energy Camshaft in use !

"If we were to sum up the role that the valve spring plays in regard to its function as part of the overall valve train with one word, that word would be control. Considering that it is the predominant part responsible for keeping all of the valve train components in constant contact with the camshaft lobe, it’s easy to see how important getting the correct amount of spring pressure can be. Insufficient or excessive pressure will cause engine performance to suffer, along with the possibility of damage occurring, which can be severe. In conjunction with getting the correct pressure, there are other areas to address that will make sure you’re getting the best spring for the application."

https://www.enginebuildermag.com/201...ring-pressure/


"The valvetrain is one of the areas where properly matched parts are vital to ensure that the engine functions properly and the valvesprings are the key to this.

https://www.dragzine.com/tech-storie...ring-pressure/



.

[tom s]

You should have 150 on the seats.Tom

[mgarblik]

I found a couple Howards cams with very similar specs, lift and duration @ .050". They recommended 120 and 122 Lbs. on the seat. Spring rate of 330-350. Not sure why the machine shop could not shim them some. Unless coil bind was an issue. Starting at 100 lbs. on the seat means 90 lbs. after it runs about 10 minutes. That's pretty weak.

[Tim Corcoran]

Originally Posted by tom s

You should have 150 on the seats.Tom

What Tom said X2

[1968junkerjim]

Ok thanks I will get some new springs. And new machine shop.

[steve25]

The average hydro roller lifter is at least 10% heavier then a flat tappet lifter.

If you want to rev a 2.11” size Pontiac intake valve driven by a flat tappet lifter to 5500 rpm with a good margin of safety then you need 120 to 125 psi on the seat after the springs break.

Like wise a hydro roller cam would then need a minimum of 140 psi to make up for the difference in mass.

To run a cam of 236/240 with over .500” lift and no be able to buzz the motor to 5500 seems like a flat out boring waste of money to me!

[Steve C.]

It was a mismatch to begin with. The valve spring pressure chart in my old Crane valve spring catalog lists the 99838 spring at 91 lbs at 1.700".


.

[1968junkerjim]

Thanks everyone can’t believe shop told me to run them Think iam going with comp 995 -50 locks and shim them to 0.1650

[blueghoast]

Originally Posted by 1968junkerjim

Thanks everyone can’t believe shop told me to run them Think iam going with comp 995 -50 locks and shim them to 0.1650

Where abouts are you I have a seat cutter for the spring seats
I could lend it to you if you like the you could shim your springs
to your likeing. But if your going that far you mi9ght as well replace?

GT