roughskinjrz

hey i have 16 pushrods

2 different size sets

(8) competition cams 7963 7.700 0.80
(8) competition cams 7993 7.900 0.80

im running trick flow g2 twisted wedge heads, and i was wondering if this is correct

8 7.700 on the intake valves and 8 7.900 on the exhaust valves?

roughskinjrz

anyone?

8Mike9

Pushrod length checker...you may not want either.

roughskinjrz

what do you mean i may not want either?

and how do i check the pushrod length checker.

8Mike9

A PR checker is basically an adjustable pushrod. Install the PRC as you would a normal PR, rotate the engine and check contact pattern on the valve tip and rocker. Search here or on Comp/Crane/etc site for the method of choice.

roughskinjrz

ok i get you.

you can move the pushrod up or down until its the right length.

how would you know tho, when you tighten a roller rocker, its gonna tighten to the pushrod either way isnt it

8Mike9

I think this is the correct link, and can explain much better than I.
http://www.compcams.com/Technical/Products/Pushrods/

roughskinjrz

ok its just the guy that sold me this had the same setup i did except a bit bigger came and different roller rockers.

8Mike9

Well, then I would definitely want to measure for the correct ones.

Ofcourse you could always install one each and check contact pattern, if correct, then use as-is...my guess is you will be getting new PR's

roughskinjrz

sorry im new to engines

what do you mean install one each and check contact pattern

when i put the pushrod in onto the lifter and put the roller rocker on

how would i tell if its too long or too short or just right?

8Mike9

You'll need some marking compound, etc...when you rotate the engine, and the lifter goes up and down, look at the contact pattern on the valve stem and see whats rubbed off. Take a look at the link. If you can visualize the valvetrain from cam to lifter to PR to rocker to valvetip...then you can see how too long or short of a PR will affect geometry..i/e where the roller will contact the valve.

8Mike9

What I meant by "install one each"...is just that, put what you have on one intake and exhaust and check pattern, then reverse them, check again...you might get lucky and they are correct, but I would not bet on it.

roughskinjrz

too technical for me. lol.

im gonna sound like an idiot here but what a valve stem?

if i just install these pushrods, and turn on the motor, what chance am i taking, just bent lifters?

8Mike9

I'm gonna make a suggestion.

Pick up a copy of "how to rebuild your smallblock Chevy" and "how to hotrod your smallblock Chevy" before you begin installing those heads.

I know it's neat to dive in, but you need to know the basics of what you're working on first, so you avoid expensive mistakes.

roughskinjrz

yeah i know, the heads and intake are already torqued on the motor.

thats why im asking this.

Damon

Last time I ran the Twisted Wedge heads (a few years ago) I ended up needing custom length pushrods (.100 longer than stock) but both the intake and exhaust were the same length. Pushrods that are .200" different in length int vs. exh sounds out of whack to me, based on my expereince with the heads.

roughskinjrz

what is stock 7.8?

i have a full set of 7.7, 7.8(stock), and 7.9

i was just told to use the 7.7 for the exhaust to open and close faster? and the 7.9 for the intake. does that make sense.

Damon

The length of the pushrods has nothing to do with when the valve opens or closes. It's length must be correct to give proper rocker arm geometry. That is the only purpose of using different length pushrods- to make sure that geometry is correct for your combination of cam, lifters, heads, rockers and valves.

If you want a "quick and dirty" way of checking for proper pushrod length get yourself a cheap Moroso pushrod length checker. It's just a piece of plastic that shoves on over the rocker studs and contacts both the pushrod tip and the valve tip. If it hits the pushrod tip first the pushrods are too long, if it contacts the valve tip first they are too short. Checking is always done with the lifter on the heel of the cam (valve fully closed).

In the case of your G2 heads you want to do your checking on the EXHAUST side since that is still a standard 23* SBC valve angle (the tool is built only to work with a stock 23* SBC valve angle). Whatever length you determine you need on the exhaust, use the same length on the intake and you'll be close enough. If you're using hydraulic lifters it's better to have pushrods that read slightly too long by the tool. When you set your lash down 1/4 - 1/2 turn as usual you're effectively "shortening" the purshrod when the lifter guts are compressed slightly by that 1/4 - 1/2 turn on the rocker arm adjusting nut.

How close do you need to be? Well, for a street motor anything withing .050" of perfect is plenty close. Again, it's better to err on the side of slightly too long than slightly too short in most cases, especially with hydraulic lifters.

ALWAYS check one other thing when playing with different length sticks..... the clearance between the bottom of the rocker arm and the "shoulder" at the base of the rocker arm stud. If the "ideal" length sticks are so short that it's causing the bottom of the rocker arm to rub against the shoulder of the rocker stud you need to use longer sticks- REGARDLESS of what that does to rocker geometry.

roughskinjrz

ok if i do that, and what if they the exhaust ends up being too short, or too long, what will happen to the motor when i turn it on?

Damon

Within reason, nothing bad will happen. That's why I say not to sweat it if you're +-.050" from ideal. If you get too short you'll have clearance issues between the bottom of the rocker arm and the shoulder of the rocker stud plus you may have clearance issues between the bottom of the rocker arm and the top of the valve spring retainer (more common the bigger the diameter of the valve springs in your heads). Too long and you can run the rocker arm out of travel at max lift or (rarely) hop the tip of the rocker right off the valve tip (or close enough to it to cause damage).

roughskinjrz

well i put the roller rockers on today, because its the set i was given, 8 x 7.700 and 8 x 7.900

i was told if it hits the pushrod first they are too long, and if its hits the valve tip first the pushrod is too short

but when i put them on, they hit even

so i assume this is good then

roughskinjrz

ok, well i just purchased comp cam 1.6 pro magnum roller rockers, got rid of the trick flow roller rockers.

i also got a 7.8-8.8 comp cams pushrod checker.

i had 7.9 7993 comp cam pushrods installed, but the rocker arm was hitting the base of the rocker stud, and leaving indents on the rockers, so im guessing the problem is i need longer pushrods.

now i read triple times each thread on how to check geometry, like use a marker and put a mark on the pushrod, and turn the motor 2 full revolutions. and look and what impression it leaves, do i look at base/mid/max lift and see if they put on outer/middle/inner?

is this the easiest way, i am running trick flow twisted wedge heads, with just a .454 lift cam, hoping to get .486 out of it with the rocker arms, haha.

can someone explain again how this is done, the easiest way

Lo-tec

The wear pattern on the valve tip will be a thick line. You want it to be centered on the tip. If it's shifted towards the intake manifold (too short), lengthen your checker. If it's shifted towards the exhaust, shorten the checker.

Also, you mark the valve tip, not the pushrod.

roughskinjrz

thats pretty simple, do i even need the marker? or is it better so you can tell exactly where it is.

so at max lift on the intake side, if the geometry is correct the valve tip should be centered, and not on the inside or outside.

Lo-tec

Yes, you need to use a marker. You want the wear pattern centered on the valve tip, not the position at max lift.

roughskinjrz

ok so centered at all times while i rotate the motor?

Lo-tec

Instead of 1000 words!!

roughskinjrz

i know what that meant, but i was just wondering at max lift, mid lift, and base it should be centered on the valve tip at all times right

roughskinjrz

ok so it cant be this easy

i used my comp cams adjustable pushrod, and used one rocker, but it on one of the valves. if your on the driver side the #1 it was on the right one.

i used a marker, made a line like you showed in the center. put the roller rocker one til zero valve lash, then i did a half turn and tightened the allen key. i turned the motor 2 full revolutions, took off the rocker arm, and the line was still in the center, it didnt smudge anywhere else, is this perfect? which means i had the adjustable rocker set on 8.000"

the ones before were 7.900", also these roller rockers are HALF the size of the big trick flow rocker arms i had. i watched the rocker as i turned the motor and notice it didnt even come close to hitting the stud or anything.

Lo-tec

here is a link to where I got the pic, along with a couple other pics of what it looks like with the pushrod too long a too short.

http://images.search.yahoo.com/searc...tt=30&ei=UTF-8

Change the length of your checker by .050", check it again, and see if it moves the mark on the tip of the valve. You may have guessed the right length the first time. Also, check more than one cylinder .

sofakingdom

iTrader: (1)

Get it straight from the horse's mouth.

http://www.compcams.com/Technical/Cu...ML/306-307.asp

It doesn't matter that the pattern that the rocker makes on the valve stem is centered; what matter, is that it's as narrow as possible.

roughskinjrz

lo-tec thats perfect, should i check intake and exhaust on a few cylinders it doesnt matter which one?

those diagrams are perfect, ill have to do it over, since the line i made was kinda thick, and not thin LOL

roughskinjrz

ok in that picture Lo-Tec it looks to me like he used a market to mark the whole valve tip except a narrow center line? is this better then just using a marker to make a small narrow center line

Lo-tec

Mark the whole tip, run it a couple of times around with your checker installed, and remove the rocker arm. It will leave a mark on the tip just like in the picture.

roughskinjrz

i should be able to pull that off, thanks for all the help, you simplified it big time, haha.

roughskinjrz

oh man i am confused, i tried on a couple different cylinders, and 8.000 looked too long

i tried 7.900 again on the first cylinder on the exhaust side and it was perfect, so i was like ok ill try 8.000" and it showed that it was too long, wtf

7.900 is the same size pushrods i already had on the vehicle with the trick flow rocker arms.

could the roller rockers be the problem?

could 7.900 work with these roller rockers?

roughskinjrz

also with the trick flow's they would hit the rocker stud, and loosen up everytime they would be on base lift.

these ones stay nice n tight the whole time through 2 revolutions and on 7.900 it didnt leave an imprint moving in the direction of the pushrod being too long or too short

i am confused, lol, and it sucks because i sold those 7.900 pushrods when i found out i was getting new pushrods and rocker arms.

roughskinjrz

ttt

Lo-tec

So, check a couple others at 7.900. If that length looks correct, then use it.

roughskinjrz

its just that i had the problems WITH the 7.900's, im asking if the difference between these pro magnum's and the trick flow's could be the problem.

Lo-tec

If the old rockers hit with 7.900's and it is the correct length, the problem was with the rocker, not the pushrod. If your new rockers don't hit now, and the length looks good, then use them along with the 7.900 length pushrod.

roughskinjrz

thanks, i just sold the old set to, that was stupid, oh well time for new ones.

KillerMiller

Ok. I also have a set of Trick Flow Twisted Wedge Generation 2 heads on my 69 Corvette. Great head, once you get the valvetrain geometry figured out.
1st, what makes these h3ads flow so well is that the intake valve angle is at 15 degrees, instead of 23, and the exhaust valve angle is at 18 degrees, instead if 23. Which allows air and fuel to flow more directly. Rumored to have great mid and low lift flow numbers at and below .500 lift. You will notice that the rockers sit slightly angled.
I did some port work on mine. They flowed 273 cam at .500 before the port work.
Anyhow, when I bought the heads, they had around 3500 miles on them. Had previously been on a 4x4x4 truck. I quickly realized I needed the pushrods that went with them. They were very long, at 8.750 length. But they worked. Had trick flow laser engraved on the pushrod.
TFS said to not exceed .525 lift, 236 degrees of duration on a 106 LSA with flat top pistons, to avoid piston to valve clearance issues. Previous cam was a Lunati Bracket Master 2, with .515 lift, 248 duration @ .050, on a 108 LSA. I checked, and had adaquent clearance, so long as I didnt float the intake valve. The intake valve was closing as puston came up, and just got out of the way before top dead center. While the intake valve does not line up with any valve relief whatsoever, the exhaust valve looks like it lines up perfectly with the relief on the top of the piston, although the valve may be slightly bigger.
That cam ate 2 exhaust lobes and began spittibg back through the carb. Ugh.
Now, just today I am installing a Comp hydrolic roller. The roller lifters are longer than a regular tappet lifter, and made the 8.75 too long. However, with the standard sbc pushrod length, 7.8, still too short, making my roller rockers hit the valve retainer. So, off I go. What I find is a big block Chevy intake pushrod length is 8.23, and i am hoping it works. I bought the 4 they had, waiting on the other 12. They were .99 cents each at Autozone, and I usually always go to O'Reilly's, but summit has these for 1.99. Anyhow, part # MPT-379. Made my Mailing.
I have an old video, but will make some more today.
While I have not in depth checked the geometry, I observed that while I had the 8.750 pushrods with the flat tappet lifter, the rocker's roller tip looked a little long, as in hitting the exhaust side of the lifter. Praying these 8.2s are the answer.
By the way, this roller can't specs are .560 lift, 230 @.050, and 110 LSA. I realize the lift far exceeds TFS recommendations, but being on a 110 LSA will help the intake valve close a little sooner, and with tighter springs, maintain more control over the valves. Being a street car, the 230 duration should be more street friendly, and seal the compression better, be happier on N20. I'm at 11.4-1 on compression. 3500 stall. Original motor for my 69 Corvette, but motor is currently in my 71 Chevelle after the big block in the Chevelle died.
Excited for this build to come to life today. I will take a few pics and write back soon.
btw, cam part # 286HR10 by Comp.

KillerMiller

Melling part # MPT-379 for the 8.23 inch length pushrods. Stupid autocorrect.

NoEmissions84TA

iTrader: (1)

Pushrods in any length are commonly available today.
Usually in increments of .050", but you can even find increments of .025".
The correct length pushrod, whatever length that ends up being, will give you the sweep pattern pictured below.

KillerMiller

Well, hold the presses! Here is a very important message. The 8.2 inch pushrod is a hair too long with the longer Retro-fit roller link-bar style lifters from Comp. I noticed that the end of the slot on 1 of my rockers was contacting the poly-lock, and moving the entire rocker stud, slightly. While the other 15 we're extremely close. Determined that from reading these articles earlier, that indeed, a stock pushrod length would just barely work correctly! While I do not have the ultra-gold, super magnum rockers, mine are rollers, just the regular kind. And the sholder of the spring retailer just does clear the rocker when the valves are adjusted. Reason for it is that the roller lifter are just long enough longer than a tappet lifter to work. So, finally, this motor is purring like a kitten, and growling like a Tiger!
Thanks again for being a very valuable resource.