pushrod length and valvetrain geometery (merged threads)

[jade76]

I had my 350 heads redone with a Comp Cams Magnum Series setup, double springs, 2.02/1.6 valves, 1.52 Roller Rockers and 292 hydraulic cam. I replaced the pushrods with 7.8" Magnums but I'm not sure they're the proper length.

I contacted some techs at the Comp Cams 800 number, but they offered no help whatsoever and so far everyone else I asked (service garages) just wants me to bring it in and charge me. I was considering buying a pushrod length checker, but I'm not sure how that works either.

Can anyone tell me how to verify what pushrod length I need to use? Thanks for any help and suggestions!

[joey d]

Get the pushrod checker, trust me its worth knowing you have the right length, I learned the hard way. take a magic marker on your #1 intake valve tip and blacken it. Use the rods you have now as a starting point and set the rocker up as normal. After you tighten the rocker 1/2 turn, move it back and forth to create a line a the valve tip, now take it back apart a check the line. It should be on the inner 1/3 of the valve tip. If not use the adjustable pushrod to get a length that will put that mark where it needs to be. Look in summit for the available sizes and try those first(custom push rods aren't cheap). You might need a good ruler with 100ths on it to set up the checking tool. Search for this topic if you want a beter explanation, I think chevy muscle of one of those did an article on the whole subject.

[jade76]

Thanx for the tip. I kind of figured I'd have to do it the hard way, but that's also usually the correct way as I've found out.

[DriveWFO]

Here's the article that helped me out:
http://www.carcraft.com/techarticles/116_0401_push/index.html

[Deluga10]

Since I've had all of these problems with the heads on this 350 I'm wondering if the right pushrods were used. How do you determine the length of the pushrod necessay? The engine is running a Comp 292 hydraulic cam with Comp springs .

[69NovaSS]

there is a tool for checking that:

http://www.speedwaymotors.com/xq/aspx/dept_id.905/display_id.536/qx/product.htm

I believe for the SBC the stock length pushrod is 7.800"

[DriveWFO]

Good info here as well for checking length: http://www.carcraft.com/techarticles/116_0401_push/index.html

[Nova67ss]

there is a tool for checking that:

http://www.speedwaymotors.com/xq/aspx/dept_id.905/display_id.536/qx/product.htm

I believe for the SBC the stock length pushrod is 7.800"


I´ve used this tool, simple and easy and quite acurat..

Boroved a orginal pushrod from a friend and started to check, and OHOOoo it was 0.6" to short??? I mesured the rod and the distance and wanted pushrod with a length of 7.8" but I used a STOCK rod??? it was stock for the factory hydr roller 7,2" surprise my books are from before 86 so theres only one faktory length on pushrods. :D

[new2novas]

can anyone tell me if the process used for checking length in the car craft article WFO posted is good for both hyd..and solid lifter cams...i was wondering why that wasn't even mentioned, i would assume the amount taken up in lash has some effect:confused:

[bowtie0069]

good for both hyd..and solid lifter

Shouldn't make a difference.
--I have the tool, but you're kinda far away. They don't cost much and makes it real simple.

[kracon]

Oh crap this came up??

There should be another string on this some where. My buddy has a 68 Camaro 350 and we rounf and round with issues.

Found out the push rods were too short :eek:

[Paul Wright]

I found it and merged 'em together.

[PDXNova]

Does someone know the right way to set up my valve train geomentry? I'm trying to figure the right lenght of pushrod to use. 327, 202 fuelie heads
11.5 compression Comp cam 292/292 lift.501/.501. I have crane roller rockers.
If not, does anyone know of a site that can help me.
Thanks
Steve

[tpinovaII]

Here is a pretty impressive tool for checking that...
http://www.holley.com/80120.asp

Buy it at Summit:
http://store.summitracing.com/partdetail.asp?part=LUN%2D80120&N=4294925139+4294925138+4294859056+4294908216+115&autoview=sku

Or there is the cheaper way out:
http://store.summitracing.com/partdetail.asp?part=MAN%2D42137&N=4294925139+4294925138+4294859056+4294908216+115&autoview=sku

[tpinovaII]

I must be getting old. I had forgot this one.

http://popularhotrodding.com/enginemasters/articles/hardcore/0607em_11_z+engine_assembly+rocker_sweep
http://www.popularhotrodding.com/enginemasters/articles/hardcore/0607em_high_performance_engine_building/photo_11.html
The rocker's sweep across the valve tip can be found by marking the tip with layout dye, and rotating engine through several lift cycles. A centered pattern with minimal sweep is ideal. With stud-mounted rockers, the sweep and position of the roller depends upon the pushrod length. Longer pushrods generally move the pattern out, while shorter ones move it in.

Source:http://www.popularhotrodding.com/enginemasters/articles/hardcore/0607em_high_performance_engine_building/valvetrain_variables.html

How to check for pushrod length:
1.With the cam, crank and timing set installed, bring number 1 cylinder to top dead center on the compression stroke.
2.Install the two lifters that will be used for checking on the intake and exhaust lobes of the cam for number one cylinder.
3.Bolt the cylinder head on the block with no head gasket. (Do not torque the cylinder head, just make it snug).
4.Install the guide plate and rocker arm studs. Again do not torque the studs, just make it snug
5.As a starting point, adjust your checking pushrod to the same length recommended by cam manufacturer for the cam and lifter combination you are using.
6.Install the checking pushrods in the engine.
7.Take your black magic marker and color the tips of the intake and exhaust valves.
8.Install the intake and exhaust rockers and adjust the rockers to zero lash.
9.Rotate the engine over by hand several times.
10.Remove the rockers and note the contact pattern the rockers made on the tip of the valve.
11.If the pattern is centered on the valve tip, pushrod length is ok. If the pattern is wide to the exhaust side of the head, your pushrod length is too long. If the pattern is wide to the intake side of the head, the pushrod is to short.
12.If adjustments need to be made, remove the rockers, recolor the tips of the valves, lengthen or shorten the adjusting pushrods as needed, reinstall the rockers and rotate the engine over again by hand. Repeat the process until the desired pattern is achieved.
13.Once the desired pattern is achieved, remove the checking pushrods from the engine and measure them. Take that measurement and add the compressed thickness of the head gasket being used. The sum of this will be the correct pushrod length for your combination.
Rocker Tip to Valve Stem alignment:
1.With the cylinder head still bolted on the engine, loosely install the guideplate and studs for number one cylinder.
2. Bring number one cylinder to top dead center on the compression stroke.
3. Install the correct length pushrods for the application.
4. Reinstall the rocker arms and set to zero lash.
5.Now you want to check and make sure the rocker arm tip is centered on the valve tip. If there is any misalignment problems, the guide plate can be moved side to side or for and aft to achieve proper alignment.
6.Once proper alignment has been achieved, remove the rocker arms and torque the studs to the proper value. Reinstall the rockers and verify that the guide plates did not move during the torquing process. Repeat the procedures for the other cylinders.
7.Due to varying tolerances in lifter bore indexing, adjusting the guide plate as mentioned above may not allow enough shift to achieve proper rocker tip to valve stem tip alignment. If this is the case, Isky adjustable guide plates may be used in the small block Ford and small block Chevy applications. Since there are no adjustable are guideplates available for the Big Block Chevy, the only alternative would be to slightly bend the guideplate in the center to achieve proper alignment. Since the guideplates are made of a hardened material, CAUTION should be taken when bending the guideplate on Big Block Chevies as cracking may result.

Source:http://www.worldcastings.com/docs/valvetrainadjustments.doc