HARDCORE A/O

I've just discovered that I need some longer pushrods for my AFR heads. I'm changing from Merlin VRs and wondered if anybody had done this swap already and knows what the length difference was. I tried checking with a dial indicator and as far as I can tell I need like a +.250" Intake and a + .100" Exhaust. I'm about to order a pushrod length checker (adjustable pushrod) but would like to be able to order the pushrods at the same time (since the shipping will be like 3X the cost).
BTW: I'm running a standard deck height Merlin and Comp Hyd Roller cam, Crane lifters and Crane gold race rockers. The rockers and lifters are unchanged and I'm pretty certain that the base circle on the Comp cam is the same as the Crane it replaced (since the lift didn't change much). Any Idea anyone?

Turbojack

I did that head swap. When I get home tonight I will try & find the box that the pushrods came in since I do not remember the length.

KAAMA

iTrader: (1)

I had to change my pushrod length going from Dart Pro-1 heads to the USED 357cc AFR heads I initially had on, and then I had to change the pushrod length again with the NEW 315cc AFR heads----but then pushrod length should always be checked from engine to engine as it can or will usually vary from one engine to another anyway. This is especially true when the block decks have been cut or the heads resurfaced, gasket thickness, etc.

HARDCORE A/O

Thanks Guys. The heads are not cut nor was the block decked, but I take the point that the pushrods should be carefully checked to determine the length needed for each application, especially when mixing and matching a couple of different brands of valvetrain parts.
BTW: My Merlin came with 7.55" Int. P-rods and 8.68" Exh.
From what I'm seeing with the dial indicator, I need like a 7.80" on the Intake and a 8.8" Exh. I'm setting the geometry so that the rocker's roller tip is very slightly on the intake side of the valve stem with the lifter on the base of the cam. Is this how you do it?

Vinny P

Try this link. It has all you need to know.

http://www.compcams.com/Technical/Products/Pushrods/

HARDCORE A/O

Thanks Checkmate.

HARDCORE A/O

Walgreen:
Thanks. I never thought of the marker thing. That makes it much easier than squinting at the rocker tip while you're cranking the motor over. I have a friend who is going to lend me his Comp Hi-tech adjustable p-rods (I think I need two because of the difference in lengths of the int & exh.) which are the one that extend 0.050 per turn. Once I've measured them, I'll post the lengths so at least it might be some use to people who are using similar components to mne in their BBC.

Turbojack

I checked & I must have thrown out the box. I thought I had taken the old ones & put in the new box but all I found was the old push rods. Sorry

HARDCORE A/O

Thanks again guys. The factory stock P-rod length for flat tappet cams is 8.25" Int. & 9.25" Exh, so it makes sense that Walgreen's were 7.85 and 8.75 because they would be like a 1/2" shorter to allow for the taller roller lifters. Most of the time from what I've seen and read the 8.25/9.25 is what everybody uses for stock GM heads and block and a flat tappet set up.
The thing that gets me is that there was so much difference in length between the ones that were in my motor (7.55" Int. and 8.68" Exh.) which tells me that there must be some difference in valve lengths or angle on the Merlin VR heads, especially on the intake. This is confirmed by the fact that the 8.68" rod is very close to perfect (on the Exh.) when I checked it on my AFRs, but the 7.55" Intake is so far down in the giuideplate that the rocker nearly touches both the g-plate and touches the spring retainer. I believe the AFR's also have a different angle on the intake (like -2 deg), so that would explain the slight variation needed on Walgreen's setup.
I'll bet that when I measure them properly, I'll end up needing very close to a 8.75" and a 7.85".

HARDCORE A/O

Just out of curiousity, I checked the Comp Cams catalog and they have recommended part #'s pushrod listed for all of their Hyd. Roller cams which measure 7.725" Int and 8.684" Exh respectively. Sounds like we're close. I might end up only needing a different length Intake P-rod. I'm still going to try to get the best length I can with the adjustable pushrod though.