I am currently building a 350 for my Camaro. It's a base model 350 block from a 74 corvette. I have a Comp Cams Magnum Hydraulic Camshaft in it and Comp Cams Magnum Rollertip Rockers to sit on top. For heads, I found a set of the Protopline Vortec heads. We bolted on one of the heads and tried to install the rocker arms. With the rocker arm tightened down far more than it should be, the pushrod was still far too short, somewhere between a half inch and an inch too short. I called the guy I got the heads from, and he told me that the Vortec heads use stock length pushrods. I have been told numerous things by different people, suggesting I need a roller cam, or self aligning rocker arms, or pedestal mount rocker arms, or just longer pushrods. My stock heads work fine, but I would really like to use these Vortec heads. What exactly do I need to make this work? If I do need a roller cam, what do I need to put that in my older block?

 

Do you have regular hyd flat tappet lifters in the block? And maybe a set of pushrods for factory roller lifters? There's about 1/2inch difference.

 

yeah, the lifters and cam came together, non-roller hydraulic. the pushrods were from the 74 vette block.

 

So you're saying, the pushrods you have that are too short with your new heads were the same ones installed on your engine before and they used to fit right with your stock heads?

 

yes, when i put the old heads on, the pushrod length is fine, but with the new heads, they're too short.

 

It must not be true that the protopline vortecs use stock length pushrods. Unless the pushrods that you have aren't stock length...
IIRC 7.794" is stock length for flat tappet SBC, all years.

 

i think my pushrods are 7.6", which is a little shorter than what you're saying, but i'm talking at least 1/2", probably close to an inch.

 

That's bizarre...
Maybe your new protopline vortecs are defective. Or maybe the valves are way too long.
There's only a limited number of things thst can upset valve train geometry that way. It might be time to measure everything.
Where are all the other guys who have protopline vortecs??

 

I have good news and bad news....the problem your having is that you are assuming Proline Vortecs are too similiar to factory Vortecs. The Proline Vortecs have increased cooling around the valve pockets, enhanced flow, drilled and tapped rocker studs and .....the source of your problem....a much increased deck thickness. The factory Vortecs are a little thin in this area and area somewhat limited to how much you can mill. The Proline Vortecs are capable of being safely milled to a 50 cc chamber !! This is great news for those wanting high compression or have a small displacement motor to be used on. Unfortunately this thick deck will require a longer than stock pushrod length. I know your bummed...I sure was when I installed mine. Your best bet is to buy a pair of adjustable pushrods from Jegs (Crane brand are listed) or Summit (Summit has their own, as well as Trick flow listed) and do a mock up with the adjustable pushrod until you get the right length. The "right length" will be determined by the geometry of your rockers. Put some machinists dye on the valve stem tip....turn the motor over two full times...and adjust the adjustable push rod until the full travel of the rocker tip stays in the center of the valve tip. You will be able to tell where it's riding by the elimination or wiping of the machinists dye. Some people like sticking a small piece of paper in the gap instead of machinists dye. Works just as well. IT DOES NOT HAVE TO STAY IN ONE PLACE...but it does have to ride in the center area, not anywhere near the outer edges of the valve stem tip.

 

yes, i do remember reading about the increased deck thickness. so for the adjustable pushrods, you install those, find the right length, then get a set of real pushrods in that length? that's cool, we were probably going to go in that direction anyway. the guy helping me build the motor was a gm mechanic for like 12 years, but he got out of it before gm came out with the vortec heads, so he's not real familiar with them. he said we might try the adjustable pushrods, but he wanted to research the problem a little further first. thanks man

 

I'm still waiting on my adjustable pushrods. If you get yours mocked up before me, post the length. It will give us Topline useres good data to start off with.

 

i will let you know if i figure it out, but i am still undecided what car the motor will actually end up in, so i doubt it will be very soon.

 

I'm mocking mine up in the next couple of weeks. I am using retro-fit hydraulic rollers but I will post the original retrofit size and the new size I come up with. The difference in length should be helpful to any set-up.

 

how many adjustable pushrods do you need to check the length? do you just test one rocker at a time, do you need to do 1 cylinder at a time?

 

You only really need one. Two is easier but not necessary. Verify motor is at top dead center on #1. You can check both intake and exhaust for #1. That should be sufficient for getting your length. The length should be the same for both assuming your running the same ratio of rocker for both intake and exhaust. If it's not, something is wrong.