valve train geometry, angle of rockers relative to valves, affected by new parts Options

[Tking327]

Good Morning. Doing rebuild of my '70 1.7L. new parts include pistons, jugs, cam, and had new valves, valve guides and seals and springs installed and seats ground. For cost reasons I decided to re-use original pushrods (in good condition) and rocker assemblies. Upon adjusting valve lash i found there was a larger than expected gap between the tip of valve adjusting screw and the top of the new valve (visually about 3/16 inch gap, at TDC, uniformly on each cylinder). I nevertheless the adjusted the screws to 0.006 according to normal procedure (there was plenty of thread) but now worried that my geometry is off and i may get damage at startup, or poor performance. Visually, after adjustment, i would say the angle between rocker arm and top of valve stem is about 85-88 degrees but thats hard to eyeball. Am i crazy to move forward without custom fitting/ordering new pushrods to make up the gap? Why do I have such a large gap given the new parts are stock from reputable suppliers? I waited 7 months for my cam to be made - i am getting impatient and dont want getting new custom length pushrods to delay me by more months - but at the same time want to protect my huge time investment and have it run well

[930cabman]

Good Morning. Doing rebuild of my '70 1.7L. new parts include pistons, jugs, cam, and had new valves, valve guides and seals and springs installed and seats ground. For cost reasons I decided to re-use original pushrods (in good condition) and rocker assemblies. Upon adjusting valve lash i found there was a larger than expected gap between the tip of valve adjusting screw and the top of the new valve (visually about 3/16 inch gap, at TDC, uniformly on each cylinder). I nevertheless the adjusted the screws to 0.006 according to normal procedure (there was plenty of thread) but now worried that my geometry is off and i may get damage at startup, or poor performance. Visually, after adjustment, i would say the angle between rocker arm and top of valve stem is about 85-88 degrees but thats hard to eyeball. Am i crazy to move forward without custom fitting/ordering new pushrods to make up the gap? Why do I have such a large gap given the new parts are stock from reputable suppliers? I waited 7 months for my cam to be made - i am getting impatient and dont want getting new custom length pushrods to delay me by more months - but at the same time want to protect my huge time investment and have it run well

check and double check, but if I recall the valve stem and rocker adjusting screw should be in plane at mid lift.

[Ninja]

Iann Karr made a bunch of vids when he built his T4.
He has a couple that deal with valve train set up.
They are awesome!

Find and watch those, they will answer many (if not all) of your questions.

https://www.youtube.com/iankarr

[VaccaRabite]

You won't like this answer - but if you built anything other then a bone stock engine, using stock pushrods isn't going to be optimized. And even if you did build a bone stock engine, its still not likely to be optimized even if it works.

You want the rocker stem to be perfectly aligned with the valve stem at 1/2 lift. Which is found by figuring out the peak lift on the valve, and then going to 1/2 that amount of lift and visually checking the alignment of the valve stem and the rocker stem. With re-used pushrods you should be "close" but aside from swapping pushrods around you are just going to get what you get. And if swapping pushrods around does significantly change alignment - that means your pushrods are worn and are different sizes...

The good news is that LOTS of engine get built and reuse the pushrods. And they work "fine." You won't ever have it fully optimized - it may not last quite as long, and you may not get quite as much power - but you may not ever notice. And an engine that only lasts 20K miles - thats 20 years of weekend cruising for most owners these days.

In your case - rotate the engine by hand. Does it bind? Probably not. And that means you won't get catastrophic failure on startup. At least not due to valve train. It just won't be optimized.

If you just want your car driving, optimized may not matter. If you are making a performance engine, maybe it does. I'm guessing you are in the first bucket. If you are in the second bucket... dude don't reuse your pushrods!

Zach

[VaccaRabite]

Since you said you reused your pushrods - be mindful that other things being re-used in the valve train may cause you issues even if the engine spins fine by hand.

If you also decided to re-use your lifters but changed to a new cam (or reused the cam and bought new lifters) - STOP! Your lifters and cam MUST be matched. A mismatch in cam and lifter can wipe out a new cam within just a few minutes and fill your entire engine case with metal shavings. It happens. It SUCKS! It leads to a complete engine teardown and redo.

If you even suspect a cam and lifter mismatch, stop and make sure that is not the case.

Zach

[Jack Standz]

Good Morning. Doing rebuild of my '70 1.7L. new parts include pistons, jugs, cam, and had new valves, valve guides and seals and springs installed and seats ground. For cost reasons I decided to re-use original pushrods (in good condition) and rocker assemblies. Upon adjusting valve lash i found there was a larger than expected gap between the tip of valve adjusting screw and the top of the new valve (visually about 3/16 inch gap, at TDC, uniformly on each cylinder). I nevertheless the adjusted the screws to 0.006 according to normal procedure (there was plenty of thread) but now worried that my geometry is off and i may get damage at startup, or poor performance. Visually, after adjustment, i would say the angle between rocker arm and top of valve stem is about 85-88 degrees but thats hard to eyeball. Am i crazy to move forward without custom fitting/ordering new pushrods to make up the gap?

Why do I have such a large gap given the new parts are stock from reputable suppliers? I waited 7 months for my cam to be made - i am getting impatient and dont want getting new custom length pushrods to delay me by more months - but at the same time want to protect my huge time investment and have it run well

A new cam is not "stock". Building a Type IV motor reasonably means you will have to measure things and not "eyeball" clearances. Ian Karr's videos will give you good insight into his process, especially setting up valve train geometry.

If you don't have good valve train geometry (which includes proper length pushrods), you won't get your money's worth from your cam because you won't get its full lift and full performance. And you will have increased valve guide wear and thus shorter engine life with more oil burning.

Building a Type IV motor requires patience. Because you're using a non-stock cam and other factors (like reground/new valve seats, seals?, etc.), custom length pushrods with the length determined by mocking up your motor and carefully measuring things to get a good valve train geometry is what you should be planning now and/or during the 7 month wait for your camshaft. Rather than order custom length pushrods and delay your motor build by "more months", you could cut your own if you follow Ian Karr's videos. Depending on your abilities and if you're confident you can cut your own pushrods, it should only take a few hours to do so.

Best wishes for a successful project!