Stumped on valve geometry

[volksdragn]

Hi all,
As all of these posts on valve train geometry start, I have read as much as I can on the topic and I believe I have it by the fuzzies, however I have a hiccup. I have the cylinder 3 and 4 side done with good geometry using lash caps and stock rods; perfect setup, on the 1 and 2 side no lash caps and stock push rods and the rocker is hitting the Valve stem. I can do the combinations to make it work, but it seems odd to have two different set ups on the opposite sides of the engine. My question is, is it common to have different length pushrods on either side of the engine/ and or different combinations of shims etc. to make the geometry right? I would think the solution for one side would be the same for both. The engine is a 1914, scat c45 with CB 1:25 ratio rockers. Thanks John,

[Piledriver]

If the heads are different deck heights abandon all hope of both sides working out the same...
Or maybe even running well for long.

Might want to measure everything again and fix the differences side to side.
4 holes making the same power makes for a happier engine.

[volksdragn]

I agree with you on that, it's just really weird. The deck height is the same on both sides. I pulled the heads off and swapped sides with them, re torqued them and the issue swapped sides. So the issue is in the heads luckily I have another set that I'm getting cleaned up and going to go through them tomorrow before work. So as it stands the issue lies in the heads being different but I just can't imagine why, I'm really not set up to measure anything efficiently, I'm using a machinist rule and straight edge so it's hard to find the difference on the bench with the heads not mounted.

[Piledriver]

Heads same part#?
Have you CC'd them?

Might reveal past shenanigans...

[Marc]

A syringe-based CC'ing kit only runs about $25 and is a worthwhile investment if you're going to be doing engine work. You can even make your own using Plexiglas scraps and a horse syringe (got a vet nearby?)
While more difficult to get accurate readings with than a burette setup, it still gives you a much better idea of what your C.R. is going to be than any other measuring tool.

Even if the raw castings are identical, the depth of flycut, the height of the rocker stand pads, and the installed height of the valves will all affect the valvetrain geometry. If the latter is different there'll also be implications for the valve spring tension.

You should be able to detect gross differences using just your straightedge & rule, but considering how much differences in the chamber volumes will affect the success of the build I'd strongly recommend that you CC any heads you're going to use.

[volksdragn]

Yes I have cc'd the heads and they are all very close to the same, I would say they are the same there is just that slight bit of fluid that gets lost in translation. Marc I have been rolling those same thoughts in my head for the past few days and I busted out the ruler and a straight edge and could only come up with slight differences a few hundredths here in there on the fly cut, I believe he main difference was the height of the valve, I'm thinking maybe at one point one of the heads had some work done. So I started over from scratch tonight and four hours later I'm satisfied with the results. I got the geometry right on both sides, the only difference is that on one side the adjusters are screwed farther out than on the other side but it's not to bad. After measuring and re measuring and re measuring I think the difference lies in the valves. So as bad as I hate to say it I Chauck a lot of my difficulty here up to lack of experience in he valve train department. But the last three days have been a vast learning experience. Thank you for your help! -John

[Piledriver]

A good head guy would set it up with all valves/seats uniform depth/length, trimming each tip for length if needed
(not on a new big valve/seats job though, they should start consistent at least)

...and when finished you should be able to put a straightedge across the ends and hit all 4 within a few thou with the rockers off. (They should also stay that way, makes for an easy test to watch your exhaust valves stretch over time )

Makes life easier starting with a good foundation.

[volksdragn]

The foundation is key. Especially if you aim to keep your sanity. We will see how she runs here shortly hopefully