Race it, Don't rice it!
ACL says to put it on the cap but it doesn’t really matter. Seriously. It’s in the catalogue.
We did this with the Briggs and Stratton 5 hp single cylinder motors for my son's racing go kart. It was pretty wild. You could hear it go into float at the end of the straight and the kart would just jump. You couldn't cheat, because the motor got tech'ed if you won, but he won a lot of kart races with that little trick!One advantage of less pressure over the top is with solid lifters you can use the inertia of the valve train to loft the valve beyond the cam’s stated lift.
Did you do a geometry check when you made that length assessment??If you're using a standard base circle cam, and tie bar lifters that are +.300, I'd expect it to need 7.6 pushrods.
7.8 - .300 + .100 (the valve height should be +.100 on those heads).
My 383 has a .050 smaller base circle cam, and it measured out to needing 7.650 pushrods (+.300 lifters and +.100 valve height).
Is there something I'm not aware of that would make you expect 7.4 to be right?
I don't know how far you can fudge it, I'm just saying it wouldn't be the "correct" length.
I won't say the 7.650" is for sure wrong, just the math you gave didn't track, and that 7.650" is a number I have never seen in an SBC before....so I just wanted to be sure you had figured things out and ended up with a good geometry.Well that would be a big misunderstanding on my part then...
The odd thing is that I did do that whole geometry check, and came up close to 7.650...
I guess I'll have to go through that whole check again.
The pushrods in my 383, Profiler heads with HR cam uses 7.45 pushrods. I am just finishing my coffee, then going through the mid-lift method on the new motor. I expect it to need 7.45's but maybe I'll get lucky.I'm not sure what I had done differently before, but I just ran through it a few times, and it does appear that 7.45 - 7.5 seems like it's pretty accurate.
So based on the correct base numbers, provided by Eric, I'd assume that 7.450 would be where I'd expect to be...
Since this whole process is based on "eyeballing", it now seems to me that it might actually be easier to "have the correct numbers in the first place"... and start with your checker pushrod at the length you expect to need.
Snug up your locknut, then perform the process backward... back off your locknut 1/2 the gross lift, then check to see if the line on your rocker is parallel to the spring retainer.
If it looks good, it most likely is.
If it doesn't look good, then repeat the process in the normal order and see what you come up with.
I'm willing to bet that if you have the right numbers in the first place, the reverse order process will work out.
If it doesn't, then either something is wrong, or you had the wrong numbers for some reason.
So it would be changing it from "figuring out what it should be" to "making sure it is what it should be".
I think I was aware of the correct numbers at some point, but that was last year, before the virus and waiting and waiting and waiting months for my machine work and heads...
To the OP: sorry for questioning what you were doing... I'm glad it at least served a purpose... in reverse.
Dang, I just went through that too short of a rocker stud problem with my build.Yep, just what I figured. The 1.8" studs are too short. They are what came with the Profilers. The start of the mid lift deal is to get the lifter perpendicular to the valve stem on top of the closed valve. When I do that I can't get a poly lock on. It's flush at the top of the stud. I tried to use a dial indicator on the valve and set it at half lift and set the height of the trunnion from that, but my light checking springs pushed the oil out of the lifter. I will just have to wait on the taller studs and do it Foxwell's way (Straub).
Well, my ring filer is here so I can get back to short block assembly.