Don Terrill’s Speed-Talk

Im working on a smallblock ford with blue thunder 3.6 heads. We had a set of a3 heads before this. We used a 1.8 rocker on previous setup but on this head i have the rocker contacting poly lock just before full lift. Same cam etc. Is it likely the rocker stud location is in different spot?

I've also tested a crower 1.73 rocker and it nets more lift than the 1.8 did on old head.

Are you using the same push rod?

Stan

No Stan these heads are thicker so im using a adjustable to find length. Had to add .300 to get nice sweep. Heres crower.

I have no idea why pics turned??

Steve,
If you change the push rod length to get the 1.8:1 to work what doe the sweep look like?

Stan

Thanks for straightening!! Stan if i shorten enough to clear the rocker belly hits on hex of stud. Likely valves are a smidge short for 1.8. I could I guess notch the back of 1.8 behind poly locks and see where that goes.

Steve,
Do you have any lash caps you could try?

Stan

Stan I dont have any buy no reason why I couldn't get. The keeper is set up for them.

Steve,
Any update?

Stan

Are you sure the rockers are for both applications? Are they Cleveland BT heads or just standard BT3.6 heads? From my research, and I admit I know very little about Ford heads and their valvetrains, it appears that they use different valvetrains. Are the A3's Cleveland heads?

If so, they may explain it. The BT Cleveland heads use a rocker that's only 1.52" where the standard BT3.6 uses a rocker arm that's 1.65" in length. Using the shorter arm on the standard heads would likely give you results exactly as pictured, I think.


I'm no professional and I know very little about Ford heads but this stuck out to me so I thought I'd bring it up.

Or is it a known fact that A3 valvetrain is supposed to swap between A3's and BT3.6's?

Of course to evaluate the effect of a lash cap, you could just use a feeler gauge or metal scrap of the correct thickness on the valve tip.

Steve.k wrote: ↑Mon Nov 04, 2019 9:53 am Im working on a smallblock ford with blue thunder 3.6 heads. We had a set of a3 heads before this. We used a 1.8 rocker on previous setup but on this head i have the rocker contacting poly lock just before full lift. Same cam etc. Is it likely the rocker stud location is in different spot?

Steve.k,

If those are the heads with the Cleveland valve angles, and the rocker is part number 4580 (1.8 ratio), then:

1) The rocker arm does not have the exact design geometry for achieving optimum installed geometry on those particular heads*
2) The pushrod you are using is way too long and/or the overall length of the valve stem is too short for cylinder head setup
3) The rocker arm is over-arcing and effectively diluting the camshaft lobe's information
4) (All 3 of the above points are compounding overall set up & setup results)

*but can be made to work if you fix Points 2 & 3 (above)

Forget "roller sweep" right now as it's the least of your problems; first fix what's wrong with the parts combination.

Paul

P.S. If these are not the heads with the Cleveland valve angles and/or that is not a p/n 4580 rocker, then please advise and I'll try again to help.

P.P.S.: All of the above assumes rocker stud is correctly located

The only trivia I can add is that those 2 rockers will require different pushrod lengths.
If already noted ...carry on.