Yes, i use checking springs. I notice as the intake is opening and at 10*ATDC the intake is the closest to the piston( mine is tight against it), but i feel no binding while barring over. Exhaust is closest at 10BTDC while it is closing, i have about .095.
My old SFT that i just removed had .118" p/v clearance measured with clay at the time and it had a .403" lobe lift with same 1.65 rocker. New cam has .430" lobe lift and with same 1.65 rocker has 0" clearance measure with dial indicator. The numbers don't add up here and the cam is in at 103.5 with a spec of 104. It seems like the cam was not ground properly. Open specs jib with the cam card, but the exhaust don't. I tried checking closing points .050 before close and as the valve closes. Can't get the correct number. What am i doing wrong?

Thats scarey. The piston is in contact with the piston at 10*ATDC using checking spring. I can not feel it in the breaker bar as im barring engine over, but i can not open valve at that point by hand with that rocker, thay are tight together. I think it would be a good idea to replace the 1.65 intake rockers with 1.55's to be safe, what do you think. I didn't want to pull the heads to check this time. I only use the clay method while engine is on a stand. Thanks

I have trouble seeing that process as checking v/p clearance. 0 lash, light checking springs, none of this represents the engine in operating conditions. This is more of just a check of "will I crash anything AT o lash, then I definitely won't at normal operating condition for sure". At 0 lash with checking springs you probably have enough clearance if it hits. I am not saying this won't keep you out of trouble. It is very good (generous) at that, but this is not checking actual v/p clearance.

Lobe lift has very little to do with it duration/ cam timing has much more effect than lift.

Move the cam to 106 and see what you get.

I did check open lifts with 1243 springs installed and .020 lash. Intake opens .665" and the exhaust has .625" max lifts.

A few times that I have needed to know what the V/P clearance after the engine is on the dyno, I used a length of some .090 acid core solder, just put it in through the spark plug hole, towards the intake valve and crank the engine over by hand, put it out and measure with some calipers, then do the exhaust.


Joe

Great idea. I used to do that on 2 strokes years ago. Thanks

Which is least harmful on hp, swapping out 1.65 for 1.55 or retarding cam 2*?

what lash setting are you using?

.020” on both valves. Harland Sharp just told me there could be as much as 1 full ratio deflection between a checking spring and a heavy valve spring. Measure the rocker as valve opens and then the retainer as valve opens to figure deflection using checking and 1243 springs .Changing to a 1.5 rocker won’t fix it.

Put it at 106, check the clearance, then measure/figure in the deflection.

That’s what I do on the ones where the measured clearance when using checking springs is close/marginal.

Since the spring pressure hasn’t gotten real high with the lifts you see when the V/P clearance is closest, there usually isn’t all the much deflection at that point.
I checked some HS “1.6’s”, and they were 1.67 with a checking spring......and still 1.63 with 700lbs open load at .700-ish lift.

I’d say, if everything was as it should be, and you come up with “zero” V/P intake clearance with a checking spring, and you already have the exhaust clearance near the min....... you’re not going to be able to get to what most would consider “adequate” intake clearance(for me that’s about .050” min) by changing the RR by .1, and moving the cam 2*.
Plus, whatever you gain on the intake side by moving the cam...... you’ll lose a similar amount on the exhaust.

Off the top of my head I’d say moving the cam 2* will give you about .016”, and dropping the RR by .1 you’d get another .020” or so.
You’d go from zero with the checking spring to .036”. You’d need another .015” deflection at that lift point to get it to .050”(and then there’s the question of if you’re comfortable with .050 on the intake, and whatever you lost on the exhaust by moving the cam).

Thanks for chiming in Dwayne. Something I failed to mention is I had 0 lash using the checking springs, so add .020. Also I don’t have my new pushrods yet, using my too long pushrods from the flat tappet setup. The rocker adjusters are turned all the way out to get the pr to fit. I know it’s not right, but does that cause any real issues in measuring? Appreciate the help Dwayne

Ran my numbers thru a simulator which jibs with my Moroso slide rule with my SFT511. my new roller shows best performance at 106 install compared to 108 and 104. 108 wouldn't be a bad place to land either, It just moves the power band over giving 6 more peak power and same torque as at 104. I think i might be able to make this cam work without destroying anything. I need to order a new pushrod checker(loaned mine out) and some new pushrods, retard cam to 106 and see what happens. Thanks guys

You have a lot going on and I know myself I would have to go over the info several times with a clear head.Thank you for your post.

No problem Clinton. Looks like retarding the cam fixes a couple things. I don’t think long stroke BB like a lot of advance cam timing anyway.

You will never know what that motor in the car will like until you try it both ways
Sometimes making more power slows the car down due to traction limits, same thing on making less power
I've always made more power on the engine dyno by advancing the cams, lost power retarding them. Not the same results at the tracks
Fuel supply can limit the power and you will never find that out until you fatten it up enough to slow the MPH down in the 1/4 mile I've seen some really fast cars have that problem and the owners-tuners didn't know it until they tried to speed those cars up in the 1/4 mile by fattening them up Once they fix the fuel supply the cars would run quicker and faster, another reason to test all the time to make sure you have maxed that combination out

That’s very true. I won’t know how much clearance I gain by retarding the cam til I try it either. Depends on how aggressive the lobes are.