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New Cam and lift numbers - Frustrated - HELP

2K views 7 replies 5 participants last post by  arnoldtx 
#1 ·
289
Bored .040
4 valve relief pistons
Deck height .016

Replaced the bone stock heads with press in studs with a set of stock heads ported and polished and just back from the machine shop.
The heads have GM valves 1.87/1.60
The heads came previously ported and polished with the valves already in them.
I cc'd one of the chambers at 53cc.
Pulled previous PBM hydraulic flat tapped cam

Installed new:
Thumpr Hydraulic roller cam 31-600-8
Comp Cams timing set 2120 Dialed in at 0* and spot checked with degree wheel
Howards Retro Link Bar roller lifters for SBF 91168
Felpro Head gasket .047 compressed and 4.100 bore- torqued to 50/60/70 ft lbs with new ARP head bolts.
New ARP Rocker studs with 2.000 effective length - previous studs were too short for the Miller's per Paul @ Hyflodynamics
Comp Cams springs - 986-16 installed to spec'd height by machine shop.
Miller SBF 1.6 roller rocker arms (PVS 3060 part number)
Verified 10* angle between rocker stud and valve

Cylinder #1 - removed dual springs - replaced with checker springs on intake and exhaust

Cam card calls for .3320 lobe lift and gross valve lift of .531
Dial indicator verifies what the cam card calls for using just push rod with max lobe lift on intake of .3320

Did Mid-Lift process on push rod only in bringing push rod to .166.
Installed rocker - adjusted nut until I got mid-lift number on retainer/valve from 0 to .265.

Checked for 90 degree from rocker top to poly lock - ended up with a push rod length of 6.646 per Miller - mid lift instructions.
(as a note I get the same results with 6.3 to 6.550 length push rod lengths.

I am totally stumped. I place the dial indicator on the retainer or even the roller ( have tried both multiple times - verifying everything is as perpendicular as possible.

Max lift continuously gives me a dial indicator number of .550 (too much lift).

Any ideas?

I have to use checker springs as the Howards have a rivet for the link bars that do not allow me to convert it to a solid lifter.

So as long as there is no binding on the rocker - push rod length should not matter - as lift is lift....

I'm frustrated as I have walked away from this the last 2 nights not understand what might be happening?

I'm open for any suggestions at this point.

I haven't ordered push rods as I was double checking the max lift before I ordered them. So here I sit , frustrated.

Thanks for and advance and the counseling session :)
 
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#2 ·
You probably did this, but was the dial indicator zero'd out while the lifter was on the base circle of the cam?

Could your rockers be 1.65 instead of 1.6?

Have you measured just the lifter lift and is it .332?
 
#4 · (Edited)
Yes - 0 out the indicator.
Yes - .332 just at the pushrod only side.
Im going to go out and measure full lift again. To be honest once the indicator got past 540/550 I wouldnt finish it out to see what the lift ended up at...
Maybe they are misprinted.
Think is I sent am email to the rocker vendor before double checking that these were 1.6 ratio - making sure the right part numbers matched up... and then at one point I thought I was getting the .532 ... once I did, I called it a night and went back to it and since then I have been getting the .550+ number. (maybe the 1 time I got it the lifter was in proload somehow ( I had a previous pushrod checker tool that I was using that was catching on the pushrod guide) I have since replaced that tool with a different tool. I get the same results when using an actual 6.4 length pushrod I have that were sent as part of the kit by default. I know to not just throw them in but to measure - but PR length shouldnt matter on these numbers as long as the rocker is not catching on anything/hitting/clearance in the good.

Ill post my results, going to do it now ( total lift numbers).
(EDIT) .555 on the dial indicator.
Thanks for your feedback and anyone else that cares to chime in it is appreciated.
 
#3 ·
hello;

its impossible to get more lift than the cam and rocker provide, therefore, either your cam is bigger than spec or your rockers are exactly 1.65 as was suggested because your lift calcs out to 1.65 rockers. if they were advertised as 1.6 i would call miller and see what they say.
.
 
#6 ·
Checked for 90 degree from rocker top to poly lock - ended up with a push rod length of 6.646 per Miller - mid lift instructions.
(as a note I get the same results with 6.3 to 6.550 length push rod lengths.
Welcome to the Forums. This part confuses me. Any change in pushrod length should change both the the valve lift and rocker angle at cam mid-lift. How are you getting (or what do you mean by) "the same results" with pushrods from 6.3" to 6.646"?

David
 
#7 ·
I think what I meant (lol) was not worrying about geometry, with ZERO LASH, I got the same max lift no matter the length of the pushrod.

Im going out today sometime and going to reset my thought process, take a deep breath and then go about matching mid lift, 90 degree rocker arm and pushrod length, dialing in all 3.

Then I should have the best overall geometry and whatever result I have it what I think I am going with.... :)

We will see, I am sure I will talk myself out and into it between now and then :)

Thanks,
CK
 
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