Valve lash, how much is to much?
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Valve lash, how much is to much?
I am looking to gain as much low end TQ on a 580 BBC with 12 degree spreadport heads to help with the 60' times. Running a Comp Cam custom solid roller that calls for I-.024" & E-.026" lash. Rockers are: Int 1.8 and Ex 1.7 ratio. How loose can I "safely" run this setup to find more lower RPM TQ without hammering the cam or valve train to a point of damaging it? I will be checking back as time allows to answer any questions that maybe required to get your answers. Thanks in advance for any real world feedback, Walt
Re: Valve lash, how much is to much?
I wouldn't use lash to Increase torqueMesik Motorsports wrote: ↑Fri Oct 19, 2018 10:55 am I am looking to gain as much low end TQ on a 580 BBC with 12 degree spreadport heads to help with the 60' times. Running a Comp Cam custom solid roller that calls for I-.024" & E-.026" lash. Rockers are: Int 1.8 and Ex 1.7 ratio. How loose can I "safely" run this setup to find more lower RPM TQ without hammering the cam or valve train to a point of damaging it? I will be checking back as time allows to answer any questions that maybe required to get your answers. Thanks in advance for any real world feedback, Walt
Increase launch rpm, and or converter flashpoint.
Radial or slick?
@580 inches you should be making plenty of torque.
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Re: Valve lash, how much is to much?
Can you advance the camshaft?Mesik Motorsports wrote: ↑Fri Oct 19, 2018 10:55 am I am looking to gain as much low end TQ on a 580 BBC with 12 degree spreadport heads to help with the 60' times. Running a Comp Cam custom solid roller that calls for I-.024" & E-.026" lash. Rockers are: Int 1.8 and Ex 1.7 ratio. How loose can I "safely" run this setup to find more lower RPM TQ without hammering the cam or valve train to a point of damaging it? I will be checking back as time allows to answer any questions that maybe required to get your answers. Thanks in advance for any real world feedback, Walt
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Re: Valve lash, how much is to much?
I wouldn't deviate from the recommended lash settings. If you are seeking more low end torque, change the cam. Advancing or retarding the cam will confirm that the cam is wrong for the application . . . . . . that is all.
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Re: Valve lash, how much is to much?
It is a slick tired rear engine dragster. Agree it is not the ideal method, however it is an option to learn and a HELLUVA lot cheaper and easier than swapping converters if not subjecting anything to damage. The converter will be re-stalled eventually, the run graphs show a downward hook in the launch (flashes 6400 and drops to 6300 @ .4 -.5 into the pass) where the converter "grabs" and the effort is to flatten the graph to see the ET gains, not run it there forever.
Re: Valve lash, how much is to much?
Advancing the cam or loosening lash will not have a big enough impact to change the 60. He needs more launch rpm or to short stage.E.R. Racing wrote: ↑Fri Oct 19, 2018 12:00 pmCan you advance the camshaft?Mesik Motorsports wrote: ↑Fri Oct 19, 2018 10:55 am I am looking to gain as much low end TQ on a 580 BBC with 12 degree spreadport heads to help with the 60' times. Running a Comp Cam custom solid roller that calls for I-.024" & E-.026" lash. Rockers are: Int 1.8 and Ex 1.7 ratio. How loose can I "safely" run this setup to find more lower RPM TQ without hammering the cam or valve train to a point of damaging it? I will be checking back as time allows to answer any questions that maybe required to get your answers. Thanks in advance for any real world feedback, Walt
Assuming he has a cam in the mid to late 280s@.050 it should be making north of 800lbft.
It could be chassis, rollout, gearing or launch rpm. If it's doing a wheel stand and blowing past the 60 on the rear tire, it will show a slower 60.
Or get a better converter, you may be blowing through it.
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Re: Valve lash, how much is to much?
Can you advance the camshaft?
Already advanced 4 degrees and will need to go through the entire P to V clearance checks again. When building it I did not check P to V clearances at anything beyond 4 degrees ADV. My notes indicate OK to 4 ADV with nobody to blame but me for not documenting data rather than OK...
Already advanced 4 degrees and will need to go through the entire P to V clearance checks again. When building it I did not check P to V clearances at anything beyond 4 degrees ADV. My notes indicate OK to 4 ADV with nobody to blame but me for not documenting data rather than OK...
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Re: Valve lash, how much is to much?
Assuming he has a cam in the mid to late 280s@.050 it should be making north of 800lbft.
Camshaft is 288/308 @ .050" 328/348 adv with 114CL
TQ is 905 @ 6000
Myself, I did not completely buy into the cam data. The cam to me is better suited if the combination was a 632 using the 4.75" stroke. I am a 4.53 bore with a 4.500" stroke.
Whats your thoughts on a camshaft vs what I have?
Camshaft is 288/308 @ .050" 328/348 adv with 114CL
TQ is 905 @ 6000
Myself, I did not completely buy into the cam data. The cam to me is better suited if the combination was a 632 using the 4.75" stroke. I am a 4.53 bore with a 4.500" stroke.
Whats your thoughts on a camshaft vs what I have?
Re: Valve lash, how much is to much?
sounds like a great choice to me. Thats what i would run for an engine of that size. I agree with the maybe you are blowing through the converter.Mesik Motorsports wrote: ↑Fri Oct 19, 2018 12:27 pm Assuming he has a cam in the mid to late 280s@.050 it should be making north of 800lbft.
Camshaft is 288/308 @ .050" 328/348 adv with 114CL
TQ is 905 @ 6000
Myself, I did not completely buy into the cam data. The cam to me is better suited if the combination was a 632 using the 4.75" stroke. I am a 4.53 bore with a 4.500" stroke.
Whats your thoughts on a camshaft vs what I have?
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Re: Valve lash, how much is to much?
Why don't you post up the graph?Mesik Motorsports wrote: ↑Fri Oct 19, 2018 12:07 pm It is a slick tired rear engine dragster. Agree it is not the ideal method, however it is an option to learn and a HELLUVA lot cheaper and easier than swapping converters if not subjecting anything to damage. The converter will be re-stalled eventually, the run graphs show a downward hook in the launch (flashes 6400 and drops to 6300 @ .4 -.5 into the pass) where the converter "grabs" and the effort is to flatten the graph to see the ET gains, not run it there forever.
Stan
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Re: Valve lash, how much is to much?
If you want to know the valve lash workable range you need to know the lash point lift where the lash ramp ends. Ask comp cams for this design spec on your 2 lobes. Multiply by rocker ratio, deduct .002".
Why not first try tighter lash to see if the car slows.
Less risk in that try .016"--- .018" say.....
Why not first try tighter lash to see if the car slows.
Less risk in that try .016"--- .018" say.....
Last edited by F-BIRD'88 on Fri Oct 19, 2018 2:44 pm, edited 1 time in total.
Re: Valve lash, how much is to much?
With a real 6400 stall speed on launch you don't need more low end torque, you want more top end torque. 6000++ rpm.
You may want more converter stall torque ratio.
It will then hit harder at launch, if the tires can use it.
Tires are a big factor. Smaller tire dia= more launch torque.
You may want more converter stall torque ratio.
It will then hit harder at launch, if the tires can use it.
Tires are a big factor. Smaller tire dia= more launch torque.
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Re: Valve lash, how much is to much?
I will do my best... have to figure out how to get it from the Racepak software to an image for posting. It will be a few days before I can make anything happen, we are heading out for a race shortly.Why don't you post up the graph?
Re: Valve lash, how much is to much?
If you want to know that you still have enough vtp clearance if you advance the cam then first advance it a LOT, say 10 MORE DEGREES. now set lash at 0 on #1 and #6.. Now By Hand turn the crank slowly by hand.
Thru 2 complete cycles. If the valves don't touch the piston, you can now reset the cam advance to say +4 or +6 and reset the running lash.
As you advance the cam the intake valve gets closer to the piston and the ex gets further away.
Thru 2 complete cycles. If the valves don't touch the piston, you can now reset the cam advance to say +4 or +6 and reset the running lash.
As you advance the cam the intake valve gets closer to the piston and the ex gets further away.