Re: pick a solid roller for this combo
[Re: mopar dave]
#2849650
11/21/20 05:28 PM
11/21/20 05:28 PM
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Joined: Jan 2003
Posts: 31,203 Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,203
Oregon
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Ok, maybe i'm wrong here, but the .119" number was using clay to get that number. That is fine but it doesn't really help you too much unless you know exactly where the cam was when you recorded the 0.119 number. The only practical solution is to use published numbers which is lift at TDC for the lobe. The cam catalogs usually publish lift at TDC and then you have to do a valve drop test to see how much room you have at TDC. Once you know those numbers then you can figure out which lobes will fit and which won't.
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Re: pick a solid roller for this combo
[Re: mopar dave]
#2849702
11/21/20 07:31 PM
11/21/20 07:31 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
master
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master
Joined: Apr 2006
Posts: 4,220
West Plains, MO
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Piston is chasing the exhaust valve as it closes, and the smallest clearance is something like 5-10 deg BTDC. The intake is opening before the piston starts down, so its clearance is the tightest at 5-10 ATDC. Unless I got those backwards Anyhow, the rule of thumb I usually see is around .080-.100 intake, .120-.140 exhaust - but if you're brave, you can run it closer until you start seeing witness marks on the piston top!
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Re: pick a solid roller for this combo
[Re: mopar dave]
#2849743
11/21/20 09:15 PM
11/21/20 09:15 PM
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Joined: Aug 2003
Posts: 43,744 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,744
Bend,OR USA
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You determine how much P to V clearances you like I've ran as little as .030 on the intakes and .060 on the exhaust accidently on my old NHRA M.W. Stocker after having the heads milled to NHRA blue print specs without thinking about rechecking the P to V clearances. That motor had its tongue out around 6400 RPM I'm thinking back then NHRA only allow stock Mopar valve springs specs. which were 110 Lbs. on the seats and and right at 300 Lbs. at .509 lift on both valves. I never had a bent valve or any evidence of valve hitting the pistons, I did see a lack of carbon build up on some of the pistons on the exhaust valve sides of those pistons with stock rods which had some of the pistons closer to the heads than others I know many good SO CA Mopar engine builders that recommended .060 P. to V. clearances on the intakes and .080 on the exhaust on automatic tranny cars, .080 on the intakes and .100 on the exhaust side with stick shift cars back then with stock valve spring pressures I'm good with .060+ on both valves with todays roller cams and valve springs Let me throw another rock into the pond on this discussion on P to V clearances with a solid lifter cam compared to a solid roller cam with the same specs and same LSA, I've seen a lot more P to V clearances on solid roller cams than with the same size solid lifter cams My message is to make sure you check every motor for P to V clearnces on both sides of the motor and make sure and verify TDC on your balancer and degree wheel when setting the cam intake lobe center or verifying the LSA on your cam, check both the intake and exhaust lobes I've had more than one cam not be ground on the LSA that was stamped on the cam and cam card
Last edited by Cab_Burge; 11/21/20 09:33 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: pick a solid roller for this combo
[Re: mopar dave]
#2849841
11/22/20 08:58 AM
11/22/20 08:58 AM
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Joined: Jan 2003
Posts: 10,088 Frostbitefalls MN (Rocky&Bullw...
gregsdart
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,088
Frostbitefalls MN (Rocky&Bullw...
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I'm curious to your cam specs if you don't mind. My specs are for a 15/1 compression 550 cube motor, so the specs won't compare. 285/296/114 with .867 int and .800ex lift. On my 499 low deck motor with 13/1 compression and bowl ported 440-1 heads i ran a Ultradyne 283/290/108 with .740? And .680? Two things come to mind to help. That cam needed SPRING! I picked up a bunch by putting a 300+ seat pressure spring in it, and looking back there was more power available if i would have gone to a better pushrod. So if you have good enough valvetrain parts you can run a more agressive cam. That is why i mentioned Jones. You need a plan= lifters,pushrods,rockers, springs, all spec'd to fit the cam design or vise versa.
8.582, 160.18 mph best, 2905 lbs 549, indy 572-13, alky
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Re: pick a solid roller for this combo
[Re: mopar dave]
#2849843
11/22/20 09:03 AM
11/22/20 09:03 AM
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Joined: Jan 2003
Posts: 8,082 Tulsa OK
Bad340fish
master
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master
Joined: Jan 2003
Posts: 8,082
Tulsa OK
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I rolled the engine with clay on top of the piston. I thought the best way was by measuring 10* ATDC? While that may not be the best way to tell it does tell you how tight it is at the tightest point. But since you don't know exactly where that point is it makes it hard to use that data to compare to another camshaft.
68 Barracuda Formula S 340
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Re: pick a solid roller for this combo
[Re: mopar dave]
#2850426
11/23/20 12:55 PM
11/23/20 12:55 PM
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Joined: May 2005
Posts: 2,072 Apollo, PA.
B1MAXX
top fuel
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top fuel
Joined: May 2005
Posts: 2,072
Apollo, PA.
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I called comp and asked for the lift spec at TDC and they did not have that. They tell me the valve should be closed at TDC. I did find some of my notes and did find a valve drop spec at TDC , 368 on intake. WOW......
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Re: pick a solid roller for this combo
[Re: mopar dave]
#2850542
11/23/20 03:11 PM
11/23/20 03:11 PM
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Joined: Jan 2003
Posts: 31,203 Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,203
Oregon
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Lift is .141@106 and .124@110*. So .368-.141=.227? Don't you have rocker arms?
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Re: pick a solid roller for this combo
[Re: Cab_Burge]
#2850589
11/23/20 04:45 PM
11/23/20 04:45 PM
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Joined: Mar 2009
Posts: 2,490 Sydney,Australia
tex013
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top fuel
Joined: Mar 2009
Posts: 2,490
Sydney,Australia
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this is what i do when having any doubt Tex
New best ET 10.259@129.65 . New best MPH 130.32 Finally fitted a solid cam, stepped it up a bit more 3690lbs through the mufflers New World block 3780lbs 10.278@130.80 . Wowser 10.253@130.24 footbraking from 1500rpm Power by Tex's Automotive
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