TNT trouble (sorry long) Update
#473887
09/20/09 08:12 PM
09/20/09 08:12 PM
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Joined: May 2003
Posts: 1,562 Clinton Twp, Michigan
DerickS
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Clinton Twp, Michigan
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Just got back from test n tune and i have a question. I changed cams from a MP .508 that went soft to a Comp .508. No other change and I did not swap the 5 year old valve springs. I encountered a lean pop anything over 6000 rpm in the top of any gear. I thought it was just lean and I jetted up, 2 sizes up front and 4 sizes out back and no change in the lean sputter or pop. BTW the car did not slow down either??? Are the springs shot with the new cam even though it is no bigger than the old one??? I did make a gear change a while back and before the car never went over 6100 with the 4.30, now with the 4.56 it traps around 6400 rpm missing from 6000 up. I let out everytime about a 1000 foot. Any help?
Last edited by DerickS; 09/24/09 08:29 AM.
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Re: TNT trouble (sorry long)
[Re: DerickS]
#473888
09/20/09 08:28 PM
09/20/09 08:28 PM
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Joined: Mar 2008
Posts: 89 Cedar Rapids, IA
69Mcode440
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Cedar Rapids, IA
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Spark plugs, maybe or too much timing causing high rpm misfire.
6400 rpm may be pushing it with the hydraulic lifters and old valve springs.
Mike 69 440 Cuda 71 Dart drag car 70 Duster drag car Best et 9.32, 145.9 mph 2019 Ram 2500 4x4
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Re: TNT trouble (sorry long)
[Re: DerickS]
#473890
09/20/09 08:49 PM
09/20/09 08:49 PM
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Joined: Jun 2006
Posts: 824 NH
72challorange
He's Game
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He's Game
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NH
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Re: TNT trouble (sorry long)
[Re: DerickS]
#473893
09/20/09 09:08 PM
09/20/09 09:08 PM
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Joined: Aug 2003
Posts: 43,129 Bend,OR USA
Cab_Burge
I Win
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I Win
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Bend,OR USA
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A motor will not lean pop in every gear unless it is the jetting or a restriction in the fuel supply like the needles and seats or the jets. If it didn't miss before the cam going flat it is probally the valve springs like you suspect The reason I say valve springs is you didn't say which Comp Cam grind you bought, it is very possible that the new cam needs more spring [list] pressure to keep control of the valve train than the old design Mopar cam did It is also possible like some of the other posts say about the ignition, check the plug wires first I have had a motor miss in high gear above 6000 RPMs due to bad spark plug wires
Last edited by Cab_Burge; 09/20/09 11:42 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: TNT trouble (sorry long)
[Re: DerickS]
#473895
09/20/09 09:43 PM
09/20/09 09:43 PM
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Joined: Jun 2006
Posts: 824 NH
72challorange
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He's Game
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NH
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Re: TNT trouble (sorry long)
[Re: Cab_Burge]
#473897
09/21/09 10:00 AM
09/21/09 10:00 AM
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Joined: Jun 2005
Posts: 6,257 gulfport, ms, west mi
rowin4
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master
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gulfport, ms, west mi
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The reason I asked the rev limiter question was a friend had the same problem. miss at the top end. First thing he thought of was the springs, nope, wires? no, plugs?no switched out the msd box, no, pulled the high limit chip, BINGO!!!!! Give that a try first,good luck
it's ok to butt heads, just don't do it with a butthead
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Re: TNT trouble (sorry long)
[Re: rowin4]
#473898
09/21/09 10:17 AM
09/21/09 10:17 AM
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Joined: May 2003
Posts: 1,562 Clinton Twp, Michigan
DerickS
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Quote:
The reason I asked the rev limiter question was a friend had the same problem. miss at the top end. First thing he thought of was the springs, nope, wires? no, plugs?no switched out the msd box, no, pulled the high limit chip, BINGO!!!!! Give that a try first,good luck
Thanks, man I hope it that simple! it would make my year!
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Re: TNT trouble (sorry long)
[Re: MR_P_BODY]
#473900
09/21/09 11:03 AM
09/21/09 11:03 AM
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Joined: May 2003
Posts: 1,562 Clinton Twp, Michigan
DerickS
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Quote:
Thanks, man I hope it that simple! it would make my year!
You jetted up... did it pick up speed... if so, keep jetting up.... it could be your springs, the hyd cam springs dont like rpm much above 6000(too light to handle the weight).... we had this same problem(my buddies ford pick up) last week during the Hot Rod Drag Week, we tightened the pre-load some and it helped a little. Also you jetted the front 2 jet sizes and the rears 4 sizes... try going up the same amount on each (if you were in the ball park)
It didnt pick up at all....the reason I staggered it front to back so much was because it still has a 3.5 PV up front. I started at 76/82 and ended up at 78/86 and it did not pick up or slow down for that matter. I couldnt run anymore than 32-34 degrees of timing either, i put in 38 and it seemed to hurt it and dropped 2 mph...I've been going over the timeslips and i'm coming up with more ideas. The current cam is ground on a 108 and manfu recommended installed at 104...the old one was ground 108 and installed 106. could this new cam be building more cylinder pressure causing me detonation problems? I have no real numbers but the TRW's are approx 18 thou out of the hole and i'm using a 40 thou fel pro, the heads are 308's with maybe one or two clean up cuts on them...where's my comp ratio most likly at??? With the old cam and no other changes i could run 40 degree's or timing on 93 octane
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Re: TNT trouble (sorry long)
[Re: Hemiroid]
#473902
09/21/09 11:53 AM
09/21/09 11:53 AM
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Joined: May 2003
Posts: 1,562 Clinton Twp, Michigan
DerickS
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Quote:
This appears to be a simple case of operator error!
Its a brain malfunction, clearly i should have sold this car years ago!
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Re: TNT trouble (sorry long)
[Re: Paul_Fancsali]
#473905
09/21/09 01:22 PM
09/21/09 01:22 PM
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Joined: May 2003
Posts: 1,562 Clinton Twp, Michigan
DerickS
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Quote:
My 70 340 ran best with 32 degree's with the 509 if the 509 is old it is a racer brown model I'm talking mid late 70s. The Comp is definitly building more cylinder pressure. Have you tried 30 total and or racing gas? at least 100 octane? Just curious, I also had 340 do the same thing and it was the valve springs but I would check the timing before going threw the hastle
I was caught off guard by the problems so i went up in timing instead of down and had no access to race gas even if I thought of it but I think you are on to something
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Re: TNT trouble (sorry long)
[Re: Aspen7695]
#473906
09/21/09 01:23 PM
09/21/09 01:23 PM
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Joined: May 2003
Posts: 1,562 Clinton Twp, Michigan
DerickS
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Quote:
I had the same problem about three years ago. After a lot of jetting changes it turned out to be the plugs. If pulling the chip out doesn't work, changing the plugs is a cheap way to go. By the way, my Duster is running 11.70's now.
Good luck,
Raul
Raul thats awesome i'm glad your car is running so well!
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