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Author Topic:   High RPM miss
fordsblow
Dirt Roller

Total posts: 14
posted June 05, 2002 03:30 AM
I have a MSD billet distribitor with the Cap-A-dapt cap on it and MSD 6AN box ( all bought used at an auction), with a 7000 rpm rev limiter chip. The car starts, idles and rev's up fine in the pits, but under load on the track it breaks up and pops through the exhaust. I have swapped out the box ( with another unknown MSD 6AN ) and it still does it. I put back in my old stock HEI and it ran fine again. The coil is a brand new MSD Blaster 2 so I don't think that's it, I have a good ground going direct to the MSD box from the battery and a heavy ground engine to chassis. I'm thinking the distribitor must be bad?
Thanks, Ken

dirtbuster
Dirt Maniac

Total posts: 106
posted June 05, 2002 09:30 AM
Make sure your battery is good. We had a bad battery that caused a miss at higher rpm's. If the MSD box doesn't get enough voltage they won't work right. It didn't pop like you described just caused a vibration but it may be something to check.

Mudrat454
Dirt Roller

Total posts: 17
posted June 05, 2002 10:41 AM
Be sure and check all your electrical connections at your MSD box and your ignition switches. I had this problem and it was a loose connection at the ignition switch. It would only miss under a heavy load but not in the pits. Also on the bad battery issue, I think an MSD box will run with 10 volts where an HEI takes closer to 12 so I would think the battery would not be the problem.

fordsblow
Dirt Roller

Total posts: 14
posted June 05, 2002 11:17 AM
The battery is good, and all the connectors on the boxes are brand new GM weather tight connectors. When I went to put the constant hot and ground in the GM weather tight connectors I had to strip the wire a little smaller to fit in the terminal end. Would a couple less strands at the terminal matter?

sdhnc29
Dirt Freak

Total posts: 349
posted June 05, 2002 10:51 PM
If you have the cap adapter , I assume you have an adjustable rotor too . You need to phase the distributor . Drill a hole in an old cap next any terminal , and shine your timing light in the hole as the engine is running . Look to see if the rotor tip is pointed directly at the terminal when it fires . If it is not , and it sounds to me like it's not , then loosen the ***** 's on the adjustable rotor and "phase" it so that it is pointing at the terminal when firing .

What you have discribed is in line with the rotor being out of phase . A few more thing's to look for that could cause this problem are ........ Mag pick-up wire's being crossed , and the mag pick up wires running parallel to the coil wire or any other high tension wire . Any of these thing's will cause the problem your describing . To check the mag pick up polarity , simply time your engine , and then reverse the mag pick-up wires . At this point your engine will either advance a ton , or retard a ton . The correct polarity will be in the most retarded position .

Hope this helps !

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

[This message has been edited by sdhnc29 (edited June 05, 2002).]

dirtracer14
Dirt Freak

Total posts: 333
posted June 05, 2002 11:26 PM UIN: 23443678
I have had probs with the blaster 2 coil and so have 2 others at are track. The car would sputter at high rpm then a few races later they were done. This weekend a buddy came in from the heat were his car sputtered and died he hit the button and fired right back up so we changed to the blaster 3 and no probs, i found out the hard way and got a DNF when mine went out since then i allways run the 3 with no probs. just my 2 cents

fordsblow
Dirt Roller

Total posts: 14
posted June 06, 2002 02:43 AM
I E-mailed MSD, and without telling them how my coil was mounted they said:
"Make sure that the Blaster 2 coil is mounted in an upright position and not horizontal. This would cause a problem with the coil because the oil inside would not cover a portion of the windings resulting in the coil overheating, arching internally."

I had the coil on the side firewall horizontaly,so hopefully now it will run fine after changing it to vertical.

Thanks for the help,
Ken

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