I don't get any spark when I try the jump wire test at the crank trigger connection. Should I see a blink on the LED whenever I break the connection with this test? I don't have a spare coil, so anything that will help diagnose the lack of spark may help here. I see when I turn on the ignition I have 12.8v at the small red wire and the led is continually blinking. 1 1 code, or cam sync problems. Any ideas?

When my coil quit I could hear a high frequency sound from the coil when the trigger wires were shorted but no spark from coil.

DOA THATS MY DIAGNOSIS
Tried other coils, checked all wiring, voltage. Sooooo,, about a grand ($) later, a new box is on the way. My old one is a 7530. So old, it can't be rebuilt. Potted, not rebuildable. Nice paper weight though!

Sorry to hear your box died, and that it was so expensive to replace.

I’m glad to know that my ignition needs can be satisfied with lower cost options.

Did you ask MSD or someone else about repairing it? Pat Collins at TechWest Racing in North Carolina repairs a lot of MSD stuff.
I have no experience w/ those boxes, just wondering if MSD was just trying to sell you a new one.

This is off the OP's original subject, but does anyone have some experience as to the upper limits of an original MSD-6al as far as max compression ratio/ RPM before needing to upgrade to a 7?

I was running methanol. At 13/1 and went from a 6m to the digital 7. No gain. A big part of it is plug gap. If you think you are on the edge try different gaps, from as tight as .025 to .045 and see how the car reacts.
My digital 7 was a dinosaur, and one of the first built which were potted with resin and impossible to fix in a reasonable amount of time.

Thanks for the reply. I seem to have hit a 6600 rpm wall and not sure what is causing it. it's not really a miss, more like a rev limit....it just seems to go flat, but not like it's the end of the power band.

the cam is a .904 intake lobe flat tappet with 150 lb. seat press. and what I think is good geometry (used a B3 rocker relocation kit) with Stewart 3/8 x .120 wall pushrods.

I'm at 13.3-1 gasoline. I have a 6A and tried a 6AL with no chip....still the same, tried various plug brands and heat ranges and gaps....re-did and added some grounds to both the engine and MSD...new tach (old one had a built in shift light)

I have an O2 recorder and when it hits 6600, it goes rich. I tried various jet/ bleed combos and they reacted as expected till 6600. next on the list is another distributor.....currently a stock one I've used for years up to 7200 in previous engines, but they weren't as high compression ratio.

Imo....... and acknowledging I don’t know everything about your combo........I bet it’s a valvetrain issue...... most likely springs.

Do you know the spring part number and installed height?

Check your sparkplugs.
From experience you might be going real lean at WOT.


I'd add 3 or 4 jet sizes richer.

The springs were installed at about 1.95. I say "about" because I was shooting for as close to 150# as I could get juggling the shims.

The 150# figure is at the low end of the recommended range of 150-160, and maybe with what gets lost from new till they settle in a little, I guess could be it.
The open pressure was also close to the recommended setting, but there again, it would have been at the low end. (can't remember the brand or p.n off the top of my head right now, but they would have most likely been Crower or Comp....i'll check my notes tomorrow)

I've not run into a problem like this on any previous builds, but maybe this lobe's a little more aggressive than most. I didn't think with a flat tappet, that spring pressures were super critical. Maybe I'm wrong in that thinking.

it's a 4.35 x 4.15 w/7.1 rods, bushed lifter bores, indy ez's ported standard port, tunnel ram 2-750's , 1.6 int./ 1.5 exh. rockers, 2"x 32" pri 3.5 x 18" collector


It's a Mike Jones cam
272/280 @.050"
.407"/.406" Lobe Lift
110 LSA
You'll need a spring with 150-160# on the seat, and 360-380# at max lift

I must say that I am quite pleased with how it runs up to the point where it flattens out....I do think there's a bit more to be gained when/if I can get it to RPM a little more.

I have not found that to be the case at all.
What I find is that people are worried about running high open loads and the cam going flat, and often aren’t running high enough loads for the rpm they’re turning.

You didn’t say if you were running 1.5 or 1.6 rockers, but 1.6’s would require more load.
I don’t know which heads you’re running, but if it’s something that uses big heavy offset intake rockers...... that needs to be taken into consideration as well.

In a BB bracket race build, looking for say 7200rpm capability, with a reasonably fast rate design lobe...... I’d be looking to be in the 420lb open range........ maybe more depending on how fast the lobe is.

Lobe design is a big player.
The first cam I ran in my 383 went 7k clean, no problem.
Second cam, which had a little steeper closing ramp struggled to get past 6500..... with all the other valvetrain components the same.

It’s a nice idea that you don’t need high spring loads on flat tappet cams for high rpm use........ but many times, that’s just not how it plays out.

Obviously I don’t know for certain if that’s your problem, but based on what you’ve outlined as what you’re running for spring loads...... I wouldn’t rule it out.

I have tool steel lifters, so I wasn't too worried about the going flat part, I just stayed on the lower end figuring less spring pressure= less rotating power consumption.

Could the 10 or so pounds less than the max recommended rate make a 4-600 lower rpm limit?
I also realize things like spring checker accuracy comes into play here and I surely won't swear that mines 100% accurate, but I have assembled some "other brand" pretty high rpm (8-9000 rpm) roller-cammed stuff and spring pressures seemed ok on them.

Sorry about the previous post, I didn't see that there was more to your response when I replied.

The rockers are 1.6 int. and 1.5 exh. that is what Jones suggested to use. The rockers are standard offset from Hughes.

Thanks for your replies to my questions and if the distributor ends up not being the problem (I really don't think it will be since it's been to 7200+ before), I'm going to move to springs next.
Do you have a spring preference in the poundage and installed height we've been discussing assuming it is what would be considered a fast rate designed lobe? I do know the intake lobe is a .904 designed one with the exhaust lobe a .875 one

I agree completely, those springs are way too light IMO for a .650 lift solid cam. I run that much spring on a .509 cam. Contrary to popular belief, I believe too light of a spring causes way more problems then heavy springs do. Valve train instability ( harmonics, vibration and valve bounce) kills way more cams then premature wear from heavy springs. I'll take the extra parasitic drag resulting in a stable valve train any day of the week.

No, 10lbs or so isn’t likely going to fix it.
40-50 is more like what it will take.

The other issue is trying to find something where the distance to coil bind is within the desired range.

Something like an Isky 8205-SP or 8205-Plus, and then adjust the IH to 1.900(-.050 locks).

More than likely, you could just do the intakes.
The slower lobe, 1.5 rockers, and lighter ex valves probably aren’t having any problems.

I agree with your thoughts completely, I was just under the assumption that I had sufficient pressure.

Years ago I ran a 282* @ .050 .570 lift solid with 130 lb. seat pressure to 7200 (didn't make power up there, had a little too much gear)....But, it sure didn't run like this one.....I guess that was then and this is now.

Thank You for the advice, I think I'm going to take it and give new springs a try....that seems more likely after our discussion than my next thought of different distributor.

Thanks again, i'll update you when I get some results.

It may be the issue, it may not be........ but it has the symptoms of a lack of valvetrain control.

I did an RPM headed 451, 272@.050 solid using very smooth high rpm lobes.
.650 lift with a 1.6...... springs 150/410....... peak power at around 7k.
Ran it to 7400........ slight signs of a loss of control on the dyno sheet at the very end of the pull, but the power barely dropped off, and there were no audible signs of any unhappiness.
Had I used MM lobes, I think it would have struggled to get past 65-6600.


Now...... back to your regularly scheduled “dead MSD-7” thread

Taxi, If you want to go really fast just borrow your brother's Hemi and rev it!