On a digital msd6 box I remember a discussion about the pick up wires from the crank trigger being oriented differently than on an analog box but can’t remember which way is which. Can I get some help please? Got a 565 on alcohol that had blown head gasket twice now in fifty runs. Made it 11 runs this time before it popped. 4.610 bore Merlin block, is domed piston edelbrock race heads. Last time had block milled and heads milled, both minimal just enough to ensure flatness. Timing is locked at 36* as was when we got it. I need to stop this carnage.

A few thoughts.

You may not need that much timing. May very well be worth some dyno time to get timing right and you may be surprised to find it likes 30-32 better and easier on parts to.
Also I know many say you do not need to re-torque heads but I lost a head gasket one time. After that I started re-torquing heads and never an issue since for what that is worth. Get motor good and hot and run it through a few heat cycles then let it cool and torque heads. You will find that many get some rotation before they reach full torque again.

Pick-up wires orientated so that…………

Digital Ignition = most advanced
Analog Ignition = most retarded

I know about the retorque on the heads. Been my standard practice for years. This one didn’t get it last time because the owner insisted on taking home immediately so I didn’t get to retorque heads or recheck the valve lash after got it started up for him. I agree timing maybe too high but that’s where it was when he got it. I’ve heard but can’t find it now that the crank trigger wires must be oriented differently digital to analog. I know when he changed to the digital box from the old 6al the timing advanced way up and I had to back it down to 36*. Just looking to stop the detonation. I’ll set at 28* to start this time.

Thanks makemark, that’s what I was looking for. Just couldn’t say it.

It can be checked with a timing light on the crank trigger pickup. The magnet should be lined up with the pickup if it's not swap the wires.

Another thing to consider is your timing marker may be off a few degrees and same with your timing light and that could add up to a problem.

So you are thinking your box may be advancing timing at higher RPM?

Curly timing pointer is correct. I checked and corrected it when I degreed the cam. Just this is the third time in this thing in 18 months. First time he broke a lifter on his fifth pass in the truck. I refurbished it with a new cam same as before. New crower hippo lifters new billet oil pump all new bearings and gaskets. He wouldn’t go for new pistons just rings and a hone. Around 30/40 passes later is billowing smoke out the puke tank on vacuum pump. I told you so. I get it back got it honed .010 on a rottler cnc hone with plates. Ordered new 4.610 pistons, same part # as before. New rings gas ported pistons. But found on tear down two blown head gaskets where the “ missing bolts” are on a bbc. Block has the lugs so on rebuild added the four extra bolts. Even had head’s lightly milled and also the block. After that rebuild it now has 12 passes and has blown gasket between cylinders 6&8. I just want to verify the box is wired correctly because it is detonated itself to death again. I just want to make it last for him.

What is the compression rating on the engine ? Is the block 0-ringed and using copper head gaskets ? The timing at 36* sounds too much, especially if the compression is high.

Just some thoughts that popped into my head. I'm not an expert.

Block is not o ringed. Have been using felpro gaskets but going to mls gaskets this time. Compression I don’t know but the shop that ordered the pistons told me they were 14:1. That said I haven’t cc the chamber so it probably is more than that.

Not all timing lights will work correctly. I have 1 of my 4 that I trust with MSD ignitions.

I'd set that up at about 32-34 degrees, and let the plugs tell me where it needs to be.

Cometic MLS gaskets from .040 to .050 thick
14+ to 1 BB 565-584
35-36 degrees of timing
116 race fuel....
MSD 7al3 and a Grid or full grid
Crank trigger or dist. pickup triggered

Never any head gasket failures

I am pretty picky about my tire gauge and timing light because they do not all read the same.

As for the MSD ignition box mentioned here I have not said anything because I do not know which boxes retard or advance and how much. My understanding is some change more than others. You should try to find out if timing is moving at high RPM.

Mark Mark, Can you expand on what you mean by wire orientation in your May 24 th Post? Thanks

quote:

Originally posted by S/S Dart:
Mark Mark, Can you expand on what you mean by wire orientation in your May 24 th Post? Thanks

He means that if you have a digital box, the crank trigger pickup wires should be hooked up in the orientation that provides the most timing. In other words, if it’s hooked up one way and the timing is checked and it’s 30, then you switch the wires and the timing retards to 15 (don’t recall exactly how much it retards) then it was hooked up correctly in the first place since that orientation produced the most timing. The opposite for an analog box.

Note that this does NOT mean the wires need to be reversed when switching from analog to a digital box.


To the OP, we run 34/35 degrees of timing in our 555s. I doubt 36 is enough to cause your issues with a conventional head, but it might not hurt to try it at 34.

quote:

Originally posted by 183N:
Note that this does NOT mean the wires need to be reversed when switching from analog to a digital box.

I think that is an important piece to point out. The pickup wires should generally not need to be changed for any particular type of ignition box. It's simply something to verify if you are chasing an issue.

quote:

Originally posted by Lenny5160:

quote:

Originally posted by 183N:
Note that this does NOT mean the wires need to be reversed when switching from analog to a digital box.

I think that is an important piece to point out. The pickup wires should generally not need to be changed for any particular type of ignition box. It's simply something to verify if you are chasing an issue.

Agreed. It’s setting the polarity of the pickup so once that is matched to the magnets it shouldn’t need to change.

This link says the following: Polarity of the green and violet wires on the crank trigger sensor will likely affect your timing. MSD advises that the correct polarity is the one that has the most timing advance on a Digital Ignition. For analog ignitions, this is opposite, and the correct polarity is the one that has the most retard. Do not assume that just because the violet wire is connected to the violet wire that the polarity is correct, you must try both polarities to see which one generates the most advanced setting on a digital ignition (or most retard on analog ignition).

Thanks for the explanations!!

Are the deck surfices straight, and to the right finish for the head gasket?

I had the machine shop I use now lightly deck the block and heads last time. They provided the gaskets used. We even added the extra head bolts in the lifter valley because the block and heads would use them. At the moment we are waiting on new arp studs to arrive so we can replace the arp bolt that are currently being used.