Ok, I didn't know where to ask this, so I'm just putting it in here. I have a built 460 with a complete MSD ignition (box,dist.,wires) Well my truck had been sitting for like 8 months because the transmission died and now that I have a new one in it and have been driving it I've noticed that it's been running rough lately, to me anyway. People that don't know me just think I have a bigger cam in my truck than I do. It's just kinda lopey at idle and it still has a ton of power but when you're running at a steady pace at any rpm you can tell a difference in the exhaust sound. I thought maybe a wire was loose, so I checked everything like that and it looked fine. So I took off the dist. cap and wow.. all the contacts were toast. I'm assuming this is my problem, I haven't looked at the plugs yet. What I'm wondering is what would cause this? I mean my engine has maybe 3,000-4,000 miles on it. It has the same plugs that were used to break it in on the dyno, they're NGK. It ran sweet when it was put into the truck. It only has a 262 cam in it and it didn't even have a lope at all when I first drove it. How long are the cap and rotor supposed to last? Is it a timing issue? I can't remember what the engine builder set the timing at, but I remember him saying I had 39 degrees of total advance on it when we were running it on the dyno. Nothing has been changed since it was dropped under the hood. All I've done is a couple oil changes to get all the break in "gunk" out.

Also, where's the best place to get a replacement cap and rotor for my MSD? I had completely forgotten that they're different than the stock stuff. Any help is appreciated, thanks!

 

I got a new MSD cap and rotor at Advance Auto for about $25.00 it was on sale.

John

 

Try summit racing no shiping charge.

 

Wich MSD box are you running? I have had 2 MSD 6 off-road boxes go out on my 78 over the last 4 years (only 5,000 miles/year). Seems the off-road box doesn't get along with cold weather very well. I recently switched all my stuff over to Crane and so far so good.

 

It has the 6A hooked up to it. It runs "ok". I mean it'll still smoke the tires and chirp the gears, but there's no way it's running 100% or even 90%. I'm getting a new cap and rotor tomorrow to see what happens, i just don't want to change them every 3,000 miles.

 

the dist in my race truck has been used for 3 yrs now, and never replaced the cap or rotor and no corrosion, you must have some moisture in there, you might try putting some dielectric grease on the contacts to keep them from corroding but my point was thats not the norm with the msd stuff.

 

ok that's something i was wondering. I'll clean it up and try that and put on the new cap and rotor and see if it happens again within another 3k.. if so then something's up. the contacts didn't look orangey like rust, they were black/grey like they had just burnt or is that what moisture does, make them burn?

 

Dean, I am a huge fan of Crane ignition as well. I run Crane Cams HI-6R ignitions in my 2 pulling trucks and I can go mis-fire free to 8700 RPM and it fires clean and hard with the E-Core coils they have. I also think that Cranes 25 Ohm per foot firewire plug wires are the very best on the market....period. If your not running the Crane wires, your throwing away perfectly good plug fire power! The cap on MSD and Crane distributors can be picked up at any parts store, they use a commonly stocked part. Crane also has a new line of Distributors that have fully digital and adjustable advance curves built in, all adjustable with 2 POT switches.

Why did you get those rotted contacts...I agree 110% with Monster, moisture. As you run an engine the vented cap and the extremely fast moving rotor causes air to travel in and out of the vented cap, if not you would have an atmosphere in the cap that would allow for spark scatter from the ionizing effects of the spark. When you look at the rotor tip and the cap contacts you will notice there is physical degradation of the material. This is the slow process that causes you to need to replace the cap and rotor accasionally to maintain a good spark...or any spark. If you parked the truck and it was in a moist inviroment, the contacts (Most likely brass on a performance cap) would tend to promote a growth of a microbe that would attack the material. Similar to growth you see on underwater adventures on the learning channel....but in a smaller scale. So by having this engine running now, and replacing the cap/rotor with nice new parts you will likely end this issue.

As for the timing issue....Most 460 engines I have played with on Dyno's like 34-36 degrees of TOTAL timing. Base timing is less of a concern to me, I use a dial back light and adjust out 34 degrees and get the 0 mark of the ballancer to be at the tip of the pointer. If you have (You already have said that you do) an aftermarket cam, your cam may be ground out a couple degrees from the intended position, so you would need to blueprint the cam/crank positions and remark the ballancer to get this right. In the case of an average hot rod its not that big of a deal....stick with 34 total timing and you should be all set. If you pushed for 36 you may be actually at 37 or 38 and not know it and be starting to give up power from being too advanced. Remember, the dizzy is registered off of the cam, so if the cam is not ground exactly on 0 of the crank, things are not exactly where you think they are......thats racer knowledge :]

 

thanks fordtrkpuller, that actually makes a lot of sense. as far as the timing goes, a racer built the engine for me so I'm sure he knew what he was doing but on the other hand his specialty is the BBC. But this wasn't his first BBF of course. I was with him when he broke it in on the dyno and we did about 8 runs. he started out at the low 30's and said that most of the engine's he's done, probably chebbies, liked around 39-40 degrees total timing. He got mine up to 39-40 and it started to go downhill on power and the total curve so he backed it off to 38 ish. He chose most of the parts for the engine with my input as to what i wanted performance wise out of the engine. All I have to say is that tuning on a dyno really helps. had I built the thing myself (would have been my first) and had everything as far as the bolt on parts just the way they were out of the box, i would have ended up with around 380hp and 470lb.ft. rather than the 425 and 510lb.ft.I ended up with after tuning. plus we got the a/f ratio set up for highway cruising. it's a daily driver.... i don't know about anymore though, lol.

 

Umm I don't usually disagree with you too much (although we will disagree on ignitions but thats another issue and thread) but the dist may be turned by the cam, but timing has absolutly nothing to do with, cam degrees whatsoever, and you should know that. the timing light triggers on the firing of the coil through the plug wire, and by the method of a strobe makes the balancer appear to stop so you can see it, well the balancer is always in the same position on the crank, and in the same position in relation to the piston no matter what you do with the cam. so if the plug fires at 36degs on the balancer, it will be 36 degrees no matter if hte cam is advanced or retarded. now what you do have to do is make sure that TDC on the balancer is actually TDC on the piston, but like I said that has no reference whatsoever to the cam. I think your confusing the part where if you put in a different timing set and change the adv of the cam, without moving the dist it will change the ignition timing but thats anothe issue.

 

But the The cam is registering off of the crank via the chain.
The dizzy is registering off of the cam via the cam gear.
If the cam is ground 2 degrees off of the crank 0, the dizzy see's the the same 2 degree mistake.
On my newly built engine, if you were to assume the everything were as it says, and you timed the engine with your light on the zero mark on the ballancer, you would be timing the dizzy over 2 degrees off. We blueprinted the engine referancing crank rotation and cam actions and found the cam to be off a bit, so we found the true 0 on the ballancer by referancing the cam events and milled a new and proper 0 into the crank dampener. Now when I time the engine, I am using true 0, not the old 0 that was close......Your description above assumed that the ballancer's 36 degrees....was actually 36 degrees....but was it? If you dont have the ballancer 0 lining up with true TDC, and the cam events are not what they are advertised...you need to know all of this and account for it in your tuning....for a race engine. I hate to cloud this post by talking about things that most folks should never even need to read about...lol....we are showing our power geek-ness here Monster!

 

No, your looking at it all wrong, the timing is when the spark plug fires, and has nothing to do with the cam or the valves. you can move the dist by loosening hte bolt and turning it that changes it's relationship to the cam? well yes but it doesnt' move the teeth it moves the reluctor that tells the ignition when to fire, which changes the timing. What you are describing has nothing in the world at all to do with the cam. If you doubt me, try this, take your engine, now you have hte balancer marked for perfect TDC right? ok now go move the cam 10 degrees and see if the balancer moved. bet it didn't. the reason is the balancer is keyed to the CRANK not the cam, and moving the cam has no affect on that keyway or the timing pointer at all. and since number one piston is physically hooked to the crank also, the piston and balancer relationship can not move no matter what you do to the cam. Now if you will notice I did say you have to make sure that TDC on the balancer actually corrosponds to TDC on #1 piston. Most factory balancers don't, and aftermarket balancers are actually worse, thats why people make adjustable pointers, and timing tape to get that relationship right. you just did it by grinding it into the balancer, heck my balancer was off by 80 degrees, why you ask? because the balancer timing marks were setup for the timing point to be in a different position on teh timing chain cover than mine is setup for so I had to remark the balancer to get it right too.

 

Your right. The dizzy in my engine is not effected by rotating it....my crank triger tells it when to fire. The dizzy fires in relation to the crank, as directed by the cam. If the cam is ground off 0, you would still be firing in relation to the crank where your ballancer says. The ballancer may or may not be accurate....mine is not..and it sounds like with your relocated pointer, yours is not. The cam should be taken a look at to decide if the valve events are as you think, or if you should advance or retard the aftermarket cam to put it where you want it, or where its advertised at being. But, in the end...your right, I do check crank to cam timing to ballancer and get the entire train of events in line...and in the end I know when I time my engine at 34, its at 34....not near it, or close to it...but at it. We also do dyno testing to find the point where timing is best placed, and I find on BBF engines base timing (Or locked out timing) does not make a whole big change....but total timing can be changed 4 degrees and you may experiance a 20+ HP loss.

 

I Know how to settile this argument!!!!
RACERS TO THE LINE!!!!!!!

 

Bill, I am not arguing, as a matter of fact I agree that he is correct about the cam to distributor timing being uneffected by the crank. But I do know that rarely a cam is where its advertised at being at any given time. If you find true crank 0 and relate valve opening and closing events to it, you often find the cam is a bit off. I agree with Monster on this situation, and I also concede in the fact that I took the detail level way beyound where it needed to be....sometimes its hard to not go overboard. Sorry, no argueing...just a couple gear heads talking shop and comparing ideas...its how we all learn and we all get FASTER THAN CHEVYS!