And the plot thickens...

[justaZcarguy]

Now, while we all scratch our heads on the '71 Braking issue, I thought that I would throw one more car into the mix for good measure...

The victim in this case is my '74 260. This thing is built from hell and recently had an issue due to a cam gear bolt that worked it's way lose and slipped the cam gear on the end of the cam. By the way, check that bolt ladies and gentlemen, I have been told that this has been thedeath of many a valve...

At any rate, Phrindley Phred was kind enough to redo the head and I threw it back on hoping for the best.

Here's the issue: Car HAD unreal power previous to mishap. Now, the power is ok but after the inital acceleration it suddenly feel as if some on has attached a trailer to the Z. This has NEVER been a problem. The funny thing is, it gets this "feeling like it's missing a cylinder thing" going on. I bravley grab wires and unlatch them from the plugs and low and behold it seems like number 2 is non effective in the idle when connecte or no. So, thinking that the plug is bad (since I have white spark at the plug) I replace the plug. No change. So, thinking that I may have lost compression in number two for whatever reason I do a quick compression test with the engine warm and all the pluge removed, along with the throttle wide open upon the cranking of 5 revoltions...

Compression is normal (for this build) at 240 lbs on the nose on EVERY cylinder...

Remember this engine is running about 11:1 compression and the mallory dual point ign. with som kind of spark discharge by the name of a "Delta Mark Ten capactive discharge system" that is tied into the Mallory dual point.

The distributor is self advancing, not vacumn driven.

To me it feels as if the engine is 1: not advancing and 2: somewhat missing a cylinder that seems to be number 2 but the spark and compression are good.

What the hell?

This should be fun (and has been) juggling 2 threads and 2 cars with problems....

Lemme know, I need the imput...

Have a great day!

~Brian

[2ManyZs]

Whew..... well, if it were me... I'd get rid of the dual point dizzy and go with either the ZX conversion or just a stock dizzy with the Pertronix system.....

One set of points is a PITA, two is rubbing the pain with Ben Gay, if you catch my drift.......

That's just my opinion.....

Only thing I can think of is to check your points and see if you have any pitting on the points and re-check your timing. Could also be that CD ignition box too.....

[justaZcarguy]

Yep, I agree, I had friend throw me an MSD discharge system that i am thinking about finding the skematic to and throwing it onto the system...

I am planning on eliminating the "second set of points" and seeing if that changes matters...

I think that the ZX conversion is the way to go, I can't see where this engine is going to suffer by removing the "hyped up" system and taking it back to the Z stock (or close to it with a ZX ign.)

hmmmmmm....

[justaZcarguy]

Hey 2 many....

What is this Pertronix system that you are talking about?

~B

[Gav240z]

To my knowledge the Petronix system replaces the points in a points driven distributor.

As for your issue, I had a fowled out spark plug cause me grief and it was slowly building carbon on it i'd say till one morning I started with choke out and realised it wasn't firing correct.

Just in case check the spark plug lead it's always a long shot but I don't think you mentioned anything about the leads.

http://www.geocities.com/zgarage2001/z.html

Brian Little's website will tell you what electronic dizzy you will need and what module. For a carbed Z

[2ManyZs]

The Pertronix system is just another way to get rid of the annoyance of adjusting points.....

I didn't want to say this before but........ the only thing it could be besides the ignition is that when you installed the head and cam chain, you didn't get the cam timed correctly. If everything else is the same as it was before, perhaps when you were putting cam gear back on, maybe you bumped the cam or it wasn't at TDC when you installed the chain and it is now either retarded or advanced? It could be off only by one tooth on the cam gear and that could possibly cause the engine to be way off in its performance.

I know you didn't want to hear that, but since you just had the head off there is always that possibility.......

[justaZcarguy]

I think that you are right about that...

And that has been on my mind...

If it was one tooth off tho, wouldn't adjuting the distributor compensate for that?

I tried to figure it out last night and still have a headache...

What is the best way to line everything up?

Thanks!

B

[Victor Laury]

Brian Little's website will tell you what electronic dizzy you will need and what module. For a carbed Z http://www.geocities.com/zgarage2001/z.html

That's a pretty good write up. I have the 79-83 N/A ZX dizzy on my 72. I did not have the Tach problem, But others with the SAME set up, do.

I must admit, it a big improvement! Cold start, and top end performance.

[LanceM]

Being a tooth off on the cam affects the cam timing not the ignition timing.

If the cam was advanced too much the intake valve would close too soon, loss of fuel charge, and the exhaust would open too soon, less of a problem power wise but could cause a burnt valve.

A retarded cam the intake opens too late, loss of fuel charge as the piston may push some of it back out before the valve closes on the compression stroke, exhaust valve opens late causing exhaust vapors to be compressed (power loss) before they can escape, and maybe causing some to be drawn back in on the intake stroke (because the intake hasn't opened, even though there is valve overlap) reducing fuel charge.

Really a bag of worms if you look at worst case

Best way to check is to take off the valve cover and hand crank the engine around to TDC on #1 cylinder compression stroke and check to see that your timing mark on the cam is in the right place or off a tooth or two, I don't think it would run if it was more than that.

[justaZcarguy]

This is starting to sound like what the problem is, it is mostly efecting number two and four. I can remove the plug wires off of number two espically and see no difference in the engine.

I don't believe that I have run it long enough to burn a valve...

At least I hope not....

I think that it's time to take it to top dead center and see where the timing mark is.......

how far off can it be on the mark? It seems that it was slightly off when I put it together but I figured that i could work it out with the timing, now I see that is not the case. But I so remember that it was close - real close...

Thanks again!

B

[LanceM]

It could be that chain streach is getting you, a guess, it's been a long time since I cammed a Z and don't remember for sure now how to dial it in, have to check the books.

One way to check, not that's it's less work, is loosen the valves .010-.015" this would have the same effect as retarding the cam, if it is better driving you know that the cam is advanced, worse, that it is retarded. At least that way you would know which way you need to slip the sprocket. Faceing the front of the engine moving the cam clockwise would advance it, CCW would retard it.

Good luck!

[LanceM]

Just want to be clear, I mean to loosen the valves .010-.015" more than stock clearances. It will be noisy but won't hurt anything.