(I think) Timing chain issue... might explain dyno/starting/timing issues..

As a few people on here probably remember, Ive had some issues getting my car running right after the H/C/I build over summer. My car is/was impossible to time and timing would change after starting and wouldn’t stay set, leading to hard starting, poor performance, and now a massive backfire last night as i was tunning it.

I now believe the timing chain, a Comp Cams Magnum unit CCA-2135, has either stretched or some teeth have been taken out (probably just stretching). My only issue with this prediction is that the timing chain was new, installed with the cam/heads over summer and has maybe 2,000 miles on it, mostly highway/easy driving… I have a hard time imagining it failed on its own.

My main concerns now are:
1. What might have caused it to fail so fast?
2. What else in the engine might have been damaged because of it failing?
3. Whether I should go to a more elaborate timing chain (CCA-3135, supposedly heavier duty, or another brand… open to recommendations) or just get a gear drive and be done with it?



See next post for reasons why I think it’s the timing chain, please feel free to tell me what other things to look at. I was also going to take the valve covers off and measure how much each rocker is being lifted to ensure there are no shaved cam lobes or lifter/pushrod issues, but it ran really well for a moment so I have to think the cam/lifters/valves/etc are okay...

Thanks for your help

As far as why I think its the timing chain...

For some background, I had a lot of trouble getting my timing set. Initially, I said that I didn’t think the timing marks were on the right spot because often the initial timing, with no advance, was in the 25-45 degree range, and wouldn’t even run below that. I also had some incredible difficulties starting it sometimes, while other times it would start right up. I tried several times to tune it, with the help of Rusty67 and my dad, and it never did run just right and there was a huge variance in performance day-to-day.

Yesterday pops and I decide to take another shot at it. We have replaced the plugs, wires, distributor, coil, and also turned the idle mixture leaner (it was running way rich). Initially, it starts right up but still isn’t running perfectly. But it would consistently idle for did maybe 30 seconds max decently and then start running really rough or die outright. Also, vacuum would max out at about 12 psi, usually less and rpm’s would bounce around.

We decide to re-stab the distributor to try to get it more perfectly in line with the #1 plug and try to establish TDC. Curiously, the balancer marks read exactly at 0 after manually turning the engine over to the #1 cylinder and restabbing it. We turn it over and…

Holy crap!! Its running orgasmic-ly! Yes, that good. Vacuums at 18-20 psi (I think that’s good considering the cam…), rpms are up and steady, and more importantly just sounds smooth. It runs like this for about 3 minutes.

… and then the same old crap comes back. Kind of defeated, I try to take it for a drive. Its running okay up till about 2500 rpm in 1st and then emits a backfire the likes of which my suburban town has never seen (gets the cops called on me) and dies. After a while I manage to get it to run long enough that I limp it home at about 1500 rpm in 2nd. I kick the tire to tell the car how pissed I am at her and go inside to soul search

My theory is that the chain has stretched, and the dyno probably finished it off. That would explain a) why my timing would start at 0 and then end up between 25-45, b) why, for a moment after we restabbed the distributor and presumably un-kinked the timing chain, it ran perfectly for a moment, before it started skipping again, and c) is enough to explain my engine’s horrendous performance on the dyno (at least some of it). According to other websites and threads, a timing chain that is skipping teeth or stretched will run well in certain rpm and terribly outside of that… that’s what I’m seeing in low rpm until the mid-2000s. Those same sites also had a number of people reading what I am… initial timing in the 20-50 degree range.

Think I'm at all on the right track?

D.Hearne said:

It ain't the timing set. My best guess is your MSD system is at fault. If it was the timing set, it would run bad all the time. My other guess is the cam gear on the distributor is loose.

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But its done this with both distributors. I could understand on an old stocker alone but doing the same thing on a brand new MSD? We can check that easily enough I guess.

Is there a way to test if the MSD is working right? I've had it for several years, and it always worked extremely well even on my near-stock 351w build up until summer. And I've had the hard-starting problem, timing problem (and the its not 400 hp like it damn well should be problem) since day 1...

mrmustangman357 said:

check with the breaker bar like dhearne suggests. it will tell you if your timing chain is loose or messed up. Also you can pull the dizzy and check the gear to see if its chewed up? Is your dizzy gear material compatable with the cam thats in it? does it spin freely? whats the backlash of the gear?

check your total timing at 3800 rpm. with your combo you should see 36 degrees with the vacuum port disconnected. if its all over the place (i.e. more than 4-5 degrees varation) check your slop in the timing chain and distributor gear, and then move to the distributor to diagnose further. MSD has some good tech info on their site if you want to look for mor einfo there

Also, what are you getting for fuel pressure and what do the plugs look like? just to check. . .

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I'm 99.999% sure the dist gear is iron, its whatever comes stock on the 8478 distributor. We've pulled it out a few times and the gear was fine, though it hasn't run that long.

But the problem existed with the old distributor too, in exactly the same form, and I know that gear was fine. So I think you can rule out anything distributor-related.

As far as total time... it doesn't make it to 3800 rpm. As it sits it backfires and dies at 3000 (at most). I plan to tune total timing once I get running smoothly but I don't think its an issue here.

My plugs were a little fouled, appearing rich. However, that was because a crappy shop (known well on this board) thought it'd be a good idea to screw the idle screws a few turns rich without doing any tuning. They've been since turned out and I imagine the plugs won't be as fouled. I think I burn a little oil at rpms but not much.

Fuel pressure I'd have to check

woodsnake:
yes, i measured and I'm using 8.7" pushrods, hardened for guideplates. I believe I checked for valvetrain geometry (basically kept the rocker pivot points and contact points in the range tolerance Trick Flow recommends). Don't remember specifically checking lash...

Crane 1.6 rollers (came with heads). Using the .600 max lift springs that came with the Trick Flow heads (better than most Twisted Wedge, p/n 514000005 i think).

Yes, using new and aftermarket balancer from 'Professional Products' from PAW. Looks/ed like a very good product.

Cam specs: .519/.523, 274/280, 230/236, 10 LSA

woodsnake said:

I'm using that same cam in my 69 Cougar.
I did not check for PR length, and am not using guide plates, nor did I get a new balancer.

I'm very surprised that my motor hasn't come apart yet, but I don't drive it much now either.

"Timing", as I understand it relates to "valve timing", I.E. When the valves open and close, in relationship to where the pistons are in the bore.

I don't know what trick flow uses for 'specs', but it probably follows what most other manufacturers use as far as guidance goes.

(I'm just kind of thinking out loud here...)

Other than your lash being set too tight or too loose, I think you are going to have to start thinking more outside the box.

I mean, you have a new balancer, new timing gear, new distributor. If you aren't losing your ignition somewhere else, what COULD it be?

Is it possible that your cam pin that drives the fuel pump eccentric some how moved, and maybe your cam gear slipped? Highly unlikely....
Do you have a different carburetor you could throw on, just to rule out the one you are using?

"Springs good till XXX lift", always scares me. I have learned a very hard lesson about springs,push rod length, and other valve train geometry issues. Lots of guys bolt **** to gether and run it, I'm batting 50/50 with that. One engine is still going(my W in my 69) one engine had major, major catastrophic issues. (My 68 with a performer RPM cam, 496/520)


I'd almost be willing to bet you are suffering from some kind of coild binding issues.

Did you check your installed height requirements for the springs? And you have the right valve length, right? Or are you just using stuff OOTB?

Also, are you using any hi-tech tools while you are tuning, like a timing light and a vacuum gauge?
Another easy way to test your timing gear set is to put a timing light on it, and 'snap' the throttle. The timing marks should come "RIGHT" back in place, and not 'slide' up and down on the balancer.
Also, triple check your firing order........

Over on s b f t e c h dot com, there are some good animated vacuum guage readings/diagnostics, you might do some reading over there and see what you come up with.

By the way, aren't you the guy who was taking bets on HP numbers??????
I think you owe me a 6 pack.

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Haha, the rules in that thread were the guy who was the farthest off bought the guy who was closest a 6 pack. I didn't submit a bet on the basis of fair play. Besides, if I were to have bet, I likely (I think I even mentioned a 280rwhp prediction in the thread) would have picked a pretty low #... and someone would owe me beer But if the other guy doesn't get you a 6 pack AND you help me figure out wtf is wrong with my car, I will gladly ship 6 brews your way.

Yeah, I was using a timing light and a vacuum gauge. The timign light isn't a particularly nice one, however.

The springs are the ones that came with the heads. They're rated for higher lift than most Trick Flow springs (the heads PN was 51400005, which is supposed to come with springs good for up to .600 lift). I did ask both compcams and trick flow if they thought the springs would be okay and they both said yes, but neither sounded resoundingly sure.

The valves, also, are what came with the heads. Stock Trick Flow valves as far as I know...

How could I check to see coil bind is happening? If I take the valve covers off, are there any wear patterns or other indications that would point towards improper valve geometry or something?

What indications should I look for if I didnt' set the lash properly?

Don't have another carburetor handy, unfortunately sold my 600 cfm Edelbrock (which, for the record, has so far proven to be a FAR superior piece... ).

Keep the ideas coming

woodsnake said:

I must reiterate that you should do some reading over on s b f t e c h .com.
There are a few really good pages on adjustable valve train and proper geometry.

Wear marks will show on the valve stems, you want to keep the wer marks as thin and as close to the center as absolutley possible.

Again, "springs should be good to xxx lift" as a statement, scares me!

You need to KNOW exactly what the requirement is, and then how close you are to actually meeting the specs.
Even out of the box brand new stuff needs to be confirmed. People have bad days at work, and springs look a lot alike when they are loose in abox.

Try and borrow a carb just to check yours out.

Is there ANY mechanical noise that you can hear with the engine running?

A static method to check for coil bind, is to check the clearance between the coils on both valves when the cam is at full lift. Google it, or maybe even on you tube there should be a more solid example.

When planning a cam, there is a LOT more to consider than just gross lift. Spring rates, coil thickness, installed height,shims, piston to valve clearance issues.
And, just because you may have just enough clearnace when the motor is cold, don't forget how much stuff 'grows' when the engine is warm!
A difference of".015" is a TON at normal operating temerature and 4500rpm, but to see what that measurement is physically, is like four pieces of paper stacked on top of each other.
Try to create a pass/fail check list for your engine.
Timing chain wear?
Ignition?
Firing order?
Piston to valve clearance?
Coil bind height,correct installed height?
Carburation?
Direction of engine rotation?
Balancer?
#1 on TDC, rotor pointing at #1, pointer pointing at "0" on balancer before starting?
You know the engine does run, you just need to figure out why it doesn't run like it is supposed to.
These are a few things to confirm, deny, double check, and make notes, so you can answer these questions when they come up again.
The guy that did my machine work ALMOST had me convinced, that I was breaking valvetrain parts due to bad gasoline, and had nothing to do with mechanical failure.
I was suffering coil bind. I went through two sets of roller rockers, three sets of push rods, and two cams before I was able to PROVE what was going on.
So then the guy says, coil bind, and the bad gas.....

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Ha, you must really want that beer. Apprecaite the effort you're putting into your post here...

Item by item:

Noise: Yes, there is some mechanical noise when the engine is running (some of it either wasn't noticeable or wasn't there during that 3 minute stretch that the engine was running great, for what its worth), but its hard to pin down or describe. I could try to take a stethoscope to it and narrow it down...

Springs - I did research the closing/opening pressures and spring rates and, as I said, mentioned that the to CompCams and Trick Flow techs. They weren't exactly the #'s that Compcams recommended but they said it would be okay. That said, I could see that not being the case... the springs (and heads in general) were designed mostly for later 5.0s, with roller valvetrains, faster ramp rates, etc. However, I am still unclear as to how I could prove one way or another that coil bind is the issue. Is there a # for what the clearance between coils (coil to coil?) should be?

Roller/stem wear - I will check that to see how they're looking. I believe I did refer to the SBF tech article you're referring to when I actually measured out my pushrods, but I will re-read it this weekend.
'
Carb... I'll work on it, most of my buddies with carbed cars round these parts have moved out or are broke and don't have their cars now, but I'll try.

Timing chain - will try to check at first opportunity visually or via one of the othe rmethods suggested. I will say we actually did try the breaker bar idea but too much stuff was in the way.

Ignition - unfortunately I really don't know how to check this, I suppose the entire issue could be due to the MSD failing or something but there has to be an easier way to know than plugging in a new MSD. A faulty MSD would explain the hard starting, the backfire... just about everything. Do MSD's fail often? This ones about 5 years old, maybe 10k miles. Outside the MSD, I highly doubt any other ignition components are at fault. I've changed everything else and the problem didn't change with them, so I think my current parts (and probably the old ones too) were fine.

Piston to valve clearance - we put big ol' blobs of clay in the combustion chambers, fabbed one of the heads up and rotated the engine... the piston didn't even make a mark on the clay(stock 72-73 low compression engines... i don't think piston to valve clearance is an issue lol).

Firing order.. I'll check but yeah, doubt its an issue but what the hell.

Whats the best way to check for vacuum leaks? The summit guy said something about spraying carb cleaner (but also said to be careful but i forget why...). I doubt that the primary problem is a vacuum leak, but I wouldn't doubt that one might be contributing...

Carb - the sheer volume of instructions out there on how to tune Holleys is scary. Whats the quickest way to check the floats and ensure that the power valve isn't 'loose', as someone above described? Besides messing around with the choke and idle mixture more, what else can be wrong?

Current list of possibles include:
Timing chain stretch/damage
Ignition module dying
Carb being a piece of trash
Coil bind/improperly set valvetrain geometry
Coils being mismatched

And is there a guy in socal I can just pay $500 to do all of this? A lot of this is going to be hard to check without running up a $1000 summit bill and checking components until I figure out the one that failed and returning everything else, it seems *crosses fingers*


Have to work be back in a second

woodsnake said:

Here is some (yvehc) help on valve spring coil bind, I just googled it.

How Valvesprings Work - Tech Article - Chevy High Performance Magazine


The Step-by-step Guide to Engine ... - Google Book Search more good reading...

Accelerated Motion: Cam Installation


Valvespring Installed Height | 5.0 Mustang & Super Fords Magazine Article at Automotive.com

Also, does your distributor a have vacuum advance? If so, is it plugged off when you are setting your initial timing?

This shouldn't cost a whole lot of money to fix, once you identify the problem.
Just be sure to identify it correctly. I'm pretty sure you are going to need at least a new gasket set, and some fluids.
Back to basics will win the race here. Find out what went wrong, and get back in it.

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Distributor does have a vacuum advance, and yeah, we did disconnect & plug it when we tried to set initial timing.

Thanks a ton for the links, I'll be reading up tonight.