Boat Buzz

Hi all, I hope you have been enjoying the summer.
The new engine is finally running on a regular basis. After being plagued with several bugs that cost me lots of extra time, I am finally able to get some hours on it.
I am running it on a stand in my garage and presently have about an hour or so on it.
I seem to be having a timing issue but it's not a major problem, at least not yet. I can't seem to make it run unless the timing is advanced well before TDC. I have tried moving the distributor a tooth either way but it's only worse. It seems to run just fine at about 30 degrees before. I must be overlooking something, any thoughts?

Craig

Are you certain timing marks are correct? Is distributor internal advance ok?

It starts and idles at 30* advance, or runs at 2000+ rpm after starting at a lower advance? I am thinking it maybe a measurement error of some sort.

It starts and idles just fine at 20+degrees before. I have moved the distributor drive gear 1 tooth then two to the point where it's closer to normal static advance- anywhere between 0 and 10 before but it doesn't like to idle. it requires quite a bit of throttle to keep it running and it has very poor throttle response, it stumbles and backfires as though it was starving for fuel (or out of time). I know it's not starving and I don't see how the timing can be that far off. I'm missing something for sure.
Internal advance works as it should advancing about 6-8 degrees at higher rpm. I don't know if it will advance farther, I don't want to run it too fast with this few hours.
I'm just speculating here but what if the cam were off a tooth? I've never experienced that but maybe someone else has and knows what the symptoms are?

Craig

Since you got a crate motor I would call the company and ask them.

What brand distributor are you using?

How about spark plug wiring? Pull the #1 plug and verify that it is at TDC at 0* and then tripe check your firing order. Also, which cylinder is #1, the GM version or CC numbering?

Check timing light connections. Hooked up to number one?

The distributor is an aftermarket unit recommended by drrot. It was the only electronic I could find that had a mechanical tach drive.
One thing I have not tried but will today is I never did confirm that the piston was actually at TDC when the timing mark was at zero, that would confirm proper cam timing. Number 1 is front right facing the front of the motor. As far as I know it's always been that way chevrolet or chris craft. Standard firing order is 1-8-4-3-6-5-7-2, if you use that order the opposite way around the distributor cap you have the reverse firing order. I've checked that several times. Another thing I have not tried is hooking it up as standard rotation, just on the off chance they sent me a standard instead of opposite. would it even fire if that were the case? again...it runs fine wired this way and turning opposite rotation, just way off the timing mark.

Craig

Chris Craft changed the numbers relative to the bow where GM numbers based off the flywheel.

Scroll down about a half dozen posts to see pictures of both FW forward and FW rear from CC manuals.

http://www.network54.com/Forum/424840/t ... ause+this-

When you check TDC, you can also pull a valve cover and watch the valves to see when the cam is opening and closing them. I would think if the cam timing is significantly off you would have very little compression.

Ok here's the latest,
I checked TDC and 0 mark on the harmonic balancer is TDC on #1 on the compression stroke so cam timing is correct.
I swapped out the distributor for another brand new OEM electronic GM distributor and had same results...engine starts and runs smoothly/accelerates very strong just at 25-30 degrees BTDC. This is getting spooky. I've never seen this before. Been running on the stand, I probably now have 2-2-1/2 hours run time on the new engine.

Craig

island time wrote:. Another thing I have not tried is hooking it up as standard rotation, just on the off chance they sent me a standard instead of opposite. would it even fire if that were the case? again...it runs fine wired this way and turning opposite rotation, just way off the timing mark.

Craig

If the engine you have has a timing chain its left hand. If it has a set of 2 gears its right hand.

What brand distributor are you using. I've had 4 or 5 engines come into the shop that had cheap electronic distributors from ebay put on them by there owners. I've have never seen one of them work correctly.

I would recommend finding an original one or a Mallory. A lot of times you can find a good used Mallory on ebay.

The second distributor I installed is an Accel, I've always thought they were fairly good. Either way the results were the same.
Even if the engine were a left hand and I were trying to run it right hand the timing should still be the same relative to TDC.

Very Strange!

Craig

ATDC and BTDC swap sides depending on which rotation your engine is.

Yes they do, this engine has a standard rotation pointer on it but 0 TDC is still 0 TDC no matter which way it rotates and yet the bigger issue is how far off the timing is and how well it runs that way. Makes no sense to me.

Craig

How are you measuring the timing?

I would expect it to be hard to start with that much base advance, so I am wondering if it is a measurement error. If the mechanical advance rolls in and you get past the mid to upper 30's I think you are going to have detonation issues, and 30 base plus mechanical will get you around 50 degrees by 3000 rpm. I would think that would be bad.

This is very puzzling, I hope you figure it out and can share the lesson learned with soon!

Using a basic timing light with an inductive pickup. I too am concerned about this much advance if in fact it's accurate.
As you say, if the timing were off that far you would expect hard starting issues and yet it starts and runs wonderfully (at least on the stand), it would be interesting to see how it acts under load.
Looks like I'm going to have a busy week but I will contact mid-city motors when I can and see if I can gain some insight from them.

Thank you all for your help on this issue.

Craig

Well Mid City Motors was no help. The only thing they told me was to contact the distributor manufacturer. I'm thinking-for what? This problem I'm experiencing is most likely a cam timing issue, or the wrong cam? It certainly does not explain how an engine can run at 30 degrees base advance. I'm at a loss, I've exhausted my knowledge based on standard rotation engines. I don't know how standard and opposite engines differ other than the unique cam grind and the use of gears to drive the cam in an opposite rotation engine versus a timing chain in a standard rotation.
I think that since the engine supplier is not offering any incite I am going to have to pull the timing cover off to see if I can confirm proper cam timing. Since I've never seen one I'm not sure of what I will be looking for.
Any help will be appreciated.

Craig Wilson

Did you ever find out anything?

Hi Jim,
It's been a while, I have been working out of town more than I like but what the hey, it pays for the toys!
I've had the front timing cover off twice, double and triple checked the timing marks even degreed the cam looking for the source of the timing discrepancy but have found nothing. It simply runs at 24 degrees advanced at idle and upwards of 40 at 3000 plus.
I'm still running it on a stand so I don't have any way to run it under load to check for pre-ignition. I now have somewhere around 10 hours on it. I've tried 3 different distributors, two sets of wires and two different timing lights. Problem must be with the cam but what? wrong grind? improper timing mark on the drive gear? I'm stumped and ready to just put it in the boat the way it is. I know I once talked about taking it to an engine builder for diagnosis but nobody wants to look at it because I didn't buy it from them. It turns out that Mid-City Motors in Fla. has been no help, just there to take your money and send you an engine but don't know you if you have a problem with their product.
I'm still waiting for that lightning bolt idea that solves the problem.

Craig

My latest thoughts on this are that the lack of load has saved you from killing the engine with too much advance, and that something else is wrong and the extra advance is compensating for it.

I would start by dialing the advance back by about 8 degrees. 32 at 3000, 16 or so at idle should be good.

Next, figure out what is wrong if it won't run well when correctly timed. It could be a weak spark, but I think the most likely issue is fuel mixture. To rich OR too lean will slow the flame propagation. Check for intake air leaks, and try to adjust your idle mixture until it idles better. Another thought, if you have a mechanical fuel pump, they can deliver too much pressure at idle and overwhelm the needle valve in the carb. This is a common issue with the Eddlebrock carbs, but it can happen with any carb or with a bad needle or seat. The symptoms are rough idle or choking that clears up with a little throttle.

As for spark, I assume the plugs were new and properly gapped (you can't trust the gap out of the box). After 10 hours of trial and error I would pull them, look at their condition which can show issues, clean and regap. A spark tester where you set arc distance, not the light kind, will verify the rest of the system is working and you have a strong spark. They are cheap, but I have one you can borrow (if I can locate it).

One other thought. I think a simple compression test will pretty much rule out cam or valve issues but I don't think that is your issue.

It just dawned on me when mfine mentioned a compression test.

What I would highly recommend doing is hooking up a vacuum gauge to a port on the intake. This is one of the best forgotten about diagnostic tools for carb engines. I'd seen one many years ago when I first started working on cars. About 15 years ago I was having trouble with a 283 that had been rebuilt. The carb shop that restored the Carter WCFB told me to get one. With the gauge I quickly got the timing and carb dialed in. Which saved me from pulling the rest of my hair out.

The one thing to keep in mind when using it. When everything is set right it will still tend to read on the lower numbers on the normal engine scale. This is due to the fact that the engine is new and not fully broken in.

I think this tool should give some answers or at the very least give you a lead in the direction of the problem.

Heres a link to what I'm talking about.

https://www.amazon.com/Carburetor-Valve ... cuum+gauge