How the heck is my engine taking so much timing?

[eagleone1983]

So I've been reading a lot of threads on setting timing so I figured I'd try it without a light and listen to the engine. So I disconnected the vacuum advance, hooked up a vacuum gauge and started turning the distributor. Paying attention to the vacuum readings and RPM. I gained about 2" of vacuum and my RPM increased so I set the RPM back down to 1000 RPM in park and shut the motor off. From what I've read if the motor is too far advanced it'll try to drag the starter down like a dead battery. Car fired right up. So I take it for a spin and it feels really responsive although if I go from full throttle to part throttle then immediately step on it she bogs for just a second and takes off.

No detonation was noticed but to be honest I don't really know what it sounds like. She is running a little fat at idle but here is the kicker. So after all that I set a timing light on it and I'm showing 32* initial. What the heck is going on, I figure that far advanced it shouldn't even be firing up. I haven't checked my balancer in about 500 miles but I'm pretty sure it has slipped before as the factory stamped line in it was off and I had to make my own line when I first built the motor.

 

[Photon440]

You might have to pull #1 plug and find TDC first, then see where your timing mark is.

 

[Meep-Meep]

If you have a high overlap cam with a late intake closing point that will tend to want a lot more timing. It's common for race engines to have the timing locked out at full advance (minus 2 deg) at idle. The remaining 2 deg will come in over a wide RPM range mainly to keep the weights from bouncing at high RPM. Or you don't have the true story, so check TDC as suggested.

 

[eagleone1983]

Thanks guys. I'll check TDC this weekend, if my balancer is slipping should I replace it? Its the OEM balancer and the engine was balanced with it (not sure if that matters any). The cam is a comp cams XE275HL http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=711&sb=2

I wouldn't consider my motor a race engine, it's a 383, FBO ignition system, RPM Performer intake, Stealth heads, Schumaker Tri-y headers. When I gave all these specs plus more to Don at FBO before I broke in the motor he said my timing should be at 18* initial and 34* total @ 3200 RPM Vac timing at 12* at 14". I don't get 14" of vacuum though when I had it at 18* I was getting around 8" now I've got 10"

 

[Cranky]

Do you know what your compression ratio is and what your cylinder cranking pressure is? A low compression engine will usually also like more timing...and replace that balancer if it has been slipping and yes, the balance of it matters. I assume it's neutral balance and if it is, a new one should be the same but it's not hard to get it checked.

 

[eagleone1983]

The builder told me the compression ration came in at 9.7:1. I don't know what the cranking pressure is but I can also find that out this weekend. I'm guessing if I get a new balancer the engine builder could probably rebalance it if needed in the car, correct?

 

[67Satty]

Thanks guys. I'll check TDC this weekend, if my balancer is slipping should I replace it? Its the OEM balancer and the engine was balanced with it (not sure if that matters any). The cam is a comp cams XE275HL http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=711&sb=2

I wouldn't consider my motor a race engine, it's a 383, FBO ignition system, RPM Performer intake, Stealth heads, Schumaker Tri-y headers. When I gave all these specs plus more to Don at FBO before I broke in the motor he said my timing should be at 18* initial and 34* total @ 3200 RPM Vac timing at 12* at 14". I don't get 14" of vacuum though when I had it at 18* I was getting around 8" now I've got 10"

I seems like you should be able to have higher vacuum than that. I've got an FBO distributor set up about the same (15 initial, 34 total by 3200 RPM - I'm starting to think maybe he sets them all up pretty much the same, but I digress), my cam has about the same duration (238 @ .050) and I get 14-15" of vacuum.

Maybe start from square one and find TDC and mark your balancer with some whiteout or something and then recheck the timing?

I could be wrong but I don't see how your engine could be rebalanced in the car. But if you got another stock balancer would it even need to be rebalanced?

 

[GTX MATT]

The balancer could be wrong. If you used a neutral balance harmonic balancer (early, forged crank) when the builder balanced it you can replace it with any neutral balance harmonic balancer, stock replacement or aftermarket race piece.

But, first, are you remembering to disconnect the vacuum advance when setting the timing?

 

[charger360]

yeah he is it is in the first sentence.

 

[Garys1969RR]

I run 20 degrees initial and 38 total on my 451. It has 13 to 1 C/R, and has tons of low end torque. Even at part throttle. Using hi octane fuel. These motors like alot of initial advance. However 32 iniyial seems a bit much. Double check your timing marks.

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Pinging sounds like clicking or rattling noises coming from the engine. Usually at wide open throttle when cylinder pressures are highest. And lugging the motor at WOT and lower RPMs can cause it to occur. Detonation is when the entire mixture in the cylinder explodes instantly like a stick of dynamite. This is very devastating to the engine, and usually begins after pinging starts. Top fuel engines have been known to encounter this phenomenom, due to the extremely high cyl pressures.

 

[Stewsta]

I was having the same problems you with my 440, FBO ignition,284/484 cam. My timing kept showing more and more advance but it was my plugs fouling from choke staying closed too long and idle air screws out too far. The plug wasn't firing correctly and showing lots of advance and irratic timing. Once I changed plugs and adjusted carb it's been fine.

 

[Gpuller]

My 440 is running 25 deg initial, its lower comp with the old 284/484 MP cam.

 

[eagleone1983]

Thanks for the input Stewsta. I pulled my plugs and the strap looked good and the porcelin was brownish but there was a ring of black around the very top of the threaded area so maybe that is my issue. I just got back from a funeral motorcade and took the RR about 50 miles round trip, no noticeable pinging just the usual valve train noise but I can't really hear that in the car. I stomped on it a few times and she took off like a bat out of hell and actually breaks the tires loose, before I increased the timing she'd have a hard time doing that.

As far as how much vacuum I'm supposed to have I've had people say I'm about right on the vacuum amount with my combo. Not sure if altitude has anything to do with it but I'm about 4,700 ft above sea level.

 

[Cranky]

Altitude does make a difference....cold weather does too...pretty much any change in the weather can make a car run differently. My 95 Dakota really likes cool dry weather and you can feel the difference. I didn't think vehicles with electronic management did that but this thing has been like this since new. Btw, the Houston drag strip usually produces lower ET's because it's near a lot of vegetation (high oxygen content) and is right at sea level. When the weather is a bit cool and the humidity is low, most cars put down good numbers so long as they are tuned for it.

 

[451Mopar]

I think the Stealth heads like a bit more advance like stock heads because of the stock spark plug position? I have ran 38-40 total with out vacuum advance, and around 10+ more with vacuum advance. I think this is around 20 degrees initial. I will be able to play with the tuneup alot easier once I finish the EFI conversion.

 

[eagleone1983]

Ok so I've done some of the checks recommended. First I pulled #1 spark plug and cranked the motor 'til it shot my finger away and my timing mark is pretty much right on. I did it a couple times and each time my mark was right near the 0 mark on the timing cover. Then I did the compression check, I've never done this before so let me first tell you how I did it. I'd pull each individual spark plug one at a time and crank the motor over until the gauge would shoot up, I'd record the findings then move on the the next plug after reinstalling the last one. I only did 1, 3, 5, 7, and 8 because the others were pissing me off trying to get the tester hooked up and I got 100 - 105 psi on each cylinder. Does that sound about right?

On a side note, the black soot ring that used to be on the top of my spark plugs looks like it is starting to burn away after the timing advance.

 

[73runner]

Sounds a little low. Takes a few spins of the engine to get to max compression. Are you letting it build to max or is the 105 the initial?

 

[khryslerkid]

Ok so I've done some of the checks recommended. First I pulled #1 spark plug and cranked the motor 'til it shot my finger away and my timing mark is pretty much right on. I did it a couple times and each time my mark was right near the 0 mark on the timing cover. Then I did the compression check, I've never done this before so let me first tell you how I did it. I'd pull each individual spark plug one at a time and crank the motor over until the gauge would shoot up, I'd record the findings then move on the the next plug after reinstalling the last one. I only did 1, 3, 5, 7, and 8 because the others were pissing me off trying to get the tester hooked up and I got 100 - 105 psi on each cylinder. Does that sound about right?

On a side note, the black soot ring that used to be on the top of my spark plugs looks like it is starting to burn away after the timing advance.

You need to have all of the plugs removed, coil wire disconnected, choke and throttle wide open to get a correct compression reading.

 

[Garys1969RR]

I think a strong running motor should have around 120 to 150 PSI. My 451 has 205 to 215 PSI, at cranking speed. And boy does that thing have some torque/horse power! Yesterday it was frying the tires in 2 nd gear at part throttle! Torque is going to be determined by the amount of force pushing down on top of the piston, on the power stroke. More pressure=more torque. This is also referred to as Brake Mean Effective Pressure, or BMEP.

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I check compression by first pulling all the plugs, then block the throttle at least half way open. Check each cyl by letting at least 3 compression strokes hit the gauge. Then record the reading for that cyl and go to the next one.

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If a cyl seems low, you can always shoot some oil in there and check it again. Or try it on each cyl. A significant increase in the reading, say from 90 before oil, to 130 after oil, would indicate a problem. Usually poorly sealing or wore out rings. A cyl leak down gauge can give you more info on a possible cause of lost compression pressure.

 

[eagleone1983]

Thanks guys, looks like I did the compression check wrong. I should of youtubed it or something before I started. I'm sure I'll have higher readings once I do it correctly since driving the car she doesn't appear to have any issues just thinking my timing seems high even though it's taking it.