Ok, another but-kicker. Who knows the correct answer?? A warmed-over BBC that will not run worth a damn with the timing under 45 degrees at idle (75 total). Thats a ton of lead for pump gasoline, and I think something isnt right. Im setting up a nitrous system on this car and I need to confirm that the ignition timing is accurate before I can set up the retard controls and turn this thing loose from the shop. Note that I have not installed anything as far as the NOS system goes at this point, I have just done my initial checks prior to installation. Here is what Ive noticed / tried: I substituted a known good distributor and cap, thinking that it was some sort of a phasing problem: same result. I checked the TDC mark on the damper and its only off 2 degrees, so what Im seeing with the timing light is real close to actual lead. There is no engine ping under load. The car feels a tad lazy when driving. The customer put the engine together. 5 to 7 hg vacuum at idle, 19+ at 2500rpm (no load) I adjusted the valve lash (so I know it's correct) I tried another timing light What do you think? Im thinking that maybe the cam is installed incorrectly (advanced or retarded) The customer claims it's installed 'straight up'. That could explain the need for a ton of lead for the thing to run fairly well. ???
I suspect your using an adjustable timing light and since your talking about a nitrous install I'm suspecting this car had an MSD ignition. If I remember right my snap on adjustable timing light would not give me an accurate reading with the MSD ignition. I have found that dial type (total advance) timming lights do not work well with MSD. I would try a plain old cheapo timing light and a timing tape, other wise I would suspect the cam timing as well. Gus
Gus, you are correct. The car has an MSD system. I removed the entire system from the picture and substituted a known good regular old stock point type distributor, coil and cap.. and it does the same thing... And tried the el-cheepo timing light: same result... So that's 2 for cam timing then??
dot to dot or dot to the 0 notch ...most rebuilds usually get a good chain.....seen that one a couple times....brandon
Maybe the cam timing... but man, that's around 30 degrees of excessive ignition advance. That's a lot! You said you checked TDC; how did you confirm this? Dial indicator or a screwdriver or a finger down inside the bore? First thing I thought as I was reading it was a damaged harmonic balancer or using a balancer and pointer from different applications that may be slightly off. I don't believe that it would start at all if it really had that much mechanical ignition advance (45* at idle / cranking)...
I verified the TDC mark using the piston stop method. Piston stop instaled in the #1 plug hole. Turned the crankshaft over by hand till it hit the stop and marked the balancer where it aligned with the 0 on the pointer. Then turned the crankshaft the opposite direction till it hit the stop and marked the balancer once more where the balancer aligned with the 0 on the pointer. The distance between the 2 marks is TDC. It was only off 2 degrees from the factory TDC mark.
Don’t you just love it when you try to solve a problem and after working on it for a while, you get the entire story? I just got off the phone with the owner. I had him walk me through what he did when he put the timing gear set on the engine one more time. It turns out the gear set was on the engine when he got it and he did not have the instructions when he assembled it. There were 3 keyways in the crank gear and he says he used the ‘middle’ keyway. I know that there is a triangle, circle and a square associated with each keyway, and I could not get him to tell me which one he used, he just remembers using the ‘middle‘ one. It sounds like I’m going to be digging the timing set out on this one, but before I do I’d really like to know what the ‘middle’ keyway is…. Zero? or is the cam advanced???… Anyone have the instructions for one of these gear sets??
Usually the 3-keyway jobs are 4-deg advanced, 0* (straight-up), and 4-deg retarded. So the middle would be "straight up." Good luck with it. I love your Model As. And I may be talking to you soon about a dropped axle. Danny
Circle or Dot = Standard Timing Location Triangle or A = Advance Rectangle, Square, or R = Retard I think it's more than just being advance or retarded, more like somehow installed wrong because of the multiple alignment marks. Let us know what you find.
I installed a new cam for a friend in his fresh 396. The timing set was new from Napa with the 0-dot and square. I lined up the dots(dot to dot= straight up). The motor wouldn't fire (no compression). I pulled the timing cover and valve covers to verify a few things. Turns out I got a mismarked crankgear. Ended up still using it, just had to 'degree' it in.
usually the straight up mark doesn't line up with the straight up dot....and most people over look it....brandon
I once installed a timing gear set and chain on a SBC, installing it dot to dot. The timing was way off. I couldn't figure out what was wrong, and ended up pulling the timing cover. A closer look at the cam gear revealed that the "dot" on the cam gear was actually a casting mark, and I had lined that up with the dot on the crank gear. Engine ran like a scalded cat after I got that straightened out.
You can end the speculation by degreeing the cam with a degree wheel and a dial indicator bought cheap at Summit or Jegs. Remember to TDC the wheel first, then check cam timing. Hope it all works out for you.
The advance canister is properly connected to ported vacuum. Far too much lead is measured with the timing light for this to be a vacuum advance issue though. Yes. I'm checking with the timing light connected to cylinder #1... I also checked with it connected to #6... same thing. I'm tearing the thing apart in the morning, Place your bets and I'll let you know what I find.
Here’s what I’ve found today: The crankshaft gear is installed on the crankshaft in the zero position. The cam is installed 4 degrees retarded according to what the cam card calls for. The alignment marks on the timing gears are aligned correctly. I’ve been thinking, and I just can’t come up with a reason why the retarded camshaft would be the cause of the problem… I don’t think it is the cause. However, the cam timing is incorrect, and if past experience has taught me anything, it’s to fix what you KNOW is wrong. So, I’m going to adjust the cam timing according to what the cam card calls for and see what happens. Any thoughts??
did they use a adjustable chain setup....use bushings....?? sounds like its time to get the degree wheel out.....ot just set it at 0....lol brandon
I was under the impression that Vacume Advance was to be put to Full manifold Vacume. I think C9 had a huge post about it.
ummm Hello? The degree wheel has already been out... that's how I knew the cam was 4 degrees retarded... The gear set WAS set a zero (I could swear I posted that already). I used the 4 degree advance keyway to adjust the cam to zero. Any other thoughts??? I'm going finish putting the car together in the morning. I'll post how it turns out.
http://www.jalopyjournal.com/forum/showthread.php?t=54221&highlight=Got+Time%3F Says Full manifold /shrug
I could be wrong, Ive been wrong before . All I'm going off of is what I remember my professors teaching me and my16 years experience as a Chevrolet / ASE Master Technician
for what its worth, its cool you posed the question here... ive got nothing to add that hasnt been said already, but im looking forward to seeing what the outcome is.
Ummmmm..... One more long shot..... Dizzie installed 180 backwards? Plug wires routed correctly? I have seen BBC's run on 4/6 cylinders before...... Just a thought..... I have been known to overlook the "simple things..." This is one of those things that will bug me as I try and fall asleep tonight....... Let us know what you find....
I was hoping you would find he had used an advance or retard keyway, but still used the straight up mark on the crankshaft gear teeth to line up the chain. Keep us posted.
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