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1966 Mustang coupe/HCI 5.0/ TKO-600/ 3.80:1 Trac-Loc
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Discussion Starter · #1 ·
I have a 91' 302 stock bottom end with AFR-165's, Comp XE264HR-12 (1.7 ratio) cam #35-320-8, Performer RPM intake, and a Holley 4160 600cfm. I built this engine last year and could never get it running right at 12-18 degrees initial and she'd lose all power and overheat at idle .

I decided to advance the timing a few degrees and I am currently sitting at 24 degrees initial and 42 degrees total (@ unknown rpm but it has light springs). I verified TDC with a piston stop so the balancer hasn't slipped. I don't know why it likes so much initial and total timing as I can wind it up to 6500 no problems and it seems to want to keep pulling.

Anyone have similar experiences with their motors wanting lots of timing? What might cause it? I read something online that mentioned that advanced or retarded cam timing (Don't remember which) might lower cylinder pressure enough to necessitate more timing as well as moving the powerband up a few hundred rpm? Correct me if I'm wrong I'm still learning!

Thank you all!
 

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Does the engine turn over easily when the starter is turning it or does the engine try to kick back? Kicking back during starting is the first sign of too much initial advance.
 

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Discussion Starter · #3 ·
Does the engine turn over easily when the starter is turning it or does the engine try to kick back? Kicking back during starting is the first sign of too much initial advance.
No kick back , no dieseling when shutting it off, and Coolant temp stays nice and steady!
 

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67 coupe, 69 Sportsroof, 86 hatchback
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Cam timing is my first thought. I bought a "Summit" branded roller timing set that was so far off on the gear markings I ended up throwing it away. (In favor of a Cloyes.) Long time ago but if I recall right, if I had put it in "straight up" without checking it with my degree wheel and dial indicator it would have been advanced quite a few degrees. I tossed it all because I lost faith in the whole thing after finding the timing marks so far off. And I'm not big on returning stuff.
 
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Discussion Starter · #7 ·
Cam timing is my first thought. I bought a "Summit" branded roller timing set that was so far off on the gear markings I ended up throwing it away. (In favor of a Cloyes.) Long time ago but if I recall right, if I had put it in "straight up" without checking it with my degree wheel and dial indicator it would have been advanced quite a few degrees. I tossed it all because I lost faith in the whole thing after finding the timing marks so far off. And I'm not big on returning stuff.
I too remember placing the cam dot to dot and double checking that I got it right. Guess I should take @sportsroof69 's advice and degree the cam next time the front cover is on to make sure!

balancer has slipped
The balancer has in fact not slipped. Confirmed with a piston stop tool.
 

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1980 Mustang, 289, C4, 8.8 axle
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I'm willing to bet it's something with cam timing. Can I ask what the expected power range of the cam in the engine is? You mentioned it seems like it will keep pulling, even above 6500, that makes me think the cam timing might be retarded a bit.

Regarding the dot to dot method, unfortunately it ends up making for a best guess. Degreeing the cam is a bit of a pain, especially with the motor in the car, but it will tell you what the story is with your exact cam. As far as I've seen, a lot of cam manufacturers are susceptible to being a few degrees one way or the other with the layout of the cam in relation to the three placement holes. Then, as mentioned, the timing set is a variable as well. That should be easier to determine once you have numbers on the cam.
 

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Discussion Starter · #9 ·
I'm willing to bet it's something with cam timing. Can I ask what the expected power range of the cam in the engine is? You mentioned it seems like it will keep pulling, even above 6500, that makes me think the cam timing might be retarded a bit.

Regarding the dot to dot method, unfortunately it ends up making for a best guess. Degreeing the cam is a bit of a pain, especially with the motor in the car, but it will tell you what the story is with your exact cam. As far as I've seen, a lot of cam manufacturers are susceptible to being a few degrees one way or the other with the layout of the cam in relation to the three placement holes. Then, as mentioned, the timing set is a variable as well. That should be easier to determine once you have numbers on the cam.
The advertised rpm range is 1500-5500.

Yeah I'm definitely leaning towards degreeing the cam the next time the timing cover is off. However If I am satisfied with the way it runs, would I be leaving power on the table by having it retarded a tad or am I only really affecting the rpm range?
 

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1980 Mustang, 289, C4, 8.8 axle
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The advertised rpm range is 1500-5500.

Yeah I'm definitely leaning towards degreeing the cam the next time the timing cover is off. However If I am satisfied with the way it runs, would I be leaving power on the table by having it retarded a tad or am I only really affecting the rpm range?
I was going to say, if it's running good right now and no valves are playing full contact sports with the pistons, it's likely not the end of the world as far as running it as is.

Regarding the part about leaving power on the table, it's hard to say regarding peak power vs peak power of the ideal timing for that cam vs where it is now.

I think the exhaust valve is closing later, due to the retarded timing, and by the time the piston is coming up and the spark goes off at 12-18* btdc, a good portion of the mixture had started exiting the cylinder, but with the high initial timing you're able to catch it and almost mimic like a high duration high RPM cam set up. These come into their own at high RPM when the velocity of the air starts to work to the advantage of air flow.

That's a lot of theory I'm throwing around, but if I'm correct, you might actually be making a few more HP on the top end, but there's a good chance you're missing some low end torque and responsiveness vs how it's running right now. Honestly it sounds like a fun motor in the current configuration, but I'm always stuck with lower rev torquey engines lol.
 

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Discussion Starter · #11 ·
I was going to say, if it's running good right now and no valves are playing full contact sports with the pistons, it's likely not the end of the world as far as running it as is.

Regarding the part about leaving power on the table, it's hard to say regarding peak power vs peak power of the ideal timing for that cam vs where it is now.

I think the exhaust valve is closing later, due to the retarded timing, and by the time the piston is coming up and the spark goes off at 12-18* btdc, a good portion of the mixture had started exiting the cylinder, but with the high initial timing you're able to catch it and almost mimic like a high duration high RPM cam set up. These come into their own at high RPM when the velocity of the air starts to work to the advantage of air flow.

That's a lot of theory I'm throwing around, but if I'm correct, you might actually be making a few more HP on the top end, but there's a good chance you're missing some low end torque and responsiveness vs how it's running right now. Honestly it sounds like a fun motor in the current configuration, but I'm always stuck with lower rev torquey engines lol.
It is very fun as is. I can even bump up the timing up to nearly 30 and it feels as strong as ever! If I am losing bottom end torque I don't even miss it since I can get as low as 1400rpm while cruising on the highway and not have to downshift to pass (except for when I need to quickly). The 3.80 Gears help a lot for that as well as getting the motor spinning up high! I think I'll just run it until it craps out on me and maybe I'll try and get on a dyno and see what that powerband looks like.
 

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Camshaft is retarded due to incorrectly machined or installed timing chain? Runs good? Just drive it and enjoy it until you need to tear it down would be my suggestion.
 
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Discussion Starter · #15 ·
Giraffe, I'm guessing that the timing set or the camshaft itself are machined offset, and your cam isn't where you think it is. We've seen that a few times. Not common, but it happens. LSG
Yeah I've come to the conclusion that comp cam or the edelbrock 7820 timing chain are off because I specifically remember checking and double checking that the dots where aligned dot to dot since this also has keyways for 4° advance or retard. Next time the cover is off I'll try and degree the cam to see where its at currently

What’s your compression ratio?
With the stock 91' 302 bottom end and the 58 cc AFRs I should be at around 9.5:1 compression
 

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low compression like that, with a spicy cam is going to take a lot of initial. That’s not an issue, the motor will tell you what it wants. Any issues starting when it hot? I suspect not. What is an issue is the total timing. Looks like you are getting 18deg mechanical advance, which I suspect (assuming stock Ford/Autolite distributor) means you are on a 10L slot on your distributor with some rubber over the stop pin. You either need to decrease the total to around 36 by increasing the thickness of the rubber bushing on the distributor stop pin, or find someone who can recurve it for you.… or you could just lock it out….
 

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Discussion Starter · #17 ·
low compression like that, with a spicy cam is going to take a lot of initial. That’s not an issue, the motor will tell you what it wants. Any issues starting when it hot? I suspect not. What is an issue is the total timing. Looks like you are getting 18deg mechanical advance, which I suspect (assuming stock Ford/Autolite distributor) means you are on a 10L slot on your distributor with some rubber over the stop pin. You either need to decrease the total to around 36 by increasing the thickness of the rubber bushing on the distributor stop pin, or find someone who can recurve it for you.… or you could just lock it out….
No issues hot starting. Yeah I JB-welded the slot to be essentially a 9L slot and installed light springs (full advance somewhere before 3000 - need to verify). However, I don't get any pinging or detonation under load at the 42 degrees its at now. If its running good with the total advance it has now wouldn't I lose power by lowering the total timing?
 

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No issues hot starting. Yeah I JB-welded the slot to be essentially a 9L slot and installed light springs (full advance somewhere before 3000 - need to verify). However, I don't get any pinging or detonation under load at the 42 degrees its at now. If its running good with the total advance it has now wouldn't I lose power by lowering the total timing?
Not sure I’d trust JB weld, the original plate is hardened steel. Anyway, you can weld up the gap and grind in a lesser (6L /12 deg?) slot. As for reducing the total timing, IMHO, I would. You may not see any detonation until you are under load, not the time to find out. And all that additional timing isn’t necessarily adding power. I’ve seen engines take up to 44deg but peak power was 32!
 

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Discussion Starter · #20 ·
Not sure I’d trust JB weld, the original plate is hardened steel. Anyway, you can weld up the gap and grind in a lesser (6L /12 deg?) slot. As for reducing the total timing, IMHO, I would. You may not see any detonation until you are under load, not the time to find out. And all that additional timing isn’t necessarily adding power. I’ve seen engines take up to 44deg but peak power was 32!
Surprisingly the JB-weld steelstick has held up for 2 years! I'll definitely create a more permanent solution once I get ahold of a new welder. I will try reducing total timing with some rubber on the stop pin and I'll report back with butt dyno results sometime before the weekend
 
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