FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: allrightmike on November 10, 2019, 10:35:48 AM
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Is it still common practice to set cam timing one or two degrees advanced for
a street use engine to allow for a bit of chain stretch or just to pump up low end torque?
Mike.
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Most cams have advance ground into them and you don't need to advance further unless that is what your engine and combination like best. There is no rule, but most cams have about 4 degrees advance already, if you install dot to dot and check to make sure it is accurate by degreeing the cam.
I think chain stretch is a misnomer as the chain doesn't exactly stretch, but rather the links wear and the timing can be affected by that.
So, in my opinion no, you don't need to advance most cams a couple of degrees for chain stretch. Just make sure it is where you want it, preferably degreed with a degree wheel.
JMO,
paulie
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Also, if you degree the cam make sure you have the chain tight when make measurements. That is, you have turn the engine over in the direction in normally turns until you get to your measuring point. That keeps the chain taut and makes the measurements more accurate. If you don't do that the chain will be loose and the measurements will be off.
paulie
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It depends on the combination, too. If you have a big cam and low compression, you might advance the cam to get some low rpm power back. If you have a small cam and high compression, you might retard the cam to prevent detonation. That is just a start.
So no definitive answer, especially without specific information about the combination and cam spec's, but just for chain stretch, I still say no.
JMO,
paulie
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Depends on the entire combo. Sometimes I’m 6-8 degrees advanced, sometimes I’m straight up, sometimes I’m a few degrees retarded.
I would like to point out that there’s a lot of “internet standards” that are wrong...for instance, advanced cam timing does not always cut top end and retarded cam timing doesn’t always make more top end.
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Sometimes I’m 6-8 degrees advanced, sometimes I’m straight up, sometimes I’m a few degrees retarded.
I'm several degrees retarded. That's what my parents told me when they had me tested... ;D
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Sometimes I’m 6-8 degrees advanced, sometimes I’m straight up, sometimes I’m a few degrees retarded.
I'm several degrees retarded. That's what my parents told me when they had me tested... ;D
Yeah, I had a double entendre when I wrote that too lol
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I would like to point out that there’s a lot of “internet standards” that are wrong...for instance, advanced cam timing does not always cut top end and retarded cam timing doesn’t always make more top end.
I said you might advance the cam to gain some low end. I didn't say it is always that way. I would bet 90% of the time in 90% of applications it is true, though. Until you advance it too far. How far is too far? LOL!
JMO,
paulie
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My cam has a 108 degree centerline and the intake centerline is right around 105 degrees. Is that right for every combination? Of course not.
What about "chain stretch"?
paulie
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Once again I really do appreciate your generosity of knowledge. The engine that is going in my Starliner is a 427 10.5 comp. comp. 282S Iron heads single plane EFI 411 gearvenders and converter to be determined. Being a heavy car I was considering setting cam advanced a couple degrees but after reading the response I will go straight up at least as a starting point. This will be for street use.
Mike.
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Once again I really do appreciate your generosity of knowledge. The engine that is going in my Starliner is a 427 10.5 comp. comp. 282S Iron heads single plane EFI 411 gearvenders and converter to be determined. Being a heavy car I was considering setting cam advanced a couple degrees but after reading the response I will go straight up at least as a starting point. This will be for street use.
Mike.
Yes, that cam already has 4 degrees advance ground into it. So If you install it straight up and everything is "right" then it would have 4 degrees advance already.
That is not always the case though. Minute differences in parts (or poor machining) can add up and alter the cam timing. I once put together a 351W with a cam that was advertised to have a 110 degree lobe separation angle and a 105 degree intake centerline. When I put it in dot to dot, the intake centerline was 112 degrees. I advanced it 8 degrees to get it close.
Still, in my opinion, dot to dot is the best starting place given your compression ratio.
JMO,
paulie
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I would like to point out that there’s a lot of “internet standards” that are wrong...for instance, advanced cam timing does not always cut top end and retarded cam timing doesn’t always make more top end.
I said you might advance the cam to gain some low end. I didn't say it is always that way. I would bet 90% of the time in 90% of applications it is true, though. Until you advance it too far. How far is too far? LOL!
JMO,
paulie
I wasn't replying to you, Paulie, just making a general statement.
I hate to harp though, but "straight up" and dot to dot is not the same. Straight up actually means the LSA = ICL. So, if you have a 112 LSA camshaft and install it straight up, the ICL would be 112 as well. Sorry, pet peeve of mine.
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Once again I really do appreciate your generosity of knowledge. The engine that is going in my Starliner is a 427 10.5 comp. comp. 282S Iron heads single plane EFI 411 gearvenders and converter to be determined. Being a heavy car I was considering setting cam advanced a couple degrees but after reading the response I will go straight up at least as a starting point. This will be for street use.
Mike.
Based on your specs, I would put that cam on a 110 ICL.
That cam should be a 110 LSA with a 106 ICL. So it's ground with 4 degrees of advance. I'd degree it to be sure, but theoretically, I'd put that cam 4° retarded. 10.5:1 with a heavy car can put you in a hairy spot and I'd be more comfortable with some lee-way there.
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I have a 282S in my current 390 Galaxie. It was off, i don't remember how many degrees
changed timing gears it was off the same degrees had to use a Ford Motorsport
timinggears with 8 positions to get it lined up per instructions 4 deg. adv
My 390 10.5 comp ironheads single plane 750 carb 2.70 isch gear 29 inch rear tires
works fine, a Little slow of the line but its more from the highway gear/Converter
as son i get rolling i begin to pull like a steam train, cruises nice at 1500 rpm very
drivable, enough vaccum for Powerbrakes, 11.5 inch/Hg idling
and you have more inches and 4.11
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I would like to point out that there’s a lot of “internet standards” that are wrong...for instance, advanced cam timing does not always cut top end and retarded cam timing doesn’t always make more top end.
I said you might advance the cam to gain some low end. I didn't say it is always that way. I would bet 90% of the time in 90% of applications it is true, though. Until you advance it too far. How far is too far? LOL!
JMO,
paulie
I wasn't replying to you, Paulie, just making a general statement.
I hate to harp though, but "straight up" and dot to dot is not the same. Straight up actually means the LSA = ICL. So, if you have a 112 LSA camshaft and install it straight up, the ICL would be 112 as well. Sorry, pet peeve of mine.
No worries. I was just clarifying. And I agree that "straight up" and "dot to dot" are not the same thing. They could be by coincidence, but still not the same things. Dot to dot is just "dot to dot".....that is however the cam is ground and how the parts go together. "Straight up" means having the same intake centerline as lobe separation. I am with you. :)
paulie
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Is it still common practice to set cam timing one or two degrees advanced for
a street use engine to allow for a bit of chain stretch or just to pump up low end torque?
Mike.
I like to line up the dots and check. I have gone 6° minus to get 109 ¼° of the advertised 110° with a Comp 282S. 4° forward on my current cam is what the engine likes.
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I dial mine in with a degree wheel to the mfg specs or what my cam consultant says. I run quality double roller timing sets and have never worried about "chain stretch".
Dot-2-dot: Out of all the engines I've built, I have had ONE cam dial in dead on the card when installed dot-2-dot. One. Crane 216/288 302 cam with a FRPP 9 way timing set. About fell out, ran it a third time to be sure. I buy 9 way timing sets out of habit.
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As we say in the airplane, plan the flight, fly the plan, picking the cam where you want it, or where your trusted guy wants it, is usually best.
The key here is having the right valve events for the use you need. It's very difficult, if not impossible, to say "early is better or worse" Too early can have it rattle like hell or potentially intake hit the pistons. Too late can lose torque and potentially hit the exhaust. In both of those cases, the wrong choice can make it run worse in general
However, if given an option, I generally like a smidge more cam early, versus a smidge less cam late, but even that completely depends.
Now, if the cam is in, and you want the behavior to change, you can tweak it, but of course it will add some/lose some depending how far you go.
What I have always wondered is where the +4 came from with the cam grinders. +4 on a 112 is way different for intake lobe postion than a +4 on a 108. It seems like maybe to make up for loss of torque due to overlap, or loss of peak power due to lack of overlap, but it's an odd "rule of thumb" that every cam grinder seems to use.
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The key here is having the right valve events for the use you need. It's very difficult, if not impossible, to say "early is better or worse" Too early can have it rattle like hell or potentially intake hit the pistons. Too late can lose torque and potentially hit the exhaust. In both of those cases, the wrong choice can make it run worse in general
I'd have to disagree with that statement. We have professional engine builders here that, between them, have thousands of builds to their credit. They can give direction and advice that will put you in the right spot 99.9% of the time. Nothing beats experience, and they have plenty of that. But no matter what ICL it's ran at, or what cam is used, the cam should be ran through its cycle and checked for minimum clearances during periods where the valves are closest to the piston. That should be a given on every build. Most people don't do that, but it should be done regardless.
I believe the +4 from cam grinders comes from the fact that most people choose a cam that is bigger than what they actually want. Cam makers realize this, and that'll help gain back some of the torque lost from a cam that is too big. That's just a guess though, so it's worth a solid plug nickle.
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I believe the +4 from cam grinders comes from the fact that most people choose a cam that is bigger than what they actually want. Cam makers realize this, and that'll help gain back some of the torque lost from a cam that is too big. That's just a guess though, so it's worth a solid plug nickle.
I lost my reply. What I wanted to say was, I am not so sure about the too big cam theory of grinding in advance. That is because even little 204 or 206 degree @ 0.050" cams typically have 4 or more degrees ground in.
JMO,
paulie
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The key here is having the right valve events for the use you need. It's very difficult, if not impossible, to say "early is better or worse" Too early can have it rattle like hell or potentially intake hit the pistons. Too late can lose torque and potentially hit the exhaust. In both of those cases, the wrong choice can make it run worse in general
I'd have to disagree with that statement. We have professional engine builders here that, between them, have thousands of builds to their credit. They can give direction and advice that will put you in the right spot 99.9% of the time. Nothing beats experience, and they have plenty of that. But no matter what ICL it's ran at, or what cam is used, the cam should be ran through its cycle and checked for minimum clearances during periods where the valves are closest to the piston. That should be a given on every build. Most people don't do that, but it should be done regardless.
As we say in the airplane, plan the flight, fly the plan, picking the cam where you want it, or where your trusted guy wants it, is usually best.
I am not sure what you are disagreeing with, I didn't mention anyone not having experience to advise someone in what you quoted...experienced or not, in fact it was the opposite
ON EDIT: Brent pointed it out by text...I wasn't saying an experienced guy couldn't tell someone to advance or retard a given cam for a given build, myself included, but my point was you can't answer generically (for every cam) without knowing at least some of the parts of the build.
Either pick a cam for all it's characteristics because you know how to pick a cam, or trust someone else, to include tweaking centerline as needed, either is perfectly fine, but just advancing or retarding a cam just as a general rule it could make things worse
I also agree you need to check clearances and degree it if you want to do it right, every time. However, many people do not
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Very much a rookie at all of this, but I really wish I had understood cam timing more when I did my build. It would have been a snap to check the opening and closing events and get the real center line when the engine was on the stand. Instead I had a more experienced friend help me and we installed the cam as per the instructions.
Scott Foxwell first raised the question about how I had installed my cam, and Brent, Ross, Barry, Drew, and a few others then very patiently walked me through what I had to learn and do in a very long thread. I will always be grateful to them and this forum for what they taught me, even though it is just a tiny fraction of what they know.
When I checked the actual timing of cam events I found I needed to use the 8 degree advance keyway to get 2 to 3 degrees of cam advance based on measuring 0.050 BTDC and ATDC and the cam specs on when those should occur. It had been installed originally on the neutral keyway. For what ever reasons it wasn't right, and after advancing it the engine runs much stronger.
This doesn't apply to a cammer, but if I had it to do over I'd buy the variable timing set and Jay's cover. I do have a question for the usual suspects - do you ever change cam timing on a dyno to see what difference it makes?
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I do have a question for the usual suspects - do you ever change cam timing on a dyno to see what difference it makes?
Yes, or do enough of the same combo to be able to tell what the difference is.
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The key here is having the right valve events for the use you need. It's very difficult, if not impossible, to say "early is better or worse" Too early can have it rattle like hell or potentially intake hit the pistons. Too late can lose torque and potentially hit the exhaust. In both of those cases, the wrong choice can make it run worse in general
I'd have to disagree with that statement. We have professional engine builders here that, between them, have thousands of builds to their credit. They can give direction and advice that will put you in the right spot 99.9% of the time. Nothing beats experience, and they have plenty of that. But no matter what ICL it's ran at, or what cam is used, the cam should be ran through its cycle and checked for minimum clearances during periods where the valves are closest to the piston. That should be a given on every build. Most people don't do that, but it should be done regardless.
As we say in the airplane, plan the flight, fly the plan, picking the cam where you want it, or where your trusted guy wants it, is usually best.
I have no idea what you are disagreeing with, I didn't mention anyone in what you quoted...experienced or not, in fact it was the opposite.
Either pick a cam for all it's characteristics because you know how to pick a cam, or trust someone else, either is perfectly fine, but just advancing or retarding a cam as a general rule, either learn quick and decide or it may teach you quickly :)
and "you" is general terms, not you specifically...LOL
Ok, let me pinpoint it. You said " It's very difficult, if not impossible, to say "early is better or worse"
I'm just saying that there's enough guys here with tons of experience, that if you pick their brain and ask for assistance, that that is not the case. They will be able to tell you where to put it, based on the owners wants/needs, and get it right the first time. I wasn't disagreeing with everything you said, just that part.
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I got it, and updated above, but we were looking at it differently
I was thinking "Hey my car is here and I am going to advance whatever cam is in it"
I think you were looking at it and saying "Here is my combo, would advance or retard help?"
I agree in the second scenario, many of us could help, and we do this kind of stuff all the time on this forum, but I understood the original question to be about a rule of thumb, and if the experts don't know the build, they can't really give advice
I am with you 100%
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Anybody want to talk about "chain stretch" and the possible need to advance a couple of degrees to compensate for that?
:)
paulie
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Anybody want to talk about "chain stretch" and the possible need to advance a couple of degrees to compensate for that?
:)
paulie
Several years ago I asked Barry R if there was a good chain that kept its composure and was adjustable. He sent me a MotorSports double roller with 9 positions. I have beat on it with a couple of FE engines. The chain has 30,000 miles on it. 1500 miles ago it was still tight when I played with the camshaft. Around 9,000 miles with a 282S dual springs
The last 21,000 stock type cam.
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I believe the +4 from cam grinders comes from the fact that most people choose a cam that is bigger than what they actually want. Cam makers realize this, and that'll help gain back some of the torque lost from a cam that is too big. That's just a guess though, so it's worth a solid plug nickle.
Reasonable guess.