Author Topic: Street engine cam timing  (Read 614 times)

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chris401

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Re: Street engine cam timing
« Reply #15 on: November 10, 2019, 09:49:39 PM »
   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.

Falcon67

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Re: Street engine cam timing
« Reply #16 on: November 11, 2019, 09:31:15 AM »
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.

My427stang

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Re: Street engine cam timing
« Reply #17 on: November 11, 2019, 09:46:29 AM »
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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Ross

- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 390 cid FE, headers, SM, 750 Holley, Crane HFT cam, 4 speed.  (461 EFI almost done!)

cjshaker

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Re: Street engine cam timing
« Reply #18 on: November 11, 2019, 11:47:46 AM »
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.
Doug Smith


'69 R-code Mach 1, '65 427 MR, 2x4, 4-spd, 4.30 Locker
2 1965 Galaxies with 390s
1970 F-350 390
1958 Ford Ranch Wagon 390

plovett

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Re: Street engine cam timing
« Reply #19 on: November 11, 2019, 12:48:19 PM »

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
« Last Edit: November 11, 2019, 01:54:57 PM by plovett »

My427stang

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Re: Street engine cam timing
« Reply #20 on: November 11, 2019, 01:46:54 PM »
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

« Last Edit: November 11, 2019, 02:06:04 PM by My427stang »
---------------------------------
Ross

- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 390 cid FE, headers, SM, 750 Holley, Crane HFT cam, 4 speed.  (461 EFI almost done!)

Yellow Truck

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Re: Street engine cam timing
« Reply #21 on: November 11, 2019, 01:52:04 PM »
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?
« Last Edit: November 11, 2019, 01:55:17 PM by Yellow Truck »
1969 F100 4WD (It ain't yellow anymore)
445 with BBM heads, Prison Break stroker kit, hydrualic roller cam, T&D rockers, Street Dominator Intake with QFT SS 830.

Paul.

blykins

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Re: Street engine cam timing
« Reply #22 on: November 11, 2019, 01:56:52 PM »
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. 
Brent Lykins
Lykins Motorsports
www.lykinsmotorsports.com
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www.customfordcams.com
502-759-1431
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cjshaker

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Re: Street engine cam timing
« Reply #23 on: November 11, 2019, 02:01:15 PM »
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.
Doug Smith


'69 R-code Mach 1, '65 427 MR, 2x4, 4-spd, 4.30 Locker
2 1965 Galaxies with 390s
1970 F-350 390
1958 Ford Ranch Wagon 390

My427stang

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Re: Street engine cam timing
« Reply #24 on: November 11, 2019, 02:09:21 PM »
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%

---------------------------------
Ross

- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 390 cid FE, headers, SM, 750 Holley, Crane HFT cam, 4 speed.  (461 EFI almost done!)

plovett

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Re: Street engine cam timing
« Reply #25 on: November 11, 2019, 05:10:32 PM »
Anybody want to talk about "chain stretch" and the possible need to advance a couple of degrees to compensate for that?

:)

paulie

chris401

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Re: Street engine cam timing
« Reply #26 on: November 11, 2019, 06:54:49 PM »
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.

chris401

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Re: Street engine cam timing
« Reply #27 on: November 11, 2019, 07:06:59 PM »
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.