74Beeper
Well-Known Member
Are any of you running on the street with your timing locked out due to a long duration cam? If so, where do you have it set? What are your engine specs? CI, cam specs, comp ratio, vacuum at idle.... ect.
Timing Locked Out On The Street?
- Thread starter 74Beeper
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moper
Well-Known Member
Just my $.02.. Locked out timing is for a race engine that stays in a small operating range. With the exception of a couple engines with cams that were low static compression, but had serious cams and tight convertors (i.e. 7.8:1 440 with a 250 degrees at .050 hydraulic cam, 3.91s, and 2200 stall) I've always run a timing curve, and always a vacuum advance off ported vacuum. Sometimes the curves are total custom deals, but you will always give up economy, small amounts of power at most throttle positions, and overall response by concentrating on a single timing amount. Over the long haul you are better served by matching components and really tuning.
Again - just my opinion based on almost 30 years of doing this.
Again - just my opinion based on almost 30 years of doing this.
74Beeper
Well-Known Member
Well I have a 440ci small block with 10.92 compression, a 724 duration cam and dual 750 Eddies. Once it's warmed up, I can't get it to stay idling. I have a hydrobooster and when I hit the brakes, it will want to die. If I hit the brakes and turn at the same time, it's all over, it drops off quick. I locked the timing out at 38* and it's a lot better but will still want to die. I've tried every tuning procedure with the carbs but the only thing that will get it to stay idling is a lot of initial.
Indy Cylinder Heads built me this motor and dyno tuned it. I wouldn't think they'd build me a motor with unmatched components. But as soon as I got it in the car with a little load at idle. It won't stay running.
Indy Cylinder Heads built me this motor and dyno tuned it. I wouldn't think they'd build me a motor with unmatched components. But as soon as I got it in the car with a little load at idle. It won't stay running.
Jeremiah
Well-Known Member
What is the idle vacuum in gear?
What do the spark plugs look like?
When it dies is it loaded up or does it need fuel to restart?
When it starts to fall off can you pump the gas ever-so-slightly to actuate the accelerator pumps and keep it running?
The duration of the cam is a lot less than 724!
Double check that numbers for sure.
What do the spark plugs look like?
When it dies is it loaded up or does it need fuel to restart?
When it starts to fall off can you pump the gas ever-so-slightly to actuate the accelerator pumps and keep it running?
The duration of the cam is a lot less than 724!
Double check that numbers for sure.
74Beeper
Well-Known Member
Damn.... My dyslexia is kicking in again!!! Duration is 274!!!! Haha
Haven't pulled he plugs yet cuz I ran out of time to work on it before I had to come back to work... (I'm an offshore platform mechanic in Russia) It's not loading up though. If I hit the throttle it recovers. It's a Tremec TKO600 and the idle vacuum is 6 to 7 but I do have a PCV valve that is taking away from that. My plan is to ditch that to try and get more vacuum.
lewtot184
Well-Known Member
i wonder if those edelbrocks don't need some serious re-calibration? what intake manifold? that's a lot of cam to drive on.
74Beeper
Well-Known Member
So far, it hasn't mattered where the idle screws are set, it runs about the same. Intake is an Indy Mod-Man.
Jeremiah
Well-Known Member
It's time to start messing with the air bleeds on the idle circuit to start with. Also make sure the throttle blades are not exposing the transfer slot too much. It should be about .020 exposed and look "square". If you want to fatten up the idle circuit a good, down and dirty way to do it is put some thin ( i.e. .010 or so) wire in the idle bleeds and see if you are able to get them to respond.
moper
Well-Known Member
First - never assum anything. Especially with product or labor from Indy. I've yet to see an engine from them make what they said it did for power, or run well overall. Plus - dyno results are normall yfor power levels. They're BS in most cases anyway, and it doesn't help you with the reality of sitting in the car. So dyno'd doesn't mean much in the real world. If they locked out the timing it's just another bit of proof they're idiots.
You have plenty of compression, but the duration needs more info. Is it 274 advertised duration (A part number would really help here) or 274° at .050? Two very different cams there.
First assumption is it's 274° advertised and probably falls in the 230° @ .050 range. It should idle fine. My impression is Indy didn' have your power steering and accessories hooked up to it, so it's probably not set to idle properly. It needs basic tuning. Not more timing.
Second assumption is it's 274° at .050, in which case I'm sure the Edelbrock calibration is off and you'll have to mess with it a bit to get it to idle cleanly as it sits in the car.
You have plenty of compression, but the duration needs more info. Is it 274 advertised duration (A part number would really help here) or 274° at .050? Two very different cams there.
First assumption is it's 274° advertised and probably falls in the 230° @ .050 range. It should idle fine. My impression is Indy didn' have your power steering and accessories hooked up to it, so it's probably not set to idle properly. It needs basic tuning. Not more timing.
Second assumption is it's 274° at .050, in which case I'm sure the Edelbrock calibration is off and you'll have to mess with it a bit to get it to idle cleanly as it sits in the car.
74Beeper
Well-Known Member
Yeah, i'm not impressed with Indy at all. I will never be doing business with them again. They make good parts for power but it's better to let someone else do the assembling.
As for cam is a Comp p/n 20-717-9 and grind RX308R-8 , it's 308/317 advertised and 275/284 @ .050 with .658/.661 lift. I'm running 1.5 T&D rollers. I'm the one who locked out the timing because that was the only way i could get a stable idle. It just wouldn't make enough vacuum until i brought the initial up. When they dyno'd it, (i was there for this) it made the best power @ 38* all in. I've adjusted the idle mixture screws every which way possible (evenly between the 2 carbs) but it didn't make much difference with the vacuum. The only difference is, i have been running a PCV valve that wasn't installed during the dyno. I know this PCV is hurting idle vacuum and i plan on removing it as soon as get home this weekend and will try tuning it again.
Bigal75
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Yes, locked at 33 or so
572 Hemi - no issues, I use a start retard of 10 degrees to start. Plugs are good, vaccum at idle in gear is 7.5 or something like that - cruising is 13.
Cam duration is 283 @ 0.50
572 Hemi - no issues, I use a start retard of 10 degrees to start. Plugs are good, vaccum at idle in gear is 7.5 or something like that - cruising is 13.
Cam duration is 283 @ 0.50
74Beeper
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Bigal75
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Compression is 11:1 and I run a single Holley 1050 Dominator.
Just out of curiosity I checked out Comp Cams specs. They list the intended usage for drag racing with an operating range of 4,800-7,800 rpm, with an example being Super Gas Class. If that's the case, trying to get a decent idle quality may be a fool's errand (please don't take offense). Is this car street driven and is that why you had a PCV system hooked up?
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=692&sb=2
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=692&sb=2
Hemirunner
Well-Known Member
A PCV valve has no business on a build like that. Add some evacs or a couple of catch cans with breathers. Adding that changed the whole tune. Locking out the timing on a big inch stroker with a big duration cam will give it back some manners and clean up the idle without having to run vacuum advance. If you're building a driver or a performance cruiser, vacuum advance and a timing curve is fine. If you want to run a big power combo on the street without hurting it or hating it, then locking it out is another tool to get that done.
74Beeper
Well-Known Member
I took the expensive route with this build and had Muscle Car Restorations do it for me. Although their paint guy is a genius, I wa not impressed with the rest of their operation. I questioned the fact they wanted a PCV and they insisted on running it. I have already ordered some evac valves and wil be installing them next week. When Indy built the motor I also questioned the cam. Their engine builder assured me it would be fine. Don't get me wrong, I'm a mechanic by trade. I started with heavy equipment and have been an offshore platform mechanic overseas since 1999 and I need to start listening to my gut.
Garys1969RR
Well-Known Member
Put in a milder cam if you want it to idle good. 308 int and 317 ex duration is WAY TOO MUCH FOR STREET. It will never idle well. What is your intended use? I run a cam with 292 degrees total duration, (242 @ .050) and it idles a little lopey, but soon as it gets under a light load and a little RPM it pulls well and runs smoothly. This is due in part, to alot of initial advance, like 20 degrees, and then 38 total. Most big blocks like alot of initial advance. I also run vacumn advance, and that helps too. Good luck! Change to a hydraulic cam such as the Comp XE 285 HL, thats about the most cam you would want on the street. 285/297 duration. .545" lift.
- - - Updated - - -
You could also try the milder XE275 HL with duration of 275/287 with a .525 lift. Better for all around street performance.
- - - Updated - - -
You could also try the milder XE275 HL with duration of 275/287 with a .525 lift. Better for all around street performance.
Burns69RT
Well-Known Member
If you've got a 4-speed, and have mech timing around 10* with the rest initial and if everything is tuned right you could get away with a 600 to a 620 lift cam. And they have that badass hard choppy lope. It just makes you think it's gonna die but it shouldn't. Never did for me.
moper
Well-Known Member
The cam is the only thing making that combo not work. Big cams get you big power, but they are not conducive to street use at all. That particular grind is not a street friendly grind either which hurts even more. IMO - wrong cam choice but definately makes a great dyno number. You have to treat it like a superstocker...lol. Evacs will help assuming the exhaust is free flowing enough, otherwise they will help the idle because of the vacuum leak plugging, but you'll start pushing oil out various weaker gaskets. The Edelbrocks are not calibrated to work with that low of an idle signal. That's why there's no response to the idle screws. Get a modern Holley based carb or carbs for it and you'll be able to tune for it.
600psi over the nose... you should be testing your valve springs once a year at least too. That cam will eat springs in an engine that idles like in a street car.
600psi over the nose... you should be testing your valve springs once a year at least too. That cam will eat springs in an engine that idles like in a street car.
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