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Discussion Starter #1
Bob, I would try an orange cam, may be better for a 4 speed car. Timing sounds about right, 34°-36° total is around what Clevelands like, even in race applications. I would stay away from the 50cc pumps, way too big for a 650. The guy that built mine only used 30cc pumps, and it flows around 870 CFM. To me it sounds like not enough fuel right off the bat. Mine has no hesitation anywhere. My intake has a 1500-7000 RPM range, and you know how big the cam is.
 

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Re: How to determine total advance for individual engine.

Another apology to the thread starter! Funny you mention that Mike! I happened to have an orange (466) cam on one of my junkbox carbs (and the 4777-7 carb had a pink (330) like yours Adam). Cleaned the orange one up and popped it on. Re-adjusted accelerator pump and tried it out in the garage. Throttle feel indicates much improved. Will drive the car tomorrow and see how things feel.

Now, to get back on topic, I know//have heard of numerous people not running vacuum advance and relying on mechanical advance alone. I have done this myself and may go back to it. But having an adjustable vacuum can I am left wondering if a combination (and limits on both to properly maintain total advance) of both is better or if centrifugal alone is "just fine". Guessing it comes down to two different curves and the one which includes vacuum would be hard to test on a dist machine unless an accurate model of ported vacuum vs. RPM was known.

What do you guys think?

Oh, and thanks for the help on the accel pump guys!

Regards,

Bob
 

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Re: How to determine total advance for individual engine.

Here's my understanding. Peak cylinder pressure should occur around 15 to 17 degrees ATDC. If it occurs after that, you are wasting energy. The higher the air-fuel density, the faster the fuel mixture burns which requires less advance. The air-fuel density is lower at partial throttle which means if burns slower and you need more advance compared to wide open throttle. You can run without a vacuum advance, but your gas mileage will suffer.
 

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Re: How to determine total advance for individual engine.

...You can run without a vacuum advance, but your gas mileage will suffer.
Well, it's doing that!, with MPG never higher than 10!
 

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Discussion Starter #5
Re: How to determine total advance for individual engine.

That could probably increase a bit with a lighter foot Bob. Not that I can say much, I have never gotten better than 5 mpg.
 

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Re: How to determine total advance for individual engine.

And I've never had worse than 13, even with a heavy foot. You have a problem if you're only getting 10 with your 5 speed transmission. Have you changed your power valve and jets in the carb?
 

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Re: How to determine total advance for individual engine.

And I've never had worse than 13, even with a heavy foot. You have a problem if you're only getting 10 with your 5 speed transmission. Have you changed your power valve and jets in the carb?
Hi Jeff,

No 5 speed (so no OD). 4 speed toploader with 3.25 rear gears. Have changed nothing on the brand new 4777-7 from out of the box except putting on an electric choke and (now) having changed the primary accelerator pump cam from pink to orange.
 

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I'd stay closer to the 32 degrees total and invest in a wide band O2 guage so you can fine tune it. Most carbs out of the box are on the rich side. In my experience, on 99 percent of the street cars I've tuned I've had to jet way down...some as much as 8 jet sizes.
 

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Bob,
Thought you had a 5 speed. Guess I shoul read more closely. When I had my car dyno tuned, the Holley 600 needed to go up a size in jets to 68 and the power valve was replaced with a 10.5. Those two things along with proper timing cured all my pinging, hesitation, stumbling and mileage issues. I haven't touched the carb in 3K miles and it runs great. Of the 5 cars at the dyno with out-of-the box Holley carbs, everyone of them needed bigger jets and a different power valve.
 

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Well test drove with orange cam on primary accel pump was still stumbling fairly bad. Advanced timing from 10 BTDC to 14 BTDC and put vacuum advance back and it is real smooth. Not sure why I'm not hearing any pinging, would have thought I would and the total advance is probably too much. With as much initial timing as this cam (and whatever else) seems to like, probably will need to take dist apart and further limit the mechanical advance and then fiddle with the adjustable vac can to set it to something appropriate as well. Going to see how the idle mixture acts now that I have gone back to what I found with this engine from the beginning, it likes a lot of initial advance.

Choke and fast idle seems to be working pretty nicely.
 

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How about this for a cheap wideband O2 setup (that I picked out the pieces for)?:

 

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The one thing no one mentioned here is the altitude each lives/drives at. Here in Colorado 5000'+ we run smaller CFM carbs. 600 to 650 on 351's and 700-750 on 390+ for the average car (not drag racing). The motors produce much more torque at lower speeds. The cars I do all go to a chassis dyno for tuning, not total HP/torque numbers, tuning! They usually go down 2-4 steps/jet & rods.

The shop I use runs Vintage Racing.

http://www.eps-hane.com/

Walt has an awsome history running with the likes of Carol Shelby. He was just talking w/ Bud Moore the other day when I showed up. His son Skip drives and tunes! Great guys and the stories Walt tells... Boss 302 factory inspection for homoligation rules... as the cars were counted they were brought back thru the line and counted numerous times...

Next time I'll take a recorder. I'm gonna go over to Kenz & Leslie and talk w/ Ron about the Cougar mods as I build a different / new Track Cat!

What an honor to be able to talk w/ such great motorsport icons!
 

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Hi Bill,

I don't think you were referencing me/what I have decribed specifically, but here is the data anyway: 4777-7 650 CFM double pumper with mechanical secondaries and the car runs at anywhere from sea level to maybe 100' above sea level. If I had to guess, from the way the cars exhaust smells, the gas mileage and the color/smell of the oil after about 1500 miles, I would bet I am running a bit rich. Better too rich than too lean as a buddy always says.

Some dyno tuning time would be helpful I am sure, but figuring adding A/F measurement to the cars instrumentation is probably a good and cheap investment that will allow some tuning at home to be done.

P.S. EPS looks like a slam dunk kind of place, good for you having that available to you. Wonder how to go about finding a similar place locally. I would have reservations about going just anywhere.

Regards,

Bob
 

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Bob, your right I was not directed "totally" in your direction.

My point here is just simply do it once.
The cost on average has been around $325.
The time spent buying, making and adjusting on your own far exceeds that cost in most cases.

NOW wait, if you like/love doing this stuff, then forget what I just said.

My basis here is:

Our time is worth X.

Example:I finish a car for the customer as a turn key item. Emission test, road test/debug, all done. I can't afford not to have this final critical item done to the max. All the money spent on the motor and not having the dyno done...

What about dist. advance curve, shift points, transistion between idle and cruise circuit, accel pump & spring, fuel pressure, etc. Possible problems show up too!

All that is done and more. You need this once. Unless you change cam, or intake, or like items.

Quite honestly this is the best money spent on your car!

So, Bob...

crack open the wallet, then floor the pedal!
 

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right on cougar bill---vac advance is just icing on the cake ---if you have your foot in it you have no vacuum
my good friend drives a radicle vette with a mag locked in @ 34 deg---pushes a starter button and gets her turning and then flips the ign on----the point i'm trying to make here is initial timing really effects the startability of the car--i personally like to advance the timming until it bogs the starter and back off---its easier to limit the total amount of timming
doctordesoto
 

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Bob, your right I was not directed "totally" in your direction.

My point here is just simply do it once.
The cost on average has been around $325.
The time spent buying, making and adjusting on your own far exceeds that cost in most cases.

NOW wait, if you like/love doing this stuff, then forget what I just said.

My basis here is:

Our time is worth X.

Example:I finish a car for the customer as a turn key item. Emission test, road test/debug, all done. I can't afford not to have this final critical item done to the max. All the money spent on the motor and not having the dyno done...

What about dist. advance curve, shift points, transistion between idle and cruise circuit, accel pump & spring, fuel pressure, etc. Possible problems show up too!

All that is done and more. You need this once. Unless you change cam, or intake, or like items.

Quite honestly this is the best money spent on your car!

So, Bob...

crack open the wallet, then floor the pedal!
Thanks Bill. I do like doing stuff, especially like the idea of having another instrument on how the engine is doing and doing it on the cheap. However, if I can find someone reputable in my area, I would spend $325 in a heartbeat, nothing I can do will be as comprehensive. But, that too is a concern, I need to have confidence in whomever would be doing this that they would do (and knew what to do) regarding the various things you have pointed out. Not interested in buying dyno time where what happens is totally up to me and my knowledge. That would be a good way to waste my money. Wonder if your guys know any guys in the NE, NJ preferably?

Thanks again,

Bob
 

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ya know Bob, I'm only about 1 tank away.... that is one of them 18 wheeled tanks!



Dyno shops around here have "dyno" days for clubs. They give you one pull for less than $50.
Another item to add to the shop (kinda big) is an old Sun tune machine w/ scope, and an emissions test machine. Got both for $400. Item by item can be checked, like advance w/ timing light.

But bottom line chassis dyno is so valuable. Look for a racing shop that runs Fords. Vintage racing... Mustang clubs newsletter ads..

F1 starting gotta go!




Thanks Bill. I do like doing stuff, especially like the idea of having another instrument on how the engine is doing and doing it on the cheap. However, if I can find someone reputable in my area, I would spend $325 in a heartbeat, nothing I can do will be as comprehensive. But, that too is a concern, I need to have confidence in whomever would be doing this that they would do (and knew what to do) regarding the various things you have pointed out. Not interested in buying dyno time where what happens is totally up to me and my knowledge. That would be a good way to waste my money. Wonder if your guys know any guys in the NE, NJ preferably?

Thanks again,

Bob
 

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ya know Bob, I'm only about 1 tank away.... that is one of them 18 wheeled tanks!



Dyno shops around here have "dyno" days for clubs. They give you one pull for less than $50.
Another item to add to the shop (kinda big) is an old Sun tune machine w/ scope, and an emissions test machine. Got both for $400. Item by item can be checked, like advance w/ timing light.

But bottom line chassis dyno is so valuable. Look for a racing shop that runs Fords. Vintage racing... Mustang clubs newsletter ads..

F1 starting gotta go!
Yes, at this juncture, my thoughts harken back to the time I spent working in a garage that had an emissions tester, was very helpful for seeing how the engine was doing. I know I can benefit from some timing work but have gotten some improvement thus far but (to your point) getting the car in front of some people with skills such as your guys have would be invaluable, money well spent, more efficient, more expedient.

"Look for a racing shop that runs Fords. Vintage racing... Mustang clubs newsletter ads.." Check. Will do that. There is a (recent) road course in SNJ, I'll start poking around there and my buddy who owns the machine shop has a (local) customer who does this sort of racing, will check him as well.

Yes, I woke up to a little F1 this morning myself.

Thanks Bill.

Regards,

Bob
 

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Discussion Starter #20 (Edited)
You don't know SCCA Bob? Sports Car Club of America, only the best racing there is. Fun road course racing http://www.scca.com/. Mostly vintage stuff, but just about anyone can race if their car meets the specs. I would like to do up a 67 or a 70 for SCCA one day.

I too will say that dyno time is about the only way to truely tune a car properly. If I can ever get my rings to seat properly, I will be taking mine. Most of the guys around here only do dyno runs for peak HP, therefore they are almost always full throttle runs and only really change timing and jets. My plan is to do idle, part throttle, cruise, load acceleration (to check power valve), and then finally full throttle. I am less conceerned about max HP, than I am about drivability (not that my engine is much of a streetable one, but still want it to be the easiest it can be).

Good luck Bob. And for what it's worth, my initial is set at 16°, and I had to take some slack out of my advance to keep the total to around 36°. I also have no vacuum advance in mine. The trick to getting away from vacuum is to have a lighter spring for the initial advance, and a stronger one for the above 1500 to 2000 RPM advance.
 
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