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GranTorinoSport View Drop Down
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    Posted: 03-June-2015 at 3:26AM
75 Sport, 521 engine, 600 cfm edelbrock carb, c-6, 2.75 rear

So I have been driving my Sport this week (it now has no interior, quite loud and annoying). As I had experienced in the past, I get a touch of knocking going up a hill on the way home from work.

To be a little more specific, this is a BIG hill. It is very steep and straight (I do not have a grade for you, sorry), but let's say the 99 VW Bug has to be in 2nd gear (5-spd manual) and still struggles with it. Of course the Torino does not struggle with it, but it is working to get the 4700 lb carcass up the hill.

So, the engine is not running fast (say 2500 RPM? My tach is non working with the new ignition system), but vacuum should be high because it is under sustained load. I am not going very fast (25 MPH max) either.

Anyway, I have noticed some knocking when going up the hill. I wanted to get some timing recommendations, as I think I probably have an issue with vacuum or mechanical advance.

Some facts:

1. Mallory Unilite Distributor, factory advance settings.

2. Edelbrock 600 cfm carb (yes, I know it is too small, it was sitting around at the time I needed a carb). It is pretty close to factory rod/jet combo, a little rich I think but AF ratio is pretty good although I have not checked in a while.

3. Here are the engine specs:


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 3:58AM
521cu ?

And you're trying to feed it with 600? Waaaay too small


Edited by Nuggets - 03-June-2015 at 4:01AM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 4:01AM
I don't reckon its timing, I reckon its running too lean at rpm when under high load......

See if you can borrow an 800cfm carb as a minimum, I'm going to be using a 750cfm carb on my 440 and thats too small really.....ideally I need an 800
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GranTorinoSport Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 4:30AM
So I searched Mallory's website and found the distributor has 24 deg of mechanical advance at 3000-3200 RPM.

I had heard somewhere that heavier cars need their distributors recurved for advance?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mcford Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 6:50AM
WHATS YOUR TOTAL TIMING?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GranTorinoSport Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 7:04AM
Originally posted by Nuggets Nuggets wrote:

521cu ?

And you're trying to feed it with 600? Waaaay too small


What can I say, I had it sitting around so I used it? Due to roof and other problems with the poor car (nothing related to powertrain, the thing runs great) I just never went back and did anything about it. I was thinking fuel injection, but at $2000+ I think I need to get the body fixed first to make it driveable... Then focus on such things.

However, a larger carb is within a reasonable price range.

I was thinking the Edelbrock AVS 800. I wanted to stay E-brock of course (I have all the tune rods and jets, and other stuff), and that is the biggest they have, plus it has adjustable secondaries.

I just want to make sure I am not affecting low end driveability, but here is the estimated performance of the engine from the builder (CarsByCarl):



The theoretical cfm at 4000 rpm actually exceeds the capability of the carb...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GranTorinoSport Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 7:15AM
Originally posted by mcford mcford wrote:

WHATS YOUR TOTAL TIMING?


Unknown at this time. I believe I initially timed it at 10 BTDC last year. I guess that would make a total of 34 at or around 3000 rpm. Although I am a little fuzzy on the contribution of vacuum advance and when/how it is a factor.

In the specific knocking instance I refer to, the engine is not running that fast, maybe 2500-3000 rpm. If my tach worked, I could give you a better number, but I will have to send it in for modification...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote aquartlow Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 8:18AM
My "small" 472 w/ Dove heads and 9.33 to 1 CR running a Comp Cam's 280 Magnum(not the best choice, but is was chosen MANY years ago-engine built in '92) installed 1.5 degrees advanced, it likes 18 degrees initial with 35 degrees total all in by 2800rpm. I know I had a recent issue with a Crane HI-6 and it would pop and sputter at around 3K rpm(this was happening while trying to tune a Holley 870 Avenger, which sucked as I was blaming the carb for my ignition issues). At 3K my wideband gave an AFR of 14.0 but since I was experiencing the pop/sputter, I went up on main jets, down on air bleeds and ended up really tuning my carb out of the "ballpark". After changing ignitions I was able to correctly tune the carb. Definitely go bigger on the carb size, 850 at least and try to stay with vacuum secondary(Holley 870, Holley 80531 or possibly Quick Fuel 880 VS). I believe you will find that raising initial timing at least to 16 BTDC while keeping the total between 32-36 will REALLY wake up that beast, I would think with only 10 degrees initial you would be seeing glowing header tubes with prolonged engine running above idle(1200-1500 rpm). Good luck. Todd    
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Bird Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 8:54AM
Basically, you are "Lugging" the engine, lowish RPM, Heavy car, uphill... Your vacuum advance is going to be maxed out, even though the mechanical advance isn't going up much. You either need a smaller amount of vacuum advance, less initial timing, or more octane. Your carb shouldn't be leaned out at that RPM, (Ford used much smaller 2-bbl carbs on 390s, 400s, and 429s, all flow about 400 CFM max or less)
Oh, more gears in the rear (3.25 or 3.50) will help this as well.
The above post should be read in a "Grumpy Old Man" voice.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GranTorinoSport Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 9:00AM
Won't the additional advance just make the knocking under heavy load worse?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Bird Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 9:07AM
Don't ADD advance, reduce it. Are you hooked up to ported or manifold vacuum?
The above post should be read in a "Grumpy Old Man" voice.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GranTorinoSport Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 9:15AM
ported advance on the carb

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Post Options Post Options   Thanks (0) Thanks(0)   Quote aquartlow Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 9:23AM
  Have you run a timing light on your engine to find when the mechanical advance starts and how aggressive it is and/or at what rpm it gets to total amount of mechanical advance? 10 degrees of additional advance from the vacuum advance canister is "usually" a good place to start(but every vehicle is different), is the Mallory unit adjustable?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Bird Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 9:25AM
I would start with less vacuum advance. This might even let you run a little more initial timing, which your engine should like.
To see how much advance you need to lose, retard the timing until you can get up your hill without problems, subtract your new initial from the original, and that's how much less vacuum advance you need. You can use a vacuum pump to see how much advance you currently have, and get one with less, or get an adjustable one and set it using a timing light and vacuum pump.
This is the cheapest mechanical route, swapping the rear gears would be the expensive route, (but the most fun). 104+ or any other octane booster is a quick-fix. - BTW, the gas in your tank isn't months and months old, is it? Stale gas will give you a lower octane and ping under load.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote VorbottenO Quote  Post ReplyReply Direct Link To This Post Posted: 03-June-2015 at 1:21PM
The big blocks do like higher initial and sounds like you could benefit from dizzy recurve.
I am running a Unilite as well, bought the curve spring kit and set it up for a two step mechanical advance so that i had a faster initial climb. Felt like I added 50hp.
The kit also includes keys to ser the total advance limit so you can use a higher initial timing. I.e initial set at 14 degrees + 22 more mech (vs factory 24)= 36 total.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GranTorinoSport Quote  Post ReplyReply Direct Link To This Post Posted: 04-June-2015 at 2:48AM
Originally posted by VorbottenO VorbottenO wrote:

The big blocks do like higher initial and sounds like you could benefit from dizzy recurve.
I am running a Unilite as well, bought the curve spring kit and set it up for a two step mechanical advance so that i had a faster initial climb. Felt like I added 50hp.
The kit also includes keys to ser the total advance limit so you can use a higher initial timing. I.e initial set at 14 degrees + 22 more mech (vs factory 24)= 36 total.


Eric,

I think I have the kit around somewhere, I purchased it when I got the Mopar Performance electronic distributor kit for my Chrysler (the distro is also made by Mallory and uses some same parts).

Specifically what springs and in what locations did you use? I think that would be a good first step for me, along with dialing down the vacuum advance.

Hopefully this weekend I can bust out the timing light and do a little research.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GranTorinoSport Quote  Post ReplyReply Direct Link To This Post Posted: 04-June-2015 at 3:16AM
So to answer a previous question, I do not actually know if the vacuum advance on a Mallory Unilite series 47 is adjustable or not? There is nothing I can find anywhere about it?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 04-June-2015 at 4:11AM
Originally posted by GranTorinoSport GranTorinoSport wrote:

Originally posted by Nuggets Nuggets wrote:

521cu ?

And you're trying to feed it with 600? Waaaay too small


What can I say, I had it sitting around so I used it? Due to roof and other problems with the poor car (nothing related to powertrain, the thing runs great) I just never went back and did anything about it. I was thinking fuel injection, but at $2000+ I think I need to get the body fixed first to make it driveable... Then focus on such things.

However, a larger carb is within a reasonable price range.

I was thinking the Edelbrock AVS 800. I wanted to stay E-brock of course (I have all the tune rods and jets, and other stuff), and that is the biggest they have, plus it has adjustable secondaries.

I just want to make sure I am not affecting low end driveability, but here is the estimated performance of the engine from the builder (CarsByCarl):

The theoretical cfm at 4000 rpm actually exceeds the capability of the carb...


The AVS series of carbs is pretty good, I've used the 650 on my old 351c. VS wont make a difference to low end as the engine will still only draw through what it needs its how I could run a 500cfm edelbrock on my puny 215 rover v8
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Bird Quote  Post ReplyReply Direct Link To This Post Posted: 04-June-2015 at 11:32AM
http://www.summitracing.com/parts/maa-29332
Adjustable advance for Mallory 47 series. Your existing is probably adjustable as well. usually the adjustment is done with a small allen wrench that you put in to the vacuum port on the advance canister.
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