Total timing with 10.5:1 Compression

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Re: Total timing with 10.5:1 Compression

Post  kim on June 16th 2015, 4:10 pm

Based on a target peak of 6000RPM the ideal carb would be 950cfm.  Thats just letting it get enough air.

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Re: Total timing with 10.5:1 Compression

Post  78ranger on June 16th 2015, 5:25 pm

If youre going to run the eddy for a while, spend the 15 bucks to change to the high flow needles/seats. A big block really will empty the bowls at wot. I've seen it on AFR. The quick fuel carbs are pretty nice. At least an 850.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 16th 2015, 6:44 pm

78ranger wrote:If youre going to run the eddy for a while, spend the 15 bucks to change to the high flow needles/seats. A big block really will empty the bowls at wot. I've  seen it on AFR. The quick fuel carbs are pretty nice. At least an 850.

I have heard this about the Edelbrock's. The last tech I spoke to even admitted the bowls might be an issue in a performance situation. Their manual says this:

High Fuel Flow
When evidence of fuel starvation exists, first ensure that proper pressure (4-5 psi minimum) is
maintained at WOT. If proper fuel pressure is supplied and fuel starvation still exists, it may be
necessary to change the needle and seat to a larger size (#1466). Do not make this change unless
absolutely required, as the smaller inlet is preferred for proper fuel control under most conditions.


I wonder what "Fuel Control" issues they mean?


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Re: Total timing with 10.5:1 Compression

Post  78ranger on June 16th 2015, 6:59 pm

It means on a small block chevy its probably too much gas Smile I've never had flooding issues with it. Buy a cheap AFR. It's worth every penny.

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Re: Total timing with 10.5:1 Compression

Post  supervel45 on June 16th 2015, 7:29 pm

From my experience with a mild 429, I think you will be happier with a 750cfm carb. 850's are great on the hot 429's and 460's, but a little much for what you describe. It also sounds like you have a midrange lean spot and or the timing curve is still off. You could raise your timing curve 500rpm to total advance, and see if it helps. What I am trying to say is you may have too much timing at the point the secondaries are opening, before they get a good metering signal, and it is causing the problem.

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Re: Total timing with 10.5:1 Compression

Post  supervel45 on June 16th 2015, 7:43 pm

What you're combination,ie gear ratio tire height stall convertor intake headers vechicle weight. I was going under the impression this was a stockish 1970 car. As for the high flow needle and seat, it is a very good idea.

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Re: Total timing with 10.5:1 Compression

Post  maverick on June 16th 2015, 8:21 pm

I'm not totally convinced that there isn't a vacuum leak somewhere...possibly causing one or more holes to go lean, hence the pinging as it climbs in rpm and builds vacuum. Fattening this thing up and changing timing curves seem to help a bit, but won't cure it. I've never seen a ping that couldn't be corrected with some combination of air/fuel adjustment, fuel quality and timing corrections...unless there was a less obvious cause. Just a thought....maybe I'm all wet. I have been before.Rolling Eyes
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Re: Total timing with 10.5:1 Compression

Post  supervel45 on June 16th 2015, 9:23 pm

What distributor are you using?

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 17th 2015, 1:20 am

supervel45 wrote:What distributor are you using?

Accel 52000 series with mag pickup. It's locked at 44deg. My MSD is programmed to pullout timing for a curve. Seems odd but it works well once you understand it.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 17th 2015, 1:27 am

supervel45 wrote:What you're combination,ie gear ratio tire height stall convertor intake headers vechicle weight. I was going under the impression this was a stockish 1970 car. As for the high flow needle and seat, it is a very good idea.

1969 Mach 1 with 3.00 gears, stock stall in C6 trans, 3650lbs with a full tank without me in the car. I have 3" mandrel exhaust with and X-pipe. I'm still using the factory exhaust manifolds. Intake is Eddy Performer. Cam is unknown but I hear a small bit over overlap in the idle. Its definitely not a stock cam. Tires are 255/60-15 so 27.05 tall. New needle and seats have been ordered.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 17th 2015, 1:29 am

maverick wrote:I'm not totally convinced that there isn't a vacuum leak somewhere...possibly causing one or more holes to go lean, hence the pinging as it climbs in rpm and builds vacuum.  Fattening this thing up and changing timing curves seem to help a bit, but won't cure it.  I've never seen a ping that couldn't be corrected with some combination of air/fuel adjustment, fuel quality and timing corrections...unless there was a less obvious cause.  Just a thought....maybe I'm all wet.  I have been before.Rolling Eyes  

A vacuum leak is a good thought that I explored. I have replaced the base gasket and looked for other leaks. None have been found so far.

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Re: Total timing with 10.5:1 Compression

Post  TommyK on June 17th 2015, 5:35 am

jgkurz wrote:
supervel45 wrote:What distributor are you using?

Accel 52000 series with mag pickup. It's locked at 44deg. My MSD is programmed to pullout timing for a curve. Seems odd but it works well once you understand it.

Except for the pinging.

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Re: Total timing with 10.5:1 Compression

Post  supervel45 on June 17th 2015, 6:55 am

http://www.msdignition.com/instructions/Products/Ignitions/6520.pdf?terms=6520 Sounds like you have a good distributor, wanted to rule out a stock worn out points type that may be causing timing problems between cylinders because of a unevenly worn cam or excessive points gap. I actually had a problem like that with a old Msd 6AL, and a Mallory dist., and had to reduce the points gap to make it run past 5,550rpm. Did you have to cut the green loop on the Msd box for your application? I doubt it's your problem, but thought it might be worth mentioning. From the way you describe your vechicle combination, I will stick with my 750cfm recomendation. Try the needle and seat and see what happens. A O2 sensor and a viewable fuel pressure gauge sure would be nice to sort all this out.

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Re: Total timing with 10.5:1 Compression

Post  maverick on June 17th 2015, 6:56 am

Got power brakes?
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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 17th 2015, 10:25 am

maverick wrote:Got power brakes?
Yep. I could plug the vacuum line to the booster and see if my idle changes. That's the best test I can think of.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 17th 2015, 10:34 am

supervel45 wrote:http://www.msdignition.com/instructions/Products/Ignitions/6520.pdf?terms=6520    Sounds like you have a good distributor, wanted to rule out a stock worn out points type that may be causing timing problems between cylinders because of a unevenly worn cam or excessive points gap. I actually had a problem like that with a old Msd 6AL, and a Mallory dist., and had to reduce the points gap to make it run past 5,550rpm. Did you have to cut the green loop on the Msd box for your application? I doubt it's your problem, but thought it might be worth mentioning. From the way you describe your vechicle combination, I will stick with my 750cfm recomendation. Try the needle and seat and see what happens. A O2 sensor and a viewable fuel pressure gauge sure would be nice to sort all this out.

I have the MSD 6AL2 Programmable which is pn 6530. I read my installation manual thoroughly and don't recall having a green loop. I simply had a green and violet wire that went to the mag pickup (in the correct polarity of course) I do have access to an LM-1 but I don't have bung in my exhaust yet. I suppose to could put my GoPro under the hood with a flashlight to view the fuel pressure gauge at WOT. Very Happy

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 17th 2015, 1:45 pm

Just scheduled a quick DynoJet chassis dyno pull or two next Wed. I'll get AFR's then. I'm doing this early in the morning and with a race gas mix to keep the engine safe. The larger needles and seat will also be installed by then.

With the C6 I'm guessing 225hp at the wheels with 400ftlb. Any predictions on rear wheel horsepower and torque?

429ci
C6 with factory converter
Block: D1VE 6015 A
Heads: D0VE-C
Performer 460 intake
MSD ignition at 32btdc total
Exhaust manifolds with 3" mandrel x-pipe exhaust
Eddy 750 carb (we all know this!)
Slightly bigger than stock cam

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Re: Total timing with 10.5:1 Compression

Post  maverick on June 17th 2015, 6:06 pm

Unplug brake booster and plug the port at the manifold to rule out a leak there.


Do you want hp guesses with or without the ping? Razz
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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 17th 2015, 6:28 pm

maverick wrote:Unplug brake booster and plug the port at the manifold to rule out a leak there.


Do you want hp guesses with or without the ping? Razz

You're killing me!  WITHOUT THE PING.

I will vacuum test the brake booster tonight.  I have a hand pump tool that will verify if it will hold vacuum. Thanks for the reminder.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 17th 2015, 10:29 pm

Well it turns out I had a leaky booster. I'd apply 5psi vacuum to the booster and it would be down to 0psi in roughly 10-15 seconds. Before I pulled the booster (major work) I decided to spray water around the surface to see if the crimp around the perimeter was leaking. It turned out to be the mating surface between the booster and the master cylinder. Obviously I need to replace the booster. I'll probably replace the whole assembly (booster and master cylinder).

Would this be enough of a vacuum leak to cause a lean condition? Somehow I doubt it but I've been wrong before.

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total timing with 10.5 :1 compression

Post  farreldean on June 19th 2015, 3:23 pm

I had the same problem in 1973 with a 71 Lincoln running almost 11:1 on a bone stock motor.
It is not the timing.
Running a mild cam is not the solution.
The best way to reduce your compression is to install a much larger cam than you are running now.

Like you, I choose a mild cam that required 11:1 compression as a minimum. Not a good choice.
I could not advance my ignition more than 3 degrees without pinging. Before 1973, before they took the lead out of gasoline, I was running 8 degrees advance at sea level, with no problems.
I should have gone with a much more radical cam. The more that a cam opens the intake valve early, the higher the compression is required.

In 1964-65, in the days of the 327 Chev, I ran a 389 Pontiac, bored and stroked to 421, with the most radical solid lifter cam Crane could do with their special grind. I told them the compression would be 13:1, at most 13.5:1. Yeah right.

Running a Joe Hunt magneto, using a timing light, turning the magneto while running, knocked me back against the wall a couple of times. Mounted a Budweiser beer can opener, the sharp end pointing down to a degree wheel mounted to the block. I ran 10 degrees advance at Lake Tahoe, or else it wouldn't even fire up, let alone run. Taking compression checks, knowing the altitude at Lake Tahoe, the actual compression ratio was 14:1. I drove the 1957 Corvette to San Francisco several times and had to retard the timing three times on the way down to sea level, or else it would ping like crazy. The Budweiser pointer was great, with the engine off, I knew exactly where to set it.

It ran stronger at Lake Tahoe than at sea level.
Sorry, can't remember the cam specs, have them somewhere. Like I'm 80 yrs.
Have pics of the 57 Corvette somewhere. Not on my computer. Like everything is somewhere.

Ah Ha, found a pic, can't get my printer to talk back to my computer?
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Re: Total timing with 10.5:1 Compression

Post  IDT-572 on June 19th 2015, 5:50 pm

jgkurz wrote:
78ranger wrote:If youre going to run the eddy for a while, spend the 15 bucks to change to the high flow needles/seats. A big block really will empty the bowls at wot. I've  seen it on AFR. The quick fuel carbs are pretty nice. At least an 850.

I have heard this about the Edelbrock's. The last tech I spoke to even admitted the bowls might be an issue in a performance situation. Their manual says this:


I wonder what "Fuel Control" issues they mean?


Bigger diameter needle is harder for the float to control and keep the full shut off when needed..............
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Re: Total timing with 10.5:1 Compression

Post  IDT-572 on June 19th 2015, 6:05 pm

A factory 429 is going to be hard to keep from pinging on 92 or 93 pump gas.

If a performance cam was added the running compression now could be higher too, and that is what it sounds like with it pinging worse as rpm increases.

Lowering timing wont help, it will make more chamber heat,

Retard the cam timing, (not the thing to do in my book) . Fattening the fuel ratio is just cooling the chamber, and killing power.

The answer is seeing that the chamber is made more low octane fuel friendly tighter quench, polish chambers, colder plug, and polish piston tops, no sharp edges. Low 160 degree stat, shin groove, ect. or dropping compression or running the correct fuel.

JMHO
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Re: Total timing with 10.5:1 Compression

Post  FalconEh on June 19th 2015, 11:25 pm

IDT-572 wrote:A factory 429 is going to be hard to keep from pinging on 92 or 93 pump gas.

If a performance cam was added the running compression now could be higher too, and that is what it sounds like with it pinging worse as rpm increases.

Lowering timing wont help, it will make more chamber heat,

Retard the cam timing, (not the thing to do in my book) . Fattening the fuel ratio is just cooling the chamber, and killing power.

The answer is seeing that the chamber is made more low octane fuel friendly tighter quench, polish chambers, colder plug, and polish piston tops, no sharp edges. Low 160 degree stat,  shin groove, ect.  or dropping compression or running the correct fuel.

JMHO

^^^^^^^^ This, and you can cheat on the fuel I believe it was mentioned earlier, but if you add a gallon of C-16 to 3-4 gallons of 92 you can get the octane you need, right now I run 12.69:1 with the juice with a 50/50 mix and it works.
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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 21st 2015, 3:28 pm

I changed the seats and needles to the larger size. There were filter screens under the original seats that had some crap in them. I removed the filters when I put in the larger seats. Something strange happened. My fuel pressure dropped one PSI and the engine was extremely rich and would barely run. With the improved flow this all makes sense. I was jetted far past the calibration chart. With flow resolved I think it makes sense that the engine is rich like it is suppose to be. I changed to the #23 calibration and will test later today.

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