Total timing with 10.5:1 Compression

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Re: Total timing with 10.5:1 Compression

Post  supervel45 on May 18th 2015, 4:11 pm

Did you look at page 15 of the Edelbrock PDF I posted above. That page is for your #1411 Carb and has alot of info. The metering rods the tech guy recomended are richer and #23 on the chart. I would try to get the next larger set of secondary jets also with the metering rods if you are ordering and can get them all together.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on May 18th 2015, 4:24 pm

I agree, the manual is very helpful. I may change secondary jets but my personal preference is to make a single change (richer metering rods) and test the results before jets.

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Re: Total timing with 10.5:1 Compression

Post  supervel45 on May 18th 2015, 4:29 pm

I agree 100% with one change at a time and test. I thought you may be ordering the parts and could save time and shipping if the cost of the jets are minor. I have heard that Edelbrock sends out free metering rods sometimes, hopefully that is your case.

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Re: Total timing with 10.5:1 Compression

Post  rmcomprandy on May 18th 2015, 5:06 pm

jgkurz wrote:Just spoke to Edelbrock regarding my 750cfm pn 1411 carb. The guy in tech support was very helpful and suggested I first change the metering rods from .075 x .047 to a small diameter .070 x .042. I thought we should change secondary jets given the car runs so well other than WOT but he was confident this was the first step. This was because the factory calibration was for economy not performance. Stay tuned... HA!

The biggest issue with that carburetor is that the IDLE system is set-up for latter model LOW compression engines.

The Idle tubes need to be increased in diameter about .003" more for a higher compression application in order to drive half way decent.
The metering rod change will help but, wont get you where you need to be.  While you have the top off to remove the primary venturi clusters in order to get access to the idle tubes, simply increase the primary jet size to .113", (from .110"),  and leave the metering rods alone.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on May 22nd 2015, 1:36 am

I made some progress tonight. I changed the thermostat to a 160deg, added Water Wetter, and changed the metering rods. Now the engine doesn't ping when on a flat road. When I hammer it going up hill it still rattles noticeably. I think the next step is to reduce total to 28.

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Re: Total timing with 10.5:1 Compression

Post  supervel45 on May 22nd 2015, 6:14 am

http://www.msdignition.com/Products/RPM/Timing_Controls/Timing_Controls/8680_-_Adjustable_Timing_Control.aspx You could just turn a knob. I am glad you made progress. Trying to go up hill full throttle may be asking alot. I would reduce the timing to 30* and see how it does.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on May 31st 2015, 8:44 pm

supervel45 wrote:http://www.msdignition.com/Products/RPM/Timing_Controls/TiHehehming_Controls/8680_-_Adjustable_Timing_Control.aspx    You could just turn a knob. I am glad you made progress. Trying to go up hill full throttle may be asking alot. I would reduce the timing to 30* and see how it does.

I finally got time to work on this again today. My MSD is programmable so I can easily set the timing curve with my laptop. I took total timing down to 28 deg and it still pings. It is slightly better than 32deg but not much. The fuel is fresh 92 octane bought yesterday. The only other option I have without putting in a new camshaft is to re-jet. The curious thing is it only pings at WOT. The car runs strong in all other situations including cruise on the freeway where I give it 40deg at light throttle.

I'm starting to think that when the secondaries open that there just isn't enough fuel. rmcomprandy said I need to increase the idle tubes and primary jets. I'm open to anything but the idle circuit and low-mid range seem to work great. Why wouldn't I want to simply increase secondary jets?

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Re: Total timing with 10.5:1 Compression

Post  gmsmkr on May 31st 2015, 8:56 pm

I know you say it pings are you sure it's a ping or sputter?

You say it drives fine and it "ping's" at WOT does it "ping" while going up hill under a load at light throttle?
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Re: Total timing with 10.5:1 Compression

Post  jgkurz on May 31st 2015, 9:32 pm

gmsmkr wrote:I know you say it pings are you sure it's a ping or sputter?

You say it drives fine and it "ping's" at WOT does it "ping" while going up hill under a load at light throttle?

It never pings/rattles under light load. I'm certain its not sputtering or hesitation. In all fairness, I never try to drive through the pinging so if there is a lean sputtering it would be hard to know.

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Re: Total timing with 10.5:1 Compression

Post  supervel45 on May 31st 2015, 10:43 pm

supervel45 wrote:Did you look at page 15 of the Edelbrock PDF I posted above. That page is for your #1411 Carb and has alot of info. The metering rods the tech guy recomended are  richer and #23 on the chart. I would try to get the next larger set of secondary jets also with the metering rods if you are ordering and can get them all together.
Thats why I said to get the jets also, just in case.

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Re: Total timing with 10.5:1 Compression

Post  supervel45 on May 31st 2015, 10:50 pm

A fuel pressure guage you could watch as you are driving would be nice also, to make sure the fuel pressure is not dropping off, when the secondaries open up.

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Re: Total timing with 10.5:1 Compression

Post  rmcomprandy on June 1st 2015, 10:24 am

jgkurz wrote:

I'm guessing 10.5:1 compression with iron heads is the issue. Any suggestions?  

Thank you!

Put 100+ octane gasoline in it and find out if the detonation goes away ...

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Re: Total timing with 10.5:1 Compression

Post  the Coug on June 1st 2015, 1:25 pm

BOSS 429 wrote:
jgkurz wrote:I have a 70 429ci with original iron heads and original compression which I believe is 10.5:1. It also has a slightly larger cam, 750cfm carb, Edelbrock intake, and a programmable MSD. I run fresh 92 octane unleaded but can't keep the engine from pinging when accelerating. I can easily customize the timing curve but can't seem to find one that works well. I've tried as low as 32deg all in at 4000rpm and the engine still noticeably pings. I will probably try 28deg next but that is awfully low for any real power. The engine runs well until I get hard into the throttle then ping ping ping.

I'm guessing 10.5:1 compression with iron heads is the issue. Any suggestions?  

Thank you!


compression is over 11 to one on all 70 429s, I bet  WRONG FUEL is your problem, it takes a lot of work to get these to run good on 92 oct.and the larger cam may be making a little more comp also


Bingo we have a winner I am like Rich in 70s we had way better gas which in turns more compression, in the 70s we could drive up to any pump and get premium fuel, not like this crap they are trying to stick up our butts now.... and I would take that Edelecrap carb and throw it in the junk pile where it belongs, when Carter had that company it was good carbs but not any more....
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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 1st 2015, 1:49 pm

I have no doubt higher octane fuel would help but I also think my Edelbrock 1411 is causing a lean condition. I'll put a different engine in before I pay for 100 octane on the street. If I jet up and it still pings I'll try the race gas. If I get really motivated I'll weld in an O2 bung in the collector and datalog the AFR's with an Innovate LM-2.

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Re: Total timing with 10.5:1 Compression

Post  BigRigTech on June 2nd 2015, 1:58 pm

As Randy stated I would try some 100 octane fuel too. My buddy runs a 10.5:1 347 on the street and the dyno operator recommended he add about 20% AV gas to bump the octane and control detonation. He mixes it 20-30% with no issues so far and it works good. Wink
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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 5th 2015, 1:09 pm

To test fuel pressure I bought a fuel rail with the fuel pressure port built in. I added a small gauge that wasn't fluid filled. I hear the fluid filled are only accurate when they are cold. After starting the engine the gauge fluctuated wildly from 0-7 psi. It seemed to average around 5.5 psi but never really settled down even when the engine is rev'd. I'm using a stock mechanical fuel pump that should be internally regulated. After some research, the consensus is that the check ball in the factory pump is probably causing the fluctuation. I will put in a street Edelbrock pump and see if that help. In the end it may not solve the pinging but it sounds like the pump may have issues anyway so I have no problem replacing it. I'll post the results.

PS: I agree that the final resolution will probably be higher octane fuel but I want to run through all the possibilities first. Jetting, fuel filter, and fuel pressure are the last things to try before I full concede that octane is the issue. If I was a betting man I would put my money on too much compression for 92 octane.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 6th 2015, 10:44 pm

New fuel pump definitley smoothed out the fuel pressure. I jetted up the secondaries but the pinging continues. Time to put in some 100 octane.

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Re: Total timing with 10.5:1 Compression

Post  supervel45 on June 6th 2015, 11:30 pm

Give the 100 octane a try. If you still get preignition at 28*degrees total, the balancer may have spun, causing your initial to be off, as mentioned before.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 9th 2015, 9:38 am

100 octane did the trick. I added 2.5 gallons of race gas to 16.5 gallons. I set total to 34 deg all in at 2800. The engine ran great with very little pinging. I'm sure the pinging would be completely gone with pure 100 in the tank. I will still check TDC but in the end I think the engine just has too much compression for pump gas.

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Re: Total timing with 10.5:1 Compression

Post  DanE on June 9th 2015, 1:54 pm

As has been said before, your carb is probably the problem.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 9th 2015, 2:50 pm

DanE wrote:As has been said before, your carb is probably the problem.

Respectfully, I really want to believe this but I have changed jets, metering rods, fuel pressure and didn't see any real benefit. Trust me, I would MUCH rather deal with a carb issue than a new engine build. Given that 100 octane fuel was the only change that made a significant difference, I am thinking my last option is to verify the timing mark. If it's correct then I need to make some major changes on the engine to resolve. Please elaborate on what more I should do on the carb. The engine is a slightly warmed over 429. I can't imagine the 750 Edelbrock is not enough and that I am running lean. My plugs are a nice brown color but the car spends most of its life under 3500RPM where it runs well. Maybe I'll borrow a Holley from a friend and see if it does the same thing.


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Re: Total timing with 10.5:1 Compression

Post  kim on June 9th 2015, 3:31 pm

Reading a plug on a street driven engine allows you to confirm there isnt a catostrophic failure somewhere.  Other than that the plug cant tell you much.  The variables of timing and fuel curve from idle through part throttle operations to WOT contaminates all the plug surfaces.  Through a known good carb prefurably off something with similar  displacement on it and give it a test.

The whats wrong with the chromed carter carb starts with anything you "tune" by bending linkage isnt sufficiently precise


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Re: Total timing with 10.5:1 Compression

Post  DanE on June 9th 2015, 8:12 pm

On page 3, reread what the "Coug" had to say.

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Re: Total timing with 10.5:1 Compression

Post  jgkurz on June 9th 2015, 8:29 pm

DanE wrote:On page 3, reread what the "Coug" had to say.

Just re-read his post. The bulk of his comment was about bad fuel which I proved was accurate. He's obviously not a fan of Edelbrock carbs but he didn't really go into why. I have access to a Holley 780cfm vacuum sec that I may try. I'm highly skeptical but the swap should only take an hour or two so not too much time. I'll check the jets and power valve before I put it on to make sure it's got a decent chance of working well. Anyone with 3036 posts like "The Coug" is probably worth listening to.

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Re: Total timing with 10.5:1 Compression

Post  supervel45 on June 9th 2015, 9:22 pm

The Edelbrock 1407 and 1411's don't have a very good rep.. If you try a good Holley 780, and the pinging stops you will know it was a carb problem. I would have kept pulling timing with the pump gas to see if the preignition would stop. Another thing you might try is to decarbonize the pistons with the water method, in case they have carbon buildup causing a hot spot. It's a long shot, but worth a try.

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