RacerHog

Ya....Ok... Like your going to take it to the track with a bunch of spark plugs and do that test? Rite?????

All this looks good on paper I suppose....
But your plug reading is going to be you best bet......
Light tan on the electrode.... Heat ring about half way around the ground stem.

All I can suggest is to get a Strip kit chart for all the rods and jets to help you in your direction at this point.

Just my 2 cents

demetri

Some more updates ... No plug cut yet, due to practical reasons.


However, did another stage of enrichment. Still saw some improvement. I still think the car is lean though. No black smoke at night. Also, there is an exhaust leak on the right side, which brings exhaust fumes in the car at WOT. It turns out that from the smell, I can tell it is not rich yet. Not the best way to measure AF ratio, but that's the info we have right now.


I think the car is progressively getting better and better. I think I should not do any more enrichment on the primaries though, I think now its time to go after the secondaries jets. The speed shop told me that I have a .107 jet in there, so I need to go bigger there. Wondering how much bigger.


I also have a feeling that the modifications we did on this engine (.477 lift cam, bigger valves, mild porting) will really help torque above 3000 or 3500 rpm and will not have much effect (positive or negative) in the 2000-3000 range. Yes. no ? Which is of course not surprising, and this is what I really wanted anyway.

demetri

The speed shop has a .110 jet to replace the .107. Is this worth the trouble, or should I go bigger?

demetri

Well, I did the swap. The mixture is now probably just above stoichiometric, as I now start smelling unburnt hydrocarbons from my exhaust leak.


Still no black smoke. So, there may be more benefit.


The performance constantly improves. This engine will have the most performance above 3500 rpm, which is what I expected and wanted.


Next: Advance timing a bit more, and go richer yet. .113 is the next available stage. It looks like an increase in the secondaries makes larger difference than the metering rods, but this is pure intuition.


It is fun tuning the carburetor. I think the test drives is the most fun!

demetri

Hey guys , some more updates.


After my recent adventure with the distributor, and after lost my prior timing adjustments, but prior to replacing the distributor, I decided to do a quick test and see how the enrichments have affected overall performance. This time in daylight, which allowed me to observe the vacuum gage.


At WOT and just below 4000 rpm, the vacuum had reached about 2 inches. That is a bit too restrictive. Each 1inch costs me about 3.5 % in torque, and it may have reached 3 inches at 5000 rpm. According to some Chrysler literature, the 750 cfm AVS (I have the 750 AFB from Ederblock) should generate 1.2 inches at 540 cfm. At 4000 rpm and 90 % vol. efficiency I was not sucking more than 450 cfm (of course, at 4000 I may have had 95% vol. efficiency, but still not anywhere near 540). I will check again the linkage and see if I can open it more, but my guess is I need a bigger carburetor. Which sucks, after all the effort in tuning it (but I learnt a few things).


Any suggestions on what carb to get, something that will not be too lean and require too much adjustments, and something that is reliable for every day and/or long distance driving (no power valve replacement). Anybody has a used carb that could work well for me wiling to sell?

demetri

False alarm!


As I was adjusting the kick down linkage a month or two back, the horizontal part of the linkage got too long, and there was interference with the valve cover, preventing the carb from opening up. I only had 2/3 opening. I shortened that, and extended the vertical part of the linkage. I am still having problem to get the transmission to shift properly at higher throttle openings, but the manual shift works well. Of course, sound changed, and in the 3K range I got the chance to test around the block, torque increased too. I expect the high rpm range will be substantially improved. It is amazing that the car almost pegged the speedometer so quickly with secondaries barely cracking open....


Also, this bad throttle opening prevented me from getting the timing right. I was advancing until I would hear knock at WOT, but did not really have WOT ... so I kept advancing.


I will be able to fix all these now.

RacerHog

Hummmmmm....

demetri

Well, may be I did not explain my self too well


I first install the carb on the car, and adjusted the throttle linkage to ensure the carb opens fully.


Then, I was trying to adjust the kick down linkage. I kept on extending it, to make it shift later ... I had to add extra length on the linkage via an allthread, kept on extending it. Still the transmission kept on shifting too early. I extended more. Until, without realizing, the linkage interfered, and the throttle did not open wide open, without me knowing it. My helper kept on saying that the vacuum at WOT was zero, so I did not suspect that. On top of that, I was advancing the timing expecting to hear knock at WOT, but did not realize that I never had WOT, so I went past optimum.


Now, that I saw what happened. I shortened the horizontal section of the kick down, and extended the vertical. That eliminated the interference, and now the throttle linkage works properly again ...


I know, mess. But I finally figured it out.


I may soon be able to do a real proper acceleration test since the enrichment with proper WOT and proper timing.

RacerHog

Agreed... The T.V. is only going to hold it till the governor over rides it to shift.
Only way to get past that is to Manuel Shift it....
I'm With you on that now....

Gorts 5th

With all that extra hp you should put a improvment kit in that trany PACT.com has some kits they also have some linkage parts you may find very usefull

moe7404

your post #60 ask about fuel flow. this program that my son made will tell you the flow change EVEN if you change both, jet and rod. other wise change ONLY one at a time. like my first post said a little is a LOT. BUT it can not tell WHAT to set it to, you have to figure that for your self. the edelbrack rods have to much step from the cruse to power step. DO change rod to be more like the Chrysler AFBs. this is for cams close the chrysler O.E.M. cams. a full race cam is total different. and DO set the float level to 5/16. here is my sons program. *http://clarkehackworth.com/files/JetsAndRods.html

demetri

If I stick with this carb (it may prove a bit too restrictive, will see), I may contact PACT for linkage parts. That will also help with stronger shifts. But I have not seen much evidence of slippage during shifts yet. Part of the reason is, since I control the shifts, I back off the gas a bit during shifts.


Carburetor: I really like this AFB 750. Simple, and now I am learning how to tune it. Also, like all carters, should prove reliable. But I have to see how many inches of vacuum it will give at WOT over 4500 rpm (have not been able to get the reading yet, I am busy watching traffic). If I see anything above 1.5 or 2.0 ", I will consider replacing it. This carburetor is really causing the problems with the linkage, because the primaries open too fast for a given throttle movement. If I replace it, it will probably be a Q-jet 800 cfm. These are not very reliable, and have very small bowl volume, but they are less restrictive. I have one on my other 440 (closer to stock), and the throttle linkage works fine.


Moe, I could not figure out how that program worked. Not sure what all these entries asked for. But it looks like via trial and error I am able to get the mixture richer and richer, and its not too rich so far.


Thanks

moe7404

that program is not displayed very good. my son did it. he is not a carb guy. ill go look at it and try to explane it. i do know it works right i double checked it. may not get back till 9-10 PM please note the program will not tell what to run. YOU will still have to say if the carb is lean or rich. just did more testing but have to leave, will come back and give more detail.

moe7404

This is a verson of a program I did for the Commodore computer. That my son did for PCs.
1. this program can not tell what jets to run. It can only tell you % diff of the jet you are looking at to change. When doing jets only enter .000 for all rod enterys.
2. 2. the label jet#1 , or jet#2, means the jet and the two steps on the rod.
3. The top box is for the jet number only like this .065
4. the second box is for the economy step, the largest dia of the rod. .085
5. the power step smallest dia goes in the bottom box. .075
6. test#1: jet#1 .100-----jet#2, .110 = 17.355% arrow will point to the left meaning more fuel.
7. Test#2: jet#1 .100 jet, power step .065 econo step .075 jet#2 .100 jet, power step .067 econo step .077 = 6.948% leaner arrow points to the right.
8.
9. All this means you CAN calculate both jet AND rod changes
10. for Carter AFBs and AVSs.
11. http://clarkehackworth.com/files/JetsAndRods.html

demetri

It has been a while. Here is a quick update.


I put the largest jets on the secondaries (.119) and smallest metering rod (.070-.038) for the 750 AFB. I still did not get sufficiently rich mixture. I am definitely not over- rich, no smoke on the back.


I got an 800 cfm AFB in the hope that with the same jets and metering rods, it would give me the mixture. I doubt there was much difference.


As a reminder, I have not done a plug cut yet due to the location where I live, but I have an exhaust leak on the right exhaust pipe/manifold connection, and I would smell hydrocarbons if I was rich. I do not smell much.


When I rev it through the gears, it feels like it has reasonable torque between 4000 and 5000, but when you shift, the torque drops. I have clocked for example 4000-5000 on 2nd (which should be a true 80-100) in about 6 seconds (remember, this is a very heavy car). I think this is reasonable, but it could use some improvement.


Other than shifting to a gas guzzling Holley, I am not sure what else to try.


Also, question on the timing. I think my harmonic balancer has slipped, so I cannot know for sure what the timing is. I try to advance until I hear knock (about 10.2-10.3 compression ratio) with 93, but I think that process gets me to exceed optimum. The car is hard to start (I still have the stock advance curve with the single point distributor).


Other than that, it is certainly fun driving it around and try to tune it. The only bad news on the car is a leak on the rear main, which may be very expensive to fix.

moe7404

warning: most chrysler AFBs and AVS used a 3 tall step rod with a tall main jet and a dome cover. but they did make some with a short rod 2 step with a short jet and a flat cover. do NOT mix these parts. and dont force the jet to get it out. here is the trick. get your torch out heat the jet till the flame color changes then dump water on it. and no you wont melt the aluminium housing. and they dont need to be real tight just snug will work.

demetri

Thanks Moe. I am using Ederblock hardware. Whatever was on the carb was Ederblock, and whatever I bought from the speed shop was also Ederblock, so I hope they are compatible.


I filed some the tip of the metering rod hoping for some more fuel flow there, but I am not holding my breath!


D

demetri

Here is another observation I had when testing the car this morning. I was on 2nd gear, revving it up. When I was on the upper rev range, 4500 heading to 5000, I noticed the temperature gage on my mechanical gage going up to 220-230. As soon as I let off the gas and shifted, the temperature went down to about 200 very rapidly, within 2 seconds. The engine was not hot, just the coolant coming out of the thermostat housing was very hot. I do not recall if this has happened before, but seems to be a high rev range issue. Some hot rodder I was talking to today said may be a stuck thermostat. Any other ideas? Thanks.

demetri

Update. The warm temperatures were apparently due to a slightly loose water pump belt.


Also, I retarded the timing by about 10 degrees and performance improved. I am totally susprised that the high compression engine did not knock when over advanced. Apparently the big cam is suppressing knock. My other 440 will knock when you over advance.


Anyway, car is running better, it is plenty fast, but still I am fairly confident that it is running a bit on the lean side, and there is more power opportunity. I just do not know how to get richer mixture out of this 800 cfm AFB. I have maxed out the metering rods and secondary jets. I can install a larger jet on the primaries, but that will enrich the part load more than the full load. I can keep on filing the thin part of the metering rod, and may be I can drill out the secondary .119 jets.

demetri

Here is another update.


Since the 800 cfm AFB does not offer any smaller metering rods to go richer, I took the primary metering rods and filed the small end substantially. Unfortuately there is no precision here, but I took out about 30-40% the surface area. I left the maxed out secondary jets alone.


I did not test the car on 2nd or 3rd gear, but there is defintely an improvement up to 4500 rpm that I did try, but its mainly the lower rpm where the improvement is. I even heard it spark knocking in the 2500-3000 rpm range. So, apparently it was so lean that the cylinder pressures and temperatures were too low.


Slowly, I am getting there. Lesson: Ederblock AFB's are not good for souped up 440's. They do not provide enough fuel. I think I may be able to get it to work by pushing the envelope past the design range, but I wish I had started with another type of carburetor.

RacerHog

this would help with the lean spot.... 2-600 CFM Carbs....

http://www.edelbrock.com/automotive/...-quad-bb.shtml

Got to hand it to you.... You are a go getter....

demetri

Thanks racerhog ... Right now, I have an Ederblock CH4B intake, which is the predecessor to the Performer. Supposedly, these manifolds were better than the later ones in high rpm's (presumably over 4000). The option you are suggesting is going to cost probably about $500+. If I go to such high expense, 2xAFB plus manifold, I would rather find one of the ram-tuned dual AFB manifolds. The intake tuning should provide an additional 10-15% increase in torque (which would bring this engine when fully tuned to ... 450-480 hp ?).


Right now, when I am ready to replace the carburetor only, I will probably try a Q-jet 800 cfm. Not very good carburetors from the reliability point of view ... but ... these should provide me with all the fuel mixture I need, or so I have been told.


Funny, one or two tuning steps earlier, I was out late at night testing the car on all 3 gears when a Toyota Tundra V8 tried to race me (probably the 310 hp 4.6 version). If he had the 4x4 version it would be about the same weight as my car, if he had the 2x4, he would be about 400-600 # lighter. But he lost anyway. These trucks have a zippy 6 sp, and I was on the mid range of 2nd gear, and I was inching ahead. His engine ran out of revs and shifted to the next gear, while I was still in 2nd. So, he knew he had no change and gave up. There would be no contest at higher speeds. ... and I was not even racing, I was just testing!

RacerHog

The Rochester Quadrajet is a good carburetor.. I have used a few if those. I picked them off some of the early Cadillac's with 500CI Motors. Once you rework them they seem to work good for performance for the most part.
Keep us posted on how things go...

demetri

Here is an update. This relates also to my earlier thread on "electric fuel pump troubles" ...


Rear glass replaced yesterday, so back to tuning.


As you may or may not recall, I had been trying to set the timing by ear, since I do not trust the harmonic balacer location. As I have been doing that the past few months, I never heard any spark knock. In the same time, I kept on enrichening my 800 CFM AFB, until I took it to its limit and beyond, and I am still a bit on the lean side at WOT. Then, all of a sudden about 30 miles ago, the engine started having severe spark knock at low rpm and anything less than 8 inches of vacuum. So, I kept on retarding and retarding, plus some octane additive. The knocking issue may be improving, while the engine does not seem to have lost any torque at the high rpm range, say 3500-4500 (no spark knock up there). That makes me think that it was over advanced, so I gradually retard and test drive. Until my rear glass was shattered 2 weeks ago, preventing me from driving it. Until yesterday.


So, back to duning. I retarded the timing more yet. Again, once it gets warm it starts knocking. Also, the idle has considerably deteriorated. The response off idle is very crappy. Also, it appears that crud in the carburetor have returned, but this is not the major issue (I am still hoping to weather this out and not have to clean the tank, no time for that right now). At high rpm the engine seems to be doing fine, as said above. I reved it on 2nd gear up to 4500 rpm, and from 3500 up or so there was no knock and the acceleration is not affected by the retardation (I am hoping it has improved, but hard to judge on 2nd gear). I think that the main issue here is that the stock distributor has too much centrifugal advance, so it is over retarded at idle and advances too rapidly in the 1200-2000 knock range. Why this was not happening before is a mystery, but this behavior may now be normal. Anyway, do you guys agree with this possible diagnosis? Again, the cam I have is Comp Cams 268-280, .477 .488, 1600-5800. Reasonably mild cam. I have a single point distributor with the stock 440 advance curve.


If this is correct, then would I need to replace these springs with stiffer ones?


Next short term step is more retarding, and drive the car more to clear away the fuel system, anticipating even more deterioration at idle.

Coronet 500

I would not come to any conclusion or take any action until I did a piston stop TDC then use a timing light to confirm initial and total timing without vacuum advance. Guessing at this will waste time and possibly damage the engine.

Iowan

Also I would replace the harmonic balancer if the timming marks are off.

demetri

Well, at this point, there is no issue of damaging the engine. The spark knock has started to go away as I continue retarding the timing. The small step the day before yesterday made the part load knock almost go away completely. I did one more small step in retarding the timing yesterday (not driven since), and I am expecting that the part load knock to be completely gone. Then, let's see what happens at higher loads.


The idle is continuing to deteriorate. I only have 10 or 11 inches of vacuum on a 900 rpm idle. It used to be 15 or 17 with the advanced timing. As soon as the rpm goes to 1500 or so, the throttle response seems good. I suspect that the further retardation wll have little effect at the high rpm power, similar to the previous steps, but will see.


Replacing the harmonic balancer is not a project I would be ready to jump on right now. I should have done that when the heads and cam were off, but did not think that far. I should have also asked the mechanic to check where the TDC was when the heads were off, but again, I did not think that far. I did not expect setting the timing to be such a big deal ...

Coronet 500

It is not a big deal with TDC mark and timing light, 15 minutes and your done and driving.

Chasing this knock with by the ear timing could be hiding a more serious problem and all the trial and error could be damaging, seen it before many times.

Iowan

As far as the nock, you didn't louse track of a washer when you put the carb on did you? I would pull the plugs and use a boar scope on your motor.
I've heard of it happening, and it does make a nock after it gets past the valve.

demetri

I had also suspected more serious issues causing the knock, since it started all of a sudden. But it is confirmed to be spark knock. It is not present with the engine cold, and it gets progressively worse as the engine warms up. Also, it appears only under load.


It is now, with retarded timing, all but disappeared.


Anyway, thanks for your advice. I will stick with this approach for now, and hope for the best. harmonic balancers are just not in the menu right now.