With the OD kicking in early I notice the rattling more. I thought maybe it was too much timing or too much fuel. I tried some 93 octane and the rattling is none existent. I'm thinking its more timing related now, yes? If it were fuel related it would have gotten worse.

I got to thinking that since I'm running a #60 main that I could somehow deactivate the power valve to see if that would help mileage. Removing or compressing the spring would do it. I'd hate to get too lean under a hard load though.

I think I've over geared the engine with the 3.55 rearend and 31inch tires. That may be why I'm dipping so low in the vacuum so much.
________
Chrysler SOHC V6 engine

Do you know what the vacuum can is stamped? 8.5R 11R?
Total timing is the problem....you want to have 30 degrees total, that is initial plus mechanical. Disconnect the vacuum pod and verify with a timing light.

3 options to consider: You may just need to purchase a different vacuum advance such as a 6.5 which would limit total. Or reduce initial to 5 degrees or use a heavier springs to limit mechanical advance.

What rpm are your turning in OD when it pings? This is important to know so you can tune for more power at that rpm. Let us know....

It sounds like your very close on the tuning, as little as a 5 degree reduction in total timing may stop the detonation so you can run mid grade or regular.

Hope that helps....

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

3.55's in overdrive isn't a good truck drive ratio(2.59 final ratio)...the low power to weight ratio needs a kinder gear to make use of the torque....3.91 would be better(2.85 final ratio)...4.11's (2.99:1 final ratio)would be much kinder... I'm figuring why the vacc. reading is so high is the load the slant has to haul is keeping the throttle plates open much farther than they should be for reasonable cruising and mileage...Some of this might also get aleviated by running a 2 barrel super six setup since the plates don't have to be open as much to get the same CFM as the 1 barrel...

-D.Idiot

I agree my old trucks with that tall of tire did fine with 4.11 gears. A stock slant doesn't really have allot of power until you hit 2500 rpm. From there on up it is great. Below that the vacuum gauge reads between 12 and 15".
With a E254 cam and 9.5 compression you can add another 3 to 5". Cruise is 16 to 18" at 2000 to 2500 rpm.

You can still reduce the ping with a different vacuum pod.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I'm pretty sure the vacuum can was a 8.5r. I couldn't find an 11. I've got a lot of initial, so as soon as it warms up I'll retard the static timing 5 degrees. I'm going to switch to a shorter tire to see if that improves the mileage as well. Most of the driving is 65/45 city/highway, so I could use the extra oomphf around town. I'd like to drop the back 2 inches and build a wedge topper and a front air dam to optimize my aero as much as I can too.
________
extreme q vaporizer

I've had to do some more tuning and I'm still way off. I had a fuel pump go bad on me and I'm positive I'll have to get some kind of regulator in line to get control of my fuel pressure. Would 3 Lbs be a good ballpark figure for fuel pressure on a Holley 1920?
I finally got a mechanic to dial in the timing to where I can start it up without excessive effort and I was able to do a compression test. The plugs were utterly fouled. I've never seen them that bad ofter only a year of driving on them. With just that info I've been able to back the accelerator pump setting back from max to the 1st hole without any hesistation problems and I put the stock main jet back in over the #60 I was using.
Compression was something like 150,160,160,165,162,160 from front to back. I think that's pretty healthy. Was my first time doing a comp test.
I even reassemble the front grill, headlight doors and attached the fenders to the header. It looks much better even if its still rough.
________
RC145

kafer65,

Another thing I have done on the Holley 1920 is to buy extra power valve gaskets and shim the mechanism up so it doesn't engage as quickly. That beats cutting the spring. Just use 3 or 4 gaskets and it makes a big difference. That will help keep it out of the super rich mode. However, changing your rear end ratio to a 3.73 or 4.11 is the best fix with those tall tires. It would be nice to get the engine to run in the pocket around 2500 rpms at cruise.

Something to consider next time you upgrade your coil or spark plugs.
Try a E-core coil to clean out those plugs. I recently installed a 3 ohm 60,000 volt HV coil part #60130 from Pertronix and by passed the ballast resistor which you can do with this coil. It will sure clean up your plugs and keep them that way.......It runs super clean! and fires up so quick it's amazing! I am still running the orange MOPAR ECU.
I run the the NGK UR4GP part number 2869 platinum plugs. They are awesome! I have a 78 peanut plug head on my 74 block. I also use this set up on my 1980 SL6.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG