advance curve tuning

[Knebel]

tires are..... 15" as i remember correctly, 225 front and 245 rear bfgoodrich radial TA. I do not know the rear gears but like I said, going 55 is around 2000rpm, yeah, by no means would I say "performance", it feels like the converter is very tight, I dont think it is a higher stall.

I need to get a compression tester anyways, its the only thing missing in the toolbox. So, the PSI give direct info about the overlap? I dont think the rings are worn either, barely and blow out of the egr hose and I dont notice any oil consumption. I just cant imagine that they dropped a ultra hot cam in an otherwise stock motor, but ya never know...

with the holley, I had to idle it at 12.6:1 to be stable, with the efi, 13.5 is fine but 14:1 gets rough. maybe I can make a video showing how it runs and sounds, i would imagine a cam that hot would be lopey but I cant tell.

 

[fury fan]

I need to get a compression tester anyways, its the only thing missing in the toolbox. So, the PSI give direct info about the overlap? I dont think the rings are worn either, barely and blow out of the egr hose and I dont notice any oil consumption. I just cant imagine that they dropped a ultra hot cam in an otherwise stock motor, but ya never know...

The PSI won't directly tell you about overlap, but can give some clues about valve timing if you know how well the cyl seals and what your CR is. But I'm thinking we don't know enough about your engine to determine that fully.

As you probably know, as a cam gets bigger, overlap gets bigger, there is more time when the valves are both open so that exhaust leaving the cyl can help suck in the intake charge (which helps at higher rpm). that drops cyl pressure, so it usually helps to raise CR to compensate. (I'm simplifying that a bit)

In my experience, an 8:1 setup with good ring/valve sealing might build say 140-150 psi (roughly, for discussion purposes). But let's say you are at 9:1, which should give higher PSI, but if your cam is retarded (and I'm presuming retarded as that drops bottom-end torque, which you need for MPG) maybe you see 137-142 on all 8. For a mild engine we'd be excited as all cyls are close to each other (a sign of health), but in actuality you're missing some cyl pressure that a 9:1 ought to have.

But we can make some conclusions depending on the #s you get:
1. if you come back with numbers in the 120-130 range, there's a problem, either with cam timing, or it's a low CR engine with proper cam timing and the cam size just dropped the CR a bit
2. if you get 170+, then I'd say those are good numbers for an engine with a 'hotter' cam and your EFI/ign tuning might be the correct path
If something in between, well, more evaluation is needed.

If you can afford a leakdown tester, that would be good too, that is the truest way to determine cyl seal. I've heard you can remove rocker arms so that both valves close, pressurize the cyl from an air compressor, then listen at carb and tailpipe for leakage, but I don't know how much leakage would be acceptable, I've never done that. A leakdown tester puts numbers to it and lets you watch a gage.

 

[fury fan]

Did you get your car straightened out?
I have something that may interest you, it's an MSD-8981 adjustable timing module, it takes the place of the mech advance setup in the dizzy, and is electronically adjustable.

https://www.summitracing.com/parts/msd-8981
Here's a thread on how to use it:
MSD 8981 programmer - Hot Rod Forum : Hotrodders Bulletin Board

Mine is new in the box, bought it some years ago and never used it as I thought it was not compatible with vacuum advance, but the hotrodders thread says that's incorrect. There's also a link to the instructions in that thread. Send me a PM if interested and we'll work out a price.

 

[Knebel]

Thats a pretty interesting device and thank you for the offer. My EFI has the capability to fully control timing tho, It just needs to have the Rotor phased 10° and then locked which I have not yet tried to figure out with the stock distributor and my Pertronix (ideally I need a MSD Distributor for this but just put new plugwires and such in and they are not HEI compatible).
Thats why I am messing with the springs and the limiter plate for now. I also have changed the springs in it to some lighter ones and was in contact with Don from FBOignition, with the plate, I now know exactly what total timing I have and what initial I need to set it at. I did 22° Initial and have a total of 36° in by what could have been 3000rpm, maybe less, the timing mark is so hard to see and revving the engine, checking timing and keeping an eye on the RPM is hard with 1 person and only 2 Hands...lol. Don said thats a good starting point. The Fury already responds waaaaay better to this now and especially flooring the throttle releases a bark and puts you down in the seat like I have never expierienced before since I had the car.
The vacuum has not changed much, I Idle in drive at jumpy between 8 and 9"Hg now and when I open the throttle fast or going up and incline with more opening it goes down, half way throttle going up an incline til flooring I see quickly approaching 1.5"Hg. Cruising with it barely cracked it between 17 and 20"Hg. If that says anything. Cant say anything about the mileage, have the cover on because rainy season is here and I moved on to do something with my crazy rusty cop wheels.

Oh and I adjusted the AFR table a bit more in the EFI settings to more economy friendly numbers.

 

[fury fan]

Sounds good, progress is a great thing! Keep us informed!

 

[70bigblockdodge]

I finally got off my *** and took my own advice and fixed my timing on my Challenger ended up at 25° btdc initial and it would take all the way to 28 before it started acting up but I did not want to leave it out that far for fear of kickback on hottest days. I welded the slots to get .110 movement in the slot which equates to 11° of mech advance the Chrysler engineers thought of it all .010= 1° so now I have 25 initial, 36 total and 57° with vacuum advance total. Car starts right up idles better and cruises nice hopefully when I get the new power valve in there I hope the lean spot will go away.

 

[Knebel]

Are you running ported or manifold vacuum? Don from FBOignition said that manifold vacuum is the way to go....

 

[70bigblockdodge]

Mine is ported, it did not pull enough vacuum to do anything but float my idle up in neutral.

 

[johnnymopar]

i have acuired the limiter plate and springs from 4secondsflat for the distributer and will be doing some curve tuning soon. Im curious (since this is all wonky in my dizzy), at what travel in the slots should the weights be caught by the heavy spring (or the loop) to slow down the curve?

should the pin in the weight travel half way or more through the advance plate before it hits the loop of the heavy spring?

 

[johnnymopar]

i have acuired the limiter plate and springs from 4secondsflat for the distributer and will be doing some curve tuning soon. Im curious (since this is all wonky in my dizzy), at what travel in the slots should the weights be caught by the heavy spring (or the loop) to slow down the curve?

should the pin in the weight travel half way or more through the advance plate before it hits the loop of the heavy spring?

I have a 69 383 that had 69,000 on it in 2000 when I bought it and put the Mopar Performance distributer on it with new plugs and Mopar wires. Set the timing with a timing tape and adjusted the dwell like 3 degrees. I put another 69,000 on it without any miss just checking the state of every other plug per year. This spring I changed the plugs and they looked new, I use the Orange box and the blue 69 Electronic voltage regulator thingy. I set my carb with a vacumn gauge at the rpm at idle that I feel is right for this motor about 800. I want to use the REVINATOR but I don,t think the one person I let drive my car that floated the valvetrain will ever be sitting in it ever again. These motors are so totally reliable never one problem ever.