First real drive

[dstryr]

on the 505 was Friday night. Only went a couple of miles and it ran terribly.  Saturday I couldn't get it started.  Pulled the Pertronix and dropped in the old points and it fired up so I could at least get it back up the driveway and into the garage... Pulled the NGK 4091 plugs, 6 were fouled pretty bad, the other 2 were dark but with just a little tan on the tip.  Oil smelled like fuel from trying to start it so drained and refilled it and put in NGK 4291s, heat range 6 instead of 7(6 is hotter).  Fired up and it went to 2500 rpm because I had the idle set so high with the bad plugs.   I set the idle down and went for a short drive.  Everything was working ok, so went a little farther, dropped in on an old friend, took him and his GF for a drive, and just got home.  60 miles and its running like a top!  No shortage of power.

[1970Moparmann]

Trial and error.  Glad it worked out.

[67440chrg]

Good deal. The picture is great.

[firefighter3931]

Congrats Frank, that had to be a great feeling ! 

The 6 series plug is definately a better choice ; i ran those in the old 446 and in the current 572 

A little tuning and you'll be there ! 


Ron

[10secBEE]

 Sweet, sounds like you had fun. Should be a screamer. 

[dstryr]

Needing some tuning advice now.  I put another 40 miles on(so about 100 miles now with new plugs) with very little idling or low RPMs and the new plugs are black but not fouled this time.  What's the next step in tuning to determine if the plugs are still too cold or if it is jetted too rich?  Jets are 66s in the center and 83 outboard.

Thanks!

[dstryr]

 

[firefighter3931]

Frank,

I went back and reviewed your dyno data and noticed that you guys jetted up to increase power. Did you have an air cleaner assembly on the 6-pack at the time ? If not, then you'll probably be too rich so my suggestion would be to jet the center carb back down 2 sizes and do a plug reading. 


Ron

[dstryr]

Here's an update that may help some others less experienced at tuning(like myself). 

I started with 66s center and 83s outboards on the dyno, no aircleaner as Ron correctly suggested above, and NGK R5671A-7 plugs.  Not sure where I got the idea to use them but it is a cold plug and they fouled pretty quickly.

I changed to NGK ZFR6F-11, aka 4291s and fouled the first set in about 60-80 miles so jetted down to 64s in the center carb and put in a new set of the same plugs.  These fouled in another 70 miles or so.

Today I rejetted down to 63s in the center carb and 81s in the outboards and also changed the power valve because it was idling very rich and I couldn't set the idle speed down.  The PV was a 6.5 so I went down to a 4.5.  This seemed to help overall but I didn't have another fresh set of plugs so wire-wheeled them, used contact cleaner, and a razor blade to clean up the electrodes then went for a 20 mile drive.  I still had a misfire occasionally, not sure if was due to the 'cleaned up' plugs but when I went WOT I could feel the outboards kick in which I can't say I could feel before.   60mph to 95mph seemed instant.   

Pulled 3 plugs tonight after the motor cooled and they are tan, maybe a little dark still, but looking MUCH better. 

Could the plugs I cleaned up be glazed and still causing a misfire?

[firefighter3931]

Sounds like you're headed in the right direction with jetting 

Could the plugs I cleaned up be glazed and still causing a misfire?

Definately....i'd replace those plugs. I've never had much luck cleaning off severely fouled plugs and having the engine run 100% 



Ron

[dstryr]

8 new plugs last week, 20 miles one night, 90 miles last night.  After the 20 mile drive some were tan but had a lot of soot down in the insulator well, others pretty dark again.   
#1 was very dark, 5 looked fairly good so I swapped them before last night's drive.  Here are what they look like after last night. 


Top row left to right, 7, 5, and #1.   #1 came from hole #5, started tan and is now dark.   5 started in 1 and is now pretty clean. 





Bottom pic, left to right  8, 7, 5, & 1  As far as the intake goes, stock dual plane 6bbl manifold.  1,4,6,& 7 are on one plane, 2, 3, 5, and 8 on the other. 
There are dark and light plugs on both planes. 

Should I keep working down jet sizes or maybe I'm having an issue somewhere else?   Cap and rotor are both fairly new, plug wires are firecores, and the distributor is a stock, un-rebuilt Prestolite dual point unit. 

[elacruze]

How's your valve adjustment? Tight valves can cause a reduction in cylinder pressure, showing as rich plugs. If the exhaust valve is tight, exhaust can be pulled back into the cylinder and act to contaminate and cool the mixture, just like an EGR valve. This theory is reaching, but if nothing else presents have a look.

[firefighter3931]

It's odd to have that much variation with color. Almost looks like a weak ignition on certain cylinders. I've allways ran an electronic distributor with MSD box and the plugs burn uniformly 

Wondering if there is an issue with the "un-rebuilt Prestolite dual point unit" 



Ron

[elacruze]

It's odd to have that much variation with color. Almost looks like a weak ignition on certain cylinders. I've allways ran an electronic distributor with MSD box and the plugs burn uniformly 

Wondering if there is an issue with the "un-rebuilt Prestolite dual point unit" 



Ron

Good catch, I missed that. #1 and #8 are both dark, but sequential in the firing order; If the points were the issue I'd expect to see the color alternating by firing order, corresponding to a each set of points. If one side of the carb was spilling gas, I'd expect that to show up corresponding to the manifold runners, which doesn't seem to be the case either...

What about a worn shaft bushing, changing point gap (maybe even failing to open or close)? That would account for 1-8 being dark, firing sequentially, and for 5-7 being light, firing sequentially...

I love playing telephone diagnosis.

[firefighter3931]

Good diagnosis/explanation, Eric 

I was hypothesizing that the dwell & gap might be an issue if the shaft had excessive play....



Ron

[dstryr]

Update

I knew if I didn't ask for some help I'd ruin this motor, so had a local racer have a look.  It was the promax metering block in the center carb dumping fuel.  Why?  Who Knows?...

Anyway, Jim cleaned up the carbs, put the stock metering block back in and its all good.  Runs like it should.  He thinks easy mid 11's by the seat of his pants.  I'm OK with that.


BTW, forget all the stuff about hotter plugs, etc.  Probably lucky I didn't burn a hole in a piston. 

[Chryco Psycho]

that is what it looked like to me , on a dual plane intake 1-7 are on one plane 3-5 on the other so it looks like one side of the carb was rich .
Did you have the pertronics power wire on the coil , this is what most people do & it is wrong , the power wire Has to connect to the 12v feed Blue wire , the coil will only get 8v after the ballast

[dstryr]

It was hooked up to 12v correctly, but when I was having trouble I pulled the Pertronix and put the points back in.  I will probably try the pertronix again at some point after I am confident that everything is for sure sorted out. 

I appreciate as always the help and insight here!

[Chryco Psycho]

I have had numerous problems with Pertronics so I don't use them anymore
if you go back to electronic use a better system

[BSB67]

on the 505 was Friday night. Only went a couple of miles and it ran terribly.  Saturday I couldn't get it started.  Pulled the Pertronix and dropped in the old points and it fired up so I could at least get it back up the driveway and into the garage... Pulled the NGK 4091 plugs, 6 were fouled pretty bad, the other 2 were dark but with just a little tan on the tip.  Oil smelled like fuel from trying to start it so drained and refilled it and put in NGK 4291s, heat range 6 instead of 7(6 is hotter).  Fired up and it went to 2500 rpm because I had the idle set so high with the bad plugs.   I set the idle down and went for a short drive.  Everything was working ok, so went a little farther, dropped in on an old friend, took him and his GF for a drive, and just got home.  60 miles and its running like a top!  No shortage of power.

What a cool pic.

Glad to hear that it is getting straightened out.  Going to the track?  Let us know where you end up on the jetting, plugs, ignition and the like.  

[firefighter3931]

Great news Frank....glad to hear it's running properly 

If you decide to go electronic ignition have a look at the FireCore distributors ; very adjustable/tunable and nice looking too 




Ron