spark plug and jets

[Al]

Hello
My Charger has a 383 engine with MSD ignition, TBI headers, Lunati 303 cam (268°) and a 670 Holley street avenger. It came with 65 jets front and 68 rear. Engine was running lean. By Trial and error I upped the jets to 74 front and 76 rear.

What do you think of my plugs? Too rich or is it ok?

greets
Al

[69wannabe]

Looks rich to me but i'm no expert. Might back the jets back down to maybe 72's in the front and see how the plug's look after that. What distributor are you running and what is your timing set at??? Initial around 14 to 18 is usually good with around 34 to 38 total depending on your compression and what heads you are running...

[Al]

I run a Mopar distributor. Timing is 18°@800 rpm, timing total 36°@2500. That should be in the ballpark.

[jlatessa]

Those are 383 plugs? What heads?

Joe

[Al]

Eddy rpm heads and eddy Performer rpm intake manifold

[69wannabe]

Timing sounds good that should work fine, does the car still seem to be running lean after you upped the jets or is it running good? Them street avenger carbs are not my favorite. I had one on my 383 and had to jet it up quite a bit to get it to run good and it was just using stock heads and a low rise dual plane intake. You may be better off to go up to a holley 750 DP carb or a 750 vacuum secondary carb with them bigger valve heads and RPM intake...

[c00nhunterjoe]

How much idle time for those readings? Was that only on primaries or did you make full throttle runs too? Lots of variables to consider when reading the plugs. Overall, yours are a touch rich, but not overly excessive. Better then being lean.bigger cams have dirty idles and can give you a "false" reading if youre not careful.

With your setup i would try bumping the timing to 20/38 and see if she likes it before doing a jet change. If you do change the jets, just do the primaries.

[firefighter3931]

Looks slightly rich to me but that could be idle mixture depending on how/when the plugs were read. 

To dial in the cruise jetting run it at 2000 rpm  under load for 15-20 minutes then shut it off immediately and pull a few plugs to see what they look like. 

Adjust idle mixture for max vacuum. It probably wants more timing at idle as well.....probably 20-22* BTDC. The closed chamber e-heads are more efficient than the open chamber iron heads so they don't need as much total timing. Mine allways made best power at 35* on the dyno. 

Al, what plugs are those ? An NGK 6 series plug works well with pump gas compression (9.5-10.5:1)



Ron

[Al]

Hi Ron,

the picture of the spark plug reading was taken after a 30 minutes drive on the primaries. By the way they are NGK BCP6ES.

greets
Al

[Al]

Looks slightly rich to me but that could be idle mixture depending on how/when the plugs were read. 

To dial in the cruise jetting run it at 2000 rpm  under load for 15-20 minutes then shut it off immediately and pull a few plugs to see what they look like. 

Adjust idle mixture for max vacuum. It probably wants more timing at idle as well.....probably 20-22* BTDC. The closed chamber e-heads are more efficient than the open chamber iron heads so they don't need as much total timing. Mine allways made best power at 35* on the dyno. 

Al, what plugs are those ? An NGK 6 series plug works well with pump gas compression (9.5-10.5:1)



Ron

To find the best timing at idle, do I aim for maximum manifold vacuum too?

Al

[c00nhunterjoe]

You can try, but with the choppier cams, its hard to judge the gauge imo. When you are talking about 1-2` changes you probably wont notice it on a gauge. Advance it 2 degrees at a time and give it a drive. Dont forget to make sure total timing doesnt get out of hand. Advance it til the engine is happy, or she cranks hard, whichever comes first...lol. fwiw, my 383 is at 25 initial and 40 total.

[firefighter3931]

Looks slightly rich to me but that could be idle mixture depending on how/when the plugs were read. 

To dial in the cruise jetting run it at 2000 rpm  under load for 15-20 minutes then shut it off immediately and pull a few plugs to see what they look like. 

Adjust idle mixture for max vacuum. It probably wants more timing at idle as well.....probably 20-22* BTDC. The closed chamber e-heads are more efficient than the open chamber iron heads so they don't need as much total timing. Mine allways made best power at 35* on the dyno. 

Al, what plugs are those ? An NGK 6 series plug works well with pump gas compression (9.5-10.5:1)



Ron

To find the best timing at idle, do I aim for maximum manifold vacuum too?

Al

That's how I do it....keep advancing until the vac guage peaks then lock it down and try a hot re-start. If it doesn't kick back you're good to go as far as base timing is concerned. Check the total and adjust your mechanical advance accordingly. 

A combo like yours should be in the 20-22 BTDC at idle and 35-36 total all in by 2500 


Ron

[Al]

Looks slightly rich to me but that could be idle mixture depending on how/when the plugs were read. 

To dial in the cruise jetting run it at 2000 rpm  under load for 15-20 minutes then shut it off immediately and pull a few plugs to see what they look like. 

Adjust idle mixture for max vacuum. It probably wants more timing at idle as well.....probably 20-22* BTDC. The closed chamber e-heads are more efficient than the open chamber iron heads so they don't need as much total timing. Mine allways made best power at 35* on the dyno. 

Al, what plugs are those ? An NGK 6 series plug works well with pump gas compression (9.5-10.5:1)



Ron

To find the best timing at idle, do I aim for maximum manifold vacuum too?

Al

That's how I do it....keep advancing until the vac guage peaks then lock it down and try a hot re-start. If it doesn't kick back you're good to go as far as base timing is concerned. Check the total and adjust your mechanical advance accordingly. 

A combo like yours should be in the 20-22 BTDC at idle and 35-36 total all in by 2500 


Ron

I'll try that over the weekend  Thank you 

[Al]

Looks slightly rich to me but that could be idle mixture depending on how/when the plugs were read.  

To dial in the cruise jetting run it at 2000 rpm  under load for 15-20 minutes then shut it off immediately and pull a few plugs to see what they look like.  

Adjust idle mixture for max vacuum. It probably wants more timing at idle as well.....probably 20-22* BTDC. The closed chamber e-heads are more efficient than the open chamber iron heads so they don't need as much total timing. Mine allways made best power at 35* on the dyno.  

Al, what plugs are those ? An NGK 6 series plug works well with pump gas compression (9.5-10.5:1)

Ron

To find the best timing at idle, do I aim for maximum manifold vacuum too?

Al

That's how I do it....keep advancing until the vac guage peaks then lock it down and try a hot re-start. If it doesn't kick back you're good to go as far as base timing is concerned. Check the total and adjust your mechanical advance accordingly.  

A combo like yours should be in the 20-22 BTDC at idle and 35-36 total all in by 2500  


Ron

Over the weekend I played around with ignition and carburetor.

I set the ignition advance for maximum vacuum and that is 10" vacuum at 22°@850 rpm. The difference is noticeable, the engine has better response. I also set the ile mixture screws for maximum vacuum, i went from 1,5 turns out to 2 full turns.

I'm a bit astonished about the vacuum: only 10" ! A bit low for my new power brakes? Well maybe a bit too much cam ... but the lope at idle always makes me grin :-)

Al

[Al]

Is this enough vacuum for power brakes?

[firefighter3931]

Is this enough vacuum for power brakes?

Try it and find out ?  A buddy of mine has about the same vacuum (MP 284 purple cam/426 ci street wedge) in his 64 Polara with power drum brakes and it stops great. 


Ron

[Al]

Is this enough vacuum for power brakes?

Try it and find out ?  A buddy of mine has about the same vacuum (MP 284 purple cam/426 ci street wedge) in his 64 Polara with power drum brakes and it stops great. 


Ron

thanks for your reply 

Al