Carb jetting

[js29no]

I bought A quick fuel HR-750 for my 383, idles well but smells A little rich. came with 72 primary 82 secondary jets.any thoughts on what size to start with to lean it down?

[cudabob496]

if don't have an O2 sensor, put in a new plug and check color after taking car out.

[Chryco Psycho]

What cam ?
 Any cam that lopes at idle is doing so because cylinders are misfiring so there is unburned fuel going out the exhaust

[js29no]

What cam ?
 Any cam that lopes at idle is doing so because cylinders are misfiring so there is unburned fuel going out the exhaust

   I will nave to look that up!

[js29no]

The only thing I could find is it's an Elgin E939P!! I know far more about body work then mechanical work, so any help would be appreciated.            Mark.

[cudabob496]

increase your idle to see if that helps

[Chryco Psycho]

What I am saying is if the plugs look good & it runs well then smelling the exhaust is not a very accurate test .
 SO if you can hear a lope in the idle it is pushing raw fuel down the exhaust & may smell rich even though everything is fine

[js29no]

thanks I will check that out. And Chrycho if you could take the time and look up the cam specs and tell me what you think. as stated I am far more of A body man then A mechanic.    thanks, mark. 

[CUDA JAS]

The main and secondary jets have no impact at idle...the jets only come into play once you get into the throttle.

That being said the smell at idle could be lean or rich...it is hard to tell with out an AFR gauge.

Your best bet, other then installing an AFR gauge is to hook up a vacuum gauge and tune the idle mixture screws (those are the small slot headed screws on each side of the primary metering block), to gain maximum vacuum.  That should get you in the ball park.

There are a few great threads on here about tuning a holly based carb that should give you enough information to tune the carb.  If not just keep asking questions and we can all help out!

Jason

[Chryco Psycho]

Actually more correctly if the carb is set up properly jetting front or rear will have no effect on idle

[js29no]

Thanks. 

[CUDA JAS]

Actually more correctly if the carb is set up properly jetting front or rear will have no effect on idle

hmmm... fair point!!

[barnett468]

thanks I will check that out. And Chrycho if you could take the time and look up the cam specs and tell me what you think. as stated I am far more of A body man then A mechanic.    thanks, mark. 

GOOGLE is your friend!

That is an odd cam and an old school grind.

http://catalog.elginind.com/download/PROSTOCK.PDF

E-939-P

Advertised duration 288 288 . 218 218 @.050 . Lift .444 . LSA 112 . ICL 107 . Overlap @ advertised duration 64 . Overlap @ .050 duration -6

Plug the vacuum advance and set the timing for highest idle.

Reset idle.

Set fuel mix screws equally for highest idle then turn them in 1/16 of a turn.

This will be your best idle setting.

Your idle will likely clean up a little and smell less bad if you install a multi fire ignition box like an MSD.

[js29no]

I am not much of A mechanic, I am A body and paint guy.I know what the job is that A cam dose but I am no engine builder.so I would like An opinion on this cam. is it worth keeping in there or find something different.  Its in A 70 barracuda, 4-speed. I like low end torque. 323 gears In it for now. I live in the country so I can play A little, any input would help    

[barnett468]

I am not much of A mechanic, I am A body and paint guy.I know what the job is that A cam dose but I am no engine builder.so I would like An opinion on this cam. is it worth keeping in there or find something different.  Its in A 70 barracuda, 4-speed. I like low end torque. 323 gears In it for now. I live in the country so I can play A little, any input would help

ok, it would be very helpful to tell us what you like about the cam and what you don't like about it, otherwise we are kind of guessing.

Also, what heads and intake and carb and exhaust do you have.

I general, you can move the entire power band up or down with a cam, if you are willing to give up some rpm on the top, you can get a little more power on the bottom and vise versa . I can also tell you that compression is king and if you have less than around 150 cranking compression, you will benefit from increasing it but this involves milling the heads and possibly using thinner head gaskets etc.

There are lots of guys here that also know quite a lot about cams so you should get a lot of suggestions.

Here's just one option . Overlap @ advertised duration 46 . Overlap @ .050 duration 1

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=706&sb=0
.