STRONG Exhaust Fumes.
 

So I got a 91 rs, 355 .0040 over 2.02 041 heads street ported,rpm intake w/ holley ultra 750 dpump msd dig 6 ignition. cam specs r 511 522? mother thumper retrofit roller cam. when I stand behind the car and listen to idle or talk lol. the fumes smell rich i guess .there just real strong. they will just about choke ya. flowmaster 3" catbac.with 9.6:1 comp, ive tried smaller jets adv, retard timing lower power valve. also no catconverter, theres no smoke at all. any ideas.

Re: STRONG Exhaust Fumes.
 

What type of distributor do you have? does it have a vacuum advance?
Is the advance plugged into full manifold vacuum or ported vacuum source?

Re: STRONG Exhaust Fumes.
 

You will probably need a bunch of initial timing with that cam.

Re: STRONG Exhaust Fumes.
 

Idle mix adjustment? Crap in a float valve? Or might just be a consequence of 80 + degrees cam overlap.

Re: STRONG Exhaust Fumes.
 

im using a msd probillet w/ no vac adv. i was using a hei vac adv. still had same prob.
comp cams said intial should be 16-19, im @ 19.total is 32-33deg. The plugs look good, I did sum fine tuning last nite carb adj timing adj. gonna check plugs today. cam specs are 235 249 @ .050 w/ a 107 lobe sep installed straight up. my vac is low @ idle 6 in. but in park. the stock 6.5 power valve is in it. would lowering it help? or a catconverter help. that cam was supposed to help w/ vac . thats what they said. mine is low. no black smoke at all. but stand behind the car and the fumes are really strong. Does anyone else have this problem?

Re: STRONG Exhaust Fumes.
 

Had it. Primary float was set way too high (by someone who was supposed to know their stuff). I readjusted as Holley recommends and, voila, issue gone.

EDIT: BTW, in my case the giveaway was gas stains and/or gas pooling a bit on the pass side manifold from time to time.

JamesC

Re: STRONG Exhaust Fumes.
 

If you suspect your powervalve then you could temporarily plug it to test your idle for the fumes. It could be that it is starting to kick in at your idle.

Also as mentioned, check your float level to make sure you're not getting a little bit of internal flooding in the carb at idle.

With that much cam duration and overlap you are always going to have pretty strong gas fumes at idle. The best you can do to reduce it is to run a lot more spark advance at idle, which will require an adjustable vacuum advance unit on your distributor.

With a lot of hydrocarbons passing out the exhaust like you describe, a CAT would not last very long.

Re: STRONG Exhaust Fumes.
 

yup I thought the same, if the rain holds up I'll try go at it again!!

Re: STRONG Exhaust Fumes.
 

Not much idle vac there, 6" vac with a 6.5" pv - sounds like the pv is open at idle. Needs to go lower or - no vac leaks?

Re: STRONG Exhaust Fumes.
 

that is sumthin i need to check. I put a new intake, holley carb, and distr on it awhile back. the vac gauge reads fairly steady within 1- 1 1/2" .but that much cam its gonna do that. whats the best way to check for vacuum leaks?

Re: STRONG Exhaust Fumes.
 

I unplug all lines (except a vac gauge) and cap the nipples and run unlit propane or mapp gas around the intake gaskets. If there is no change in idle RPM, consider that your baseline vacuum. Start plugging in one line at a time and check the gauge.

What is your idle RPM?

Re: STRONG Exhaust Fumes.
 

Also, read this very closely

http://www.chevyhiperformance.com/ho...498/index.html

Re: STRONG Exhaust Fumes.
 

That is a really good article. I wish Icould of read that about 1-1/2 yrs ago, i can honestly say I done everything they did about 99.9% of it. the car idles at 700rpm in gear. same for park 700-720rpm. orginally i had 670 street avg/ 2200-2400 boe tie overdrive stall/ hei dist. stall was to tight hei was stickin, and had hard time keep idle down low. 1000 rpm in park so it would idle at 850 in gear not good. which is why I done a new top end intake card dist 3000 stall. now it idles dam good, great tip in to full throttle. oh yeah the street avg still got it , drilled those holes 3/32 in each valve , would'nt run at all after put new stall in it. I think i can fune tune alittle more but like yall said w/ that duration cam that mite be about it

Re: STRONG Exhaust Fumes.
 

Those (excess/rich) gas fumes will burn your throat, make your eyes water, choke you up, etc. Nasty. Had it on a TBI 305 one time will we replaced the injectors. It was tough to stand around that car when it was running.

Re: STRONG Exhaust Fumes.
 

I dont have a air fuel monitor/ gauge on it, I have the o2 bund already welded to the header just have to drill the hole. that mite be my next lil project. My wife loves the car but she wont even walk outside when i'm tuning on it. BUT you described just right.

Re: STRONG Exhaust Fumes.
 

I have this same problem the exhaust is so strong it's killer. Also the exhaust is leaking inside though the ac vents. So how do you adjust the primary float?

Re: STRONG Exhaust Fumes.
 

Oh and I have a little bit of black smoke when I floor it

Re: STRONG Exhaust Fumes.
 

http://www.youtube.com/watch?v=ge-mIk6nEYQ

JamesC

Re: STRONG Exhaust Fumes.
 

Is it the same to adjust on a eddelbroke carb

Re: STRONG Exhaust Fumes.
 

No.

Sorry, I was under the impression you were running a Holley.

JamesC