siduramaxde

A couple years ago I came across a slightly used 383. I bought the motor and installed it in my 86 Berlinetta. I bought a 750 cfm Holley with electric choke and VS. I have followed sofakings directions for holley tuning on numerous occasions but I still have a very rich exhaust smell.

A little bit about the my setup: 383, 1.5 roller rockers, iron world products S/R torquers that are supposed to be ported and polished, performer rpm intake, MSD HEI dizzy, Hooker 2055 shorty headers with no cat. I know the roller cam is decent size by the idle it has but I don't know the exact specs on it because the guy I bought the motor from lost the cam card. I do have about 15 inches of vacuum.

Its been awhile since I messed with the timing but I know it's right. If I remember right it is set at about 15+/- and centrifugal advance gets it to about 35 total all in by 3000rpm. I also have vacuum advance hooked to ported vacuum. I tried hooking Vacuum advance to manifold but it did not like that. I am also running a built 700r4 with a 3000rpm stall.

The motor is supposed to be about 400hp. I have ran it at the track a couple times and the best it's done is 13.3. Right now it runs good and has plenty of power. It will melt the tires if I mash the pedal when in 2nd gear. My fuel mileage is terrible at 10mpg and I can't hardly stand to take it through a drive through. The exhaust stinks terrible. I have adjusted the idle mixture screws many times to no avail.

I am starting to think my carb may be too big. I am thinking of getting a 680cfm Quick Fuel with adjustable idle air bleeds. What do you think? Any help would be great.

sofakingdom

iTrader: (1)

Glad you found the tuning info helpful... I hope it made a big improvement, even if there's still this one thing.

IMP a 750 is pefrectly fine for a 383.

It actually sounds to me like it has the wrong power valve gasket in it. I can't recall the exact details right at the moment, but there's 2 PV types - one with small "windows" and one with 2 large ones. There's also 2 PV gaskets - one that's just a circle, and one with 3 little nibs around the inside. If you put the one type of gasket on the wring type of PV, it leaks; specifically, it leaks fuel into the vacuum side of the PV diaphragm, and then into the manifold. I can't remember which is which though. But that's what I'd suspect. Could be on either the pri or the sec side, or even both. (although the car probably wouldn't even run at all if it was both)

siduramaxde

Thanks for the quick reply. I did replace the stock PV that the 750 Holley came with. I think I installed a 9.5 PV on the primary side (as per your instructions) and I left the sec side alone.

Most people I talk to say that the 750 is fine but I can't get rid of the poor exhaust smell for the life of me. I may end up spliting the difference between a 750 and 680. Quick Fuel makes a 735 I may get and then I have a better carb.

Sofakingdom,
Your tuning guidelines are great.

hdavis2005

The 750 should be fine. Check PV as sofakingdom suggested and also make sure you are using the correct metering block gaskets. You should check your fuel level also.

articwhiteZ

iTrader: (56)

I would not go any smaller then a 750.

also if this is the 3310 type. check to make sure your 2nd drys are working right. and your jetting is right for the primrys.

love the Holleys have run them for a long time.
but i LOVE EVEN MORE.. EFI

bestracing

I would think that the power valve should be around 6.5 on your motor

Also having raced a stroker motor 35* total timing is just too high for most applications. We ran 32* total timing with a cam that had a LSA of 106, 509/518 lift, 240/245 Dur@0.050. Anything higher really didn't improve anything.

With the smell, are you getting a blueish colored smoke out the tail pipe or black smoke during hard acceleration? My bet is that your carb size is just fine but you could also have some of the following issues:

*Burning some oil, more common with stock heads though (blue smoke) this does cause a smell of what some will think as running rich but it's the oil not fuel

*Not enough spark energy at the plug - A low coil output, high resistance plug wires can cause a poor burn. Usually you will get some mis-fire in the high rpm ranges with this but not always.

*A small LSA and/or large valve overlap will cause raw fuel to come out as well to help better fill the cylinder. The exhaust valve remains open while the intake opens causing the draw of exhaust gases out the exhaust valve to start the draw of the fuel air mixture quicker and some of that does go out through the exhaust.

siduramaxde

There is no smoke from the exhaust and I am positive it is a "rich" smell coming from the exhaust. The dizzy was new as were the 8mm plug wires when I installed the engine. Is there a way to test the spark energy? I do not have a mis-fire ever.

The cam is a big question mark. As I said, I do not know the cam specs because the guy lost the card. I know its not a small cam...it does have a nice rumble at idle but its not like I can't drive the car on the street. Car is very street friendly.

After reading through the replies here I think I may just save a bit more $$$ and go with something like FAST EFI or something similar. Then I know it will be right. I'm just sick of smelling like the inside of a muffler after I drive the car.

Thank you to everyone that responded.

bestracing

I just posted a few things for you to consider and help track down where you might have problems besides the obvious

There is if you have an oscilloscope to check the coil output.

I wound up with a Craftsman brand one for free. The garage my dad worked at threw it away because it was intermittent. I got it and fixed it. Not something I'd expect most people to have but you might find one at a mom and pop service center and talk them into just hooking it up just to see.

camarito

maybe your idle is too rich, you be surprised how low you have to go on does screws to get it to 13:1-14:1 I'm at little more than 1/2 turn on my Speed Demon

mmadden55

Power valve issue or it is jetted wrong or leaks, float level or stuck inlet valve. No carburator is too big though it can be too small. Yours is a good size for your motor.

cuisinartvette

750 AED would be perfect for you

Custom built to your car/combo, incredible service.
straubtechnologies.com good place to go through talk to Chris

You wont have any more of the issues youre having.
Stock holleys with non adjustable passages like IAB will give you fits like this. BTDT money very well spent!

camarito

how can the jets or the power valve be a cause of rich idle?
there should be no vacuum signal above the throttle blades at idle, either you have the transition slots too exposed or the idle mixture too rich.
Check the spark plugs

urbanhunter44

iTrader: (3)

Try rechecking your timing. A higher initial timing can give you a better idle, reducing the need to cover it up with extra fuel from the carb. I have a holley 750 and made this mistake at first with it. My initial was too low, and I had to give it a lot of idle screw to get the idle where I wanted it. With a built 383 your motor may want as much as 20 degrees initial. Now that it's properly tuned it's far more friendly. It's still got a bit of a rich smell at idle but I also have a cam with a lot of overlap.