am I over carb'd?

[69Pony]

I am running rich at idle and through out acceleration.

Here are my specs:

351 Cleveland stroked to 408
Pro Systems (4150 style) 950cfm mechanical carb
all hydraulic
Comp Cam
duration @ .050 240 / 244
intake lobe lift .360 / .363
1.7 rockers
valve lift .622 / .627

I've taken the 4 corner idles down to hesitation and then backed out a 1/4 turn
checked my idle screw (idles @ 900)
checked my floats.

I was thinking about downsizing to a Holley HP 830 but that's a lot of $ based on a guess.

[zbugger]

I would think you are. The 830 would be a better choice, but something around 800 would be better. At least in my opinion.

[Rick Dorion]

You'll have raw fuel at idle with any carb with those cam specs. I do even using an Innovate to get my idle mixture to 15:1. The other richness you see is based on using a wideband O2 sensor or how?

[69Pony]

Richness determined by site only right now. I have a set of SS bungs ready to go into the MagnaFlow exhaust for true testing. Yeah the cam is a bit radical and has a long duration. At idle it almost burns the eyes and on fast accelaration it could be a bug fogger. Of course worse in the summer.

[Shaker455]

That carb is not too big for your combo, it's venturi size is the same as a 750 (1-3/8") with a baseplate size of an 850 ( 1-3/4") it's typical to see a 950 out of balance but once there dialed in they perform great!

I had to modified a Pro-Systems 850/1000 cfm unit that was on the same engine in a Factory Five Cobra, I had to jet the transition circurt to balance the A/F.

If you carb is new then call Patrick James and tell him your not happy with it and he should as I do my customers advise you or replace it with something else...if it's old then your welcome to contact me.

[69Pony]

That carb is not too big for your combo, it's venturi size is the same as a 750 (1-3/8") with a baseplate size of an 850 ( 1-3/4") it's typical to see a 950 out of balance but once there dialed in they perform great!

I had to modified a Pro-Systems 850/1000 cfm unit that was on the same engine in a Factory Five Cobra, I had to jet the transition circurt to balance the A/F.

If you carb is new then call Patrick James and tell him your not happy with it and he should as I do my customers advise you or replace it with something else...if it's old then your welcome to contact me.

Carb is about two years old and I have talked to Patrick before. Nice enough guy. The "problem" is my engine builder (MME racing) built the engine with a strip dominator intake and then realized it would not fit under my hood with my shaker. So he instead went with the Torker II intake. Then MME simply down jetted from 76/86 to 71/83 which was way off. Patrick suggested I go to 73/83 to start. I did that but I'm not a carb guy. Maybe I need to speak with Patrick again and send it back for tweaking.

[Shaker455]

Should work good on the T2

You should have the build or spec sheet from Patrick so how was it jetted, powervalved,airbeeds, size boosters, when you got if from him?

Typically those like to be jetted a bit fatter...

What heads are you using and what do they flow?

The 408 I did had AFR heads with the Dom intake and a MSD dist

[69Pony]

I do have the build sheet from Patrick - however, MME dorked with some of the settings.

I kept the Iron heads and had MME do an angle job. They flow just over 300cfm.

Torker II intake and MSD Pro billet dizzy with MSD AL6 box.

[hotrdblder]

you answered the question yourself, call patrick again start at square one, then go kick the engine builder in the balls

[Shaker455]

Good stuff... no reason for it not to kick!

How about those specs and your exhaust size?

[My427stang]

I would look at the transition and idle circuits, a good carb builder can lean out those areas pretty easy

If you havent taken it off yet, drop the float level a little, it'll lean out the transition circuit significantly and may take an edge off

One last thing, dont use your nose, get it on a dyno or use a meter, too hard to tell rich from advanced timing and cool EGT at low RPM / low load

[MonzaRacer]

probably got the power valve opening go down in size try a 3 or 4 power valve I had problems and figure out I was going the wrong way and my carbs were doing similar things.
Depending on your idle vacuum in gear (if auto) and go about 2 or 3 numbers below that.
I generally use the 3 or 3.5 till I see its lean then go up. Starting lean just woks better for me.
Also double check your timing, advancing the timing will let you cose the throttle blades and get a better idle signal and less chance of opening the PV.

[69Pony]

Carb isn't off yet so I will lower to the bowls a bit for the short term. Patrick responded to my email and said he could rework it but it would cost $160 and take a week. I have to do some clutch work so the week downtime isn't a concern but $160 may be if it doesn't fix my problem.

My vacuum is around 10~12# at idle - my cam plays havoc with vacuum. To fix that I'm looking into the Hydro-braking option for the fall.

Shaker455 - my exhaust is 2.5" MagnaFlow SS straight out the back. Very nice sound. Sounds like a late model Mustang at idle and gets loud under load.

Timing is 14 initial - 30 all in at 3K. No vacuum - all mechanical.

[Shaker455]

Exhaust size sounds good!

That cam wants plently of intinal and it will help clean things up.

I'd suggest you bump your intinal up to 18 and install the black 18 degree bushing also the 2 light blue springs (3rd fastest rate of advance) and try to get the advance in a little eariler...like 2500

[My427stang]

The timing advice is good, and dont look at float level as a "will do for now" crutch. It IS a tuning parameter, it basically times the fuel based on how easily vacuum can pull it through the circuit

You wouldnt believe how many undriveable carbs I have fixed with float level, guys think that "level when assembled" or "rock the fender until it leaks" is close enough

Float level is critical to the idle circuit and transition circuit, its not a "close enough" type of adjustment to guys that really tune carbs

However as I said before, dont just use your nose, any car running a bunch of initial timing will be stinky due to reduced EGTs (one of the reasons that retarded timing makes cars pass the sniffer, exhaust heat burns the residual fuel)

[69Pony]

A follow up to my carb issues;

I did end up sending it to Patrick at Pro Systems. For around $200 with shipping he recalibrated the carb, new power valve, bleeders and re-jetted. It still run uber-rich but any hestitation I had in the engine is gone. The engine is very responsive now.

I did take the initial to 16* with 34* total. Any more and with that cam it won't start - especially when warm. A bit embarrassing at the gas station. No ping though on 93 pump.

I do think the bowls are a bit high as is the idle (1250) so I will tweak them a bit.

I had bungs welded in just after my collectors and the A/F unit I borrowed from a buddy shows me to be around 13.5 which I'm told is near perfect at idle and WOT.

So for now I guess I'll just stink a bit like gas when I'm driving around.

[My427stang]

Good work, with the initial advanced and a quick curve they can smell rich, mostly due to lack of heat in the chamber.

Same heat in the pipe that makes headers glow when you retard the timing will clean up the exhaust smell

Thats why early emission cars ran such crazy timing curves, 4-6 degrees initial with lots of timing that didnt come in until almost 4000 rpm

Sounds like yours is good now, one last thing, take it for a good long run and get the exhaust real hot, it may still burn a little cleaner. Its amazing how some mufflers can hold the smell for a long time