I'm having a bear of a time tuning my new 383. I was chalking it up to changing weather, but I have had it two years now and am no closer to getting it right. My problem is that it seems so cold blooded. It will only run well if I let it sit and idle for 30 minutes or more, then as soon as it has been driven a bit it will start to run like it is cold again. Just like if I had first started it on a cold morning. I have chased every bug I can think of except one. I have tried three carbs, two ignition systems, and three fuel pumps, cleaned lines, new filters everything I can think of.

What I am beginning to think though is that the carb is too cold because I didn't open the manifold heat riser passage from the exhaust valves. Which means I have no heat under the carb other than the oil in the lifter valley bouncing around. This is about the only thing I can think of that might be causing the engine to drive "cold" all of the time.

Thanks for your thoughts and ideas guys, I am pretty fedup at this point. The worst part is that I have to remove the engine from the car to take the heads off. :(

I think you can drill a hole in the block off casting, call world products and see.

What exactly do you mean that it runs like it's cold? Bogging, stumbling, backfiring or black smoking like the choke's on?
I'v run blocked heat motor in some pretty severe cold spells and as long as the engine is up to operating temp (160-180) I've never had a problem. And actually they ran better when the air density was up.
So, I wouldn'd drill holes just yet. Elaborate on the driveability problem and let's see if someone has suggestions.

Randy

after thinking a minute, I feel your problem is somewhere esle too. I'm running Sportsman II's with an air gap intake and have no problems. Do tend to oil foul one spark plug at random times? Will this problem come and go as you drive or shut down and recrank?

Are you running a thermostat? If so, what temp?

The problem is worse in cold weather, below about 60 degrees. The car drives cold. The low speed torque output is bad. It likes to die when leaving stop lights unless I really have the revs up. I don't have any plug fouling problems. I have never gotten it rich enough to run well. I was as high as 84 jets in the primaries of my 3310 Holley and was still lean. I was told if you have to go more than 5 jet sizes from factory then you have a problem, so I stopped there and reevaluated other systems. If I let the car idle in one place it runs ok, and leaving the stop it will be ok. But as soon as I drive a little(less than one mile), if I have to stop, then go imediately it will usually cough and stumble like I just fired it up cold. If I run it awhile and get it warm driving or just sitting idleing, then shut it off and let it sit, then start it back up again, it runs pretty well when I first start driving, but the next time I stop, then start imediately, it will drive cold, coughing and bucking. There is no choke so I know that isn't closing. I have great vacuum at idle. 21" @700rpm. And the needle is steady as a rock.

Last winter I had a Victor Jr. on the engine and assumed that was where my cold driveability problems came from, but last spring I switched to a standard Performer RPM and the problem is still there. I don't foul spark plugs anymore, but I still cannot get the carb to stay put.

I tried three 3310 Holley carbs and all worked really well on my Dad's and my Brother's 383s, but none worked any different on my engine. They all showed the same problems.

I have a 180* thermostat in it. The temp runs just over 180* in the winter and summer too.

The car drove the best over the summer when it was 90* outside. It is marginal to drive at 70* and gets better the warmer the ambient temperature is. Below about 60* and it is pretty much useless to get in the car.

If anybody has more questions, I will answer as soon as I can. Thank you for the help.

Rad, my daily driver is a Comp x274 equipped 350 with sportsman II and victor jr. with Holley 750 "2" pump. Runs like crap cold, I've come to live with it, tried everything, one of the drawbacks to driving a real musclecar in real world conditions. I just get up 15 min. early. Same symptoms though, have to launch a little harder at stops, feather throttle at idle, runs a little richer, stumbles leaving stops. Been like that about 6 years now, I've tried everything, it only lasts from about Nov. until March. Oh well. Good luck, maybe you'll be more persistent than me.

Ok I have run 350 with XE274, 11:1CR, Torquer I Single Plane, Ported 462 Heads, with blocked off heat crossover, and a Holley 750 VacSec Carb. I have driven this truck in January and February here. In February it was -30C for two weeks. I had zero cold driving problems. I had to richen up choke and up jet 2-3 szies I belive. But the truck ran just like it would on a summer day.

May I suggest getting the car dyno tuned, with a wideband O2 sensor. 84 Jets seem alittle big to me. So I would check the fuel system problems. Low pressure, blocked or kinked line. Something like that.

Good Luck
Steve

I suspected the fuel system also, so I removed everything and cleaned and checked all of the lines from the pickup in the tank to the carb. I also replaced my Holley 60gph pump with a Holley 6 valve street pump. Now my fuel pressure holds 6psi all the time.

The low end output is dissapointing to me. I figured an engine with 21" or vacuum at idle would be able to leave a stop light without bucking and kicking. I am starting to believe my problems may be related to the 200cc intake runners. I didn't figure they would feel this big on a 383 though.....

k i had the same problem with my car turned out to be timing. replaced my dist and that didnt fix it. took it to chassis dyno. the tuned it and runs perfect now

I built a couple of 355s with Sportsman IIs, RPM intake, Comp 280H Magum cam. I drove the car across the country all types of weather climates from very cold to real hot. I don't think the problem is in your combo - there is something mechanical or electrical wrong with the engine.

Could you have a weak coil? A weak ignition can cause some weird problems.

If you said you were up to 84 jets and it was still lean, you definately have a fuel delievery problem somewhere. Plugged filter or those sintered bronze filters in the carb inlets?

What about a vacuum leak? maybe a leaking intake gasket? or a leaking power brake booster or transmission vacuum modulator?

Tried two different coils, three distributors, two MSD boxes, two sets of plug wires, three sets of spark plugs, checked all grounds, and fuses.

I took out the sintered bronze filters in the carb bowls. I was told they where a restriction.

I used a vacuum gauge while driving and the vacuum is ok unless it is stumbling.(natch) The idle vacuum is high and rock steady. The car is a stickshift so no vacuum modulator.

What rear gears where you guys running? I only have 3.31s, maybe that is making leaving the stops harder.

I'm not sure if icing is your problem, but it's easy enough to check.

Keep in mind if the air moves fast enough thru the venturi, icing can occurr at almost any temperature.

Next time you come to a stop and it will barely idle or is running like trash, pull over get out quickly and put your hand on the base of the carb. It will be ice cold, also there may even be FROST on the outside of the main body,, YES even in 60 degree weather.

Second part of the test would be to shut the car off but don't touch a thing... let it sit for 4 or 5 minutes, this allows the heat of the manifold to de-ice the carb base. If after sitting for those few minutes the car starts and runs fine until a long part throttle drive starts it all over again, then your problem is carb icing.

Remember it's the speed of the air thru the venturi that is causing the cooling effect in this case, not the weather or the tuning..

Good luck, hope this info helps.

Sean

I drove it last year and did have ice on the carb and intake. But that was with the Victor Jr. Now with the Performer RPM it is cold. Even after 50 miles of driving the carb and intake are very cold to the touch. Not icy anymore, but cold. The only explanation I can fancy is that without the manifold heat the carb and intake are never warming up with the ait flow over them from driving. Thats why when I sit it will warm, but once I start driving the air flow cools the carb and causes a mixture fluxuation. Is there even a chance that I am barking up the right tree here? I am mostly out of ideas. If it is on the outside of the engine it has been replaced. I have changed the timing from 4btdc to as far as 20btdc at idle and never fixed the problem, I've run ported and manifold vacuum for the advance. Seems like I just need more heat.

What size are your tires??

I ask b/c my 3.31's and 26.5" tall great big L-60's were kinda hard to roll over until I was up like above 25 to 3000rpm with my 9.5 to 1CR., 406 with a 292/230, .480" hy- RV el-cheapo cam.

pdq67

Tires are 24.5" high, 3.31 rear gears, 2.52 first gear, running a 274/274 Crane Energizer cam in a 383 with 9.7:1 compression static.

I was running 3.23 gears with a Borg Warner T-5 overdrive tranny.

IMO it really has to be either fuel delivery, a vac leak, or ignition.

It sounds like you have the fuel delivery and ignition part covered. What about your intake gasket? A steady vac reading won't necessarily prove/disprove the presence of a vac leak.

The next step IMO would be to try your carb and ignition (including distributor) on another known good engine to see if you can make your problem show up on another car. It might be hard to find someone to let you try your ignition out on their car, but the carb should be an easy swap.

The reason I suggest trying your parts on someone else's engine is because sometimes multiple problems will screw up your troubleshooting. If you replace one of two bad parts and the problem does not go away we assume that we didn't find a problem right?

For timing, set the total timing for 36*. Optimum timing for power will be within a degree or two of that --- just let the base timing fall wherever (would usually be about 22-24* base), as long as you have 36* total you should be OK.

I did that. :( I used my ignition and carb on my brother's 383. Ran like a champ, just like his always does.

How can I find a vacuum leak? I tried carb cleaner and the vacuum gauge. Any other ways to find one?

I am positive it isn't ignition related by now, I have replaced every part in the system already with known good parts from other 383s.

I am beginning to think it isn't icing as much as cooling. When it warms up it runs ok, but then I drive it and it cools off, throwing my calibrations out of wack. So I change it to make the cool temps run ok, but then when it heats up it runs poorly. I need something to stabilize the temp of the carb and intake. I checked with WP and I can drill the passage out with a long drill bit. I think it is just going to have to come apart.