351c Engine help PLEASE!!

Also try this in alt.hi-po.big-block-ford-mercury. Cleves are on topic there.

CobraJet

I put the problem to the guys at the group you recomended but have not gotten any help there yet. Does anyone have any ideas? Could the carb be too small?

As you have no doubt discovered by now, the BB group is not as large as this one, and you must have a little patience before writing off any replies.

CobraJet

Which Holley 4150 are you using? They feature 4150 model carbs with various CFM ratings.

You should *at least* be using a 600 CFM rated carb - preferably a 650 CFM rated carb.

Yet another $.02 worth from a proud owner of a 1970 Mach 1 351C featuring a

If it stumbles at a steady rpm, like a on,off,on,off it is either running out of fuel, or the front jets are to small, start by setting the floats so gas will be level with the bottom of the sight plug hole,if that doesn't help install larger front jets, go up 2 sizes at a time until it runs smooth.

I'll keep with them, I got a few replies now.

Holley 600 with Vac. secondaries and electric choke.

It runs fine on steady throttle or light accelleration, but stumbles on accel. from a stop and just dies on a hard accell from a stop or if I get on it like when getting on a freeway on ramp. I have to accel. easy to get up to speed.

I agree that this sounds like fuel starvation. Definitely not an ignition timing problem. Go up in jet sizes, but I would set the float bowls for the middle of the sight glass, then go down from there.

Accelerator pump shot too small or non existent?

I'm getting a full shot, but the squirter is only .025" so I will be putting a .028" in it tuesday night as well as a 6.5 high flow power valve. Just waiting for the parts to come in.

I have a bigger squirter and a new 6.5 power valve coming in tomorrow. I believe I have #66 jets in it now, but I want to check the size before I order bigger ones. I'll do that when I put the power valve in.

very possible the pump diaphram is busted or the squirter is clogged,or the arm is out of adjustment, you should see fuel squirt into the carb when you barely move the throttle? if you remove the squirter be carefull not to drop it into the engine, and don't loose the small gaskets, keep check on the screw to make sure it's tight, if it falls into the engine while it's running the results will be serious engine damage, there is also a check ball or needle under it that will be pushed out if the throttle is touched while the squirter is off, it's best to remove the carb from the engine to work on it. been there,done it! LOL

Well, I got it working better but still not right. To make a long story short... Threw a used 750 cfm on it and it helped a little and I was able to get the thing to idle, but it still died at 2500-3000 rpm. Cut back the timing to 34 deg. total advance and the cutting out mostly went away but the idle had to be turned back up to 1000 from 750 rpm that the bigger carb let me set it to. Looks like I might have to play with the dist. curve now to cut back on the total advance and still let me get it to idle at a decent rpm. Maybe if the advance comes in a little later, say around 3000 max instead of 2300 rpm the cutting out will go away.?