413 Sucking Air??

[KEVSWS6]

This engine starts and runs fine. Once it warms up it hunts for an idle real bad. It stalls after a minute or two.

What is the easiest way to check for a vacuum leak around the intake manifold. Its not sucking from the top. I think its sucking from the valley. From the intake port to the valley?

My dad had the engine rebuilt. He had the heads shaved 6 or 7 thousands?? The intake manifold was not touched.

[cuda66273]

Sounds like you could be dumping fuel through the idle circuit.

Vacuum leaks can be tested with a spray bottle full of water, but first you have to get it running reasonable.

After it stalls pull a couple of plugs and see if their wet or black and sooty.

Lemme know and we'll go to step 2

What kind of carb are we working with here?

[Doug Wilson]

Do you know exactly how much the heads were shaved? I'm thinking maybe a leak at the parting surface between the heads and intake.

[cuda66273]

Hey Doug, I think he mnentioned 6-7 thou.
That shouldn't hurt anything.

"After it warms up"...maybe it's going lean after the choke opens....could very well be a vac leak.

[KEVSWS6]

Originally posted by cuda66273
Sounds like you could be dumping fuel through the idle circuit.

Vacuum leaks can be tested with a spray bottle full of water, but first you have to get it running reasonable.

After it stalls pull a couple of plugs and see if their wet or black and sooty.

Lemme know and we'll go to step 2

What kind of carb are we working with here?

Wow you guys are fast. I didn't know what kind of traffic this site got. Its a factory Holley made for Chrysler. 750 if I remember with vacuum secondaries. The carb was rebuilt professionally and the ignition was upgraded to the Mopar electronic set up. The plugs actually look a little white....like maybe its hot....lean?? It was all rebuilt to factory specs...less the cam and the bore.

[beepbeepsrule]

It is not real easy to get the intake to seal to the heads on MoPar big blocks especially with milling done to the block or heads. Even the newer head gaskets can change the geometry. Did the assembler use the fiber gaskets with the valley pan or just the valley pan between the heads and the intake? The fiber gaskets weren't around when these engines were new and can make the job easier. Another thing to check is if they tried to block off the exhaust passage with the thin piece of sheet metal that comes with some valley pan kits. That could cause some mating-up problems.

[cuda66273]

Are all the plugs on the white side?
If it's just one or a couple that are side by side you probably have found where the leak or lean condition is coming from.

If so try checking the float levels, with engine running you should get a pretty good leak when you pull the plugs out.

Have you set your idle screws with a vacuum gauge?

Does it make any difference when you turn the idle screws? If not you probably have a leak.

and ...Yes we're faster than a Mickey D's drive up but with 1/2 the calories and twice the fat.

[KEVSWS6]

Originally posted by beepbeepsrule
It is not real easy to get the intake to seal to the heads on MoPar big blocks especially with milling done to the block or heads. Even the newer head gaskets can change the geometry. Did the assembler use the fiber gaskets with the valley pan or just the valley pan between the heads and the intake? The fiber gaskets weren't around when these engines were new and can make the job easier. Another thing to check is if they tried to block off the exhaust passage with the thin piece of sheet metal that comes with some valley pan kits. That could cause some mating-up problems.

I'll have to check into that. Dad had taken the intake off a few hundred miles ago with this same problem. I'll have to ask what he used for a gasket. He used a bunch of rtv gasket sealant.

Thanks

[KEVSWS6]

Originally posted by cuda66273
Are all the plugs on the white side?
If it's just one or a couple that are side by side you probably have found where the leak or lean condition is coming from.

If so try checking the float levels, with engine running you should get a pretty good leak when you pull the plugs out.

Have you set your idle screws with a vacuum gauge?

Does it make any difference when you turn the idle screws? If not you probably have a leak.

and ...Yes we're faster than a Mickey D's drive up but with 1/2 the calories and twice the fat.

No they all looked the same.
I don't know how to set my idle screws with a vacuum gauge?? I don't own a vacuum gauge

I will check if it makes a difference when I turn them.

You guys are great. I'm new here and get some good help right off the bat.

Thanks!

Would you hate me if I posted my pride and joy?

[beepbeepsrule]

Originally posted by KEVSWS6



...... Would you hate me if I posted my pride and joy?

Only if it is sweeter than anything we could ever possibly own ourselves!!!!!!! let's see it ...

[ajmopar]

Silicone doesn't work so well on intake manifolds, at least around intake ports. Gasoline eats and swells the silicone, and in no time it is useless. If you have to use sealer on intake ports, something is wrong. It sounds to me like the heads were milled more than 6 or 7 thou, more like 60 or 70 thou, in which case the intake definately needs machining. I usually mill the intake the same amount and use the fibre gaskets dry.

[KEVSWS6]

Originally posted by beepbeepsrule



Only if it is sweeter than anything we could ever possibly own ourselves!!!!!!! let's see it ...

I wont post a picture on this site cause its not a Mopar.

http://community.webshots.com/user/kevsws6/

I have a love hate relationship with my Mopar vehicles.

[Doug Wilson]

That's what I was trying to get at when I asked if you knew the EXACT amount the heads were milled. There is a formula that any competent machinist has on hand as to how much to shave off the manifold compared to how much you cut the heads.

Also, you are correct in assuming that pix on non-MOPARs are not really wanted. Any time we want other stuff, we can always look at Popular Hot Chevying or Ford Craft... or even Porsche and Driver or Ferrari and Track.

[cuda66273]

Wait a second...are we talking about a Fire Chicken on drugs here or a 413 Mopar???????

Confused minds need to know????

[Doug Wilson]

I believe he is referring to his motor home.

[dirty dan]

There is a suplementl intake gasket availible at most any parts place. Ask for it on a 78 440chry new yorker. It comes as 4 paper gaskets. 2 for each side of the vally pan (top&bottom) this will solve any intake leak you have. as long as you are correct on how much the heads have been cut.
Happy trails

[KEVSWS6]

Originally posted by Doug Wilson
I believe he is referring to his motor home.

Yes it’s a motor home that has the 413. You guys have been great help. I adjusted the idler screws and float bowls. That made a big difference! I haven’t had a carbureted car since....well don’t shoot me.......my 70ss nova.

Dad says it has an aluminum one-piece valley pan gasket with rtv sealant gooped all over it. What brand or kind of gasket should I go with?? Valley pan one piece with fiber around the ports??

Dads looking for the machine work papers. The engine ran before he had it rebuilt. It was never overheated or blew the head gasket.

Is there anything on the net that explains how to use a vacuum gauge to test for a lea

[KEVSWS6]

Originally posted by dirty dan
There is a suplementl intake gasket availible at most any parts place. Ask for it on a 78 440chry new yorker. It comes as 4 paper gaskets. 2 for each side of the vally pan (top&bottom) this will solve any intake leak you have. as long as you are correct on how much the heads have been cut.
Happy trails

Thanks Dirty Dan and use no rtv sealant right??

[Doug Wilson]

Use a thin bead of RTV at the front and back only.

[KEVSWS6]

Originally posted by Doug Wilson
Use a thin bead of RTV at the front and back only.

Thanks Doug. I'm still trying to find out how much was taken off the heads and block. I will then call the machine shop and ask if I need to take it in and have it matched.

[dirty dan]

As a general rule for every 10thou removed the head you should have 12thou removed from the intake.(if memory servs). perhaps someone could verify this. When I have heads shaved I usually have the intake surface on the head done at the same time. That way any intake will fit. Unfortunately it`s to late for you on that. Without way to much extra work. Happy trails