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Well I have a prob with my 79 4 wheel drive, its running rough and tops out at 40 mph, also will over heat, I changed the plugs and points checked the timing and set dwell but that did not help matters any. I am not sure as where to go from here help please

Check your oil to make sure there isn't water in it. check radiator fluid level. might need to flush cooling system. Could the water pump...
If it has over heated and is running rough though you might want to pull the head off and make sure you didn't blow the head gasket.

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D has some good advice, take a hard look at the water and oil, and make sure they are not mixing together in one way or another. I'd do a compression check as well. That will help determine if you have a head gasket problem as well. Another trick is to run the truck with the radiator cap off, get it warmed up enough for the thermostat to open (upper rad hose will get warm) and then look for air bubbles coming out through the rad. The rad should be pretty well topped off for this and it might take a few minutes. If you see bubbles, that means the head gasket is leaking compression into the cooling system. (Or a crack in the head is doing the same.)

I've also heard that running the compression check with the rad cap off can give you some info. With all the plugs out and one hole plugged by the comp tester, the rad will burp air/water out when you test the cylinder(s) that is leaking.

If you've had it over heat and it isn't running well the head gasket very well could be toast and/or the head warped. Usually you have white smoke pumping out the tail pipe and a noticable loss of water, but they can go in ways that show very few symptoms other than running poor. The compression test should be able to rule it out as a problem though. Once you pull the head, you are already redoing the gasket so it would pay to try to pin the problem down to that before you tear it open.

Ok I am going to get get a compression tester this after noon, but what the compressions be for avgerage, can a blown head gasket really take away that much power? thanks for the advise

I have seen a plugged up cat do that too. I don't know if you have one or not.

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OK, I'm over it. Where's the beer?

I was thinking about that too!
My Corolla acted exactly the same way when the cat plugged up.

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77 2wd - Back on the road
05 Ford Five Hundred

"Love endures all things, Love never fails." - 1 Cor. 13:7,8.

Compression on bad headgaskets tends to be way low on one or more cylinders. Look for one or more to be below 100 by a fair bit. If it is two side by side the gasket between the cylinders is probably blown out. If it is one or two that are not close, then that could be cracks or just gasket blown out between the cyl and the outside or a water jacket.

I got to thinking about the cat myself. If the truck has one, that is something to consider. When you say it has a top speed of 40, what does it do when it gets there? My fuel pump is starting to go, and when I hit 75 or so it starts to just cut out and die off. It runs fine right up until it runs low on gas and then is starts to chug die like it is running out of gas.

You should also try pulling spark plug wires one at a time while its running. If you have one dead cylinder it could hold you back quite a lot. It could be something as simple as a plug wire being bad and all this talk about heads could be overkill.

when it hits its top speed of 40 mph its will keep the speed it just wont go past it, I will try all of these things in the moring and see whats going on with it, I had the head resurfaced a year ago and put a new head gasket on then but things do happen, but i'll will find some results back in the morning and get back to this post, ,thanks again for all the help

My advice, just don't drive on the freeway and you'll be fine. J.K.

ok here is what i found out so far, I started removing the plug wires and noticed that when #4 is removed there is no change in the way that the eng is running, it is the same for cyl 3 i got a new rotor and wires but they did not have the cap in stock, but how ever that did not solve the problem now what do I do?

I had the same problem with cylinder #1 and #4. My brother thought maybe sticky valves. I removed plug #4, started engine for about 3 seconds, then turned it off. Put the plug back in and did the same for plug #1. Now it works fine.

If you don't have any spare plugs, you could swap the ones from 1 and 2 over to 3 and 4. The ones that aren't firing are probably soaked with fuel and perhaps even varnish if they've been like that for long. Clean them up a bit before you put them back in, even just a quick wipe with a rag would help. If the problem follows the plugs, you'll know what you need next.

You should also look at adjusting the valves. If they are a ways out of adjustment that could keep it from hitting on all four holes.

Just a brain check here, make sure the wires are on in the right order. It has happened to the best of us. 1342 counterclockwise

just make sure you start the wires at the correct spot
i put the wires on 90 degrees out on the cap, she did a lot of backfireing through the carby

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