The Shakes have me stumped.
Senior User
Joined: Mar 2001
Posts: 108
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The Shakes have me stumped.
Hi, I can not figure this engine out. It is 400. The problem is the shakes, and a somewhat rough idle. It shakes a 1000 to 1800 rpm on free revs. Don't know about in gear, its hard to notice driving. It did this before I had it rebult and after also. I've tried a carter afb 625 carb jetted it up and down, and did the same with a holly 600 vac sec. I've replaced distributor, wires module coil. All to no aval. I plan on switching the cam in the near future (for different reasons) and I would like to get this thing figured out. To add to the plot, the rotating assembly was balanced when it was rebuilt. Thought this would cure it. Thought wrong. I will answer any question, but now I will leave this mystery to the experts.
Thanks
Chad
Thanks
Chad
Moderator
Joined: Jan 2001
Posts: 57,027
Likes: 2,763
From: Virginia
The Shakes have me stumped.
Have you run it on the road and let it get fully warmed up? I was wondering if it is just cold natured. Another possibility is you have one or two fouled plugs. During the experimenting process, did you ever flood the engine? Sometimes, certain plugs never recover from being fouled. Of course you double checked the sparkplug wiring order.
Senior User
Joined: Mar 2001
Posts: 108
Likes: 0
The Shakes have me stumped.
There is about 30,000 miles on the rebuild. Its ran an hour to and from work for a while. Now its about a half hour to work. So it gets wormed up. Changed plugs, wires, cap, rotor. Still no luck. It will take fits. It will run super smooth every once in a while, so I know it can do it. The thing that help out some is when I changed the distributor. It was out of another truck. That truck ran smooth. In fact, I switch the dist, cap, wires, and module from that truck, figuring that if it ran smooth, then this one should with that stuff. The dist was the only noticable difference. Could both dist's be wore out and throwing the timeing off enough to cause this? Sorry so long, Trying to lay it all on the table.
Thanks
Chad
Thanks
Chad
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
The Shakes have me stumped.
You may have a vacuum leak on the ported vacuum. It doesn't leak at idle, because there is no ported vaccum. Above 1800 RPM it doesn't affect the mixture enough to cause the problem. Plug the ported vacuum to see if it goes away.
Lead Driver
Joined: Nov 2000
Posts: 6,652
Likes: 353
From: Albuquerque
The Shakes have me stumped.
Check your timing at idle with vacuum hooked up. These engines like a lot of initial.
1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything
1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything
Senior User
Joined: Mar 2001
Posts: 108
Likes: 0
The Shakes have me stumped.
Which vac is the ported one, I have the vac advance to one port and the egr valve to the other. I've blocked both off, switch them, same old thing. The timing at idle is about 10 btdc with or without advance hooked up. For future refrence the cam specs are, Speed pro cam, 208 intake and exaust, .484 lift. Maybe this will help. I am disapointed with this cam, so I am going to switch it for something bigger and dual pattern. Whats got me stumpted is it did the shake thing before and after the rebuild. It was balance by a quallity machine shop. New intake, 2 new carbs, new coil, new cam, new pistons, the rods and crank are the same but were balance. I have checked for vac leaks, and found none. The shake isn't real bad but it is annoying, I don't think it should be doing it. Well back to you guys. Thanks so far.
Chad
Chad
Trending Topics
Posting Guru
Joined: Aug 2000
Posts: 2,416
Likes: 4
From: PacNW
The Shakes have me stumped.
Sounds like it's time to look outside the motor. Is it an automatic or a manual? I'm thinking you may have a bad torque convertor or pressure plate/clutch disk.
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Senior User
Joined: Mar 2001
Posts: 108
Likes: 0
The Shakes have me stumped.
This has a c6 auto that has be redone at the time of the rebuild. I also got a remanufactured torque convertor. This is why I am stumped, I thought I covered everything when I rebuilt it.
Thanks
Chad
Thanks
Chad
Moderator
Joined: Jan 2001
Posts: 57,027
Likes: 2,763
From: Virginia
The Shakes have me stumped.
I agree with danlee. Egr's can get sticky and leak a little. Try taking it off and temporarily make a solid gasket to block it off. If this fixes it, I would get a new valve.
Lead Driver
Joined: Nov 2000
Posts: 6,652
Likes: 353
From: Albuquerque
The Shakes have me stumped.
For reference I have a large cam and am at high altitude but I run 18 degrees initial timing plus 6 vacuum added for a total of 24 at idle. That may be a bit much for yours but I would try getting it up to at least 18 if it will take it and try it out. For me it make a ton of diiference at idle and just off idle.
1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything
Senior User
Joined: Mar 2001
Posts: 108
Likes: 0
The Shakes have me stumped.
I have done the egr valve thing. I have unhooked it, and i have blocked it off. Question on the advance. Right now my timing is right under the point of pinging on hard takeoffs. If I advance it more it will really ping. It is a stock dist. Is there a way to change the advances? I have tried the 1/8 alan wrench. It did not seem to have a screw or anything in there to turn. I could push the diaphram in and out. Also when I advance the dist to much, it is hard to start. Its like it wants to kick back. I plan on getting a Mallory Unilite dist. when I change cams. I think that it is adjustable both in mach. and vac. advances.
Well thanks again.
Baffeling isn't it?
Chad
Well thanks again.
Baffeling isn't it?
Chad
Lead Driver
Joined: Nov 2000
Posts: 6,652
Likes: 353
From: Albuquerque
The Shakes have me stumped.
You might want to verify the timing marks on the balancer. Could it have spun? Could you have more timing than you think?
1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything
1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything
Senior User
Joined: Mar 2001
Posts: 108
Likes: 0
The Shakes have me stumped.
I checked the timing marks. They are on. This wouldn't just be a bad charateristic of this engine would it? Hope not. Would the wrong cam make it do this?
Ponder some more
Thanks again
Chad
Ponder some more
Thanks again
Chad