460 running hot
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460 running hot
Hi guys, I have a '85 3/4 ton with the 460 in it that I recently replaced the holley carb it had in it with a 600cfm edelbrock. The only vaccum lines I hooked back up to the new carb were the PCV and distributer advance which I hooked directly to the carb. The engine runs ok I guess you could say (misses a little but it did before I replaced the carb) but now after running it only a little bit the temp guage starts reading 230* to 240*F. Is this because of some unhooked vaccum componet like the EGR? I shot the top radiator hose with a temp gun and it was above 200 too so I assume the water pump is working. I was kinda curious about the VCV (if i'm calling it the right thing) on top of the thermostat housing and what it does or if i screwed up the timing by hooking the advance directly to the carb? The engine previously only ran around 190*F. Any help appreciated and TIA.
Junior User
Joined: Apr 2010
Posts: 71
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From: North east IN.
Make sure that the distributor has no vacuum going to it at idle. If it does then your getting full timing advance at idle. If you have or can borrow a vacuum gauge check the ports on the carb till you find one with no vacuum at idle, that's what you want. Anything else will be manifold vacuum, about 11 to 18 inches of vacuum at idle. Other than that just check for vacuum leaks and hook everything back up like it was with the Holley.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
I was kinda curious about the VCV (if i'm calling it the right thing) on top of the thermostat housing and what it does or if i screwed up the timing by hooking the advance directly to the carb? The engine previously only ran around 190*F. Any help appreciated and TIA.
If your routing diagram looks something like this:
You can see that it either ports full manifold vacuum or through a vacuum restriction, limiting vacuum to the advance mechanism in the event of an overheating condition.
Check your total advance and be sure you don't get beyond 40 degrees.
When I installed a new engine I needed to recurve my distributor and install an adjustable vacuum advance canister to limit vacuum advance.
Some good info can be found here: Duraspark_distributor_recurve_instructions_index
Eliminating the EGR will cause a lean condition with the stock 4180 carburetor and subsequent overheating. (inert exhaust gas displaces some of the oxygen in the incoming charge, making it seem richer than it really is)
I'm sure you can tune your Eddy to work, but be assured mileage will drop under cruise conditions.
Just my 2c, I hope it's helpful.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
ArdWrknTrk; The VCV is a timing temperature control device. If the engine start heating up in traffic, the VCV changes from ported vacuum to manifold vacuum, there by advancing the timing (not retarding), hence increasing the idle speed to pump more coolant thru the engine and air thru the radiator to cool the engine more. Since I live in the Northwest where hot in the summer isn't that hot, I bypassed this and went straight to the ported vacuum nipple on the carb.
phatjack81; No, manifold vacuum will give you full "vacuum" advance (about 18° at the most), but centrifugal advance will be minimal. After about 1/4 throttle manifold and ported vacuum have the same inches of mercury.
phatjack81; No, manifold vacuum will give you full "vacuum" advance (about 18° at the most), but centrifugal advance will be minimal. After about 1/4 throttle manifold and ported vacuum have the same inches of mercury.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
Bear,
Sorry if I was unclear.
I understand that the VCV is temperature controlled, that is why it is mounted on the thermostat housing.
But as you can see in my factory vacuum diagram that there is no "ported" vacuum in the stock setup.
Both -stock- lines from the VCV ultimately lead to full manifold vacuum at the tree near the coil mount.
The VREST itself is just a small blue plastic restriction in the vacuum line. It does not have a bleed port, connect above the butterfly or otherwise lead to a ported source.
Other years might have been different, but that is the way my truck rolled out of the factory.
Sorry if I was unclear.
I understand that the VCV is temperature controlled, that is why it is mounted on the thermostat housing.
But as you can see in my factory vacuum diagram that there is no "ported" vacuum in the stock setup.
Both -stock- lines from the VCV ultimately lead to full manifold vacuum at the tree near the coil mount.
The VREST itself is just a small blue plastic restriction in the vacuum line. It does not have a bleed port, connect above the butterfly or otherwise lead to a ported source.
Other years might have been different, but that is the way my truck rolled out of the factory.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
My '84 460 was not set up that way. One side of the VCV was to manifold and the other to the carb for ported vacuum. Otherwise it was much simpler than that diagram, but then again mine was a heavy duty F250 and was exempt for most of that emission BS since it was rated at 8800 lbs, well over the 8400 lbs rating of most F250 trucks and all that emission crap. No cat either.
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pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
^ 8'600 gvw, no cats, listed as "1987 model year heavy duty engine"
But I do agree it is likely a more complex vacuum, and emissions system than that found on your '84.
Your 1984 4180 carb had ported vacuum? Or did you replace it with a 4160?
But I do agree it is likely a more complex vacuum, and emissions system than that found on your '84.
Your 1984 4180 carb had ported vacuum? Or did you replace it with a 4160?
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Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
The 4180 had a ported vacuum but it just wasn't conducive to modifications. So I replaced a 4180 with a 4160, List 1850 Holley I had done a massage job on for my old 1967 F250 with a 390 that I built for it. The 4160 had a dual stage power valve, one step heavier spring in the vacuum secondary diaphragm and staggered jetting front and back. I also recurved the dist.
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