Hey I recently put a rebuilt 400 in my 79 F250 Ranger, and I've been having trouble getting it running decent. I've been searching the threads but haven't had much luck so here goes. It is all stock,2150 carb, no emissions other than pcv valve. First off it overheats fast after the thermostat opens. I double checked its the right thermostat with the bypass and its opening at the right temp. The radiator level seems to change as the engine is rev'ed so I would think the waterpump is working. Could it be a head gasket on wrong or can timing/carb adjustments make it overheat? The carb has been rebuilt and I have the timing set on 10 btdc. As far as the idle, it will run nice if i advance the timing way out, otherwise it won't stay running. Engine damper is new and i checked the marks with tdc #1. IT sounds nice at about 1000 rpms and it has a steady vac on 17 then. I'm hoping I'm just missing something really easy cause I'm out of ideas.

Thanks in advance!

 

What is your radiator like, I would be loth to use a seemingly good engine with an old radiator? It could be that its better and making more power than your old one so it needs better cooling.

 

get radiator checked. possible head gskt issue.

 

Seems funny that it smooths out at fast idle for head gasket. should really start to develop a miss. Reuer-fill your radiator right to the top as far as you can. look for bubbles/surging. Also smell for petrol fumes in the water. I wouldn't imagine that a headgasket failure into an oil gallery would promote heating so quickly, but check your oil and determine if you have water in it or excess fumes.

 

Thanks guys. I should have mentioned the radiator was new one a few years ago, and the old engine never ran hot. I checked it with a light and could see through it really good. Also I had run a garden hose into it and it flowed out pretty fast. I did notice it will heat with the pickup sitting and when its going down the road. Thanks again!

 

maybe looking at the wrong thing here. Does it have a temp gauge or an oil light?
maybe see if you can scrounge a temp gauge to see what it is doing.
good vac suggests most things ok. rebuilt engine may need more timing (as long as no pinging/detonation-see stickies in this forum for that) so if it runs well and starts well (again with no pinging) that is a good thing.

 

It has a water temp and oil pressure gauge. I put a gauge on the engine when I put the engine in for oil pressure, just didn't trust the stock one. The temp gauge acts like its working and I'm hoping to get a different gauge tomorrow for that.

 

Excellent. Always pays to check before expensive and time wasting repairs.

 

Yeah dad always said to use the KISS method-Keep It Simple Stupid- Haha
I did notice that the rubber intake manifold end seals pushed out so I'm going to be taking that off, but that is another topic on here as far as I have read.

Thanks again! Much appreciated!

 

Hello Reuer,

If you can drive to a local radiator shop, do so, and ask them to test the water for exhaust gases, check for heat spots and check the radiator cap pressure. This should be quick and cheap !

Exhaust gases in the water will certainly give you the overheating issues you mention, and will indicate a head gasket fault, or cracked block.

Your vacuum reading of 17 at 1,000rpm implies that you would get a reading of +/-14 at a normal idle rpm of +/-800rpm . A reading that low is not good, especially on a 'new' engine. A low steady reading has its implications.

Two major things will cause this low reading.

First is a vacuum leak at the intake manifold or carb, and you mentioned a suspect looking rubber end seal already. If an auto box is fitted, it's worth checking that vacuum connection too. I assume the pcv valve is working correctly! Basically check for vacuum leaks on all vacuum lines.

Second is the cylinder (cranking) pressure.
Cam timing and compression ratio can increase the cylinder pressure at the expense of vacuum, which is normal.
It would be useful to know your cranking pressures as these numbers are as useful as a vacuum reading, and also doesn't take long to obtain.

I assume a fan blade shroud is fitted, or decent electric fans.

Did you happen to notice if the restrictor plate was fitted in the block just below the thermostat ?

Good luck with the diagnosis.

 

Thanks for the reply.

Unfortunately I'm 80 miles from the nearest radiator shop. Is there a at home test a guy could try for the exhaust gasses in the coolant?

I'm thinking by cranking pressure you mean a compression test? I have a slip of paper with that info from the rebuilder that they sent with the long block.

The fan shroud looks good and the fans in the right direction. Under the thermostat there is a portion that is raised to match the bottom collar on the stat if that is what you mean by restrictor plate?

I've read on here that the head gaskets on these engines can be put on backwards or upside down, don't remember which. If that was the case could that somehow allow exhaust into the cooling or would it just block off the coolant to that head?

Thanks again

 

There is a dip test that can test for combustion fumes in coolant. Heavy trade use it but don't know where you are or your resources. Honestly if you fill the radiator to the tippy top, and run it any bubbles will tell you straight away. When mine failed I didn't get overheating but my gaskets were that bad it drove half the radiator water out. And yes if the gaskets are on the wrong way it probably do it. Who rebuilt it as they should be involved especially if it may be warranty. PITA if you rebuilt it sorry LOL

 

Well I got a manual temp gauge along with the stock one on it tonight. It must be reading right cause it climbed to 210 before i shut it off. I couldn't see any bubbles in the radiator but it had built up pressure.

I'll have to check with the local Napa about some test strips, maybe I'll get lucky and they will have something.

I got the engine from Tri-Star engines. I'm hoping to get a hold of them this Monday. Maybe they can give me some ideas or insight.

 

They should be involved from the get go once you have sorted out it isn't something easy or you've done.

 

Hi Reuer,

Yes, that's what I meant by a restrictor plate and cranking pressure, and yes, people have managed, somehow, to incorrectly fit head gaskets (no comment!).

I don't know 100% for sure how to check if a radiator core is blocked, and although you said the water flow looks ok, it would be worth knowing 100% for sure.

I would also want a 3 core radiator (not a 2 core) on a 400m.

I agree with crsmiffy about contacting Tri-Star.

Did they do the initial 30 minutes break in (with an immediate change of oil and filter thereafter)?

Did they set the timing after the break in? (10 degrees btdc sounds ok, but did you set that or did they?)
At what degrees do you get the smooth idle, and is that with the vacuum advance connected ? (Ported or full manifold ?)
Was the dizzy rotor pointing to spark plug lead number one when you set the damper to tdc ? (It's remotely possible that this was 180 degrees out)

Was the engine at normal operating temperature when they did the compression test ?

I'm curious as to why they gave you a compression test result and not a vacuum result too !?

I assume also that your idle mixture is set correctly, I.E. not too lean.
But once again, that should have been set at the rebuild, and even if it's not 100%, it wouldn't cause a quick heat up to 210 degrees!

Yeah, hopefully Napa has some test strips for you.