47-55.1 Exhaust manifold temp

[nvrdone]

Here's a fun one.
I just put a new 4 row radiator in MY Ad with a 327. Just for curiosity I started checking temps with my temp gun.
At the top outlet, the temp shows 177 deg. At the thermostat housing it shows 188.
I have cast iron rams horn exhaust manifolds. At the "V" in the middle of the right manifold it shows 217 deg. On the left it shows 422 deg. Does that sound right or should I be checking something? Possible coolant flow problem ?
Thanks

[leegreen]

do you have a stuck exhaust butterfly on one side that is forcing all the exhaust through the intake manifold heat riser to the other side?

[mr48chev]

Originally Posted by leegreen

do you have a stuck exhaust butterfly on one side that is forcing all the exhaust through the intake manifold heat riser to the other side?

Good point there if the truck still has the heat riser valve in the exhaust.

You should be able to tell real quick by checking the heat of the pipe down the pipes a ways. If the left side is a lot warmer than the right side that is the issue if the right side is still hotter the right side may be running lean but that doesn't fly with most manifolds that feed two cylinders on each side.

188 on the thermostat housing or just above it should mean that you have a 180 Thermostat and life is good temp wise.

[nvrdone]

no t'stat in it yet and no heat riser in the exhaust. left side is the hottest. Both sides are individual pipes from the manifold to the muffler. I will test temp next time I go for a drive.

[mr48chev]

Is there a big temp difference between the manifold runners on each cylinder?

[nvrdone]

dont know - I will check the runner temps hopefully this weekend

[nvrdone]

OK, Rob. Here's some stats. These were taken with a temp gun with 85 deg outside temps after a run into Yakima.
There is no thermostat installed right now.
Carb is an Edelbrock 4 bbl square bore. The manifold is an Edelbrock aluminum, not a high rise or air gap.
Left bank cylinder # intake exhaust right bank cylinder # intake exhaust
1 170 370 2 185 460
3 760 4 763
5 165 715 6 170 575
7 495 8 290
ON the intake manifold left front runner 207 left rear 105
ON the right front runner 208 right rear 108
At the "V" where the center exhaust ports come together left side is 760 right is 405
At the exhaust pipe where they enter the mufflers, left is 176 right is 166
What concerns me is that there is such a wide variation in temps.
The intake runner temps seem to be close to each other front & back.
The concern is the wide variation in temps at the exhaust manifolds
Any ideas from anyone would be appreciated.

[mr48chev]

I'd have to go out and dig my performer intake out of the shed and figure out if he hot exhaust is coming from intake runners feeding off the same side of the carb or same plane of the intake.

[nvrdone]

Im wondering if I have a coolant flow problem. With the old radiator I never had this problem but I didnt flush the system when I installed the new radiator. Wonder if there is some kind of blockage. Just a thought

[leegreen]

remind us why the rad was changed?

If you had a coolant blockage.....what are the temps on the cylinder heads / sides of the block?

I think mr48 is on an interesting idea: what is relationship between hot side and the the configuration of the intake runners / carburetor barrels? One side might be running lean (hot) or rich (cold); jet adjustment, mismatch jet sizes, a blockage inside carb.

have you pressure tested cooling system? Or checked to see if it holds pressure as it cools after a run.
Any bubbles coming up in tank when it is running? (headgasket?)
Valves over adjusted on one side of engine might make one side run at a different temperature - but I think it would run badly if it was that badly setup

[nvrdone]

rad was replaced because it started leaking after 30 + years. Don't know what the temps on the heads or block are. No bubbles in cooling system. Valves haven't been adjusted in years. May be time to do that. I'm thinking back flush the block, adjust the carb & adjust the valves.
I have an adapter that I can hook a garden hose to the water pump outlet hose and back flush the block that way.

[dsraven]

do you run coolant mix or plain water? coolant has antirust properties. a layer of rust is like a layer of insulation
if you have room under there you could pull the block drains and see what comes out and if worried you could remove an expansion plug and see if there is sediment build up in the bottom of the block. as a mechanic I have seen some nightmares in engines that have been neglected by the owners. coolant should be changed every couple of years for this reason and also because the coolant actually turns acidic.
have you pulled the spark plugs to see the color of each one?
do both exhaust pipes have the same color at their tips-assuming there is dual exhaust
are both exhaust pipes/runs/mufflers free flowing, no collapsed baffles, squashed pipes?
possibly a complete tune up is in order, valve adjustment, compression test, spark plug replacement, plug wire replacement/resistance check, distributor cap and rotor check/replacement, pcv valve replacement, fuel filter replacement, carb check and tune, timing adjustment and curve check, etc etc

[nvrdone]

Im now starting to wonder if I have some kind of blockage in the cooling system. When I put the new rad in, I filled the system with water to check for any leaks. I think I will start with a back flush and then refill with antifreeze. One step at a time

[leegreen]

A good working thermostat with air bleed hole might be an idea. I have seen engines run cooler at least on the gauge with thermostat that without. voodoo

[dsraven]

a thermostat and coolant is recommended because coolant has properties plain water doesn't as well as a thermostat restricts the coolant flow some so coolant has a chance to absorb heat from all areas about the same instead of cooling the higher easier flow areas better than some that flow less easily. also better for controlling heat during start up/warm up where the engine will take longer to get to operating temp, which saves the amount of overfuelling required at that temp, so less fuel washdown of the cylinder walls and pistons and also less oil dilution from that fuel getting past the pistons into the oil pan.
mr48 has a good idea to check the intake plenum under the carb to see if the hot cylinders are fed off the same carb bore. which may possibly be running leaner than the other bore(s). a spark plug color check and exhaust tip residue check may also prove the point to some degree.
if it were me I would do coolant pressure test and a rad hose/rad cap check and if that passes it would be followed by a chemical coolant flush followed by a good water flush to rid the system of anything loose. then allow to cool and dump the system completely. pull lower hose off and try to catch what you can so you can see what was in there. then pull the block drains and ensure the block is sediment free. maybe pull an expansion plug if you are not sure, pick a rear one if possible. flush the rad as well to ensure you have good flow from all the tubes if possible. if you run a heater, backflush that as well, removing the hoses of course so no sediment or debris from the heater can enter the engine. when you pull the spark plugs check for any super clean or rusty plugs as that can denote a cracked head.

[mr48chev]

I'm thinking that you don't have a cooling system problem but possibly have an air-fuel mixture issue where some of the cylinders are running lean and the exhaust gas is hotter.

One thing is that folks with old cars and old trucks get it in their head that newer engines out of cars and trucks that normally ran down the road at above 200 degrees are now supposed to run at 170 or 180 just because they were stuck in an older rig with a mechanical temp gauge.

Ideally the exhaust should be close to the same temp on the manifold where it exits the engine up and down both banks. What temp might not be as important as balanced temp. Checked as if you were checking each tube on a set of headers.

A 20/30 temp difference between idle at a stop light or in go in or out of Vintiques traffic and cruising down the street at 30 mph is normal without some serious air flow help. Gauge goes up at a light, goes back down when you hit 20 or 30 = need more air flow when sitting still. My 48 is the worlds worse at that with no shroud or electric helper fan.

[dsraven]

sorry, should have explained that a super clean plug can mean that cylinder is getting a little water in it when it's hot, so it is getting steam cleaned. sometimes an internal coolant leak can show as a milky build up on the under side of the oil filler cap, bubbles in the rad when at operating temp, steam in the exhaust that doesn't go away etc.

[nvrdone]

Just ran a compression test. Left bank compression was 95 - 132 0n all cylinders.
Right bank was 115 - 125 on all cylinders. # 3 & 5 had some carbon fouling on the plugs. Plugs are less than 1 year old. I'm thinking that the valves on # 3&5 are set too tight. Next step is a valve adjustment. Then a carb adjustment.
Wish me luck.

[1project2many]

SBC dual plane intakes feed cylinders 1,4,6,7 from the left carb bore and 2,3,5,8 from the right bore. When the readings are colored to match the bores of a dual plane intake, it appears that the problem may not be bad mixture from one side of the carb.

L cylinder # 	intake	exhaust 	R cylinder # 	intake	exhaust
1		170	370			2	185 	460
3			760			4		763
5		165	715			6	170	575
7			495			8		290

With a ram's horn manifolds I would expect the four corner ports to be cooler and the four center ports to be warmer due to the direction of exhaust flow. The temperature chart shows the corner ports (#'s 1,2,7, and 8) are definitely cooler while the center ports are warmer. Generally speaking I'd say the engine is operating normally. When you look at the temperature readings for the center ports, and subtract the temp readings from each port's neighbor, the center port temperature readings seem reasonable as well.

It can be tough to determine why there are such large temperature differences between individual ports. There are so many variables to work out. Combustion rate is affected by the combustion chamber temperature and by the actual compression ratio. Is coolant circulating properly inside the heads? Is carbon buildup causing higher compression ratio in some cylinders? Exhaust port temperature is a reflection of how the mixture has reacted before the exhaust valves have opened. Is the ignition system triggering spark at the same time on every cylinder? Is the cam ground so each cylinder's valve events happen at the same relative time? Is something slowing the speed of combustion for some cylinders? Many of these questions are very tough for us average guys to answer.

I think you're on the right track with a valve adjustment. I personally try to adjust valves with the engine warm and running on SBC with hydraulic lifters. I would also double check ignition timing and see if vacuum and mechanical advance are causing timing variations at idle speed. Oil temperature is a good indicator of upcoming issues so I migh install an oil temperature gauge. Id' probably work the idle mixture screws a bit until I was satisfied the engine is idling as well as it can. Then I would put it on the road and monitor the gauges for issues.

[nvrdone]

Hey 1 Project: Thanks for the info. Its interesting to see that the corner intake temps are fairly consistent. The center exhaust temps seem high so thats what started this whole line of questions. That and the truck sat for about 3 years until I retired an had time to play with it. FYI the distributor is an old Mallory dual point that was converted to Petronix ignition. Ignition is set at 10 degrees advanced. The engine idles well at 950 rpm. Valve adjustment is next. Maybe this weekend. Also double check the idle mixture. I think I would be happy if I could get the center exhaust temps closer to each other.
The engine still runs strong for having been built in 1973. But then maybe its time to switch to a 392 hem !!. But I'm only dreaming !! Thanks for the help.