One bank running hot vs other.

[Ramba_ral]

Alright need help again troubleshooting something on the blazer


Started running rough and found my brake booster had a vacuum lean and worn plugs. fixed both but in troubleshooting I noticed one bank is running a lot hotter than the other. This is measured on a l31 350 with long tube headers. Used a IR gun to measure. Tried doing a smoke test after fixing the brake booster but found nothing. Read this it could be caused by a leak on the valley side of the intake manifold. Before I dig into it wanted some 2nd opinions if this is even a problem and/or what else I should check.

2 267
4 285
6 310
8 300

1 430
3 500
5 400
7 458

 

[‘89Jimmy]

High temps can be observed by a lean fuel condition. You could have a clogged fuel injector on one side if running a TBI. Might be getting enough fuel to "run" even if roughly, but not enough to run correctly.

 

[Ramba_ral]

Right now I'm running a holly sniper on top of a dual plane intake manifold. I suppose one or more injectors could be clogged. From a birds eye view it seems they are flowing evenly. I've resisted the urge to crack open the sniper and swap the injectors around to see if the problem follows.

 

[Fastereddie]

Wasnt there talk of that type of issue with certain dual plane manifolds?

 

[Ramba_ral]

I've have read that a dual plane can affect how fuel is distributed but have also read(mainly on holley forums) a dual plane works just fine.

I'm running 1/2 spacer so it should help if it is a issue.

 

[Bent77]

Wasnt there talk of that type of issue with certain dual plane manifolds?

Yes there’s even a thread on here someplace

I've have read that a dual plane can affect how fuel is distributed but have also read(mainly on holley forums) a dual plane works just fine.

I'm running 1/2 spacer so it should help if it is an issue.

I wouldn’t bet on that spacer doing anything unfortunately


The other thing to be aware of is that you may see an injector “working” but it’s not putting a full fuel load


But let’s separate a few things

One bank is fed by 1/2 of a plenum charge, upper vs lower

As seen here the upper feeds 3-5-2-8
Lower feeds 1-7-4-6



You have something else going on

 

[Bent77]

 

[Ramba_ral]

I'm trying to avoid messing with the sniper injectors but will put it on the list of things to check I guess.

Unfortunately my intake doesn't have that fancy gap in the middle cut out.

Should I move away from the intake and look at maybe a exhaust leak?

 

[Bent77]

It’s possible it’s sucking air around the manifold. I would think the handheld would be giving you some really weird numbers to try and correct for the leak

What water temps are you seeing?

 

[Ramba_ral]

water temps sit around 195 even when its 110 out.

Logs seem normal to me. Nothing to erratic. Ill post some logs here.

When i did the smoke test no smoke around the manifold unless it was occurring on the valley side.

 

[Ramba_ral]

Or I would post logs if it would let me

 

[ktmoutfront]

I agree with Bent. It's not the manifold or injection system due to the split in banks. Have you smoke tested the exhaust for leaks? Witch side did you put the O2 sensor in? I assume the rich side. Add another with a gauge on the lean side to see what is going on.

 

[Ramba_ral]

I haven't smoke tested the exhaust. Just smoke tested through intake manifold. Ill see about doing that. the O2 is on the drivers side(the hot side)

 

[ktmoutfront]

the O2 is on the drivers side(the hot side)

Running rich on the right side if the AFR is showing correct on the hand held. That shouldn't (edited) be able to happen. Or you might have coolant flow restriction on the left side.

 

[imiceman44]

Running rich on the right side if the AFR is showing correct on the hand held. That should be able to happen. Or you might have coolant flow restriction on the left side.

Yeah, a good flush of the cooling system might help.

 

[Blue85]

It seems unlikely for a manifold gasket to fail almost the same on every port, unless it's the wrong gasket, or there has been some machining done to a head or the intake that prevents it from sealing properly. In that case, a coolant leak seems probable. It's also possible there is some other part mismatch side to side in play, like head, rockers, lifters, etc.

Is it possible there is some external factor in play, like one header gets more airflow from the fan, or your two headers have different thicknesses?

 

[Ramba_ral]

So the headers are the same on either side.
No machining. aside from the headers and intake manifold its a stock vortec l31 that i havent messed with
for the coolant block i do have a temp sensor on the drivers head(the hot side) that reads a stable 195( the holley system also shows 195). if there was a coolant flow problem wouldnt it reflect on the temp sensors?

 

[imiceman44]

So the headers are the same on either side.
No machining. aside from the headers and intake manifold its a stock vortec l31 that i havent messed with
for the coolant block i do have a temp sensor on the drivers head(the hot side) that reads a stable 195( the holley system also shows 195). if there was a coolant flow problem wouldnt it reflect on the temp sensors?

So this is a L31 block, I know there's something about the cooling that was different, @sweetk30 had some issues until he figured out the issue. Maybe that is causing the difference in temperature.
It was something about a bypass line going to the waterpump or something

 

[Ramba_ral]

there is a bypass going from the waterblock to the intake manifold. Im not aware of other bypasses

 

[ktmoutfront]

Check the temp on the intake manifold on each side of the thermostat.