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Cleaning Type 4 AMC Head Flashing with Engine Installed
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sallittjob
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PostPosted: Sun Sep 25, 2022 1:02 pm    Post subject: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

I recently rebuilt my 1800cc type 4 bus motor and have been monitoring CHTs & AFR. No matter what I do, it is running a little too hot for my liking (400-415 highway and uphills).

I ran a bore scope over the new AMC heads and noticed the air ports in the center are almost completely blocked on the driver's side head (didn't check the passenger side yet). I pulled the dirty, old stock head out of storage to compare, and sure enough, the ports are wide open on the stocker.

I did some research and saw this is a common issue with AMC heads. I want to try and drill out the flashing in the center section of the head but I have no clear way to do it. I was thinking my best bet is to drain the oil, pull the pushrod tubes and remove the bottom air deflector to gain access from below. I'm not looking forward to it but that seems like the best option at this point. Alternatively I could remove the top tins, but that seems like a huge pain. I should also mention, I have the fan housing pulled, so I can get my hand in there but I'm not sure an angle drill could get it from inside the tin as there is minimal vertical clearance. That'd be easiest though if anyone knows of a angle drill I could buy that would fit.

Any suggestions?

Thanks all!
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PostPosted: Sun Sep 25, 2022 6:50 pm    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

some places leave it up to you to clean the flashing. The ones I got from Len Hoffman were already cleaned up. Colin just did one in I think St Louis where it took him 401 plunges with a long drill bit to clean the flashing out. Once that was done head temps came down to a normal range.
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PostPosted: Sun Sep 25, 2022 7:32 pm    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

I would first make sure that your fuel air mixture is correct. After that, Id think an air powered pencil grinder or an electric Dremel would work best

Neiko 10649A 1/8-Inch Pencil Type Micro Air Die Grinder, 54000 RPM https://a.co/d/a8LJDS9

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Nitramrebrab72
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PostPosted: Mon Sep 26, 2022 12:19 am    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

Check your air fuel mixture. Flashing alone won't do that.
I have AMC heads and I run no more than 275f on very steep hills.
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crownline
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PostPosted: Mon Sep 26, 2022 4:08 am    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

Is your thermostat working correctly? Are the flaps opening all the way when up to temp?
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sallittjob
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PostPosted: Mon Sep 26, 2022 5:08 am    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

Thanks all for the responses. I have a DD CHT gauge, Dash-Mounted Wideband and a 5k potentiometer all in the cockpit. So needless to say, I've experimented quite a bit with AFR and timing settings. I can keep it below 380F around town. Once I hit the highway or load it up a long hill, the CHTs climb and I have a hard time cooling it back down.

When I rebuilt the engine, the driver's side flap was completely missing. I sourced a "new" one from Awesome Powedercoat. Unfortunately he used 3D printed plastic hinges riveted to the flap. These were getting soft at operating temp and the entire flap was falling off the hinges, binding my flaps rod. So I used a scope camera, removed the fan, and fished a long screwdriver up there and popped it back on. Confirmed it was opening all the way and then took it out for a test drive. Still hot.

Next move was to pull the entire fan housing. I did that and drilled out the 3D printed hinges. I fabricated new ones from some sheet steel I had. Shouldn't be an issue any more. I used the scope camera and a flashlight to check the flashing while I have it apart. The center-section of the new AMC heads are almost completely blocked. I think that is the biggest issue, so here we are.

I'm going to pull the pushrod tubes, stuff shop rags in the heads and case bores. Then I'll remove the air deflectors that are bolted to the bottom of the heads. I think an extended 1/8" drill bit is the way to go. Not looking forward to it but it seems like my best option.

P.S. static C/R is 7.3 : 1. This is an entirely stock 1.8L bus motor with stock cam. All cooling tin is in place and I painstakingly sealed up any cracks between tin. The foam engine seal is new and installed. I don't think there is anything else I'm missing that could explain the high CHTs. It's driving me nuts LOL.

Thanks
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PostPosted: Mon Sep 26, 2022 6:41 am    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

The center section of the head flashing won't contribute directly to hot CHT temps, as the intake ports are constantly bathed in a cool air and fuel mixture. The flashing towards the outer edges near the exhaust ports are much more important. Yes they should all be drilled out, but I believe your problem lies elsewhere.

How long has this problem been going on? Have you inspected the CHT ring sender to make sure it's fully seated and not pulled sideways creating a gap? In my experience it's nearly impossible to install one in an AMC T4 head without cutting a notch for the crimp and wiring.

Do the temps come down quickly if you coast down a hill in gear?

How are you setting your timing? Do the temps drop 10-15 when you retard the timing 5 temporarily?

Robbie
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sallittjob
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PostPosted: Mon Sep 26, 2022 9:58 am    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

airschooled wrote:
The center section of the head flashing won't contribute directly to hot CHT temps, as the intake ports are constantly bathed in a cool air and fuel mixture. The flashing towards the outer edges near the exhaust ports are much more important. Yes they should all be drilled out, but I believe your problem lies elsewhere.

How long has this problem been going on? Have you inspected the CHT ring sender to make sure it's fully seated and not pulled sideways creating a gap? In my experience it's nearly impossible to install one in an AMC T4 head without cutting a notch for the crimp and wiring.

Do the temps come down quickly if you coast down a hill in gear?

How are you setting your timing? Do the temps drop 10-15 when you retard the timing 5 temporarily?

Robbie


CHT probe is epoxied into a hole I drilled in the head right by the #3 plug. I should mention that I double-checked the temp with a separate thermocouple/thermometer setup and it was exactly the same temp, so I believe the gauge reading.

It's been running hot since I rebuilt the engine.

Yes, temps come down quick when I coast down hill in gear.

Stock distributor, hoses removed @ 2,500 RPM or so. I'm at 28 max now, tried anywhere between 26-30.

The intake port area is the most obvious but the area near the exhaust ports isn't clear either. I should have clarified. Only a few tiny holes of light get through in both sections. I compared to my old stock head and it was a noticeable difference.
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PostPosted: Thu Sep 29, 2022 10:16 am    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

airschooled wrote:
The center section of the head flashing won't contribute directly to hot CHT temps, as the intake ports are constantly bathed in a cool air and fuel mixture. The flashing towards the outer edges near the exhaust ports are much more important. Yes they should all be drilled out, but I believe your problem lies elsewhere.

Robbie


^^^X2^^^

You can lower cruise CHT by richening mixture.
The question becomes if its too rich.
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PostPosted: Thu Sep 29, 2022 12:31 pm    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

colin said the one he cleaned up was almost completely blocked across the head. It came from some porsche guru in St Louis I think he said. Len cleans his out.
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PostPosted: Sun Oct 02, 2022 3:23 am    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

sallittjob wrote:
airschooled wrote:
The center section of the head flashing won't contribute directly to hot CHT temps, as the intake ports are constantly bathed in a cool air and fuel mixture. The flashing towards the outer edges near the exhaust ports are much more important. Yes they should all be drilled out, but I believe your problem lies elsewhere.

How long has this problem been going on? Have you inspected the CHT ring sender to make sure it's fully seated and not pulled sideways creating a gap? In my experience it's nearly impossible to install one in an AMC T4 head without cutting a notch for the crimp and wiring.

Do the temps come down quickly if you coast down a hill in gear?

How are you setting your timing? Do the temps drop 10-15 when you retard the timing 5 temporarily?

Robbie


CHT probe is epoxied into a hole I drilled in the head right by the #3 plug. I should mention that I double-checked the temp with a separate thermocouple/thermometer setup and it was exactly the same temp, so I believe the gauge reading.

It's been running hot since I rebuilt the engine.

Yes, temps come down quick when I coast down hill in gear.

Stock distributor, hoses removed @ 2,500 RPM or so. I'm at 28 max now, tried anywhere between 26-30.

The intake port area is the most obvious but the area near the exhaust ports isn't clear either. I should have clarified. Only a few tiny holes of light get through in both sections. I compared to my old stock head and it was a noticeable difference.


Time @ 3400+ 28BTDC

How certain is the thermo-coupler installed for the DD?

What are your temps when not pulling a grade/hill?

How many miles on engine?
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PostPosted: Sun Oct 02, 2022 7:44 am    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

often the cracks in the T4 head are in the roof of an intake port. Colin theorized that the temperature differential between the ports and surrounding area contributed to that. I would clean all flashing out if it is clearly flashing or too diversionary.
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PostPosted: Sun Oct 02, 2022 8:53 am    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

I'm a lifelong Rambler guy and I don't recall them ever making VW heads! Laughing Laughing Laughing
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PostPosted: Sun Oct 02, 2022 11:08 am    Post subject: Re: Cleaning Type 4 AMC Head Flashing with Engine Installed Reply with quote

Bonesberg55 wrote:
I'm a lifelong Rambler guy and I don't recall them ever making VW heads! Laughing Laughing Laughing

AMC and AMC are different companies but you knew that Smile

American Motors Corporation of (USA)

Amadeo Marti Carbonell S.A. (Spain)

They make the head castings but it is up to the importer to add valves, springs etc.. That is why the quality varies between companies that sell the heads.
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