1931 model a engine
 

Good afternoon
Relatively new to Model A, but I recently removed the head off my 31 Model A coupe. I’m not really sure what I’m looking at as far as valve colors. Carbon buildup on pistons I have enclosed a photograph and was searching for some opinions as to what people may think.
Is the engine running incorrectly or correctly according to colors? Is it running poorly according to colors anyone ever take a head off see what the engine looks like open for suggestions.
Thanks all

Re: 1931 model a engine
 

Correct fuel mixture the exhaust valves will have a tan color like yours to me it looks like it's running very good little bit of carbon just means there's some time on the motor.

Re: 1931 model a engine
 

What prompted you to remove the head?

Re: 1931 model a engine
 

When you reinstall, use a graphite gasket and follow the torquing directions carefully.

Re: 1931 model a engine
 

Looks good to me also.

Re: 1931 model a engine
 

Normal looking. You can clean it up if you want. Use a scraper and not a wire brush as the bristles can break off and cause damage. Clean the block and head surfaces where the gasket sits and as a final clean wipe with acetone.

The pistons should not have perceptible movement side to side or back and forth. Check at the top of the stroke. The valves should have a uniform color where they meet the seats. Do not scrape these areas. There should be no carbon or other deposits at the seating area of the valves. There is lots more to look at. Get some help from a Model A person in your club.

Post your location or let us know what it is in a response.

Re: 1931 model a engine
 

Water seepage out exhaust manifold side of head ..and bubbles in water at radiator neck. Led me to believe blown head gasket ..chasing anyway .
Car sat for 25 years been running it for a year now .so looking to tighten and freshen things up a bit ..thank you all for the replies and information.

Re: 1931 model a engine
 

I re-torque the cylinder head bolts,nuts every time I change the oil. Making it a part of the oil change process keeps me on a regular schedule.

Re: 1931 model a engine
 

Usually that would indicate a leaky head gasket, so you were correct to take the head off. Clean up the mounting surfaces as I said and use the graphite gasket as Bruce said. Use the spray copper coat gasket cement. Check to make sure the head mates to the block well. There should be no more than 0.002 inch gap anywhere when you lay the head on the block without a gasket.

Re: 1931 model a engine
 

Since you have the head off, this would be a good time to get a good straightedge and check the head and block for flatness. I use 0.002" as my standard. Check it with the straightedge going both long and cross dimensions, both head and block should be flat everywhere. Most likely item to get a variance is the head, if it's not flat then get it decked at a machine shop. You can't deck the block without completely disassembling the engine, out of the car. (Checking the head on the block without a gasket is a good first step but will only tell you the perimeter of the head, and won't evaluate the area between the cylinders).

BTW, like others have said, those valve tops don't look out of line to me for a used engine. Look and feel closely at the edges of the valves to see if you see/feel any pitting, cracking or burning. You can put a small mirror underneath the valve with it fully open to see if you see any burn spots.

Many folks here recommend the Best 509G graphite head gasket (available from the usual Model A parts vendors) with copper spray (available at your local NAPA auto parts store).

Re: 1931 model a engine
 

Hmmm
Pictures are not that clear however the 4th cylinder is showing much leakage thru gasket and there is a mark between 3 and 4
I hope it is not a crack or burnt groove

J

Re: 1931 model a engine
 

Another way to check the flatness of the block and head is like

Terry Burtz show in the builders guide.
"Place short pieces of oiled Plastigage around various locations on the cylinder block, install the questionable head, and tighten the nuts to 20 lb-ft in increments not exceeding 5 lb-ft as described in “Head Torque” below.
Remove the head and measure the Plastigage. If your head is not within 0.002 inch of being flat, we recommend that it be resurfaced, or you can use a Best 509C head gasket that is more tolerant of flatness."

Re: 1931 model a engine
 

Thank you

Re: 1931 model a engine
 

You are passing some oil past the rings, but all the colors look good, and it should run for a lot more miles.

My opinion,

Chris W.

Re: 1931 model a engine
 

As long as the head is off why not put a high compression head on it?
You'll love it......

Re: 1931 model a engine
 

Yes, the power increase is very apparent.

Re: 1931 model a engine
 

With the high compression head, just don't use gasoline from 1930.