Overbored flathead experiences ?

Hey guys,

Since I have not been able to drive my Merc yet..., it has been sitting on the body shop for the last 7 months since the engine was rebuild (hopefuly it'll be painted and ready on Feb.)

I have some questions:

The 255 was totally rebuild with new parts all over, Egge pistons, french rods, etc, etc.
It was hot tanked for 2 days.., though rust just kept coming out endlessly. I think Im gonna have the radiator flushed and/or redone several times until rust dissapears.

Anyway, cylinders were bored .040

Im afraid Im gonna have to be really carefull about temperature.
What were your experiences with your overbored flattys ?


Thanks a nd happy new year for everyone
Diego
PS: I already have several bottles of distilled water, water wetter and Gunk water pump lube

 

Mercjoe,
I am .125 over. New radiator. I spent half a day rodding and cleaning out the block before I sent it out to be shake and baked. It is incredible how much junk you get out of these old blocks, sand, rust, dirt and even a piece of wire or two. I have run for two sumers now and no overheating problems. Electric fan doesn't come on unless I'm idling or in traffic. Never overheated. Oh, I also use stats.

Just my experience.

Fourdy

 

Thanks Fourdy,

And I thought .040 was the limit

D.

 

I run a 4 X 3 3/8 motor with Offy heads, it runs about 170 until it gets in heavy traffic on a 95 degree day, then it will climb to 205. I have Speedway water pumps, and stainless washers with a 5/8 hole in place of thermostats. If I used it often in cool weather I would put in 160 thermostats. I think half the heating problems in those motors was the ignition being off.

 

Some more ?

 

.040 has only scratched the surface.

 

3 3/8 is '187 over it ani't gonna run hot on you.Looks at some of the old posts on block cleaning.

 

btt

 

Flatheads are a COMPLETELY different game than modern thinwalls. 3 3/16 blocks will almost all go safely to 3 3/8, and many have raced at 3 7/16. 3 5/16 is considered a conservative hotrod bore. With engine at .040, you, your kids, and their kids cn rebuild the thing several times each,safely. Then, your great-grandchildren can press in some sleeves and start over.

 

Sizes that are or have been commonly available and used for 3 3/16 motors: Oversizes of standard to 080, and an odd large oversize for factory sleeved engines with sleeves removed
3 5/16, sometimes in oversizes...
3 3/8
3 7/16.
Oversizes used to be available for the big sizes, too. I have some oversize rebore pistons for 3 7/16 in the ba*****t somewhere!
New sizes are appearing now, because people are creating new sizes to use modern metricpiston ring technology.

 

I pulled apart a 221 that had a lot of miles at .200 over... people say i should get it sonic tested

 

Thanks for all the answers guys.