new guy with two flathead questions, if I'm allowed

danny1940

danny1940

Member
I newly registered to this forum but have lurked for many years. My name is Dan. I read the sticky about the purpose of the Barn, still a little confused but I think my questions are more appropriayely answered here than on the HAMB. I have a 1940 Ford tudor. Built it about 12 years ago, stock body. I run an 8BA with a merc crank, dual 94's, mallory, Max1, offy425 heads and a bunch of other stuff done to keep my flathead reliable and driveable. I had some head gasket seepage so I pulled the head. For the longest time I have experienced what sounded like light pinging in the higher RPM's. Timing, etc., have been checked many times and are in spec. The head, plugs, pistons don't show any signs of pinging or detonation for that matter. I have a set of Mercury heads. Can anyone comment as to whether or not I will notice any real difference in performance if I swap out the aluminum heads and use the Mercs? Also I use NGK B6-l plugs. These plugs don't reach the bottom of the threads in the head.Just found out when i pulled the head. If I stay with the OFFY heads can someone recommend a plug with the right reach? I experienced this pinging type sound with other plugs as well but don't know if these had reach issues as well. I'm leaning toward the Merc heads so any advise is appreciated. My 8BA for the most part has ran great. Thanks, Dan
 
Last edited:
A couple things to try.
Retard the spark about 2 degrees and try it...
Plug threads showing in the open is not a good deal.
It can cause pinging.
Try the right length plugs.
Read the plugs after a clean shutoff from a hard run or a hard hill climb.
Being a little lean can cause pinging.
 
AN answer to your questions,no you won't notice any change w/merc. heads unless you run wide open most of the time & then only a little. plugs not covering the threads in the head could lead to pinging because the threads will get red hot
 
Before making any changes to what you already have, if you are not already doing so fill th tank with high test gas or throw in some octane booster to see if that makes a difference. At least this may give you a direction in which to proceeed.
 
The last thing I would suggest is to LOWER the compression ratio with the Merc heads. This will reduce fuel economy, increase engine temperature, and reduce power. There have been some good comments made regarding the excess threads which should be chamfered out of the heads, using higher octane gas to determine if that might help, and working the timing back 2 degrees, at a time, to see what it will require to solve the "pinging". It has been my experience that all Flatheads gain a small amount of power, on the top end, if timing is reduced from what provides the maximum torque. This is another vote for a good, workable, vacuum advance mechanism which can contribute to cruise efficiency while allowing for a good top RPM, wide open throttle, calibration of the centrifugal advance.
 
The "points" of the threads can get hot enough to start the reaction in the combustion chamber. If you have ever welded aluminum you will see that it can become a light red color just before it gets greasy.
 
With these Offy heads, I counter bore the plug holes with a 45Deg tool I leave enough threads for a YF12 or equidistant power tip plug. Like John says you have an ignition problem with the load a matic.
 
You should deal with the thread problem first to see what the results are.Make one change at a time so you don't loose the rabbit.Chances are you will get favorable results with thread fix. Some times it is difficult to deal with detonation and pre ignition.
Another 2¢ to work with.

Ronnie
 
Thanks to all of you who replied. I'll first get the plug length issue resolved and try setting the timing back 2 degrees at a time. I'll try boring the threads or chamfering if I can't find a suitable plug. Just for clarification, I've always had to run on premium. Thanks again. I'll let you know how I make out. Dan
 
Last edited:
Another note would be on the Mallory , most came with a "dreaded" chevrolet curve , way too much advance for the flathead. Would also cause a ping.....i would be glad to check er out while you are down.......
 
Quick update. I've took my heads to a hot rod buddy of mine who is a fabricator by trade. I did some research, used the advice from you guys and we came up with a plan to eliminate the extra threads and unshroud the plug area. Bubba has my distributor for a recurve. My fingers are crossed and the excitement of resolveing the pinging issue is growing. I ordered an ARP head stud kit from Reds, so I should be good to go. I'll let you know how it ends up. Thanks again for the advice, Dan
 
nice sedan! never knew their was a "question limit" here? as a old mopar guy i find the ford tech here pretty interesting and usually correct.
 
I had a post on the spark plug issue a few weeks ago with the Offy 8BA-425 heads. What I have found is the NGK B6HS spark plug has a 1/2" reach, non protruded tip. Tried on in the head and looks correct.
 
55 dude, My first post wasn't about a question limit, I was questioning if the Ford Barn addressed problems with modified motors having read the sticky re: the purpose of the Barn. What I learned from my first post and questions was that you get great advice from an experienced bunch of Flathead lovers. What I also learned was that after getting everyone's response, my plans to change a head gasket and just freshen up my motor for the season turned into stripping the motor down to the short block, sending out my distributor, removing the grill and radiator, changing water pumps and discovering a few other odd ball things to fix up since I had everything apart. The truth be told, I'm glad I asked. Take care, Dan
 
You must log in or register to reply here.
Back
Top