Good morning Hambers. I did a search first before posting my question. A lot of information but what is the preferred method. I pulled my plugs on my very recently rebuild 8ba 53 flathead. Merc crank, .125 bored, L-100 cam, 3x2 Stromberg 97's and high compression (Merc 9.0) Edelbrock older heads. Head gaskets .060" One side of the engine has apparently less valve clearance than the other. The valve clearance without plugs installed .046" lowest to .070" on the high end. The other side was all in the .090" or more. I am now experiencing the exhaust valve closing the plug gap on those four cylinders. The plugs I am running are NGK B6L the reach is .437". 1. Should I switch to NGK B6S? The reach is .375" 2. Use plug indexing washers to pull the plugs back .030"-.060"? 3. Use thicker head gaskets and drop the compression some? I was on board at the beginning of the build for using thicker head gaskets but they were and still unavailable until Oct...... The block was mistakenly decked too much on one side. I thought I could get away with it but you know the story. Long winded question I know. I appreciate any help you experts have.
On my 59AB with Eddie Meyer heads, I need to index the plugs so the electrode runs north/south so the electrode clears the valves.
I always fit heads on flatheads on an individual side by side basis. This is especially important with used aftermatket heads; you never know what was done to such heads in a previous life. I think your best bet would be to remove the heads, check the plug reach, and modify them for proper fitment. The spark plugs should fit with the base of the plug body even with the head surface, like this : Please note that this is an extended tip plug in an Edmunds head that has the spark plug relocated away from the exhaust valve. You cannot run extended tip plugs with other make heads; this is to show the relationship of the bottom of the plug body to the cylinder head. However, it's the only picture I have handy. After you determine the proper reach plug, you should individually fit the heads for proper plug clearance and piston clearance. You should shoot for '045"-.050" clearance over the piston crown and at least .060 over the valves (depending on the cam lift). This is done my measuring these clearances (I use foil balls and a used head gasket). The heads may need to be milled to get the proper general clearances and then relieved with a die grinder to bring all of the clearances to the proper range. Please note that each kead should be fitted individually; you just can't "take .060" off and expect it to work. I believe that getting the head clearances (and thus the quench) correct on a flathead Ford is the single most important thing you can do to improve power AND fuel economy. If you need more information, check out the references produced almost 100 years ago by Sir Harry Ricardo.
I had to use ARP hardened washers on my Cyclone heads. They are .120" thick. Solved the issue with too long of reach.
Yes Flat Jack. They fit flush like they are supposed to is why I went with the .437" reach. I know backing them off isn't the best idea but for now it might serve the purpose for now until I take the heads off and do it right.
Here is the block showing the deck was cut down to the harden seats unlike the other side. Piston clearance and valve clearance were ok but never thought about the electrode sticking down over the valve. Rooky mistake for sure.
I had the same issue on my 59a motor. One side tighter piston clearance than the other. I ended up stealing a set of washers off an old set of plugs and just doubling up the spark plug washers on just the one side. Its ran perfect since.
Update: I just found some Autolite 295 in town which are cross-referenced to NGK B6S. Same plug as a NGK B6L or Autolite 216 but with a .375" reach. That will give me .060" of extra clearance. I will give them a try tomorrow and report back. I just hope I didn't bend any valves. I don't think so, it just bent over the electrodes a little. Thanks for all the input guys. You are a wealth of information for a newbie and messing with flatheads.
Here's what you can easily do and it will work perfectly. First the NGK plugs are superior to the Autolite as mentioned in post #9 just double up on the spark plug washers take them off some old plugs. Put the additional washer on all eight plugs your engine will run perfectly with no issues at all. Just to let you know that's exactly what I do with my record setting all out Ford flatheads which have all gone well over 200 MPH. The reason you have the issue on the left side is due to the angle of the seats from side to side on a flathead are different. The left side valve actually sits a bit higher on the seat due to the angle difference. Also the reason you can see the top outer surface of the valve seat has been cut a bit during resurfacing. Ronnieroadster
Now that make sense. The piston clearance to head was the same side to side. It was only the valve clearance that was different. I do now have extra washers to try. Thanks!
The double washers worked great. Both banks sound even now and no more poor firing plugs. Thanks guys so much!!!!!!
Good info fellas- I had milled stock heads on my 59a build and measured the swish & valve clearance but did not check the spark plug clearance! (L-100 cam) The ground straps contacted the valves enough to close the gap but not damage the plug or valves. I used .040 indexing shims to gain the clearance needed. It seemed to run OK. fast forward to today: I am swapping out the stock heads for new Navarro heads. Set the squish @ .040-.050, (milled the heads .040) Valve pocket clearance is good but the electrode is still is to deep and will be to close to the valve, needs .050. By using shims it will raise the plug but it is about 1 thread up into the head causing shrouding of the electrode not having full exposure. Q: is the NGK B4L the shortest plug available??? Plan A is to shim the plug to gain .050 clearance from the valve & to mill the chamber to expose the electrode in the chamber. Q: Can I taper the chamber to the plug hole or should I mill the entire chamber? I will gain a little bit of CC volume but have better combustion by exposing the electrode. Am I on the right track? Thank you in advance!!! TMAG
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