Getting ready to take my '39 flathead over to the machine shop but before I start tossing money around, I want to ask the collective brain trust a few questions that keep me up at night. It's a really clean motor to start with, was used to power a hand-clutch driven water pump onside a power plant it's whole working life then retired to a heated shop where it lived till I bought it. Other than being .015 over it appears to be 100% stock. I will be running a two carb setup w/ 94's(angling for a Weiand high rise) adjustable lifters headers stock Canadian aluminum heads merc crank stock ign. I plan to run the Isky 400JR, will stock replacement springs ok? Am I alright to leave it at the current bore (if it passes inspection by the machinist)? Should I be prepared to work the heads over for clearance/compression? Anything else I should be on the lookout for in regards to common problems a guy may find himself running into? While it's not my first flathead, it is my first time having something built for "go". I know it's been covered to death but I do appreciate the input from more experienced members. Thanks guys/gals, have a good weekend.
I definitely believe that reworking the heads (either stock or aftermarket) is one of the best thing you can do on a flathead. I built a couple BH (Before H.A.M.B.) that I just bolted on a set of Offenhausers and called it good. They ran OK, but just didn't have that crisp "snap" the last three I have done had. I spent a bit of time getting the "squish" to .050" (which also brings the compression up) and, in my opinion, it really paid off. Maybe it was the Edmunds heads that, with their relocated spark plugs, allows me to run extended tip plugs, but I really believe it's a little bit of both. Oh yeah; it's fun too. It made me feel like a real "hot rodder".
My best advice, go to Lowes and buy biggest wheel barrel they have, take to bank and fill it up. When it is empty take it back and fill it again. That should be enough.
Three things from my flathead experience: You need better ignition. You need an electric fuel pump. Proper quench makes a big difference. Pete
Three comments on the above : 1. Depends on the era of the flathead; properly set up, an early distributor set up correctly is hard to beat. On the later models ('49 to '53), you need a better setup than the stock "Load-a-Matic" if you are going to modify the engine. 2. Not necessary if you have everything else set up properly. 3. See? I told you so.
Zip over to Fordbarn and post your question for even more advice. Be clear in your mind as to what it is that you desire in your build BEFORE you start spending the dough. Have a plan and stick to it. Personally, I would use an electronic ignition no matter what you build.
Just as a point of information, the last flathead I built (about a year ago) cost me just about $2100. It is a 258" 8BA (stock stroke, 3 5/16" bore) with .010 under rods and mains and an Isky MAX-1 cam. It was also balanced. The key to the cost of the build was a set of .125 over pistons (with pins and rings) I got from Speedway on closeout for about a hundred bucks. Judicious purchase of used speed equipment (Edmunds heads, an old Mallory flattop, and any of several intakes I have collected over the years) contributed to the low cost. It also helped that the machinist at the local NAPA used it as a "fill-in" project. (I think he is trying to build his reputation as the local "flathead guy"). If you are careful and patient, the "wheelbarrow theory" posted above doesn't have to come into play. I will say that I already had a good block that I had owned for over 20 years. Without a block, these numbers are "out the window".
First have the blocked magnafluxed to check for cracks but that will not always show if a block has cracks. Many feel that pressure checking the block is also a requirement. Based on his inspection of my 8ba block my machinist felt pressure testing wasn't needed. Engine has over 5,000 miles with no issues but its up to you and your machinist. Regardless, after you determine the block is worth rebuilding take it home and clean the bejesus out of the water passages with long rods, screw drivers, whatever. You'll be amazed how much casting sand and other crap will come out of the block. Depending on how much if any you will need to bore the block you may need to sonic test it to insure the block can be bored the necessary amount. When it comes to parts buy the best you can get, preferably USA made. I bought all my engine parts from Red's Headers in Thousand Palms, CA. High quality parts and fair prices IMO and he was close to me but there are other reputable suppliers who can supply what you need. Stay away from Patrick's in Casa Grande, AZ (if he is even still in business)
A couple of things I didn't see covered. One is has this machine shop done other flatheads? Is this a referral from someone you know and trust who had one built and it came out well or does the shop have a reputation for doing flatheads well and they are the go to guys in the area? Second is are you planning to install and fire the motor right away? If not then have them do the break in while they have it so they have to deal with any problems or issues they created. You don't want to go through what I experienced with a shop who claimed they were great with flatties and then proceeded to screw my 8BA all up. The only thing they did right from what I can tell is the actual machining. I had to tear the motor all the way down and reassemble it from scratch as I couldn't get it to fire for break in. Cam gear was on backwards, rods and caps were not matched and not in the correct cylinders... it went on and on... plus I got the privilege of paying for the porking I took!
You might want to think twice about using a 400 jr cam. It might be too aggressive for street use. I have one in my roadster, kinda wish I didn't but I bought the motor rebuilt with it.
Fine so far. The car it is going into isn't finished yet, so I have only run it on my test stand. It starts fine and idles well. The only thing other than that is when I had the throttle linkage set wrong after changing carburetors, I started it and it took right off. I shut it off as quick as I could, but it left the "tell-tale" on my tach at 5500 RPM. I have never seen that with a stock flathead. I corrected the linage problem, restarted it, and everything seems fine (luckily).
I run stock Ford crab ignition on all my cars. They are a dual point design that Mallory actually used as a guideline when they developed their spark sticks. I like to upgrade to 8BA valves and guides...a lot better and cheaper then the early stuff. I also like to upgrade to the merc crank. But you'll need Merc pistons as well. If you want to keep the bore that may not be the road you want to go. But those 255's run a heck of a lot stronger then the 239. For cam, I like the Winfield SU-1A. Good street cam and has great pull. sounds good but has good street matters. But cam debates always boil down to your ultimate goal with the car/truck and also everyone has their favorite and least favorite. Drill the lifter valley if running adjustable lifters to hold them while adjusting. Keeps from having to use the goofy wrenches and have 3 hands with 12 jointed arms. All above just my opinion. Do what you feel is best and you'll do great
Sorry, not sure I follow? Will I have difficulty finding new pistons? I know they're different than the ford pistons but I was hoping I'd just need .015 over merc slugs and I'd be off and running? I had inquired about the Winfield cam when talking to the shop who was gonna do the grind and he had to check into his records to see if he had that profile. I pretty much want it to sound like your roadster haha.
I assumed you wanted to leave the bore so you could reuse the pistons. Yes, you can put Mercury pistons In it if anyone offers a .015" over (and the cylinders are good). On top of the crank and pistons, you will need 49-53 rods and main/rod bearings as well. The crank gear on the 32-48 is cut backwards from the 49-53, so swap on an early gear if you use a later crank. On the cam, I had Delta Cam in Tacoma grind my SU-1A and refurbish my Johnson lifters.
Wait a minute. He said he has a '39 engine. If it is a Mercury (239 ci) this talk of a 4" Merc crank and .015 over pistons makes some sense. However if it's a Ford with a 3 1/16" bore he will absolutely need new pistons. Either for a 4" stroke and 3 1/16+.015 bore (do they even make those?) or he will have to bore the block to 3 3/16" and get standard Merc pistons. I would expect it's a Ford, since I don't believe they would be selling the "new" Mercury for industrial use in 1939. I could be wrong.
A bit of clarification is required here. I think that most people would assume that you are talking about a '49-'53 Mercury 4" stroke crank, since the earlier Mercury crankshafts are identical to Ford crankshafts, and nothing special. If this is not the case, I'm all wet. If indeed you do have a 4" stroke crank, you are going to need new pistons, as I mentioned above, for a 4" stroke and 3 1/16"+.015 bore. I think that these are not generally available and would probably have to be custom made and would be quite expensive. In this case, I believe you would be money ahead by boring the block to 3 3/16" and get some stock Mercury replacement pistons. I don't have much experience with 221 ci engines, but I think that an 1/8" overbore is about the limit for them, so you should have the block sonic tested to see if it will go that far. What you are planning to do is starting to sound expensive for a limited gain.
ditch the 400jr. too much cam, no bottom end. use the isky springs (185G) and go with a 88 or 77 cam so you don't have to do any head work. i think that the max1--a great cam--will require some of that.
Once you determine the block is not cracked, sandblast the water jackets to clean them. Spend the time here and you will have a much better chance at a cool running flathead.
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