I'm going to build a flathead for my 31 roadster. Need some advice. I've got a good crack free 53 8cm block. I'm planning on boring it 1/8. To give me 276ci. I was going to use cast aluminum pistons from speedway, potvin 3/8 cam, chevy valves, navarro heads and intake, was also contemplating running edelbrocks as well . I'm going to run a 39 trans and a 40 banjo rear. Does this sound like a good plan? Tell me about your engines and things you would do and things you would do different. Also should I run dual carbs or a tri power? Posted using the Full Custom H.A.M.B. App!
IMHO one needs to be conservative to have a good running flathead. A stock Ford is Plenty for a Model A, the Mercury even better. The more material you grind away it the thinner it gets which means the more susceptible it is for cracks. These are 61 year old engines at the least, why grind life away? So bore...I would use the smallest piston I could and be in spec. If you are lucky enough to have a bore that cleans up to STD, by all means use them. You have a 4" stroke with the Mercury so there is really no need to milk out that few CID with over boring. Plus casting was not perfect on those days, add that and rust, it can be real easy to cut into a void or weak spot that can crack the cylinder. Valves... the the thicker this area is the better. A crack here is almost a death sentence for the block so this area needs to be thick as possible. I would hold off on oversize valves if that means removing material in this area. Heads.., My first choice would be the EAC stock Mercurys. Those heads on my stock 50 239 pushed my 50 Coupe around very very well. Should make your model A a rocket in the vintage sense. Cams.. I ran stock and it was great but a 3/4 should be nice. You may want to go with adjustable lifters.. simpler to adjust. Intake...2x2s 94s or 97s. I ran a stock single 94 and the car was powerful...again for the era. The small 4bbls do well. In a 31 I would try a 2x2 slingshot if I could find one. Exhaust... Of course headers or dual Fentons.
Unless you are building a "race horse" flatty, keep it as stock as possible but with adjustable lifters. This engine is a stock 239 inch 8BA with , Fenton headers, early style alum heads, alum. intake, electronic ignition, Johnson adjustable lifters and a 390 Holley. 1/8 bore is a waste of money and creates more potential problems, like overheating, although some will disagree. Remember , a crack free block is hard to find these days
From what I have read (no personal experience) the later flathead is slightly longer and more difficult to install. You might consider a pre '48 flathead or at least be prepared to deal with the problems you will encounter. The '40 rear end sounds good but if you run rear fenders it may be too wide. If I was running a late flathead I would consider an open drive but must admit the closed drive banjo looks great. Charlie Stephens
Agree with the other comments. I wouldn't bore it unless necessary. The thinner the wall, the more prone to overheating.
Thanks for the advice. I know big bore flatheads aren't recommended I'm pretty sure my block was rebuilt a couple times before so I was figuring it would probably end up being an 1/8th over. Im going to have my machinist check it for sure. But I don't plan on boring more than needed Posted using the Full Custom H.A.M.B. App!
Ford Heads have smaller combustion chambers then merc to offset the difference in cranks. Common to see EAB heads on a merc motor to bump compression. As for other heads most are about the same. If you study out the combustion chambers the kogels have the least amount of material machined out, but they are pretty rare. Your sharps and navarros are going to be next, then edelbrock and then offenhauser. 2x2 will suite you better than the 3x2. Set your budget before you make to many decisions. I built a 276 with Navarro heads and intake along with 2 97s and am around 3k in it. But I machined my own block, the 97s were a gift, the heads are used and only cost 475. Chevy pro flow are a good choice. You can study out this thread making improvements on flow and do your self a lot of good. http://www.jalopyjournal.com/forum/...to-nuts-pictures-details-and-opinions.420484/ I had an open drive 3 speed I was going to use but battled with the idea of a t5 for a long time. all the research I did pointed towards the t5 being about the best thing you can do to the flat motor. I also have a Rodsville QC...
If the block is good, I would use it. The engine pictured is a 49-53 with early heads and timing cover. It also has early water pumps and front pulley, making the overall length the same as a early engine.BTW you will need to use the 48 and older camshaft.
"...the later flathead is slightly longer and more difficult to install" Overall block length (adding in the separate bell on later ones) is the same, so easiest course is to build with early cam, front cover, and pumps. This saves substantial space for early Fords with short engine compartments, and the '42 type distributor is as good as and much cheaper than the necessary aftermarket replacements for the wretched '49-53 distributor. You can use the early heads, too, as on most early rods and racers. The tricks to all the parts swaps are well covered on here, all easy.
Yes I was planning on running a hood top here is a picture of my roadster Posted using the Full Custom H.A.M.B. App!
Consider flipping the firewall? gains like 4 inches I think. http://www.streetrodderweb.com/tech/1305_1930_ford_model_a_firewall_flip/photo_04.html http://www.jalopyjournal.com/forum/threads/tech-flipping-a-model-a-firewall.248034/
Bore the damm thing ! .125 is not that much for a flatie. Back in the day we usually went .187 on the bore and offset the crank pin for 1/8 stroke. That gave 296 cid. Had one built that way with 3X2s in a 1900 lb RPU ,use to hunt vettes with that ! I also was running about 9.5+ compression being we could get real fuel then. Use 94s for carbs cheaper than 97s and work just fine. I always ran Edlebrock heads -manifolds.
I don't really want to cut my firewall out. I would if i had to though Posted using the Full Custom H.A.M.B. App!
When I stripped my block and was getting ready to take it to the machine shop I took two scrap pieces of 3/4 plywood staked on top of each other I then picked up the block and would drop it from 5" to 6" off the ground at different angles/ upside down/ front words/ back words, You would not belive the casting sand that will come out even after 60 plus years. Never had a problem heating.
Your setup sounds good. My setup: 59L block .125 over, Merc crank, Isky Max 1 cam, adj lifters, Offy heads, Thickstun PM-7 w/2-97s, Fenton headers, Mallory dual point. Sweet flatty - nice idle and low end - strong to 3500 - never felt the need to wind it any further. 39 trans, 3.78s/Columbia. Pulled the Grapevine in OD on a 90 degree day and didn't get over 190.
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