All, In the planning phases of my engine build (1950 Plymouth 218) and after a couple informative conversations with Cory (Moparsled) and Mark (Hudsonator), have some good ideas on what I need to do to squeeze some much-needed power out of the little flatty. Cory & I were discussing the subject of quench on these motors, and since I'll be resurfacing the deck anyway, I might as well go ahead and see if I can't get close to an 'ideal' quench. Crude measurements show a deck clearance of 0.016" (piston sits 'in the hole' 0.016"). I've heard older MoPar 218's had a significantly higher clearance (forgive me if my terminology is not up to par)...upwards of 0.080, so maybe the decks got shorter over the years (my motor is untouched, stock bore x stroke, so I highly doubt the block has been decked). Can anyone confirm what the stock deck clearance is on the 50's Ply 218? I'd also like to hear from anyone that's decked these motors...how far can you go? 0.020? 0.030? Looks to me like the coolant passage runs about 5/16" (0.3125) below the deck surface, so I don't want to go too thin, but would like to bring the piston up out of the hole to maximze quench. Finally, does anyone know the compressed head gasket thickness for these motors? Part #'s i've come up with are; Fel-pro 7564c and Victor 1059c, but cannot seem to find specs on these gaskets via-an internet search. My old used copper gasket measures about 1/16 (0.0625) but I'm not sure how much more it would compress when mounted & properly torqued. All help is greatly appreciated! Thanks! Gary
I have a block all cut to pieces that I can measure deck thickness on. (I cut it up 'cause I wanted to see where the water was around the ports)
pop a 230 crank and pistons in it..stroke for a little more horsepower. P15-d24 probably has your specs or allpar.
Gary, check out www.p15-d24.com It's a site dedicated to these model PlyDo's with lots of info about sideys. As for your copper head gasket goes, I'd hang it on the wall and get a new Felpro one. But if you need to resuse it my advice is to anneal it first. I've heard you can shave .050" off both the deck & the head. I haven't done it to mine (yet) but I have a 201ci engine that I might rip the head off and take 040" off it. Remember, they only had like 105psi compression @ 70°F, but they have plenty of well located head studs so they should handle more. You can also do what frankie47 said, stroke it with a 230 crank & rods. Then it'll be a 230. But that'll give you about 5 more HP so it's a bit of a WOFTAM in some respects. You're looking for 40 or 50 more gg's. A friend of mine has a 250ci "big block" in a historic open wheel race car. Runs 3x1 carter carbs, racer style extractors and about 10:1 compression. In an identical "road" car he has a small 4 barrel Edelbrock carby on it but with same specs otherwise. They both fly. His race car does 140mph easy. My 48-53 manual has some good data. I can scan the pages and send them to you if you're interested. Louie
Good info here, thanks for the replies! (posted this on the P15-D24 as well...it's a wonderful resource!) Sorry for being so vague in my initial post...I'm building the engine for my era-correct '50 Plymouth stock car project, so the goal is to stick to the specifications found in the 1950/1951 NASCAR rulebook. Said rule & specification book mandates that bore & stroke be unmodified (0.030 overbore permitted) and that camshafts and flywheels be unaltered. It also specifies the use of "stock" cylinder head, ignition, carburetor, valves, valve springs, and manifolds, but here's where it gets interesting; in these specifications the word "stock" is defined as meaning any part which is listed in the manufacturer's catalog for the year/model/type of car entered. I say this is where it gets interesting because reading between the lines suggests that alterations may be permitted to cylinder heads, carburetors, and manifolds, provided that they are factory original parts, cataloged to the year/model/type of car entered, operate in the same fashion as designed, and retain original appearance. Primary source material (books, magazines, and personal correspondence with 'old time' drivers & mechanics) supports this...Johnny Mantz's Plymouth which won the inaugural Southern 500 sported Grant piston rings (among other things), and Smokey Yunick recalls watching a young Richard Petty polishing the ports on 'papa' Lee's flathead. George Asche (the near-universally recognized guru of all-things MoPar flathead) told me over the phone this evening that Cotton Owens' Plymouth was modified, in part, by decking the block 0.040". So...230 crank/rods are out; not cataloged for the year/model/type. Ditto on dual carbs, split exhaust, 'big block' DeSoto/Chrysler engine, and reground cam (although I wonder how they might have handled a Canadian Plymouth with the 25" block). That being said, I think more power can be had by cleaning up the intake/exhaust ports, and by decking the block to achieve better quench (thanks to Cory aka Moparsled for bringing this to my attention). I spoke with Mr. Asche tonight, and he maintains that these cylinder heads may be milled up to 0.125" without valvetrain interference (while using a stock lift cam, of course), but I'd probably be more comfortable with something on the order of 0.050-0.070 depending upon how much I decide to deck the block. He also told me that every head gasket he's seen for the MoPar flatty is in the neighborhood of 1/16" in thickness. On the subject of decking, Mr. Asche advised me to consult with my machinist...he said he had never decked a block that far and might be concerned with cutting too far into the valve seats...can anyone speak to this? I am also told that retarding the stock cam 2-3* might produce a little more power in the upper RPM ranges, but have no idea on how I'd accomplish that...ideas here are welcome! Cory, thanks for the info from the inliners forum...I'll have to check that out.
I'm not sure what Mr. Asche is after when talking about taking material off the valve seats. The seats themselves are hardened inserts, so there's no concern of cutting past a surface hardening. I can see where it would lower the valve closer to the tappet, but there's plenty of adjustment there, so.... Also, I guess the valve spring pressures would decrease, but that's easy enough to remedy, and with a stock cam you shouldn't be anywhere near coil bind. About retarding the cam--he's talking about degreeing. In order for us to do this you must slot the holes in the cam gear, as there are no aftermarket offerings with multiple holes. Mine was supposedly retarded 4 degrees by the builder, though I have zero trust in his work at this point. What you have to be aware of when milling the head is that too much milling can choke the flow through the transfer slot, thereby negating any gain in static compression. If you can't suck in a full air/fuel charge you're not REALLY achieving your static c.r. sorry about the fuzzy pic, but, is this the water neck you're after? This one is on a '52 Plymouth engine.
just one thing to keep in mind with the 230 crank.. its got a 5" stroke.. and im sure that 218 has a pretty big ass stroke too.. it tends to balloon out the cylenders... you should do fuel injection and a turbo lol...
Lol! That's exactly what I was thinking. I believe that's the t-stat housing...let me check my parts book to confirm that they're the same. Thanks again for all the help!
Can't comment regarding the copper head gasket. I have on in my trunk as a just incase deal. I heard they were used in marine applications. coolant sealing should not be an issue if your are sticking to non pressurized system. A little sealer on the block side should adress any concerns if everything is safe and true. Georges limit of .090 off is in regard to the limit of "regular gas" any more needs premium. I know the 230 piston sits up higher in the culinder at tdc than on the 218. On my 230 I took .010 off the block and .040 off the head. My machinist ( who was heavily involved with MOPAR and Hudson L 6 in the 40's and 50's, related acouple thing that were done back then on engine run in modifieds. No relieving, but a smoothing of the ramp between the valve area, and the space over the piston. Plus a "V" groove running between the valves from a point on a line between the stem centers to a point 3/16ths of an inch from the opposite cylinder wall. Supposed to induce a swirl inthe incoming and outgoing gasses. I gues its a hot thig to do with todays 4 cycle go cart and 1/4 midget motors. Apparently something similar has been recently patented know and the singh groove. My Cr with the .030 over 230 and the mods above is 8.5 to 1. Not a lot but certainly more squeeze than the 218 6.7 to 1. Here is a shot of the 230 piston at TDE. Just be care full of valve to head interference.
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