Hey Guys, If you've been following my posts, you've seen that I'm going to be running a low boost (at least for now 5 PSI or there abouts) 4-71 supercharger on top of a 255 Mercury flathead that right now is in good, stock shape. I'm of course doing this on a budget, and am not totally sure that the flatty is all used up, and the blower system itself seems to be doing well in the budget department. Right now, the heads are off the motor. Everything looks in good shape, no damage to the cylinder bores, a couple have a bit of surface rust but will come off with a piece of emery cloth, just that real fine rust (and only just a bit, a VERY little bit). I know it's not a scientific and probably doesn't mean ****, but I put some motor oil in each cylinder to see if it would seep past the rings, after a 1/2 hour nothing, all the oil is still there. Hand cranking it didn't cause it to get past the rings either. When I turn it by hand, it is smooth as silk, really. I know it's easy since I'm not building compression, but the movement is very smooth, there isn't any lateral movement that I can tell. I do have to replace the valves and have the seats done, I have an exhaust valve that suffered getting burnt (I was planning on new cam, lifters, springs, and valves regardless). The older gentleman I bought it from REALLY knows his flatheads; he had a barn full of vintage speed parts that HAD to be worth at least $50,000, and a pair of absolutely goregous Model A's. He said this was probably the best engine he had laying around and that other than the valve, it only had like 10K miles and ran great. I trust him as he had no reason to lie, I was gonna buy it regardless (hell, he was two hours away, I had my friend who lived in the same town go give him the $200 just so I knew I wouldn't lose it) and was extremely helpful and friendly (he gave me one of the best flatty history lessons, put some of these "engine books" to shame). For this MILD blower motor I'm building out of it, I had originally planned on reusing the cast pistons, crank, and rods (it doesn't look like the the engine will need bored) essentially as is, other than resizing the rods (only because I'd have to), just doing a re-bearing and re-ring (and re-gasket, but that'll happen anyway). This got me thinkin', if I'm only gonna do an absolute basic rebuild anyway, why not just toss the heads on it, do a leak down test, and if everything checks out run it as is? Would I be a complete ***** for pulling a stunt like this? The couple engines I've rebuilt have been full-out rebuilds, but it was also absolutely necessary, so theres no real comparsion. One day it will get a "good" rebuild like my 390; forged slugs, resized rods with ARP bolts, I replaced the crank in it, etc. etc. But for now, would it be silly to run that motor with the stock bottom end? If I do the full blown rebuild now, it's gonna be a LONG time before it's done (it'll be a long time anyway, the car it's going into is just barely started), and I don't know of a machinist capable of doing flathead work that I'd really have faith in ANYWHERE around here, and I know most of the machinists. I'm thinking, low boost, low compression, it won't take TOO bad a beatin'. But I want to hear others input. Be honest, I can take it.
Well guess what ,stock rods have the bolts forged as part of the rod no ARP bolts here. You have 2 choices as I see it 1 pull a main and a rod cap or two and if the bearings are good do the valves and run it. 2 being you are doing valves ,cam etc. at least replace rings and bearings. Recon rods? measure them first if round they are as good as they will get.
Wow! You think I'd have picked up on the rod bolt thing by now! So, it would be OK for me to pull a main and rod cap to check the bearings, and re***emble if they're OK? (Honest question, muscle car guys really over-****yze everything I honestly think, and that would be a no-no by them... But they like to fix problems by tossin' money at them). I've never re-run a set of rods, how are the 8BA rods as far as strength and maintaining roundness? If I need bearings, it's definately getting re-honed and ringed, but I'm worried I'm gonna get a bad case of the while-I'm-at-its and end up doing a full blown rebuild (I'm really bad about that "Well, I'm yanking the rods and pistons, might as well throw some forged ones in. And it probably COULD benefit from a boring. And a those mains should probably get a line bore... And........") Thanks for the opinion. Come on guys, I'm really curious what you'd do, if opinions are like *** holes, I want **** all over the place!
Bring the TP !!! Flathead rods are tuff. Check rod and main bores for round and being you got the pistons out for rings throw a set of at least rod bearings at it. Mains if they look the least bit ??? and cam bearings would not hurt. Like ya say once ya open it up where do you stop.
Say I end up not dropping the rotating ***embly, can flathead cam bearings be changed without a complete teardown? (I KNOW, I need to get a good book. All the books I have ****! No technicals, just pages of intakes and **** like that ). Checking roundness, just using telescoping bore gauges (I think thats what they're called, the T-shaped do-dads... I know thats what I called it when I was looking for one at Autozone and the 16 year old kid looked at me like I had an arm growing out of my chest)? HOPEFULLY everything is round (enough). I really don't want to have to deal with a pile of machine work because I don't have a good, trustworthy machine shop nearby (OHV motors I can take places, but these aren't high quality hi-po shops, just your basic bore and honers). That's why I just REPLACED the crank and rods in the 390 with stuff that was already machined in-house. On a good note, I just went downstairs for something and theres STILL motor oil sitting in every cylinder after 14 hours!
Dude, I'd check the bearing clearances for rods and mains, do your valves, seats and cam/springs swap, clean up the exhaust ports to help her breathe along with a decent set of 1 3/4" headers. If its a lo mile engine as the old dude said then you prob wont need cam bearings anyways. If its a Merc engine you will have the 8CM heads and the 4" crank. I'd unshroud the valves from the edge of the chamber to the centreline of the valves, careful not to go past the gasket line on the heads. This will lower the CR a little as well. I run cast pistons (heavy) in my blown engine along with std rods but manage the timing/fuel very carefully with boost retard/hi octane fuel as I have too much static CR. A set of 8R/T heads or 8CM on this engine would be just right for breathing/CR. If you really want to see if the rings are sealing ok.....bolt the heads back on and do a leak down test - this will measure the rate of leakage of cyl pressure past the rings. If it falls within a certain tolerance, you'll be good to go !! Good luck !! Rat
Check the bearings then I agree with the leak down test, if both p*** go for it. I have had a serious case of the while-your-at-its ( I actually laughed out loud because if never heard that but its soooo true)and they take more time and more important, more cash.
I haven't built a flathead in over 50 years (thank God!), but if I did, no way would I not at least check cam bearing clearances, if not just go ahead and replace the cam bearings. Oil goes first to the cam bearings, and if they're worn, the oil pressure will go South and soon so will the rest of the engine. Dave
Awesome... It is indeed a 4" 8CM. I never really even considered workin' the head castings, not like I have to worry about keeping the CR high, but that's definately something I'll do, I have everything I'd need and I'm cautious with things like that... I've considered relieving the block a bit too, but that REALLY makes me nervous (plus I don't have a router. I hate working with wood with a p***ion). Stock it has none, and it's pretty obvious where you could relieve down to the bore from the valves from the larger diameter around the valve. Definiately gonna do some clean up porting, have the stuff for that already, another freebee. I have a Crane HI-6 ignition box sitting around collecting dust, I was gonna use it (it's SO getting hidden!). I was thinkin' that the boost retarder might be a good idea, but it's more expensive than the box! Course there's the buying Crane electronics now thing . Of all places, Summit Racing has their "house" box, $225, built in 2-stage rev limiter, built in RPM lwindow switch, and boost proportional retard with a MAP sensor. For the same price as just the add on for my box? Might just say to hell with the Crane box and give that one a try. Header's will be fabbed, sorta like the Tardel books but way shorter, capped dumps that normally run through mufflers. I'm gonna leak test it soon as I get a tester... I think I can rent one from Autozone, if not I'll just buy a cheapie from the local cheap tools/****o shop (no joke. What a dirty ****in' old man). What kinda boost are you runnin' Rat Bastad, if you don't mind me asking? OH YEAH. I'm completely dumb, but I can't se anything that necessarily says whether the valve seats on my block are the replaceable sort. If it's easy to tell, I don't think they are, because I have NO freakin' idea! The things that stump me are always the most mundane little bits. You know, I'm having more fun determinin' if a stock motor is good enough to run than I ever did slappin' brand new parts in a block I paid some ***hole (because honestly, is it a job requirement in these parts you gotta be a complete jerk to work at a machine shop?!) $500 to work over... I think a basic stock lookin' motor with a little bit of a cam in here with a big *** blower strapped up top with homemade parts is gonna look SWEET! (and it does, to you guys that have already done it... I think I've looked at ALL your cars in great detail!).
I run abou 7lbs of boost on my combo. Flatoz runs a bit more - he has forged slugs that are lighter and stronger. An MSD 6BTM is what you need for boost retard - do a search on the HAMB and you'll find all the info you need. Here's few pix to get ya fired up !! Good luck Rat
Cam bearings are rarely a problem...I think it would be pysically possible to change them without a teardown (Really!) but it would be 5 times the effort of teardown. Leavem alone til engine needs overhaul. At ordinary American V8 engine levels, stress on rods is greater from high RPM than from power...I don't believe that a mild blown street engine is going to have problems there. If the engine was going to be spun fast or run at high boost levels, early or aftermarket rods would be needed. Souping what you have is the American way...if an engine has decent sealing, go to it. Insets should be visible...get a little wire brush and a flashlight and cleanup area right in close to a valve. Late engines of different years and applications can have zero, eight, or sixteen.
when I first got my blower set up going it was on what I called my 'dodgy brothers rebuild' motor. All I had done was hone the block, lap the valves and put new gaskets and rings in it. bore no.6 had 3 1mm deep pits but I thought 'what the hell' if it seals up and runs for a few years what have I lost? I ran that motor for about 2 years or more until my right foot got too heavy one day on a wet road going round a corner, engine developed a knock. it was only the other day when I was tearing down this motor that I found the problem. no.5 piston had a broken skirt. I reckon I could just replace that piston and be going again. their pretty tough motors. i would aim at about 5-7 lbs boost at the most. if your worried you could buy one of the centre mains bearings straps to help out, but your not going to be spinning it up over 5k much or for extended periods of time so probably not required. I built a killer motor to go under the blower and its given me nothing but trouble ( fingers crossed that this incarnation is the goods.) whats the worst that can happen? you break it and start again. its only money...
Stock flattie pistons are cast steel, they resist detonation better than aluminum. High revs will break skirts, though. First thing on a 49-up Ford is, REPLACE the distributor. The vacuum-only stockers are ****. Adapt a GM or Chryco electronic one to it. A low mileage uncracked Merc will run for years at double the stock HP. Never ran a blower on one, but you're talking 5 lb. boost, that's only 33% HP increase, not counting any other mods. If it was putting out 150 HP before, the huffer will make 200. No problems there. Most desired gain will be at lower revs where you want it on the street, compression loads don't hurt stock rods, it's tension loads that bust 'em.
whats the worst that can happen? you break it and start again. its only money... hahahaha that's the only thing keeping me from touching mine it runs to good I need a blower on mine but I would need to freshen mine up after 19 years of abuse and where do ya stop ?
Casey I thought the same thing, motor would put up with it, it comes down to the right foot really. and if you think the motor needs a freshen up anyway, why not play now? its only broke when money can't fix it. ( i'm not loaded, just here for a good time not a long time and I aint taking my money to my grave)
Flathead pistons have an extra oil ring below the wrist pin. That ring adds enough drag you'll need a blower to develop any decent horsepower. If you decide to rering it, leave the bottom ring off, or bite the bullet and buy a set of light weight 3-ring pistons. Definitely do whatever's necessary to keep that engine from overheating. Even a slight amount of too hot results in cracks across the exhaust valve seats. Jerry
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