Great thread! I watch with interest because I'm also using an oddball setup...'57 Pontiac engine punched to 370 and a Muncie 4 speed. I have to agree with Hank 37 regarding the 49 ford rear axle. I broke enough of them with a mild 255 merc motor/4.11 gears and a truck clutch in a shubox...prolly weighed 2800-2900 lbs. I busted more axle shafts than anything else and with skinny bias plys.
I hear the warnings on the rear, but those are the exact parts the car was originally built in the mid-'50s with so I want to keep them. 1950 Ford axles are cheap... Sent from my iPhone using H.A.M.B.
Be prepared , take along spare axle and piece of bailing wire with a loop on end to fish broken axle out of housing !
Any idea what the cam and valve springs ended up being? Curious about the specs. Did you have to cut the seats? Or did they fit the stock pockets?
Cam is Steve Long Racing Cams 275T Hydraulic. Intake & exhaust .488 lift with 1.6 ratio rockers. Duration 280 I&E, intake 34 open 66 closed, exhaust 74 open 26 closed. I have to look through my empty boxes for the spring part numbers, but they were the ones Steve Long recommended. Springs fit the stock pockets.
Hi, I'm in the South of the UK, have read a lot, pulled the 331 from my timewarp 1950 Caddy, partially stripped it and am measuring / specifying how i'm going to rebuild her. I've taken a lot of inspiration from your posts thank you and here is what i'm aiming for: Seeking a torquey motor with power useable between 2,500 & 5,500, at least 250HP + (would like to see 300+ ideally), really smooth & well balanced, nice sounding, quick revving, & patina'd so that it looks like it was warmed up back in the 50's - sticking with the 331 Crank, but i may be lightening it & thoroughly balancing the rods, pistons, crank flywheel and balancer etc - 1959 390 Heads that i'll port myself, aiming for 10:1 CR and will be paying particular attention to intake flow at low valve lifts thank you. - boring the block to 4.030" to give 370 CuIn - going with the same SCAT 671022 Connecting Rods as you - Ross #90456 Piston gives the 0.020" Deck height with my 331 block & Crank (and is really light!) - scouring through the Manley catalogue for suitable light weight waisted stem valves or may have customs made - going to light weight spring retainers, viton stem seals, may increase to 1.5" for a double spring - maybe Trend pushrods - modern balancer tbc - ive bought a Weiand Intake with twin Carter AFBs, each same spec as fitted to Caddy's in 1957 (i fear its'll be over carbed). They're set up as a primary & secondary apparently but yet to get into them. - Custom exhaust headers (or two left hand side 390 exhaust headers) That's about as far as i've got. A question in my mind though is that i'd like to run modern Oils in my shiny new engine, but the 331 is a partially filtered system rather than full flow. If i use modern oils with detergents, the oil really should be filtered by a paper filter as the detergent is carrying any nasties around with it. not quite certain yet how to either live with a partially filtered system or work out how to modify it for full flow. Any thoughts? Cant wait to see your Dyno results!
Dyno is on hold for the moment, will probably do a chassis dyno when the car is put together. Rebuilding the transmission at the moment. I cut the block and offset ground the crank to get a zero deck to the pistons (for better quench/combustion), in fact that was the only piston I could find off the shelf that would get me close. If I had to do it again, I would get a custom piston and forego the offset grinding of the crank which took months to get done (crank grinders don't seem to want to do custom stuff anymore- too many 5-liter Mustangs to fix). For years reciprocating aircraft engines have used oil screens and no filter. Use of detergent oils in those applications is not a problem. I will use Valvoline 10W40 Racing oil or Rotella T (diesel oil) because they both have zinc which you need for a flat tappet cam. Forged pistons are so light compared to the stock cast pistons (with their long, thick skirt) that you may have to add tungsten balance weights to the crank (which I did, even with the longer rods). You might want to talk to the person doing the balancing before you lighten the crank. If you are concerned with weight and are using a manual transmission, find an aftermarket aluminum flywheel. My connecting rod bolts needed a little clearancing to avoid the cam lobes. A late 1950s Eldorado 390 made 345 HP with the Tri-Power. 345 HP * 370/390 = 327 HP just based on displacement, and you should do somewhat better, especially if your valve springs are a bit stiffer to prevent valve float, a weakness of this era Caddy. That will allow you to run a higher RPM. You should have no problem with performance as long as things aren't really mismatched.
Thanks for the reply. Yes, the first thing the balancer guy said was tungsten weights may be necessary. He asked if the balancer or flywheel had an obvious weight added to it, which I couldn't see, so concluded that the Caddy crank was an internally balanced design. He's not seen my collection of parts yet so we'll see how that pans out. The other thing I'm considering is a larger intake valve, perhaps 1.955ish an 0.080 increase, maybe just a little larger, working out if an 2.020 intake valve would fit. The size of the 390 intake port cross section given that it is an approx 72 degrees turn into the cylinder, my rough garage measurement, indicates it is undersized leading to lower gas speeds in the port. I'm reading Vizard & Graham Bell & working this all out but everything is pointing toward a larger intake valve, with close attention to seat & near seat port design being beneficial. Time, sweat, thinking, money & the resulting dyno run will tell. Fingers crossed.
Yes, 331-390 are internally balanced. People have put bigger valves in, but they are pretty close together even at stock diameters and may get shrouded by the cylinder walls. The flows I got seemed pretty good, at least equivalent to a good factory SBC head. I just don't think you could ever get flow in the neighborhood of an aftermarket SBC head without some serious surgery. The intake is the area that needs the most improvement though. The exhaust is pretty good.
One other question that I'm grappling with. The valve spacing on the 390 head is wider than the 331 head that I have. This means that if I use the 331 rocker assy, I'll have to add shims either side of the 331 rocker posts to have the rocker arms sit on top of the valves correctly (I don't have the 390 rocker assy). But that in turn means that the pushrods will not be running vertical, as their spacing in the lower end of the 331 block remains fixed by the tappet locations. Perhaps I'm worrying a little too much as it's not at all likely that the engine will rev more than 6,000 & with new (stronger) fixed or adj pushrods that slight angle may not be a problem.
I see. Could I ask how they differ? I've made up a 1.6" & 2.02" blank valve heads to see how they fit into the combustion chamber. The 2.02" inlet overlaps the spark plug cavity just a fraction, but I may get away with it with new hardened & shaped seats. I'd need to further widen the valve spacing though, perhaps by 0.20", by cutting off centre guides. Hence my next thoughts are turning to understanding which rockers to use. May also cut the valve spring pockets to 1.5", use a barrel type spring and much lighter valve looks etc
I'm not sure. I just know they are not interchangeable. Even if you use the Stude rockers, you have to use the 390 shafts.
C322348, When you had the crank offset ground for the BBC rods, you said it was 390-BBC divided by 2, but I was wondering which way the offset was ground? Away from deck at BDC, or towards deck at BDC? Great thread, and thanks for taking time and having courage to leap into this build Sent from my iPhone using H.A.M.B.
Stroke was increased. I needed to get the piston as high in the bore at TDC as possible for the pistons I selected. Sent from my iPhone using The H.A.M.B. mobile app
Haven’t run it yet. May be some months before I get it in the car and hooked up. Sent from my iPhone using The H.A.M.B. mobile app
C322348, I went back and looked, and your pistons were flat, with some valve relief pockets... did you say it came out to 10.5:1 compression ratio with. Deck cut to flush with TDC? I found some 11:1 forged sbc pistons, that have some stick-up on top of piston (about 1/8” has been milled off).... might get down to 10.3-10.5:1 with removed material)... just wondering if they’d work with the 390 heads... I’d have to clay them to make sure all clears Sent from my iPhone using H.A.M.B.
Yes, the deck was cut around .042. With that kind of cut, your water pump may no longer fit to the heads though. I've got a different setup so that didn't matter to me.
I know that it is a long time ago, but can you recall what pressure drop was used when you flowed the 390 head? The reason i ask is that i've just had one of my 390 standard heads flowed at 10" of water and the cfm figures are not as large as your numbers. Interestingly, nor is the drop in flow around 0.3" lift.
Hi, do you happen to know what year & Car your block cam from. Or better still the stamped on number at the rear just above the bellhousing area. My block with thinner patches on the cylinder walls is a 1950 Series 61 9MXXXX block. Sent from my iPhone using H.A.M.B.
This may have been mentioned in the thread already...if so my apologies. What company/kit did you use for your gaskets? I’m getting ready to test-fire a ‘49-331 that was rebuilt 10yrs ago, run for a few hinder miles and then sat. Having had it inspected visually too and bottom, all looks good, I just need to seal it up. So, looking for all new gaskets top end and bottom end (oil pan, water pump, intake manifold, exhaust manifolds, etc). Don’t nee head gaskets but may grab a good set anyway. Recommendations appreciated from those who’ve done this recently so I stand a good chance of finding what I need quickly. Cheers, and sorry if this hijacked the thread somewhat. Seemed easier to share the question and answers than it would be to use PMs Sent from my iPhone using H.A.M.B.
Thanks @c322348. Interesting that the Egge set is almost double the cost of the FelPro set. I’m looking for quality over low price. Anyone have good knowledge of why the price difference? Is the Egge set better quality or just pricy? Have never purchased from Egge yet, but this maybe my first order. Sent from my iPhone using The H.A.M.B. mobile app
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