After 2 years of designing and building our GMC I finally put the pan and valve cover on it today. I swear to God I've sweated, worried and cussed more with this engine than any of the $25000 + one's that have gone thru the shop. One of the partners has to finish welding up the headers, then it's going on the dyno...hopefully next weekend. Any estimates on the peak horsepower it will make? That's assuming it doesn't shit parts all over the dyno room. The engine is similar to Roy's GMC except there are a few things on mine that Roy didn't get. Hell, I can't give all my secrets away. (Grinning) Ron
Have you not run it yet? I'll make a guess. Peak Hp 295-305 hp @ 4800-5000 rpm Peak torque, 425-435 ft/lbs @ 2800-3000 The catch to starting a thread like this - is that you'll have to tell now. Looking forward to the results. Hud
Ehh, it's gonna blow parts everywhere. Just kiddin, Bubba's never dynoed any of his Jimmy's but I don't see why a well built GMC without the high dollar head wouldn't give ya 250-300hp.
I'm hoping to make 1 HP per cubic inch (321 cubic inch). Anything over that (my fingers are crossed) will be an early Christmas for me. I wish I had Roy's header but my partners want the individual runners without a collector. They think it will look more "period perfect". Maybe I can borrow Roy's header when I dyno our engine. That way I can do a comparison. Any more estimates? Ron
I don't know what cam you are running but I'm going to guess in the 325 range hp wise and 400 lbs torque. Corrected values of course if it is as hot and humid in KC as it is here.
Cam: Intake 252* @ .050", .577" lift at the valve Exhaust 259* @ .050, .613" lift at the valve The cam was ground by Dema Elgin to match the cylinder head flow, CSA, rod ratio, etc. Kinda expensive but hopefully worth it. Hud, Have you ever had one of the Hudsons on a dyno? I considered the 308" Hudson, 320" Buick and the Ford flathead but for various reasons figured the GMC would make the most power. Ron
Actually I haven't had one that I've built on a Dyno. I hope to have one dynoed eventually. I have a project engine that has been in the making the same period as you evidently have been working on yours. I'm not finished yet, and just got set back as I found out I can't run this HA/GR - SDRA gig with triple webers. My ballgame is kinda upset right now on that account, I'm scrambling around a bit to find something else and see how that's gonna change things. Who knows? I may be running triple sidedraft John Deere Duplex carbs before this is over! Circa '55. I've just now found you guys, so I'm way behind. But, at least I have a goal for the engine and some inspiration to get the heck on with it. I'm at 358 CID. Which is as big as I can get, turn 5000-5500 rpms, keep the stock block, and any degree of reliability. I'm really only camming mine to peak out at 4800 for longevity's sake. I've heard stories about Hudson's on dynos, but have seen no papers on other's efforts to give you anything I could verify. So, I took on my own project just to know. Being a flathead fan, an inline fan, and a Hudson fan - my choices were kinda already made. I'm shootin' for the hp range I guessed yours at, but a few more ft/lbs of torque. I really like your dual pattern camshaft, alot. With lifts like that, I'm wondering at your expected rpm range. Mark
One more thing Ron, you overlooked a damn good OHV choice in your lineup. Nobody hardly pays attention to them in the inline world, but are DEMONS! International Harvester, Silver or Black Diamonds. They are in the timerange, and deadly inlines in the right hands. I'm secretly wishing you had employed your know-how to one of those. God help us all if somebody got serious with one of those! I've competed against many a Black Diamond on the pulling track, even with a 300+ hp 292 (312 CID) chevy - and LOST. BADLY. Hud
Thats a big Hudson. You should be able to make some serious TQ with your engine. I remember a black 54 Hudson that ran NHRA during the 60's. He was running one of the stock classes and held the record for years. My cam is bigger, duration wise, than I thought it would be but Dema Elgin wanted to get the intake valve open at a certain point after TDC to take advantage of the max intake flow without making the acceleration rate too high and losing reliability. He also tailored the exhaust opening point to reduce the pumping losses. The cam lobes look more like a roller than a flat tappet. I want to keep the rpm in the 5000-5500 range. Again reliability is important. I'm sure I can turn the engine quite a bit tighter but I'll just turn it tight enough to win. Each piston/rod/pin/ring package is more than 1.3 pounds lighter than the stock 302. I just hope your Hudson rods hold up. We just ported an International cylinder head for a pulling tractor. The ports have been welded twice so far and we just filled the water passages with Blok Rok. I initially looked at some of the tractor & truck engines but considered the weight to be too great. Ron
RON I hope you make your one hp per cubic inch ,has that ever been done? It should be quite a show .remember it has to go though a SIX INCH TIRE that is slightly softer than concrete .Looking forward to show at MOKAN
From a couple of books I've read the "old timers" in the 50 & 60's were making just under 1 Hp/cid. However, you have to realize the technology has changed drasticly. The days of installing a set of headers, a taller gear and a set of slicks won't cut it in todays world. One of the 2.0 L Honda engines we did the machine work on recently made 860 HP on a chassis dyno. Turbo's and #36 of boost. Will I make 1Hp/cid? I don't know. Every time I tune an engine on our dyno I learn something. After 50 years of doing this I'm finally getting smart enough to start asking questions. I think I have a decent old GMC, but fate sometimes deals us a hand we don't want to play. The thing may spit parts all over the dyno room. I have to admit, the 6" tire will be a challenge, as it has been for everyone so far. That certainly levels the playing field to some degree. But....thats racing. I love it! Ron
I can't believe a black diamond is much heavier than a 302 Jimmy. Sure we're talking the same IH engine family? I'm actually rooting for you too, I have a soft spot for any vintage engine getting the "treatment". We're gonna return your concern for my rods with my own concern for your crank above 5500.
I don't think we're talking about the same International family. Thanks for the moral support on my Jimmy. The GMC heavy crank and only 4 main bearings was the reason I went with the lighter components. I'm also going to keep it below 5500 if possible. The GMC guys that run at Bonneville say the critical rpm is right at 6000 where there's a dangerous harmonic that can kill the crank. Keep the rpm below, or above, 6000. How much compression can you get in the Hudson engines? How much valve lift? Do you run 30 degree seats on the intakes due to the low lift's? I'd like to build one to see what I could get out of it. Ron
I want to clarify my build a little. I'm not shooting for the moon component-wise. I was hoping to build a repeatable short block stroker engine with stuff anybody could find and use in an unmodified block. The only block modification I'm pulling is for a full pressure oil filter, which is a simple trick. Most folks modify the oil pump, but I wanted to be able to swap pumps without any modifications to the pump. Simple 7x valves that can be bought off the shelf, lightly modified, and installed with common valve seat machining. Not pushing the envelope there. 2.012" in and 1.650" ex. The uncommon bugger is the crank treatment and flow work. I'm departing from traditional 7x reliefs. The ports are no problem, and already excessive. Its the transition from valve to cylinder that is the nastiness. Port velocity here, is the ticket. You need just the right velocity to bend things like you want when you want, but not too much. There is where I've spent too much time on a cracked block as a dummy/test. I've been screwing around with what you can pull off under a stock valve diameter situation too - just for kicks. I'm really a budget minded fella looking to help other Hudson folk with budget oriented stuff. Which is why I really don't mind backing off the Weber thing, because they are pricey for your average Joe and I just lucked into a cache of weber carbs off sixes that were on somebody's shelf. The crank has always been the holdup to these engines, and why I dropped some bucks on it. I speculated that a serious Hudson fella would do the same. So, I'm not in your leauge - at all. But, you learn things along the way that could get you to the moon, of you so choose. Max usable compression in a 308: 9.5-10.0. Beyond this, you start hurting yourself. If you build one to run lower rpms at peak hp, you can get tighter. Its all in what you're hunting for. 358: 11.0-11.5. I'm only going for 9.75. Ya never know, when I do decide to shoot for the moon - this engine might see the open highway. And if somebody followed me, they'd likely want the recipe for the road, so I'm shooting for 9.75. Same thing applies. You can get tighter, but you're cutting your topend down. When I became interested with Hudson speed in '99, I actually called Smokey Yunick as he was listed in the HET club as an advisor. He talked to me for a long time about alot of stuff, I was too awe-struck to reply much and enjoyed listening to the tech/stories. Two things I will never forget him saying were, "Its easy to get 290hp from a Hudson 308, its next to impossible to get anything over 300. That last 10 hp will cost you as much as several 290's to build." On the topic of stroking: "It won't gain you a single horsepower, but will add 100 ft/lbs of torque to your peak." Max lift in a stock cam tunnel, .535" depending on your base circle diameter. You could get more but start having headaches. Head clearance is as much as you want to cut out of the head. Yes, 30* intake seats and 45* exhaust. The valve underside backcut has everything in the world to do with your transition action. Flatheads are strange buggers, and not to be compared with ohv's. They just aren't the same in many respects and you have to re-learn alot you thought you knew. Which is what I've enjoyed about this whole journey with mopars and Hudsons. But, there is more possible with a Hudson than any other common flathead I've seen. Mainly because of the valve location relative to the cylinders and the generous 12 ports in the block. I'd like to see you take one on, as you seem to have resources and capabilities I don't. I'm out just to have a little fun with my engine and hopefully inspire some folks to use these great old pieces. I figured the 6" tire rule and makeup of the HA/GR - type cars would be the perfect platform to have that fun. I wish I had paid more attention to this class before now. Hud
Hud, It sounds like your as deep into Hudsons as I am into GMC's. It really doesn't matter which engine you pick, their just hunks of metal. What you do with those hunks determine the end result. And that's the interesting part for me. I like to build engines. Have you flowed your intake and exhaust ports on a flow bench? I know that years ago we use to relieve the block on flathead engines but later (and wiser) engine builders relieved the head to get a better transition from port to combustion chamber. It seems the air/fuel didn't want to make the abrupt transition from valve to chamber when you just relieved the block. My best friend at the machine shop followed Smokey's every word and talked to him every few weeks for years. My Guru has been David Vizard. Between the two of them we could usually get a good answer to any question that came up. It's interesting that the Hudson hits a brick wall at 290 HP. Did Smokey elaborate on why this happened? At first thought I assume it's valve lift/airflow/CR related. By the way, welcome to the forum. It's nice to have another gearhead on board. I wish you were in the Kansas City area, I'd like to learn more about Hudson engines. Ron
To tell you the truth, I feel like I'm muddying up your GMC thread. I can't help it, I'm interested in your GMC. I don't have good, honest to gosh, flow bench numbers. All I have is an Audie Flow Quick, and a not so dependable depression device (vacuum cleaner). The materials I'm working with are junk and were used to get rough ideas. I do have an ally here, Joe Mondello. He's ready to put the real numbers to it on a better test mule block (still cracked - I have alot of those) with a new set of seats and help me jump the hump with his own input when I can scratch up the money. That's where we'll dyno it as well. Our intention is to wet flow it under a mock acrylic head and really check out my theories. There has been so much speculation on these engines with no hard data, I wanted to change that. Actually, all my parts for this engine except the head and intake - is at Joe's now. I completely agree with your flow theory, and have used it on the engines I'm running now. Hudsons have a factory relief and a valve cant towards the cylinder that has to be dealt with, so one can't escape the relief completely. However, I do install seats as high as possible in the block, deck it at least .025" and keep the relief as shallow as I can. Most of what I do is in the transfer slot of the head and using the relief area to "bend" the air stream by adhesion. I can tell a difference based on a bone stock 308 I run in my Wasp, and a mildly worked over 308 in my Super Six. I'm running a 308 on the street with 8.2 compression now. I do have a camshaft secret, that I'm not telling. Its unique to flatheads, so you can't use it. I'm hoping it breaks the 10hp barrier Smokey talked about so long ago. He gave me some general cam numbers in this area, and I know he didn't do what I'm doing with it. He never really mentioned what the 10 hp wall was, just that is was more expensive to break that it was worth. Unfortunately, he passed away before I could even get the first engine project started. He and Jack Clifford passed away within months of each other, and kinda left my generation of Hudson fanatics to reinvent the wheel. I kinda wish I was in the Tulsa area too. At least for a while. Hud
Hud, I had to laugh when you mentioned the vacuum cleaner being used to flow your ports. That's what I started with and learned a lot, especially when you shoot some dycum into the port to show you where the air/fuel will go. Kind of a cheap wet flow bench. Mondello has developed airflow to a new science. My god he must be 80 years old by now. I'd bet money on you finding that illusive 10 HP, and more. Something to keep in the back of your mind....air doesn't like to turn more than 7 degrees without losing attachment and going turbulant. It's better to make several 7* changes rather than fewer larger changes. Keep me up to date on your progress. Ron ([email protected])
I'll remember that 7* info, thanks. Does that change with different velocities? I had been using HVAC smoke bombs to watch things to the degree I could, which really isn't enough. Just holding them lit in front of the port and letting the smoke go on through. I was as awe-struck by meeting Joe as talking to Smokey on the phone. He's been really nice to me, which I appreciate a great deal. Progress is slow because money is tight. I could just finish it, but I want those hard numbers. I'm looking forward to your Jimmy numbers. Hud
The 7* becomes important when you add fuel to the mix. Check out diyporting.com . Rubber molds of a port can be used to cast plaster blocks with the port shape in them to experment on (cheeper and easier than the real thing). Home made velocity probes and a yard stick manometer can also help.
Fellas, thanks for the info. I do appreciate it very much. I have a pretty good ways to go. As y'all can tell, I'm more of an engine man than car fabricator. So, I have a steep hill in front of me to climb. So, I'm thinking the 7* situation is related to the fuel droplet's mass vs. the mass of the air molecules? This whole situation is re-inspiring me to get on with this engine project. I have admittedly let it lay for a while. Hud
The 7* is with or w/o fuel. Fuel just makes it show up more. Fuel droplet size with a surface to volume ratio approaching 1/1 would be ideal, BUT, is hard to do. So you shoot for something as close as you can get. That means you work your tail off on your fuel delivery device to get as close as possible. Good luck
Hud, 7* holds true at all velocities. Bubba, 3x2 medium cfm Rochester on a manifold I built. I'd love to have some side draft carbs to experiment with but that will have to be a future project.....when I find the carbs. CrkInsp, We use a dental mold making powder that you mix with water. Dentist's use it to make quick molds of teeth. It sets up quickly and is easy to remove from the port. However, it will dry out and shrink in a few days so it isn't a permanent mold. The rubber you mentioned make a permanent mold. Ron
Ron Can You mix a little glycerin with it to slow the shrink. Then seal it with a coat of something. Just a thought.
I've been reading that diyporting.com site on and off all day as I could. Interesting stuff on my level. I'm assuming you fellas are talking about solid molds for casting rather than the hollow ones made by silicone? Where do you find the casting rubber, any particular type? Hud
I don't have the product name in front of me but will get it tomorrow. You make a solid plug from a good (?) port, then use that to cast a matching port in a block of plaster. Remove the plug from the plaster. You them have a port replaca to do your expermentation on. Its a lots easier to work with than a metal piece. Haven't ruined a head yet doing it this way, but have lost some hair. What surface finish are you leaving on your port floors?
Was that question for me, or Ron? If me, 80 grit "tooled" finish. I will say one thing, that DIY site answered my .435" lift question, as I just wasn't seeing anything over that, with diminishing returns over .400". According to their thread sailing analysis, .300 is when the air flow starts to roll upward over the edge of the valve rather than paralell with the head. Right there might be the 290 hp wall. I have no idea how that applies to the Hudson, I'm too work-bound (with things other than this) at present to mess with it. Actually, that one tidbit answers alot of questions I've had with different flatheads. Oh well, fodder for thought I suppose. Hud
Early Chevrolet and GMC ports are not any better. You have two siamezed ports and two single ports. There is a wall at the end of the port where it has to make a 90 degree bend. I think that by raiseing the port floor and getting the air to start an upward movement towards the valve would help flow in the higher lift areas. It seems that is crazy to do that is what Mike KIrby has been doing with his 292 sixes. It is called lump port design and you direct the flow of the port by adding a lump in the port to enhance the flow towards the valve instead of towards the flat wall at the end of the port. I might try something this winter when it is cold out.Roy
The lump port is for real. I think you can actually buy "weld in" and/or "bolt in" lumps from Kirby for the 250/292 head. Hud
OK, here is the info on the product. It comes from Chicago Latex and Permaflex Mould Co. It goes by the name of Blue-Sil. Sorry, I don't have any idea on the current price.
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