And hiboy32 - I know the question has already been answered, but yes it is a 4-71. The angle makes it look bigger.[/QUOTE] Yes , must be the angle. I was wondering what you are going to do for the lower end, is main studs enough? Is there enough support for the added pressure? I thought the lower end seems kinda fragile without forced induction.
Leaning hard toward splayed main caps. Don't think I'm going with the crazy girdle setup which bolts to the pan rails and requires heavy pan modification, but who knows? This will be for the engine built specifically for the blower. I the meantime if everything checks out I'm going to strap the center main and run the stocker as is. Keeping the boost low and the charge rich... and hopefully not melt the pistons.
Load up your grinding wheels with beeswax before you grind on aluminum and use it frequently while griding......it helps to keep the wheel/disk from loading up with aluminum and makes life much easier. -Bigchief.
Bruce, In all of the GM diesel applications the blower bearing end plate (rotor drive gear end) was pressure lubricated off the engine galley and the drain back to the sump from the bearing plate was via the drain holes. The hot rod guys typically plugged the drain holes and filled the bearing end cover to the lower side of the bearings. A pressure feed would be an easy deal to hook up and better in the long run if you put some miles on it.
That's what I was thinking...why have two little half-pint oil puddles that have to be maintained separately?? I was planning on plugging the stock drains and putting in a new one up a ways so bottoms of gears are in oil, oil delivered probably to rear, line to front case, overflow at desired oil level (???) and dribble into the valley. Separate oiling of bits is like a 1910 car with a row od drip regulators on the dash...and without the drip oilers, It actually seems more primitive!
That is going to be a very nice engine. I had never heard of pruning, but as I can see it is a very good thing. can't wait to see more.
Pete Robinson pruned the 6-71 cases he ran on his sb Chevy's and Ford gas dragsters back in the sixties also. He also cast his own pruned case 6-71 blowers in magnesium. And if my memory is correct Ohio George Montgomery did the machining on them and ran some on his gassers.
Blower lube could be augmented by running a breather from the motor into the blower (?). I'm not that familiar with the types of bearings that blowers run. Blown motors are very docile on the bottom end.Remember,you are running on low compression pistons.Only when the beast roars do things get heavy. If you could keep the boost down,then you would only need minimal shorring up on the bottom end. Kool looking job Kevin.
Bruce, When you relocate your drains just make sure that you locate and size it to keep the oil level low enough such that it won't have tendancy to get sucked by the rotor oil seal in the end plate and into the intake stream. The horror stories about "total run away" two-cycle diesels would occur when you would hang the injector rack, attempt to shut the engine off via shutting the intake dampner, the blower now sucks against the dampner and rolls the lips on the blower seal and the enginne is now running on crankcase oil. Your spark ignited flathead won't do that, but oil in the intake stream still isn't a good thing.
Yeah, something I read said only to lower reaches of the gears...I need to look at an aftermarket end plate and see where they put the fill plug as a starting point. Cobbs kept his lines down low too, haven't had time to study the wretched quality pictures I have of that setup. Diesels aren't just a bad smell...they have lots of other Satanic tendencies too! Did you read the post about the diesel Volvo that committed suicide during a tuneup??
Very cool. Pruning! That's a new one on me too. That green flatty is a work of art. Nice engine man!!
The motor in my '36 ran a 371, also pruned as shown in this thread. These are Baron heads with the top water manifolds modified for additional clearance to the bottom of the case. The manifold is a repop SCOT which lowered the blower about 1/2" from the Navarro piece, allowing everything to fit under the stock '36 hood.
I just went and looked that movie up - yes you are right - DW is the man. 50 Fraud that engine is a beaut!! Did you dyno it? How did it run in the car?
It was run on a chassis dyno to get the mixture and timing optimized. It only showed about 120 RWHP, but it wasn't intended to be a horsepower tuning exercise. It ran strong, but it blew a couple of head gaskets (before dialing the boost down about 10% from an original 10#) and frequently ran at 240° despite many efforts to chill it down. I loved the motor, but I drove it in fear that I was going to overheat it or blow another gasket. Never did hammer it the way I had originally expected to.
We've got two of Ohio George's 671 blowers, one with Pete's magnesium end plates and one without. Neither of these blowers (I'm sure he has had more than a few back then) were pruned. -Bigchief.
.....of course George was running regular blower manifolds on his SBC's when he ran SBCs......so, uhhhh....never mind, these blowers would havn't been pruned. Although.....I'll have to look at the 6v71's I've got that I want to put on my Y-blocks.....they'd look great pruned and are half way there. Hmmmm, now I just gotta beat Clark to the punch. -Bigchief.
.....i gonna be the one to ask the dumb question, most if not all of you know, but what is meant when one Prunes the case? My guess is somthing with trimming the overall size of it down but i would love the full explination plz. BTW, the two pictured engines are very cool....
This pruned case style would look just as good on a 6-71 too! Keep us posted with photos as you build the car please.
Yup^^^ Bruce and Kevin, On the inline GM's there was a minimal amount of oil pressure, 3-5 psi at idle and 30-40 at speed. And the oil gallery feeding the blower had a very tiny restricor(sp) to limit the oil flow in and a large drain to let the oil back to the block and crankcase. It's been a long time since I did a blower, but I'm thinking the endplate with the bearings had drilled passages from the restricor to each bearing nub and sprayed oil at the gears, and then splash lubed the bearings, then the oil that made it's way thru the bearings lubed the seals. If I was gonna do a street blower, I would pressure feed each end and do a drain hose to the valve chamber or pan. GM was successful with this for 60 years. It seems that an oil filled housing with the gears churning up oil would get the oil really hot. OH, the seals leak air from the blower into the end plates. So a drain would relieve this pressure to the crankcase. If you have a sealed chamber, it will get pressurized. That's why sealed blowers have that little releif valve thing on the end plate. And now that you have gas mixed with air, the sealed chamber will get some fuel dillution in the lube oil. If you can drain this away, it will mix with the larger volume of oil in the crankcase and not be so bad. And GM made a nice upper mounting gasket with a window screen in it to stop trash from getting in the blower. It wouldn't hurt to use one. And the 71 blowers ran at 2 or 2.1 to 1 engine speed (I forget exactly which). 71's normally ran at 2100-2200 rpm so the blowers normal speed was over 4000 rpm. And ran for 100,000's of miles trouble free at those speeds. Normal boost at high rpm was like 7 psi, I think. So you are not stressing the blower. I hope this helps a little. Frank
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