Anybody here know anything about cragar blowers.I have a chance to buy a 671 (I think).It's suppose to be ready to go.It has 3 ribs,all the pulleys(they are BDS).What do you look for and how are they lubricated.Are they sealed bearings?I want to run this on a .060 283 on the street.I know they make blower pistons but what kind of compression can I run.
A 6-71 is a little big for a street 283, but can be undriven an work. I think a 4-71 would be a better fit though.
Most likely (not definately) you are looking at a 6-71 roots style blower with a rear cover that says "Cragar." The cover will be damn near totally smooth with Cragar in about the center. For any 6-71 you look for pretty much the same stuff..see if it has been converted to gas by looking at the drivers side bottom of the case. (which it probably has if it has an aftermarket rear bearing cover.) If there are two kinda tab looking things hanging around, it is most likely stock. If they are gone, that usually means they were machined off during the conversion process. Look for scars and scratches in the rotors and the inside of the case. Scars are not nessesarily a deal breaker, but deep ones in the case are usually bad. Also make sure it spins freely with out any tight spots or really sloppy spots. Just about any decent core can be sent to a reputable blower shop and be converted and/or checked out cheap. Even if the blower is claimed to be rebuilt, it wouldn't hurt to spent the 200 bucks to have it checked out. As for price, I paid about 800 bucks for my blower, completely rebuilt for gas and ready to bolt on. Alot of that cost is a good aftermarket rear bearing cover, like a Cragar, which this one seems to have. All the drive stuff is pricy though...I have almost an other 800 wrapped up in the front snout, pulleys, idler, belt and crank hub. Unless it looks visually fucked, I would buy it. If you get the blower itself for 500-800 with the cool Cragar cover, you did fine, even if you have to spend 200 more to have it checked out. A pic would really help.... Good luck, -Abone.
First, there;s no such thing as a "Cragar" blower Cragar makes (or made) blower drives, manifolds and parts - like the Cragar rear bearing retainer plate that is on the back of the blower you mentioned The blower itself could be almost anything - an original 'GMC/Detroit Diesel" piece or a replica made by one a number of aftermarket manufacturers - but not Cragar.. Also as someone else already mentioned a 6-71 is pretty big for a 283 and will need to be seriously underdriven. As for compression, it all depends on how much boost you plan on making. With a 6-71 on a 283, on the street and on pump gas, I'd say low - like around 6 or 6.5 to 1 - or maybe - and it's probably stretching it -maybe - 7 to 1 max. If you build low to start with and find you can tolerate a bit more cylinder pressure, you can always change the drive ratio and speed the blower up. - and a blown moter will always make more power with lower compression and more boost than the other way around.. Mart3406 ===============================
Thanks for the info.It was adapted to an offenhauser 4 barrel intake.It's all there.I'll get pics this weekend.
>>>>>,My 6;71 on my 355 SB Chevy ,,i call it a "Bastard Blower" ,,it has parts from everybody ,,,last year it ate the front main drive bearing ,,i called BDS and they gave me a part number ,,well ,,i got a new bearing localy ,,but ,,it was WAY too small ,,i sent the old one to the parts house and they came up with the right one ,,i called BDS and told em the number ,,they said they haven't used that bearing since 1968 ,,the "Smooth" rear bearingcover is home made to clear the distributor ,,i have two "grease zerks" in it to manually grease the rear two bearings ,, the main case is a large port Wieand ,,from the '60's ,,i think ,,the 2 inch drive is from the old days too ,got two spare belts from BDS ,,i run the pulleys one to one ,, static compression ratio is 8.5 to one ,,cam is a '60's era Isky 550 Super LeGarra ,,carbs are a pair of blower specific 600 Holleys ,, heads are '63/'64 'Vette Fuelie's,, since i live in a '78 GMC Motor Home full time , the "T" has been my daily driver for the last 5 years ,,,gets14-16 mpg ,,if i can keep my foot offa da floor ,,Ha,,Ha,,Ha,,, once you go "Blower" ,,you never go back ,,
I don't think I'd run a blower without using blower pistons. You won't be able to keep your foot out of it forever and the pistons are the weakest point. I get about 8.5-9 pounds of boost from my 4:71. Driven 1:1. I paid $600 for everything to include a rebuilt blower. That was 7 yrs ago. With this economy should be about the same. The front and rear bearings are sealed, they don't need lubrication help. The lub in the front is for the gears. I have always been told that you don't want fossil lubricants to leak in to you intake. Could be fatal. I use synthetic gear lub. I forget the brand or weight I use, but if you PM me I'll walk out to the garage and look at the bottle. I'm with folks who have said 6:71 is a bit large for an sbc. usually they are on a larger platform. But under-driven maybe....
If its a stock 283 i wouldnt run over 5psi so definetly underdrive it. Use synthetic 75/90 in the front cover according to weiand thats what i use and have had no problems. The lower the compression the longer it will last usually.
Well this thread solves a question I had that an old timer said he had a blower made by some company that made wheels. Now it all makes sense.
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