6-71 vs. 8-71

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Map63Vette

Map63Vette

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So I'm trying to plan way ahead for my blower build (like one year ahead, lol) and was wondering if there is a way to pick the size of blower to put on the engine. I know generically that an 8-71 moves more air than a 6-71, but does it really matter which you pick? Can you just adjust boost via pulleys to get the same sort of air out of either (ie. drive the 6-71 harder than an 8-71 up to a point)? The engine will most likely be a 318, possibly stroked, but still deciding on that. There really isn't much else I can say about the engine now since I'm still planning it all out, aside from all forged internals, a main cap girdle, and probably a set of Edelbrock heads. It will be street driven, but raced on weekends. The current plan is to drive it around town with lower boost and swap pulleys at the track for big boost and use race gas.
 
The 6-71 blower was made for a 2 stroke 426 cube 6 cylinder Detroit Diesel.

The 8-71 blower was made for a 2 stroke 568 cube V8 Detroit Diesel.

The 6-71 would probably be easier to fit and still make plenty of boost,
but I would check with experts on these blowers on gas engines.
 
Yeah, I guess the main reason I ask is that I've seen SB Mopar kits with either size. The large majority of kits I've seen are the 6-71, but I have run across a few 8-71 kits. I guess a better question might be is anyone running an 8-71 on their SB. The kits I'm looking at are from Dyer's Blowers, they seem to have some of the best pricing I've seen for a full kit and they are also one of the few I've seen that have an 8-71 kit for a SB.
 
We still make the V-8 Detroit Diesel with the 8-71 for off road use though. Pretty amazing after all these years they still make them. Jayson


yellowdartdave said:
The 6-71 blower was made for a 2 stroke 426 cube 6 cylinder Detroit Diesel.

The 8-71 blower was made for a 2 stroke 568 cube V8 Detroit Diesel.

The 6-71 would probably be easier to fit and still make plenty of boost,
but I would check with experts on these blowers on gas engines.
Click to expand...
 
Lot of good simple information on the Blower Drive Service web site.
http://www.blowerdriveservice.com/#

I think the simple answer to your question is that the 8-71 is to big for your motor size. It will require more HP to run that blower on your engine netting you less HP overall.

If I remember right the 6-71 is good for up to almost 430 cubic inches in most cases.
 
[COLOR="Blue" a lot depends on if this is an all out drag car or street cruiser????

as stated already,,a 6.71 is good up to 426 cubic inch motor,, no reason to go with an 8.71 on a small block,, unless u plan on spinning the 6.71 hard,,,

pump gas 93 will only support 9 lbs of boost,,,i am under driven by 6% and can make 13 lbs of boost if i stay in it long enough,,with a 6.71 and 7.76 compression,,,,

the harder u spin the blower,,the more heat it will make,,if you had big cubic inches and tried to make a lot of boost with a 6.71 it would make a lot of heat,, so puttign an 8.71 would cook it down a tad,,,[/COLOR]a 6.71 is plenty on a 318
 
Well, my initial thoughts were that I would probably run around 10 pounds of boost for normal driving, but I would kick it up to somewhere between 15-20 at the track when I have race gas available. From what I saw on the BDS website it seems to depend on what 6-71 I would get (small bore or large bore). I think the small bore might have a hard time, it would put out 10 pounds 1:1, but I would have to overdrive it pretty much all the way to get over 15. The big bore 6-71 looks to be almost the same as the 8-71. I can tone it down to 10 pounds with underdrive and at 1:1 it's making a little over 15. Granted all of this is just off of BDS's charts, so there's no real telling till I build the engine how much boost I would make. I was also looking at a different brand (Dyer's), so I don't know how the BDS chart compares.
 
Less than 400 cubes, I'd go with a 6-71. I ran one on a 68 426 Hemi for a number of years on the street. It made plenty of boost, and I ran a bit of overdrive on it.
A 318 with a 6-71 is a great match. One thing though. You probably already know to build the engine with forged everything. Don't waste you time, or risk the engine by trying to save a buck with cast parts.
 
Yeah, forged was the main thing on the list with the blower. Trying to figure out what else I want to do. I always hear about studs over bolts, but I still don't really think I'm sold either way. From a mechanical standpoint I don't really see a difference, but I don't think a stud kit is that expensive, so we'll see. I planned on a main girdle too, but other than that I'm not sure what else I might need to do internally.
 
Bill Dyer has been doin his thing, for a long time. Why not ask an expert ? "If" you ran E85 for fuel,(cheap inter-cooling and octane), it would tend to offset the heat-up of the compressed air/fuel. Splayed main caps, forged crank, aftermarket rods and forged pistons, a must with boost your describing. Cometic head gaskets or "o-ring the bores", a good idea. Good Luck, ateam.:read2:
 
6 71 is for a 6 cylinder diesel times 71 cubic inch per cylinder motor and 8 71 is for the same but with 8 cylinders. 6 71's will power up to 1000 hp with the right big block combo. 8 71 is probably overkill for your situation.
 
Yeah, I figured I'd talk to Dyer's at some point and see what they had to say and what sort of numbers they get from their setups. I know I'm a long way from being able to buy anything, but I can always dream, lol.
 
Well, I can't really say that I'm not interested, but I'm pretty much flat broke at the moment with all of my recent part hunting, lol. I think it's going to be next summer before I can even really think about engine work. Thanks for the offer though, I'll have to see how things pan out.
 
GTXperience said:
Map63, if interested, I may be selling my new Dyers SB blower intake (still in the box).
Click to expand...
Ok, a Dyer's 6-71 manifold, how much ? Not a 6V-71,(about 2" shorter on length)? I ask because Bill uses both styles. "Short" one moves about 10% less air. Thanks, ateam.8)
 
# 1 bill dyer is garys son,,gary dyer is the orignator of street super charging,,, and drove for mr norms funny car back in the day,,,

# 2 if you have a dyers intake,,unless you have had it 20 years,,,its not a dyers intake,,dyer got out of building blower parts for a few years and was strickly doing connecting rods for the roundy round guys,,,

in the last 2 years DYERS woke up and realized the street super charging industry he created was still alive and well,,back a few years ago GARY dyer thought the street blower thing was dead,,,

if your intake uses a plate on top of a offy 4bbl intake its a dyers,,,if it sorta looks like a real blower intake its built by hampton blowers,,sold thru DYERS,,BDS,,,BIG ALS TOY BOX,, if you want an affordable street blower motor call BIG ALS toy box,,he build complete motors ready to run,,open your wallet,,around 6 to 8 grand,,

here are some pics of a true DYERS intake,,mine,,,

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