Eagles International Forum

What is the difference between a "large bearing" blower, and a "small bearing" blower. Does it make any difference in the installation of one or the other on a 8v71N?

Jim, I had hoped that someone would have knowledge of the two bearing size blowers. I have not heard of different bearing sizes, so I decided to do a bit of research.

The research was fun for me, since I was the blower belt guy for Gates and have followed blower technology on gas/alcohol/nitro automotive engines.

As background, racers have adapted our beloved two stroke blowers to automotive engines to "supercharge" the engine. This gives huge power increases when done properly. For decades, the racers have adapted 4-71, 6-71, and 8-71 blowers for their engines (they don't use the 4V71 etc designation like we do). For the "big boys", the aftermarket has created 10-71 and 14-71 blowers with the same basic technology.

There is a ton of information about these "adapted" blowers on the internet. One fun site is: http://www.hotrod.com/articles/hrdp-130 ... 17-blower/

My research did not reveal different bearing sizes options. Part of the issue is that racers often use different aftermarket end plates. Here is a link to one blower parts list: http://www.alsblowers.com/theblowershop ... nents.html. From that list it appears that the front and rear bearings are different, but they don't seem to list different bearing sizes for one end.

Probably more that you wanted to know

Jim

Jim, you are ok with a small bearing blower on a 8v71/NA engine the larger bearing blowers came in to existence when the turbos got popular. Most small bearing blowers are 80% capacity and the big bearing blowers are 88 to 100% .
DD made 16 different blowers for the old 2 stroke.If you planning on raising the HP to 304 or 318 with 70 injectors go with the big bearing 100% blower.Lol if you need one I have a dozen or so

Clifford, I knew you would have the answer.

Now the question is to how to identify the two blowers.

I have noted some blowers have what I call "single ribs" and others have "twin ribs" (see photos)
Can these ribs be used to identify the big and small bearing blowers?

Jim

Jim, the single rib in the 1st photo is for the the inline 6-71 it bolts to the side of the block the twin rib blower is for 6v71 or 6v92 all twin ribs are for the V series.Only way to tell which blower a engine has it will have 4 numbers like 1692 stamped at the rear on the right hand corner looking from the front of the engine, the casting numbers don't mean much because you can change end plates and rotors and they have different gear ratios also the N/A engines are a higher speed gear ratio HTH

Once again, Clifford and Jim.....you guys stepped up and gave a nice clear answer, with all the info I needed. Thank you so much.
After waiting a week or so, it didn't look like anyone had the answer to the Big and Small question....so I went hunting inside my huge, convoluted DD 71 Series Maintenance CD. Deep within it, in the Blower section, I found a one line statement, that said that SMALL bearing Blowers were used on the N model engine, and the LARGE Bearing Blowers were for the Turbo's. Exactly what Clifford said. Since I'm determined to tackle this myself, it's good to at least know what the heck the bearing size is.
Yes, Cliff, I may take you up on one of your blowers. But I'm going to dig into this thing in the next couple of weeks and see exactly whats going on. I'll let you know what happens.

Thanks again Clifford and Jim. It's so rare nowadays that someone makes an effort. It really is.

Best,
Jim

One of the benefits of this forum is that if your answer is not correct (mine was not), someone will get you straightened out

Jim

If you ever need blower parts I buy from http://www.deanblowers.com he is about 1/2 the price of Detroit,he is a speed shop but knows DD blowers fwiw

Sadly, I have all the parts to make a blown early Olds engine, but will probably not live long enough to get to that project. I even have quite bit of Cad/La Salle parts and transmissions including 3 or 4 floor shifts. I have two 50 Olds that need finishing.

Can you say really old school

Jim

I know the feeling Jim no green bananas or tomatoes for me either