HondaCowboy82
Full Access Member
Just wondering if any of you have ever tried to put a 6-71,4-71, 8-71 supercharger on a 6.9 or a 7.3 ? if you have, please tell me what came of it, cuz i am considering trying it on my 86 6.9 :draw
6-71 blower/supercharger on a 6.9?
- Thread starter HondaCowboy82
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turbo69
Innocent Bystander
I think there have been one or two try it in the past with little success, but I'd say go for it. I say go for it, what have you got to lose besides a motor and your sanity?
RKOCH
Fellow Oil Burner
I have seen a 14-71 littlefield on a 7.3 it ran like nothing I have ever seen.
HondaCowboy82
Full Access Member
which do you recommend for a daily driver? 6-71, 8-71, or bigger? I dont want one so big that its goin to mess my motor up.
RKOCH
Fellow Oil Burner
6-71 I think would be all you want.
HondaCowboy82
Full Access Member
What kind of power increase could i expect? 
I wondered about the 6-71 roots too on a diesel. One thing you have to remember is that boost is instant as soon as the throttle is opened. If you ran with out a throttle plate you would have boost all the time but no fuel I guess. If you can get it to work throttle response will be wild. On 350 to 400 cu in you should be able to get about 28 maybe 30 pounds of boost out of a good 6-71. You could go with an 8-71 and get about 10% more. The drive will have to be home made unless you can use some race stuff. good luck.
bentwings
bentwings
On an IDI, that's not a good thing! With the stock compression ratio, there simply isn't enough space to shove in more than 10 psi consistently without risking breaking things (head gaskets, head bolts, pistons, etc). Head studs can help some, but I still wouldn't be too comfortable going above 15 psi or so with studs and fresh gaskets.bentwings said:
As to the original question, I don't see why it couldn't be done as long as you find a way to regulate the boost pressure...BUT, considering the modifications that would need to be done, IMHO it would be better to just put a turbocharger on it. No fabrication necessary if you get a complete kit (even used, unless parts are missing), and with a wastegate, it'll be easier to regulate boost (and, at least with my non-wastegated turbo, it's difficult to get pressures up into the "danger" zone)...
Just my $.02...good luck either way!
There has been a lot of discussion about blower v/s turbo over the years, and all agree that a turbo makes more sense, both financially, and technically. However, I'd like to see somebody post some pictures of an IDI equipped with a mechanical blower just so somebody could testify that it can and has been done, and what improvement if any was noted. I suspect they would serve as a warning to others that it wasn't worth trying, and then we could site it as such.
RKOCH
Fellow Oil Burner
My buddy had the 14-71 on his for 10 years with not the first engine problem.
RKOCH
Fellow Oil Burner
I think I have some around here. It was a pullin' machine. He was a machinist so the drive was no big deal. And we just welded a sheet metal intake to mount it on.He also had boost limting valves and it was underdrove. Instat response.
Did he lower the compression ratio as well? If he only used the truck as a puller, it would make sense...after getting the compression ratio down to the 17:1 range, you should be able to safely get more boost into the cylinders. That said, a 17:1 ratio 6.9l wouldn't make a great daily driver...there's a sound clip floating around of one of these being cold-started on a sunny summer's day using a fully-working glow plug setup AND ether, and the engine acted as though it were in sub-zero temperatures with non-functioning glow plugs.RKOCH said:
Ken (land_yaght {did I spell his handle right?}) did this with a 6.9l (in fact, the sound clip described above was of his truck), but IIRC he wound up scattering the bottom end when he tried to pull with it. Last I heard, he hadn't given up, though...
RKOCH
Fellow Oil Burner
No he did not lower the compression. He limted boost by underdriving and poppet valves. It only pumped about 20 psi but it was 20 psi right now no lag. It was a daily driver.
Freight_Train
Traitor to the brotherhood
The Warden said:Did he lower the compression ratio as well? If he only used the truck as a puller, it would make sense...after getting the compression ratio down to the 17:1 range, you should be able to safely get more boost into the cylinders. That said, a 17:1 ratio 6.9l wouldn't make a great daily driver...there's a sound clip floating around of one of these being cold-started on a sunny summer's day using a fully-working glow plug setup AND ether, and the engine acted as though it were in sub-zero temperatures with non-functioning glow plugs.
actually,he didn't scatter it.It pushed the main caps off like a old Flat head Ford.He found the weak link in a 700Plus horse power engine.I Think the Rods and pistons survived too.
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