Diesel blower to gas

55merc · #1 (**permalink**) 06-15-2009, 07:31 PM

Any one know what needs to be done to convert a diesel blower to use on a gas v8.

frederic · #2 (**permalink**) 07-02-2009, 01:56 PM

What it was from and what it's to be used for matters little.

You need to devise, fabricate or buy an intake manifold that supports the blower, devise, fabricate or buy a pulley system to your crankshaft, and devise, fabricate or buy a plate that mounts on top (or in front) to graft carbs or a throttle body to it.

Zookie400 · #3 (**permalink**) 07-07-2009, 01:33 AM

Quote:

Originally Posted by frederic

What it was from and what it's to be used for matters little...........

not true.....a blower from a 6-71 or similar detroit is not for building pressure, it is only there for scaving and the turbo builds the boost pressure. you could put it on your gas engine and it would not give you any performance gain at all, in fact you would LOSE power. you would need to retrofit the blower with seal-tipped rotors that would actually build pressure for you.

if it was a blower meant for building boost pressure, what frederic applies perfectly....you just need to mount it and spin it the right direction, and away you go!

Rcmgiasson · #4 (**permalink**) 07-08-2009, 12:39 AM

If taken off a diesel you also (assuming your talking about some kind of 71 series detroit or the like) have to be change the end plates (because the detroit runs and lubricates the the blower through a gear drive off the camshafts and not a belt), if taken off an in line 6 detroit the blower casing itself has to be machined because of a ridge on one side of the outside of the blower.

everything else mentioned above applies too...

mongo75 · #5 (**permalink**) 07-08-2009, 05:32 AM

So how do all those older NA Detroits charge thier cylinders if the supercharger doesn't build any pressure?

Rcmgiasson · #6 (**permalink**) 07-08-2009, 10:02 AM

There are no intake valves on a jimmy, just holes in the cylinder. When the piston goes below a certain point (basically BDC) air is allowed to move through these holes into the cylinder which also pushes the exhaust out. No "boost" is required to do this, just air movement... Thats why they are considered 2 strokes, the intake and exhaust strokes occur on at the same time.

mongo75 · #7 (**permalink**) 07-08-2009, 03:52 PM

I know how a 2 stroke operates, I was being facitieous (sp). What I'm saying is on a 2 stroke diesel, without a blower, you will not get the proper amount of air into the cylinder. Therefore the blower does provide more than just scavenging forces, it also "charges" the cylinder. When combined with a turbo, it charges it even more.

Rcmgiasson · #8 (**permalink**) 07-08-2009, 08:38 PM

Without a blower you will not get any air into the system... a blower is just an air mover and does not produce boost. "Pressure" and "charged" are not the same thing and you do not need one to produce the other. Lastly scavenging is a term which only refers to the process of moving air in and exhuast out on the same stroke. When the blower "charges" the cylinder on a jimmy its still considered to be atmospheric and thats why a 2 stroke detroit with only a blower is still considered naturally aspirated. Only when a turbo charger is added is boost or "pressure" created.

If want to get real techinical about it, a blower is what a jimmy has and produces no "pressure" or boost and its effiency is measured in air mass, a supercharger on the other hand does produce boost and its effiency is measured as "pressure"(units in PSI). Those of you that say a jimmy is supercharged are incorrect...

Don't believe me look it up...

Lead Head · #9 (**permalink**) 07-11-2009, 09:47 PM

The roots-type blowers on Detroits CAN build pressure when strapped to a gasoline enigne. The only problem is that you have to spin them quite fast to generate pressure, and they are not terribly efficient. Drag racers and other V8 performance enthusiasts don't call certain blowers 6-71, 8-71, etc...just for fun...

MisterCMK · #10 (**permalink**) 07-11-2009, 10:15 PM

Quote:

Originally Posted by mongo75

I know how a 2 stroke operates, I was being facitieous (sp). What I'm saying is on a 2 stroke diesel, without a blower, you will not get the proper amount of air into the cylinder. Therefore the blower does provide more than just scavenging forces, it also "charges" the cylinder. When combined with a turbo, it charges it even more.

A 2 stroke diesel without the supercharger will not run.

An interesting tidbit of information, theoretically you can take the rod caps off of a 2 stroke diesel while it is running and there will be no issues. Theoretically of course.

Freightrain · #11 (**permalink**) 07-15-2009, 05:03 PM

Ok............if a Detroit blower won't build boost, then ALOT of top fuel guys must have some secrets to why they go 300 mph on a n/a motor? (are they hiding two carb under a phony blower cover?--like alot of rodders used to do LOL!!!).

YES, a diesel blower will work on a gas motor with minimal effort. First you need a GOOD one, ie: good clearances, bearings, etc. Using a used up swap meet version usually will make you more headaches then power. I personally used a brand new blower on my '64 galaxie, but did have to do some machine work on the ends to make it work. No rocket science. Buy the intake, belt drive set up, carb plate and bolt it on.

"you would need to retrofit the blower with seal-tipped rotors that would actually build pressure for you."
Strange, mine isn't nylon tipped and builds 6# of boost all day long. Yes, people do offer that, but then again if any dirt goes get into it it will likely wipe out the case easier. In a mild power application, a stock version works fine.

It's been in the car for 9 yrs now with no maintenance or problems. I have friends that have run ones for 20 yrs and never had them apart. Granted it's not a daily driver, but does get its share of mileage.

http://www.youtube.com/watch?v=qLThOGOZLfk

85e150six4mtod · #12 (**permalink**) 07-16-2009, 05:36 PM

I didn't see this info in your gallery, forgive me if it's there. But just for grins and the benefit of the OP:

--looks like a pretty good underdrive, based on the size of that top pulley. What underdrive are you running?

--Compression ratio?

--Pistons? Forged?

--Rings? Anything special?

--Rods?

--Any other blower prep?

--oil supply for the blower, or is it self-contained?

Thanks in advance. Nice looking vehicles. Love that wheels up wagon shot....

Freightrain · #13 (**permalink**) 07-16-2009, 11:30 PM

Ya, pretty laxed in the boost dept right now(only ~6#) @ 15% underdriven. It's a box stock, stock cast piston(orig bore) '68 390 with .53 Crower solid tappet(cause I had it), stock heads with stock adj rockers, rebuild rods(ARP), oil galley mods and HV pump.

The blower was new in box, gotten at auction(cheap) as it had a broken bell end on it(was dropped?). I bought the BDS drive parts, machined the input shafts(removed the original double gearing) and bolted it on. Nothing else done to it. It's self contained oiling in front, the rear bearing plate uses sealed bearings. Like I mentioned, 9yrs and haven't touched it. I don't abuse it too much as I know the motor is a bomb until I hit the lotto and build a good piece. I have a spare SCAT 3.98 crank(neutral balanced), another block ready for crossbolting but need all the rest to finish it. It's a cruiser and I drive the wheels off it.

I keep a 6000 chip in the rev limiter and it will hit it effortlessly even with stock dizzy(ya, single points and all-no fancy MSD or boost retard). Takes 3rd gear before it tries to hook up. With a couple tries at the track a few years ago it doesn't ET very well, but pull 111 mph.

Zookie400 · #14 (**permalink**) 07-17-2009, 08:36 AM

Quote:

Originally Posted by Lead Head

The roots-type blowers on Detroits CAN build pressure when strapped to a gasoline enigne. The only problem is that you have to spin them quite fast to generate pressure, and they are not terribly efficient. Drag racers and other V8 performance enthusiasts don't call certain blowers 6-71, 8-71, etc...just for fun...

the blowers are called #-71 because they are that STYLE of blower. if you were to take the blower from a 2 stroke detroit, and not modify it, it will not make ANY boost. there are visible gaps between the rotors where all of your pressure will bleed by.

i agree that if you spin the thing fast enough, you may see some boost, maybe a few psi....but now the parasitic power draw will likely outweigh the increase from what little boost you might create.....so it would make much more sense to just buy a blower (or modify the diesel one) so it spins slower and makes more boost, so you can actually have an increase of power rather than just a cool looking spinny thing on top of the engine.

Quote:

Originally Posted by MisterCMK

A 2 stroke diesel without the supercharger will not run.
An interesting tidbit of information, theoretically you can take the rod caps off of a 2 stroke diesel while it is running and there will be no issues. Theoretically of course.

it will run, but not for long and with a LOT of heat and smoke.

detroit silver 92's had half moon rod bearings, because there was always downward pressure. the pressure wasnt enough from the blower alone, and things wore out very quickly.

Freightrain · #15 (**permalink**) 07-17-2009, 05:12 PM

"71" is the cubic in PER cylinder for the Detroit that they came from 6/71 in both V and inline versions, 8v71, 12v71, 14v71.

The "6 or 8v92" is 92 ci/cylinder, but the blowers are redesigned and won't work as the old "71" models.

Yes, you can get 8-12 lbs of boost from a "stock" blower. Yes, they aren't efficient due to the heat it creates as it compresses the air/fuel mixture(they offer intercoolers now). That is the reason ALOT of guys have moved over to turbos for easier power increases. Nothing shouts "HP" like a big huffer hang'n out of the hood.