tuning for blower

R

revkev6

Senior Member
hey guys, I know this is the "stock" section of Ryans sites but there's more flathead specific guys here I think. I'm planning to setup a blown flathead with an Eaton M112 off a late model jag. planning for 5psi max. probably 2 97s as that's about all that will fit. not looking for crazy horsepower numbers, just want a cool setup that will make some good reliable torque.

so, what do you guys do different on a blown motor and NA?? specifically ignition and carb tuning. looking to keep it old looking even though it's a "new" blower. I will be making a plate to mount the carbs on the top ribs of the blower. thinking it will look a little like a poor mans scott.
 

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Do you have a copy of the books specific to supercharged flatheads? Might find some additional help there.
 
I don't have the books yet. they are on my list to purchase. figure while I'm waiting it's always good to get first hand accounts as well.

joe abbins book is a good one correct? any others?
 
I like Joe's books. You are correct, there are several Barn members with supercharge experience.
 
Keep us in the loop as to your progress, I have some M-90 Blowers that I am hesitant about using for a top mount carb system, I see where the M-90's don't have a seal on the rear bearings , I am wondering how the M-90's will hold up as far as gasoline through the rotors, I am thinking about mabe using them for a blow through system.
Fordestes
 
My next blower will be a 371 G.M.C, I am guessing it will be twisting kinda tight for about 5 lb's on a .060 over 255 merc. I see where there is a v belt drive offered ,it sure would beat making all of the drive from scratch. lots of luck!
 
Fordestes said:
Keep us in the loop as to your progress, I have some M-90 Blowers that I am hesitant about using for a top mount carb system, I see where the M-90's don't have a seal on the rear bearings , I am wondering how the M-90's will hold up as far as gasoline through the rotors, I am thinking about mabe using them for a blow through system.
Fordestes
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I found a guy on Ebay who lists a sealed bearing for these units. They want 44 a set for them though. Tomorrow I will try to find a link. I called my local bearing house and they couldn't find me one.

I cut the center out of my intake the other day. Have a friend bring some aluminum plate tomorrow too.
 
Fordestes, who has a V Belt drive system for a 3-71? I have been working on and off on a 4-71 blower set up for my 286" Flathead. still in the mock up stages, ( has been for a few years). I have to build the rest of the car also, but am making slow progress
 
Thanks revkev6, this puts a whole different spin on my blower Idea . Alaska Jim, I sent a p.m. I hope I was able to help out . I bought my blower hub from alky Diggers a while back , It has the usual 2 inch pilot, thus making it possible to use many different ready available drive systems .
 
Fordestes, I did not receive a pm. I am wondering if there is something wrong with the Pm option for me. as I have had a couple of people send me Pm's lately , and when I send a pm back I never hear from them. I do not know if there is a problem , or if people are just not having the courtesy of answering. anyway, could you try again? if it does not come through I will try sending you a PM with my personal E-mail address. Thank you.---- Jim
 
Fordestes said:
Thanks revkev6, this puts a whole different spin on my blower Idea . Alaska Jim, I sent a p.m. I hope I was able to help out . I bought my blower hub from alky Diggers a while back , It has the usual 2 inch pilot, thus making it possible to use many different ready available drive systems .
Click to expand...
Fordestes, would you please send me the link for the blower drive also. I have a 3-71 I plan on putting on a flathead on my next build. Thank you. Bill
 
Outlaw, Check your e mail ,let me know if it made it to you , I sent my phone no. too, if I can be of further assistance.
 
Reply to Original Question: The most important aspect of tuning is to ensure that you have adequate enrichment under boost (proper air-fuel ratio) and that you reduce the timing a bit. BUT - that is a general statement and it all depends on the amount of boost you actually generate . . . and also the duration and lobe seperation of the camshaft (which can influence it a bit).

You can probably get away with 6 - 8 lbs of boost on premium fuel . . . though you need to work through the tune on a dyno (if you're smart).

Things to help: I would put dual O2 sensors in the exhaust system - making sure there are NO gasket issues/leaks ahead of the O2 sensors and that they are about 24" or so from the rear exhaust port - with at least 12" of pipe behind them. These will really help you tune it under load.

You'll want to initially keep the AFR around 10.0 to 10.5 to 1 under boost . . . hopefully more toward the "rich" side to start out. I'd probably not run it much leaner than about 11 - 1. I'd initially set my timing at 18 degrees. Then - as you make a few dyno pulls, get the AFR correct under full power/boost, then you might move the timing up 2 degrees at a time and check your plugs as you go.

I'd run NGK plugs - with around a '9' heat range (you want colder plugs and 9 is a bit colder). With NGKs, the higher the number the colder the plug - opposite from Champion.

You should inspect the plugs to see if there is any evidence of the plating coming off around the bottom (it will usually bubble a bit first). If you start seeing the plating flaking or the electrode showing signs of heat (small amount of melting), then you're getting too lean and you need to richen it up or your risking detonation and catastrophic failure.

The O2 sensors are extremely helpful for tuning - especially if you are new to boosted applications. It is hard to read plugs for air/fuel ratio these days . . . due to how our modern fuels are formulated . . . the O2 is your best friend. If you're making/buying new headers - I'd also go ahead and put two EGT bungs in the rear two cylinders - as close to the block as possible. I use both EGTs and O2s to help my tuning on any high performance engine.

Good luck! If you need any help, feel free to contact me.

D
 
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