4.0 OHV supercharging issues...

holyford86 · May 29, 2010

I got ahold of a supercharger for a gm 3.8 for next to nothing. Made a manifold to adapt it to the 4.0 OHV lower intake, and made a intake to attach the stock throttle body to it. It will start and die when cranked, and will stay running (badly) with the throttle half open. It seems to me that the engine is not getting enough air, the way that i would corrrect this would be to swap to a smaller pulley correct? The pulley that is on it now is about 3.75 inches. I'm looking to get about 5 pounds of boost out of this if possible.

Snurfer · May 29, 2010

is your bypass valve opening and closing properly? did you get all your vacuum lines hooked back up on the intake side of the blower?

cammeddrz · May 30, 2010

it sounds more like lack of fuel than lack of air. that mistake is frequently made. which year of 3.8 did your eaton blower come off of? you are using the stock 4.0l fuel rails on the lower manifold? what are you doing with your mass air meter? (or did that year of 4.0 have one?) but more importantly what abour your map sensor?

Snurfer · May 30, 2010

we will need more specs on your setup with the blower. are you using all stock parts and just adding the blower to the 4.0? you running a stock 4.0 MAF? also with the adapter plate you made to attach the blower to the upper plenum.. if it is not completely sealed and pulling air from the intake only that will cause the motor to run like shit as you're pulling air in that is not being metered by the MAF. tell us your particular set up and we will be able to further assist your issue.

Destroyer000 · May 31, 2010

its a 95 4.0 motor. has a 410 cam in it thats about it. everything else is stock. the chager came off a 97 grand prix . iam using the stock maf sensor, a few of our vaccum lines Wern't pluged off and the idle air controller wasnt hooked up. i think this might be the biggest problem of it all.

Snurfer · May 31, 2010

well you NEED to hook up the previous vac lines that went into the stock intake manifold and get the IAC valve working again.

Destroyer000 · May 31, 2010

i plan to work on it a bit more an see what i can get.

59bisquik · Jun 8, 2010

How bout some pictures of your setup... This sounds really interesting!

disciplerocks · Jun 8, 2010

Did you upgrade the injectors also? A wideband sensor will tell you which you are lacking, and if its fuel you'll end up hurting your pistons.

Snurfer said:
well you NEED to hook up the previous vac lines that went into the stock intake manifold and get the IAC valve working again.

Yes. Some vac lines can be bypassed, but its better to just hook them all up. And IAC is a must.

holyford86 · Jun 19, 2010

well some progress was made, got the IAC mounted and working, sealed up the vacuum leaks just to see if it would run, nowhere near finished but it's a good start for now.

2813josh · Jun 19, 2010

Haha that's awesome..love that sound

ZMan · Jun 25, 2010

stock 3.8 pulleys are 3.8" for reference. I would definitely NOT put a smaller pulley on, they pump out 8psi stock. Some pics and how tos on this swap would be awesome!

holyford86 · Jun 29, 2010

well, the charger is on and working. It doesn't start to build boost until about 4500 rpm + though... Did some research on pulley sizes and discovered that the 3.8 uses a 7.1 inch crank pulley and the 4.0 pulley is an even 6.0 inches. The drive ratio is roughly 1.869:1 for the stock 3.8 setup on the 3.8. The drive ratio of the 3.8 supercharger on the 4.0 is 1.578:1, using the 3.8 inch 'charger pulley. Looking to make this start building power around 2200 rpm... Is there some kind of formula that I need to know to figure out what size pulley I need for this setup. From my math a 3.2 inch pulley seems like it might be exactly what I need.

92 5 oh · Jun 30, 2010

wow that's awesome!!
i'm not a roots style expert, but i've got some hands on blower experience. so i'll put in my 2c and a few questions as well..
first, i agree with your math, the difference on the final drive is .3, so a 3.2" blower pulley should get you close to the same boost as the pontiac. assuming you've got no boost/vacuum leaks, i could see the larger pulley not creating boost until higher rpm.
what are you doing about the MAF and MAP? i wouldn't be surprised if you would peg the MAF. And for the MAP, i wonder if one from a turbo Tbird or SC Tbird would fit the wiring harness??...
and i'd also get a one way check valve on the PCV.
I'd also be curious what the A/F is under load/boost. i'm not sure what size injectors come on a 4L. 14#? stock mustangs have 19#. if memory serves me correctly, they'll support somewhere close to 300 hp. i'd guess the stock pcm would drive those ok?..
i'm not sure what options are available for upgraded MAF for a 4L. again, i'm not a supercharged ranger expert but there are a few things i faced when working on my blower....
keep us updated...

disciplerocks · Jun 30, 2010

If you are doing so, you need a wideband a/f gauge. I would not run it at all without one. Without knowing you could run lean and chew up your pistons. I know they are pricey, but its cheaper than a new engine.

Just for reference, at idle you should be at 14.8 and at WOT you should be under 11.2.

4.0 OHV supercharging issues...

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