Forced Induction Boost experts

[Scout525]

So here’s the story.
I’ve got a forged bottom end 302, stroked to a 342 and afr 185 heads, built initially for nitrous.
The motor was originally built for a track driven 82 mustang. That car frame had some issues so it was time to pull everything and go into the new car. A 92 LX.
I’ve recently switched over to the FiTech EFI from a demon carb.
Anyway, in this swap I’ve debated going to a centrifugal blower setup and getting away from the spray. Here’s the problem, the motor is 10.5:1 compression. I’m not well versed on boost. Doing research, high compression and boost is a no go running pump gas. The issue is, the 92 is gonna get street driven some. Not just a track dedicated car.
Sooooo, my question is, should I stick with the spray or make it work with some type of boost and what kind of risks am I taking going to boost. Running a race fuel doesn’t make sense to me to drive on the street. and I really don’t wanna crack into the motor.
From what I’ve read, if I run boost on it 4 pounds and dropping some timing is about my only option to drive it safely. If that be the case, I’m not sure that it’s worth the extra cost for a blower.

So bring on the thoughts and opinions.

 

[a91what]

the higher compression will narrow the tuning window, I currently have a 306 with 10:1 running 12psi with a roots blower.. pump gas and water injection.. thats the key you have to use something that will increase the knock threshold for the fuel used, I use plain jane 30% blue windshield fluid.... makes 93 act like 104.
With the 342 and good heads it wont take much more than 8psi to find the limit of the block [guesstimating power levels] simply use water injection and remove substantial timing 1-1.5* per psi should be more than safe... I usually dont even pull timing until about 6psi but thats on a standard 9:1 engine with a turbo... dont retard lower than 16* let the boost make the power. Timing will need to be a touch lower around peak torque to keep cylinder pressures happy. ect......

lets bring in some guys that have more experience in specific areas. @FastDriver @TOOLOW91

 

[TOOLOW91]

the higher compression will narrow the tuning window, I currently have a 306 with 10:1 running 12psi with a roots blower.. pump gas and water injection.. thats the key you have to use something that will increase the knock threshold for the fuel used, I use plain jane 30% blue windshield fluid.... makes 93 act like 104.
With the 342 and good heads it wont take much more than 8psi to find the limit of the block [guesstimating power levels] simply use water injection and remove substantial timing 1-1.5* per psi should be more than safe... I usually dont even pull timing until about 6psi but thats on a standard 9:1 engine with a turbo... dont retard lower than 16* let the boost make the power. Timing will need to be a touch lower around peak torque to keep cylinder pressures happy. ect......

lets bring in some guys that have more experience in specific areas. @FastDriver @TOOLOW91

I would love to add more but honestly you hit it right on the head , you will need some type of water /meth injection esp If the unit is a non intercooled variant . The tuning window is definitely much smaller but doable once you have the supplemental injection . Also it won’t take much pressure to make power with the compression in it . Also makes for a real violent car down low

 

[Scout525]

I would love to add more but honestly you hit it right on the head , you will need some type of water /meth injection esp If the unit is a non intercooled variant . The tuning window is definitely much smaller but doable once you have the supplemental injection . Also it won’t take much pressure to make power with the compression in it . Also makes for a real violent car down low

I guess my biggest question is going to be the durability on the street. Really on the fence with it from that aspect. I guess I should’ve put more thought into this when the motor was built a few years ago. It it’s been thrashed on with the bottle and never had a problem. So that’s my “worry” that I’ll send a rod to Mars if I try and go to boost

 

[CarMichael Angelo]

When comparing the two different power adders, nitrous is always more harder on the internals than a blower or turbo ( especially a turbo) due to the way the engine sees the transition from N/A, to power adder.
Nitrous is to power adders as side stepping a clutch is to the drivetrain. Big nitrous adds instant compressive loads versus a blower or turbo, which comes on in a more linear fashion.

I have 10.7:1 cr on a turbocharged engine. It’s currently at gate pressure, (7psi) but it has, and will see significantly more boost here shortly. I use water meth to cool the intake charge, slow the burn, and to add octane.

So far...everything is still spinning like it’s posed to.

 

[FastDriver]

Steve's answer is the right way to do it. It's nuanced and provides a thought process for you to come to your own conclusion, rather than a directive. I'll be a little more blunt. You already have the nitrous. If your block is stock, then you stand to gain nothing from the switch, except avoiding the hassle of bottle refills. High compression motors go with nitrous like low compression motors go with boost. The nice thing about nitrous is that it comes with its own massive cooling effect. Was just reading last night about how it comes out of the bottle at -120*. Dayumn! The cost/benefit is just on the side of going with what you already have. I expect based on the rough sketch of the combo you listed, that you're already in the 400 rwhp ball park. So, you're maxing the block with just a 100 shot. With a blower or turbo, you'll be at 500 rwhp with just 3-6 psi, depending on method (low end with turbo). Anyways, 3+ thousand on a blower kit seems excessive when you're only trying to get 100 hp out of your setup. If you already have the nitrous stuff, that $3k+ will fill a lot of bottles.

That said, if you are going to do it, some other thoughts:

Have you considered, and/or is running E85 an option for you? You sure can get away with a lot more on E85 than pump gas, but the fuel system has to be stout. It isn't an absolute necessity, but it can give you the safety factor you want/need.

I imagine you have a nitrous oriented, or at least n/a, cam. A custom cam has more impact on dynamic compression than you might imagine, and can really tame higher static ratios, which would help with your combo's streetability. There's a huge difference between 2 of my cars that are nearly identical in build. One has a blower cam. The other has a turbo cam. Both have street manners, but the turbo cam/low comp motor is a sweetheart that can drive at 1300 rpm, while the blower cam car doesn't like it below 1800.