I'm planning on installing a Weiand 142 cid Supercharger onto a ZZ4 350 Crate in the near future and I was wondering about hood clearance. I'm pretty sure that the Supercharger wont fit under a 2 3/4'' hood on a 71 Camaro but it kind of looks like it sits low on the engine. Do you think i could fit it if I put a 2'' high filter on the carb or will I have to get a new hood? right now I have a 5'' filter on the Engine and I have no clearance problems. Thanks.

 

Well, on my 78 Malibu I've got it under a 2.5" cowl hood but it was a fight for every millimeter of clearance and air filter height.

I currently run a 2.5" open element (14" diameter) in a typical parts-store 1.5" drop-base open-element air cleaner housing. I have it spaced up with a small stack of air filter gaskets to get the lid as high off the top of the carb as possible (for best airflow) without touching the hood. It's TIGHT.

If I had it to do over again I'd just get a 4" cowl hood and be done with it. It's just the little 2.5 is much more "stealthy" on the street. People see a 4" hood and think it's gotta be fast. I like people not giving me a second glance.

 

Thanks for the help, I figured that it wouldn't fit but now I think I can try to run a 2'' element (Xstream top) and it will fit, thanks.

 

KC- from my expereince with very low profile air cleaners (on my blower engine and a lot of other projects) I'll caution you about making sure the lid of the air cleaner is not too close to the top of the carb. It's not jsut about FLOW, it's also about giving the air stream room to "strighten out" before it goes down into the carb's venturis. If the lid of the air cleaner is too close you can get some WEIRD carb behavior. Bogs and stumbles that simply can't be tuned out of the carb. A Holley with the stock "tall" choke tower around the primarys is particularly susceptible to this phenomenon.

USE EVERY DAMNED MILLIMETER OF HOOD CLEARANCE YOU CAN TO GET THE AIR CLEANER LID AS HIGH OFF THE TOP OF THE CARB AS YOU CAN!!! Every millimeter goes straight to making more power and avoiding weird bogs and stumbes.

Also, if using a VERY short air cleaner element (2-2.5") and a drop-base the space between the base and the lid gets REALLY skinny- like less than 3/4" in the tightest spot. I really don't recommend an element shorter than 2.25" if you're using a typical 1.5" drop base.

Pay real close attention to detail here. I personally expereinced SEAT OF THE PANTS improvement from my initial air cleaner combination to the "optimized" air cleaner setup I have now.

If you get stuck feel free to email me and I'll help you get to the best possible combination, given hood clearance constraints.

 

Is it a good idea to use the K&N filter lid to help compensate if using a shorter filter?

 

Tried that. No good. It's the same height as a stamped steel lid on the outside but the filter pleats stick down an extra 3/4" on the inside. Makes the situation worse with a very low profile air cleaner, not better.

 

When you put the blower on you Malibu did you lower the comp. Your 1/4 times are close to what mine are now I run 13.2 on street tires no Drag Radial times yet. Well any way I want to be in the low 12's High 11's So I was just wondering what mods you made when the blower was installed.

 

This motor was built for a blower. My last motor was a "compromise" motor and it went just as fast, but a lot more of a PITA dealing with borderline detonation, etc. from the wrong cam (Crane 272 Energizer single pattern) and too high a compression ratio (9.4:1 with iron heads). The old motor ran 13.4 @ 106 before the blower went on (4bbl carb and typical dual-plane aluminum intake, street radials). After the blower was put on it went a lot faster. Not sure exactly how much faster, since with all the headache issues I never got it to the track. Probably about the same as my new motor. Not what I was looking for- having to tune on the edge of detonation. So I built the new motor....

This motor was built with KB Hypereutectic 18cc d-dish pistons (rings gapped much wider than usual per KB's recommendation for a blower application). With 74cc aluminum heads compression checks in at a blower-safe 8.7:1. I can run pump gas and never approach detonation even on 90* days. What I gave up in compression I made back on the cam. It's a Comp XE268 ground on a wider 114* LSA to help keep from blowing the boost straight out the exhaust and with more exhaust duration to get othe massive amount of exhaust gas out of the cylinder. It's not actually a custom grind- I just searched through the catalog and found that they offer the XE 268 on the wider LSA for GM TPI motors. It happens to work just peachy for a mild blower application, too.

If you're running 13.2 now I would think that just bolting on the blower would net you low 12s, all else held equal, given that your N/A compression is probably too high and you'll have to pull the spark advance back quite a bit to keep out of detonation.

Detonation on a N/A motor makes a little rattling noise and puts some flecks of aluminum on the plugs so the next time you change them you say: "Hey, I've had some detonation going on here. Better back off the spark advance." On a blower motor the first sign of detonation is when the motor goes BANG! You'll never hear it over the blower screaming and the loud exhaust. And it won't last for more than a few seconds running in detonation. Detonation is VICIOUS and VIOLENTLY DESTRUCTIVE in a boosted application. There's no time to "figure it out". It just goes BANG and you don't realize you were in detonation until you're tearing down the grenaded motor. And then you know not to do it that way the next time.

 

all this talk about a super charger has me thinking.....would it all fit under my 2 3/4" hood.....

 

At what compression do you start to deal with detonation and if I have above this compression in the new crate how can I avoid it (maybe bring back the timing on distributor?).

 

There is no SET compression that detonation happens. It is a mixture or comp. ratio, timing, and fuel octane.

Avoid detonation by retarding the timing and/or bumping the fuel octane by using a proven fuel additive or race gas.

If your comp. ratio is too high to start with, it's not worth the headaches and possible costs in the future to use the blower.
Just build a new short block with lower compression and forged slugs.

Heavy

 

did you already buy the blower?

because I read a few articles on the vortec(or other) supercharger that mounts like an A/C compressor and then uses a carb hat to get the boost into the carb

had some awesome numbers even when they put it on a 4.3

 

I read an article comparing a centrifugal blower, a roots style, and a turbo on the same engine, and the centrifugal blower (the type you're describing) really performed quite well. You make a good suggestion for someone without hood clearance who doesn't want to cut a hole to fit the roots type blower.

 

A well-chosen centrifugal is more efficient at higher RPMs and will make more peak HP. BUT.... it builds boost relative to RPM. It'll make very little boost in the low-mid RPM range. A roots blower, on the other hand, will make full bost from the instant the pedal hits the carpet. It all depends what you're shooting for. Below maybe 4500 I doubt there's a centrifugal blower that could make more power than my roots blower at equivalent boost levels. Above that, the centrifugal will probably pull ahead. It's tough to compare the two- apples and oranges.

The roots also has another advantage if used in a carbureted application..... you just bolt the carb on top with little or no changes and you go. A centrifugal setup with a carb requires a carb and fuel delivery system that is designed to work in a blow-through application. Significant expense and more trouble to tune.

There's a reason that carbs and roots blowers are a common combination. Simple to set up, and brutally effective. EFI and centrifugal blowers complement eachother similarly- they have their own set of reasons they work well together that are very different from carbs and roots blowers. Anything can be made to work with anything- it's more a matter of the shortest/easiest/cheapest route to the final goal.

 

Damon, that's some good insight on roots vs. centrifugal.........I think you're probably bang on the money (I'm not too knowledgable about blowers "yet"!).