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Old 12-24-2010, 01:59 AM
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Supercharging 350

Would like some information on supercharging 350. I am doing a complete tear down and rebuild of 70 Nova. Starting with 350 block which i plan on stroking. What crank, cam, pistons would be recommended. Also, blower used?

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Old 12-25-2010, 12:32 AM
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You have tapped into a superb resource for answering your questions, and I say that as one in exactly your position a few years back. There are several "regulars" on this website with expertise in complete blower setups. First, I recommend that you purchase and read "Street Supercharging" which is a superb, entry level, text on the basics to consider. I have been involved with hot rods for 50 years and, had I earlier understood how simple and reliably blowers can be run in street/strip applications, would have started to run them 40 years ago. Second, you will need to make threshold decisions about the combination you desire. Strictly street, with occasional boost, will indicate one setup; street/strip, with some WOT passes, will advise another. I first ran a Weiand/B&M 142/144 blower, with a single Edelbrock 800 cfm Thunder AVS on a 350 with 9:1 compression, and AFR heads, on my street/strip 3200 pound Model A sedan. This combination ran a best of 11.37 and 117 on the drag strip in a car that also easily could run to the supermarket, ice cream shop, or microbrewery without a problem. After losing the earlier A in a fire, I chose to run harder and, still using the 350 that was in the car which burned up, switched to a Weiand 250 (basically a GMC 4:71) with two boost referenced Holley 600 cfm carbs, and expect to run low 11's, and possible high 10's, on the strip, while continuing, with static compression of 7:5 - 1 in my 355, to grocery shop, run for coffee, etc.
In short, welcome to choosing a blower ! It's a great ride ?
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Old 12-25-2010, 05:43 AM
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keep the compression low 8.1 or less ( I have had very good luck with the kb hypers key is to pay attention to the ring gap they specify) cast crank will work steel is better ofcourse .wide lobecenter camshaft stock rods and good bolts . The blower is actually easier on parts than a high compression engine runs alot better and are basically trouble free . I would recommend the edelbrocks .as stated above grab the book it is good reading,they will recommend the same carbs. have enough radiator to keep it cool and keep timing around 30* and run good gas . if your spending the money go with the 6-71! No reason to stroke the 350 it will run plenty good . in my pics the altered is basically the same engine I described with 7 lbs boost a best of 9.09@151mph ofcourse this is a light car.The henryJ ran a best of 10.32 @ 11lbs with a an old dyers v6-71 both on gas had afb's on the henry and edelbrocks on the altered . I did run 110 gas and timing @35* which is to much for the street in my opinion.
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Old 12-25-2010, 09:01 PM
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1932Bantam was on my short list of experts whose advice you should seek. I add to that list Camaroman7d, ericnova72, cobalt327, carsaavycook, bentwings, dukeofbluz, and, uniquely helpful to myself, F-Bird88. Based on their input, particularly F-Bird88, we were able to solve a recurring problem with backfires through the blower and carbs upon starting. Once we locked the ignition timing at 34 degrees BTDC at idle, the backfires through the blower ceased. Particularly for street-strip use, use of the MSD 6 BTM is worth considering since it allows one to adjust boost and timing depending upon the circumstances presented, i.e., heading down the freeway to grandmas Friday evening or WOT at the dragstrip on Saturday. Also on the topic of carbs, I hoped to run a large single four on my Weiand 250 (which, for swept volume, resembles a GMC 4:71). Numerous runs, however, on an engine dyno showed that with a single carb, the direction of fuel low in the long and low Weiand 250 blower case starved cylinders 1 and 2, causing them to run extraordinarily hot, triggering backfires. Once we switched to two fours, the fuel flow evened out, and the front two cylinders were no longer running excessively lean. Finally, and I would be interested in hearing from others who have used this setup, the variable flow Predators are said to be terrific for blower setups, given their variable venturis. I do not, however, have first hand experience. Anybody out there run Predators on their blowers ?
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Old 12-25-2010, 09:34 PM
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You should be able to run around 34 degrees, and as said earlier, a BTM is worth the small cost. Also considser a methanol injection system, probably the best insurance you can get. I ran both on an 8-71 383, the one time I went without I detonated the motor severely.
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Old 12-25-2010, 10:26 PM
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Its easier to build to the required street pump gas friendly low compression ratio by sticking to a 355cid plan.
The blower makes the power.
Building the motor with the correct low cr allowing more boost
on pump gas is worth more performance than the stroker crank will.


355 -22 cc D cup pistons 5.7" rods
76cc high perf heads 2.02-1.60 (ported OEM factory or aftermarket)
Weiand 177cid blower
750-800-850-950 carb with boost reference power circuit mod.
Any cam in the area of 234 to 254@.050 duration on a wider 110-114+ LSA
will work great.
Solids are preferred as its going to want to rev.
EG: Lunati #401A3LUN Sweet street/strip best with split ratio 1.6-1.5 rockers http://www.lunatipower.com/CamSpecCa...umber=401A3LUN
Timing under boost, using 92 octane should be around 28-30deg.
10-12#s boost. (2.33:1 blower drive ratio)
Water-methanol injection allows more spark timing, power and reliability on street pump gas.

Hang on tight!

Last edited by F-BIRD'88; 12-25-2010 at 10:34 PM.
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Old 12-26-2010, 02:02 AM
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471 hit on exactly why I like to run 2x4 rather than a single 4. They even out the fuel distribution. You can't really over carb a blower motor. More carb just sharpens the throttle response and makes the throttle more critical on the street. I think you will find the motor will nose over around 4500-5000 rpm with a single. It's about the difference between a chirp in high gear vs smoking and fishtailing. haha

As far as blowers go I like the 6-71 for all out tough looking either polished or unpolished in my case ...for a reason.

Manifold ref is a must as far as I'm concerned. I also like vac advance for better gas mileage.

F-bird also hits on another good point. A 355 is easier to get the compression in the right range than a 383. 70 or 76 cc heads and a small dish piston will work every time. You can pack a lot of boost in a 355 and make a lot of power without hurting it. Do use alum heads They seem to be far less prone to detonation.

One other thing is you have to have large exhaust. I modify block huggers for 3 inch collector but it can be done on any other header too. I'd use the largest tube size you can find. Also have the headers Jet Hot coated or other heavy duty coating. They get really really hot very very quickly believe me. 3 inch pipes all the way back.

Don't forget the cooling system. Aluminum radiator, full fan shroud and good high power electric fan with relay for the power control.

Almost forgot, you will need a 3000 or so converter and 3.5 0 or so gears depending on tires...big wide one. haha

As you can see running a blower so you really can have reliable fun is much more than just sticking it on and hoping for the best.

You hit the best forum on the web for blowers. We run what we say not BS and second and third hand guestimates.

Com on and join up.
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