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I’ve gotten different information from Mr Granatelli a few years back, Craig at Paradise wheels (a few years back and today), and several sources on the internet (here and elsewhere). I really hope Speetytang chimes in, as I know he's got alot of experience.
I basically need to know if the VR4 is worth putting on my engine. It’s a big inch motor, but I’m only looking for maybe 4-8# boost max- I just need the airflow (CFM) to fill a bigger motor than the norm around here.
My engine:
STREET BUILD
360 small block dodge bored and stroked to 415 inches.
Edelbrock aluminum heads (nothing great, better than stock, NOT a high flowing race head).
Compression is 10.15:1 but will be lowered for boost, or fuel switched to straight ethanol.
Holley 850 double pumper.
This build put out 462hp at 4600rpm and 520lb/ft at 3200 rpm, while only drawing 618 CFM through the measuring turbine on top of the carb.
What I need to know, is if I set it up at a streetable tension (like those on this board that have them), will it put out enough CFM to get me enough gain to put a smile on my face?I’m not trying to sound suspicious of people’s intents, but Craig would like to buy my VR4/sell me a Novi and Mr Granatelli also wanted to sell me a Novi- Now I’m sure they are thinking I’d be happier with a Novi, but is it true that a VR4 simply WONT work on my build?
Considering that I only drew 618CFM through the carb on the NA setup- how much boost could I expect- then what would that boost equate to considering my NA starting point?
Would a lower boost pressure number equate to less stress on the ball drive and equal more lifespan at streetable tensions? I’ve heard from Mr. Granatelli that the VR4 will only put out 1300-1400 cfm,
I’ve heard from other places 1500 cfm
Craig said that the VR4 doesn’t put out any flow at lower speeds,then comes on strong (he told me today that the VR4 impeller is worse than the regular ones at lower speeds), but I’ve read that the opposite was observed –big time boost ramping in quicker than racer’s previous blowers.
Craig told me that I would be chasing rebuild after rebuild if I tried to run it on this engine. Craig also told me (today) that it’s a race only blower- but I know that people run them on the street (maybe that’s only because they have smaller engines)
Now don't get me wrong- I agree that a NOVI would be better suited to the application, but i'm on a strict budget and already own the VR4.
Anyone have a good guess about the HP increase i could safely/reliably achieve? I've got a 100hp shot of Nitrous i could put on it, but if i could get between 135-200 extra hp, then i'd be happier with the blower. Thanks- rick
Run an oil cooler and you will be fine. I have one on mine it didn't get no hotter than the sn series with the h.p impeller. Thats first hand experience!
Dont over spin the blower 44,000 for the vr-4 a 7" crank pulley and a 4" blower pulley you will be at 42,735 r.p.m blower r.p.m @ 5500 engine r.p.m you should be at 8- 10 psi I would think. My motor breathes very well and im making 9lbs.
I have one on my 408 with trickflow 205 cnc heads which are a good flowing head, and still manage to make 9-10 psi with a 3.75 pulley, I put a 3.5 pulley on it and made 11psi but belt started slipping bad and the boost fell off. This is with an 8 rib setup. I will eventually get a novi2000 or saomething bigger but I love when people nock my blower since it still has the sn2000 sticker on it, then hear it run and are like wtf!!!
I suppose you checked the belt and see if the belt is tight it should be like a guitar string, that tight. Also make sure your pulleys all line up. I have no slip with a 6 rib belt. They are noisy the vr-4s lol!
Yeah it was definately tight, still couldn't keep it from slipping. But i was happy it even made 9psi. the guy that tuned it a while back kind of laughed when I told him I was expected 7-9psi, he told me I was better off taking it off there was no way that old blower would move enough air for a 408. (He didn't know anything about vr4's) def changed his mind when he started it on the dyno.
First of all, the teacher gave you the best advice, it sounds like it wasn't what you wanted to hear so you're now asking the students (1st graders). We all have some experience with these ball drive Paxtons, I have some 15 years / 75,000 + miles using them. And a lot of high speed endurance runs as well. But my experience is not even close to the same league as what Craig has stored upstairs.
Maybe the scenario that would work best for you would be the twin Paxton set up used by Shelby on couple of BB engines.
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Originally Posted by Duke
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