[blueghoast]

I believe down the road I'll probably change to a different gear maybe
when I put this motor in the other firebird it was intended for.
As for now I'll just do a converter change and see if that works.
Lot of the guys I know that run blowers said they ran a lower 3-series
gear and some of them where spraying too.
Sounds like you got a handle on yours. Good luck with it.
I'm going to change mine tomorrow.

GT.

[Jack Gifford]

Originally Posted by blueghoast

... It makes 15+ at around 6000 rpm...

I'm having trouble making sense of your numbers. I ran a 6-71 blown iron 400 engine in my blown-alky puller for awhile; saw 8,300 RPM on most runs, with no more than 12 PSI boost.

You talk about a "mild" cam- the one I used in the puller was ground in 1958 by Harvey Crane- lift was only .478" and was not a "blower" grind.

[Tom Vaught]

Bluegoast and George both have 8-71 BDS Superchargers, as does Jim I believe.

Might be some of the difference there.

Today, Jack, if the cam does not have .800+ lift, it is a "little camshaft" vs your .478" lift deal. So don't pay too much attention to the "Mild Cam" label used today.

Tom V.

[69Goat1]

Sounds mild to me...230/240@.050 flat hydraulic on a 113ls from his earlier post...

[Tom Vaught]

Agree, It is a basic RA-IV type camshaft as far as duration, at .050"
Even with the events moved around a bit.
At one time people called the RA-IV cam a "performance cam". .480" lift with a 1.5 rocker .520 lift with a 1.65 rocker
Bigger than Jack's camshaft specs he posted.
So your post basically proves my point. You called it Mild too.

Tom V.

[GTOGEORGE]

Originally Posted by blueghoast

This is Not a full blown race car, This is a tame street car 400ci with a 8-71
and only 3 percent over driven pump gas firebird that will cruise down the
road at 65-70 MPH. Just went 11.15 @ 119.28 MPH.
I want something I can put a little spray to and hang with you LMAO.
I don't want to spin the snot out of the blower and have to trailer
every where. Now you no what I'm trying to do with this situation.

GT.

So just a little FYI.......back in the 80's.........no not 1880's , I race my First blown 74 GTO. It was a 455, it had a SMALL .480 lift hydraulic cam, a STOCK factory convertor, 3.42 gears at 3,450 lbs. the blower was a SMALL B & M (177) supercharger that I spun the SH_T out of and made between 7-9 pounds of boost (no exhaust, just headers BUT I did run an air cleaner). The car ran 11 teens - 10.80's never shifting over 5,400 rpm, so I'm thinking changing your convertor (your really not making enough power to blow through it) and your rear gears to around 3.42 should help BIG TIME.....NO NITROUS thats just an accident waiting to happen, not even taking your STOCK engine (rods, block, crank) into consideration.


GTO George

[Tom Vaught]

Listen to the Man.

Tom V.

[alloy indian]

Ok here's my two cents worth take it how you like. Back in 82 I ran a 400 cast rods, cast pistons an HO racing cam similar to the 041 cam spec's. 72 HO round ports which gave 7.2 compression. I ran a 671 blower at 12% under driven for a max of 7 PSI of boost. With 4:10 gears shifting the manual trans at 6000RPM's it went 10.50's in the quarter in a 3500LBS car. Later the same heads, cam and blower setup on a 455 with 8.5 compression, 4.10 gear and a manual trans driven 1.1 making 8PSI of boost. But in a Grand Prix weighing in at 4500LBS it ran 11.40's at 117.5 MPH. You have an 871 blower driven at 3% over with 7.8 compression this works out to 15.5 to 1 total compression! Way to high for pump gas! You are detonating at full boost and probably won't ever hear it with the blower whining. Also two 750 carbs are to small for an 871 with this much boost. You are more than likely running out of fuel at high boost hence the falling on it's face at 900ft. Also as mentioned the converter sounds very loose for your combo. With a blower setup running on pump gas never go over 12.4 to 1 total compression. You should run the blower at 12% under driven for you combination of part's unless you use 112 octane race fuel or higher but the carbs will still be marginal at these boost levels. I believe between the detonation, fuel starvation and converter your fighting a loosing battle that Nitrous will only exacerbate. You don't need forged parts if you run a smart conservative combination, sure they offer extra insurance but definitely not required. Hope this helps and good luck.

[Tom Vaught]

Great Info alloy indian and 10.50s and 7 psi you were having a lot of fun.
So how many years did you run that combination in the 3500 lb car?

Tom V.

[alloy indian]

Thanks,
That cast engine is still together but the blower is long gone. I drove this on the street from 82 till 89 when I parked it. You see the police didn't fancy that big huffer sticking through my 72 F-body's hood. Can't understand why myself I thought it was bitchen!

[bendutro]

Originally Posted by GTOGEORGE

If you have to install Nitrous on your blower engine to make power you doing something wrong with the blower.......maybe in a turbo car but not in a blower car.......specially in a roots blower car!!


GTO George

Yeah, you might have a chance to catch up to the turbo car.

[GTOGEORGE]

Originally Posted by bendutro

Yeah, you might have a chance to catch up to the turbo car.

Never raced and lost to a turbo car!


GTO George

[blueghoast]

My compression at max boost is 12:6:1 I'm at the edge for pump gas.
The carbs don't say any where what the size might be They might be
850's got to check into that. I changed the converter today man what
A difference that made. We have new black top around here so I got
after it even though the road was damp and short shifted, The guy's
Told me that the front wheels were about six inch's off the ground.
It's like a totally different car. Can't wait to get back to the track.
I guess I'll find out on drag weekend, we leave thurs. So I'll be at
Stanton on the 7th and Martin the 8th. I'll let you know what happens.
I can't thank you guy's enough for all the info and steering me in
the wright direction.
The car drives so much better and feels like it would pull al the
way to 200 mph if I wanted. I'll know more when I get to drive it
more, Right now it's raining here.

GT.

[alloy indian]

This is the last I will say about this. 15 Pounds of boost, a 400 and 7.8 compression at 6000RPMs works out to 15.5 total compression. At 8 pounds of boost you would be at 12.5 total compression with this combo. Good luck and have fun with your car that's what it's all about.

[GTOGEORGE]

Originally Posted by alloy indian

This is the last I will say about this. 15 Pounds of boost, a 400 and 7.8 compression at 6000RPMs works out to 15.5 total compression. At 8 pounds of boost you would be at 12.5 total compression with this combo. Good luck and have fun with your car that's what it's all about.

I have to agree with your numbers!



GTO George

[blueghoast]

Brought up the build pics and video of my blower motor.
It's on the race section (New Power Plant) Thought you
guys might want to see it again. Also tells about the motor.

GT.

[blueghoast]

Well heading out tomorrow for drag weekend.
Hope the car works right with the new converter.
Should be fun anyway, That's what it's all about.

GT.

[johnta1]

Good luck!