Re: Would a blow off valve work?
FYI boost article..........
I know some people will be sceptical about these claims, but we used to race with up to 24 lbs boost blowing thru a Holley without a carb box or any intercooler.
Everywhere we took the car, people crowded around it in the pits, and yelled from the stands every time it made a pass.
We used a solid (foam) float made for Holley carbs. I think they called it a nitrophyl float. ??
(hollow floats collapse under pressure)
I took an aluminum carb spacer, carefully drilled some small air passages in it to line up with some small holes I had drilled into the Holley carb base, to blow CLEAN-AIR boost pressure (no fuel mix) directly to the throttle shaft bushings so I didn't have to put seals on the shafts, and then topped the carb with a Turbo City carb bonnet that was designed for a different use.
We blew fresh air straight from the turbo into the carb bonnet on top of the bare carb.
At first we had jetted it way too rich to avoid melting anything on its' upcoming first day out at the track. We read about the warnings, and took them way too seriously.
We had only a few days before a big meet, and didn't know what to do about a waste gate or a limiting device. No money to work with or enough knowledge learned yet to build one quickly.
My friend rigged a cheap blowoff valve and stuck it in the turbo boost pipe to the carb. I'll tell you about it later.
The 9 or 10 to one engine compression needed to be lowered before adding boost pressure. My friend cut his own copper head gaskets. They leaked so badly just a couple days before the races, all we could do was stick in some more head gaskets above and below the copper spacers. With such a TALL combination there was almost no compression left, or any decent quench area with the chambers so big now.
The race was two days and a long drive away. We weren't even close to being ready.
As we scrambled to put a car together that we know couldn't be ready on time, we were trying to come up with excuses as to why we couldn't race the car when we showed up at the meet.
Head gaskets blown? (mostly true), severe carb trouble? (mostly true), new tranny that wasn't working right? (didn't know yet, but it could happen!), but all of them were weak or made us sound like quitters, so we kept going, all the while very afraid we would fall on our faces in front of a large crowd.
We tow all the way from Missouri to Nashville Music City Raceway and unload the car.
So here we are at a drag meet with a 35+ year old Studie, a tiny 259 cubic inch Studie stock-block engine, a turbo that wasn't tuned or controlled, a carb running way WAY too rich, a shockingly low 6.9 compression ratio, a fresh PowerGlide that was like starting in second gear, and a rigged-up RADIATOR CAP blowoff valve as a crude turbo control.
The rear gears were still too tall, set for the low-gear launch of a TH350 trans, much too tall for the mushy second-gear Powerglide launch. No transbrake to load the turbo against for ANY boost at launch time... everything seemed to be all wrong, and we ran out of time to correct any of them.
BUT WOW, NONE OF THAT MATTERED.
The first few runs got everyones attention, and drew a crowd.
Every time the lights went green, the "other" car would get a jump on the slow starting Studie, usually a few car lengths, then the little Stude would wind up and charge at the other guy.
Usually between half-track or two-thirds track, with the turbo really blowing and whining, the Stude would fly right past at a really high rate and leave the guy in the other lane wondering what the heck just happened.
On it's very first time out, the car took Fast Class Trophy.
We had such fun with the car. It put on such a good show that people would crowd around it to see what in the world that was.
The turbo would spin up a bit, boost higher, pull harder, wind up some more, boost higher, pull harder, wind up some more, boost higher, pull harder, wind higher, more boost, pull even harder, scream higher, boost more, pull harder, scream higher......
Near the top end of the track when it was really pulling hard and the over rich carb was dumping too much fuel to the engine, it would often put out a very noticable BLUE HALO glowing under the car (came from the 3-1/2 inch turbo outlet pipe that you couldn't see)
It was a sight to see.
So here was a car we put together in a rush at the last minute-
ONLY 6.9 compression!!! rich carb dumping fuel. gears much too tall.
NO turbo control except for a 12lb RADIATOR CAP stuck in the side of the boost pipe as a makeshift blowoff valve. (fresh air- no fuel mix)
Surprisingly, the 12 lb radiator cap actually worked quite well as a boost limiter at "normal" driving on the street, but at the track when it was pulling hard and winding high, the turbo would overwhelm the small "valve" and go past the 23-24 lbs boost mark near the finish line. That was just about the time the fuel pressure suddenly started climbing faster than the boost and an over rich carb got even richer.
The race was over by then, so it didn't really matter at the time.
Later on with better carb settings, a better fuel regulator, better head gaskets and a better compression ratio, TH 350 with better ratios and transbrake, we got it running a whole lot faster, but that first outing was the most memorable one of all.
What a blast we had. I want to do it again.
A few summers ago, a shop fire (blame a leaky 85 Corvette) took down two buildings, all the race parts, a few collector cars including a nice Studebaker Hawk, and a whole lot of tools, NOS fenders, etc etc.
No more racing.....
That car below in my signature line is no more.....
Woody
Last edited by waldig; Oct 22, 2009 at 05:55 PM.