I've lost my boost

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Coyote Jack

Coyote Jack

Member #55, I'm old
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As the title says, I've lost my boost. My setup is a Dyers 6-71 on a 340. Up until two weeks ago everything was running great. I had 9 lbs of boost and the car was a real beast. Then my EFI crapped out on me. My handheld programmer no longer worked but the car still ran fine. Then while I was at the Atlantic Nationals in Moncton the ECU stopped recognizing there was boost and the car would fall flat on it's face when I went to WOT. I got the car home no problem and ordered a new ECU from FiTech. It arrived and I installed on Monday. It runs a little rough at idle but that is a matter of tuning. Now the boost problem. All of a sudden I am not getting any boost. The best the gauge reads is 0 lbs at WOT. The gauge reads it's typical 8 to 9 lbs of vacuum at idle. I checked the connections for the gauge and all seems right. When I go to WOT now there is no boost. The car runs like there is no boost as well. I would guess that it it is running like a car with about 400 to 450 HP not the usual 650 to 700 HP. I did not hear any bad mechanical noises and the blower still turns freely with no noises. Does anybody have any ideas as to what I should be looking for? Stumped so far.

Jack
 
Bad vacuum/boost leak is where I would look first. Does your manifold have a boost plate that might be blown out.? Also check your blower base gasket.
If the blower is intact, it has to be boost escaping, downstream. Blown gaskets downstream of the blower.
 
33IMP said:
Bad vacuum/boost leak is where I would look first. Does your manifold have a boost plate that might be blown out.? Also check your blower base gasket.
If the blower is intact, it has to be boost escaping, downstream. Blown gaskets downstream of the blower.
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I am used to the bad gasket thing and I don't think that is it. Normally when you have a vacuum leak the engine will idle much higher than normal and that is not happening. I have been thinking of this for a while and I just had a thought. I know the car will run without the blower turning. I am thinking that I may have broken a snout shaft. I hope not but that would make it act exactly the way it is acting.

Jack
 
It does sound like the blower isn't turning. Since the boost gauge shows vacuum, that leads me to believe there's no fault in its reading. Even if it had a vacuum leak, it would still show boost, it would just be lower than normal.
 
I was just out in the garage. I took the blower belt off, took the hat off, opened the throttle blades to WOT and spun the snout with my hand. Sure enough, the rotors are not turning. So I broke something in the snout area. I will take it apart a little later and see what's up. Damn I hate when stuff like this happens. At least I know it's not the EFI.

Jack
 
Detonation can do very odd things to roots type blowers. Have a very close look at your plugs while it’s apart.
 
I got it apart. The snout shaft sheared off. I will be calling Dyers first thing in the morning to get a replacement. The shaft is about 5 inches long if anybody has a spare sitting around that they would be willing to part with. I will post a couple of photos in a few minutes.

Jack
 
Here are the photos as promised. The shaft thickness where the bearing surface is, is one inch.


Jack

SNOUT001.jpg


SNOUT002.jpg


SNOUT003.jpg
 
Coyote Jack said:
I was just out in the garage. I took the blower belt off, took the hat off, opened the throttle blades to WOT and spun the snout with my hand. Sure enough, the rotors are not turning. So I broke something in the snout area. I will take it apart a little later and see what's up. Damn I hate when stuff like this happens. At least I know it's not the EFI.

Jack
Click to expand...
At least it hasn't hurt the engine.
 
He’d need the Snout DriveShaft, coupler, bearings and seal.

He’s got a single key way on his crank, in which case he had to replace a harmonic balancer due to it cracking and upgraded to a better balancer .
Apparently he drives the car the way it’s supposed to be driven as he’s sheared his shaft. Upgrading to a 1.25 shaft will ultimately find the next weakest link, which will be the single key way on his crankshaft.

I’m not talking smack but it’s just a matter of time.
 
MiradaMegaCab said:
He’d need the Snout DriveShaft, coupler, bearings and seal.

He’s got a single key way on his crank, in which case he had to replace a harmonic balancer due to it cracking and upgraded to a better balancer .
Apparently he drives the car the way it’s supposed to be driven as he’s sheared his shaft. Upgrading to a 1.25 shaft will ultimately find the next weakest link, which will be the single key way on his crankshaft.

I’m not talking smack but it’s just a matter of time.
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Yeah, it's interesting how using a roots blower changes the stress on everything.
 
I believe he’s running an 8mm drive (on a 671) , there’s a fair amount of “rotor reversion” which will stress the drive components.
A 14mm drive will beat the **** out of the drive components. Forward/ backward stresses/twisting……..

Y’all know why they call ‘em blowers?


Cause you’re always blowing **** up! LOL
 
Just curious: How many years has that blower been around? I’ve always wondered how much stress is out towards the end of the pulley on a setup like that.
 
MiradaMegaCab said:
He’d need the Snout DriveShaft, coupler, bearings and seal.

He’s got a single key way on his crank, in which case he had to replace a harmonic balancer due to it cracking and upgraded to a better balancer .
Apparently he drives the car the way it’s supposed to be driven as he’s sheared his shaft. Upgrading to a 1.25 shaft will ultimately find the next weakest link, which will be the single key way on his crankshaft.

I’m not talking smack but it’s just a matter of time.
Click to expand...
I agree, it's always a game to find the weak link. Yes, I do drive the car and have a lot of fun doing it. lol What I have found is that the more boost you have the easier it is to find that weak link.

Jack
 
pauly said:
Just curious: How many years has that blower been around? I’ve always wondered how much stress is out towards the end of the pulley on a setup like that.
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I have no idea how old it is. I bought it used from a guy in Minnesota that had it on a drag boat. This is the first time I have had to actually do anything to the blower since I got it about 7 years ago.

Jack
 
MiradaMegaCab said:
I believe he’s running an 8mm drive (on a 671) , there’s a fair amount of “rotor reversion” which will stress the drive components.
A 14mm drive will beat the **** out of the drive components. Forward/ backward stresses/twisting……..

Y’all know why they call ‘em blowers?


Cause you’re always blowing **** up! LOL
Click to expand...
I have 1/2 inch pulleys.

Jack
 
Coyote Jack said:
I have no idea how old it is. I bought it used from a guy in Minnesota that had it on a drag boat. This is the first time I have had to actually do anything to the blower since I got it about 7 years ago.

Jack
Click to expand...
That's a pretty good record!
 
You can also pin the crank if you wanted. Alkydigger sells a complete kit to do so. It’s only about 120 dollars.

Pretty crazy how that shaft snapped.
 
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