[Tom Vaught]

This is a reprint of the work Ken C did years ago using a q-jet carb in Hot Rod Magazine

https://www.motortrend.com/how-to/cc...iac-400-build/

Tom V.

Mods put in Boost section if more appropriate.

Tom V.

[Jay S]

Ken’s persistence to make the qjet work with the turbo was amazing.

[steve25]

I just read that and my hat is off once again to Ken to get to the bottom of things.

That Q-jet fuel passage mod should be done on any NA motor that’s making over 400 Hp before any full throttle secondary metering rod changes are made it would seem.

[Formulas]

I dont have Roe's book so just going by the motor trend article description... they are talking about the Qjet POE enrichment circuit?
correct?

[grivera]

That’s a great article. I wonder why the Performer intake and not a factory cast iron.

[grivera]

That’s a great article. I wonder why the Performer intake and not a factory cast iron.

[steve25]

Even though a factory iron intake flows more NA air then a Performer does the performer has better fuel distribution.

Kens motor was a blow thru turbo set up and that matters more .

[KEN CROCIE]

Thanks everyone for the interest and kind thoughts.
Performer intake. I don't recall why ! The possibilities are:
1: The Engine came to us that way.
2: Mecham installed the Performer as part of the TurboForce package.
3: I just thought it was a good idea at the time.
Not all components are scientifically tested! (surprise)
BTW, we made brackets that attached the bonnet to the shaker, which allowed the shaker to look stock and shake with the engine on the TurboForce kit.
Carb. The the passage from the secondary well has a slight bend in it, and at the bend the secondary air bleed tube is positioned at the tightest part, potentially restricting flow. The amount of restriction varies carb to carb. Some limit flow , others don't. Our SS/KA Super Duty and friends SS Super Duties experienced this restriction problem. The symptom was the inability to get the secondary metering rich enough. To solve the lean problem ,we had to add more fuel than normal to the primary side- as in removing the primary rods and installing jets in the 80-84 range,
Now, I raise the secondary air bleed tube 1/4" to get it out out of kink and get full flow potential in that area. If that doesn't work, surgery is required. The procedure starts on page 134 of Doug Roe's Rochester book with copyright date of 1986. I understand some other editions have deleted this section.

[KEN CROCIE]

Thanks everyone for the interest and kind thoughts.
Performer intake. I don't recall why ! The possibilities are:
1: The Engine came to us that way.
2: Mecham installed the Performer as part of the TurboForce package.
3: I just thought it was a good idea at the time.
Not all components are scientifically tested! (surprise)
BTW, we made brackets that attached the bonnet to the shaker, which allowed the shaker to look stock and shake with the engine on the TurboForce kit.
Carb. The the passage from the secondary well has a slight bend in it, and at the bend the secondary air bleed tube is positioned at the tightest part, potentially restricting flow. The amount of restriction varies carb to carb. Some limit flow , others don't. Our SS/KA Super Duty and friends SS Super Duties experienced this restriction problem. The symptom was the inability to get the secondary metering rich enough. To solve the lean problem ,we had to add more fuel than normal to the primary side- as in removing the primary rods and installing jets in the 80-84 range,
Now, I raise the secondary air bleed tube 1/4" to get it out out of kink and get full flow potential in that area. If that doesn't work, surgery is required. The procedure starts on page 134 of Doug Roe's Rochester book with copyright date of 1986. I understand some other editions have deleted this section.

[KEN CROCIE]

Sorry for the double.
BTW- after the carb got fixed, I ran the dyno in manual mode. I saw 830 #s at 2800 rpm. I wasn't about to sacrifice a numbers matching block for the sake of more power, so I pulled the throttle back almost immediately. Official dyno runs were performed by westech's Steve Brule'

[KEN CROCIE]

Sorry for the double.
BTW- after the carb got fixed, I ran the dyno in manual mode. I saw 830 #s at 2800 rpm. I wasn't about to sacrifice a numbers matching block for the sake of more power, so I pulled the throttle back almost immediately. Official dyno runs were performed by westech's Steve Brule'

[KEN CROCIE]

Another double! dont know why

[steve25]

Ken, your not the only one with the double post thing taking place, it happens to me every darn time.

It’s a Fluke with the site that they seem to not care about since I have brought it to there attention twice and I know others have done the same at least once.

Once again thanks for your contributions here!

[RocktimusPryme]

The double post thing started a few months ago and it always tries to do it to me.

Was the power number tamed on purpose because of the factory block?

I have been considering a blow through centrifugal setup on my engine to turn the wick up a little, while still keeping street manners. I have the bottom end for it, but I sorta feel like Im nearing the top end of factory 400 block safe at NA. So Im concerned that adding a blower I might crack the block.

[turbo69bird]

If I post I have to wait a minute (and I mean a minute for the first post to go through then it doesn’t double but if I hit it again to make it work it doubles .
I used a performer on my first blow through engine everyone said it wouldn’t work (Some big time turbo guys who worked on pro 5.0 stuff ) I’ve never been able to get my single plane to run as good as my dual plane . Even w efi. So for whatever reason it was used it was a good way to go.

I used mine because I built the set up the first time. headers and all in 48 hours to show up at a friends no time - street race at LVD car went 10.00 off the trailer . Which back then was pretty fast. That was no Intercooler and a washer fluid pump and a heating system nozzle for the water meth injection I even made the carb hat in my garage from sheet metal. Still have the intake carb and. Sheet metal carb hat in my basement. Had so much fun w that set up.

[KEN CROCIE]

HP limit. 537HP wasn't chosen . I believe this combo reached it's natural limit due restrictions in some parts of the system such as exhaust manifolds, exhaust turbine housing, or the compressor itself. You will notice the boost was dropping off halfway through the test.. I could have increased the boost via wastegate adjustment But that would have increased low end torque with very little change in peak HP. Considering the customer had a limited production restored car and was probably running G60x15 TA Radials, he would have the power to "smokim" at any time.
Please note that all of the above is pure conjecture on my part.