Blow Through Intake

[CTX-SLPR]

Howdy,

Well I decided to try and pull together my scattered stashes of Turbo6 parts and I found a few things I suspected I had and others that surprised me.

The biggest surprise was the 4.1L intake that I thought I'd sold/given away. Now that I have one I'm thinking that I might not have to guy a KB or Weiand. However, I don't want to choke myself with a cheap but subpar intake. I've read the thread on chopping the center down and I'm going to be getting porting tools to help clean up the results.
I noticed the EGR passage intrudes into the intake, is it worth worrying over?
I know the KB and especially the Smokey Weiand are taller, what am I giving up in top end power with the 4.1L unit?
This motor will live largely at WOT and I will be reving it to 6000+, any experience with any of the intakes doing that?
What is the biggest downside to the factory 4.1L unit suitably modified?

Thanks,

 

[WarWagon]

In the beginning when I first went blowthru I used the 4.1 intake stock and I loved it. The only reason I switched it out is because the dedicated q-jet mount pad. No doubt porting and cleaning up would help it out but I've had it to 6000 rpm on my stock engine that I broke.

 

[dr_frankenstein]

yea id say for what your doing a good adapter on the intake would probably boost your low end really well.

 

[CTX-SLPR]

Cool, money saved. Screwing around with gear ratios and tire diameters it looks like a fatter lower end of the curve will be good for me. With more lower end power I can get away with a set of tall rear gears and tires and go with a TH350C vs a TH200-4R. Can probably DIY the rebuild on the trans too. Even more money saved.

Do you think a 4 hole spacer/adapter would be better than an open one considering that I'm only cutting the carb pad open into a pair of side chambers vs an open plenum? Thinking about maybe taking a 4 hole adapter and machining out the middle to make it a 2 hole and continue the plenum up to the carb base.

Thoughts?

 

[CTX-SLPR]

So I think I'm going to use the 4.1 intake since I have one and I spend $0 on parts to buy it. However I've not been getting a very good feeling about running an Spread-Bore to Square-Bore adapter on it and not having issues tuning it. Now looking at the one I have and the pictures on http://www.gnttype.org/techarea/pictureguides/intakes/41intake.html I think I have an idea on how to avoid the adapter.

The black dots are holes for the Square-Bore pattern carb to bolt down. The greyish bar in the back is a ~1/2in aluminum spacer block that is fit to the back of the intake and the rear bosses for the back of the Spread-Bore pattern are milled down so I can put allen head screws in them to hold the adapter bar down. This part seems pretty straight forward. It's the red work inside of the carb pad that I'd like some help with figuring out. Since it's a Square-Bore carb, the front and rear throttle bores are the same size so I'm fairly sure I'll need to open up the fronts a bit. I was basically thinking emulating a Performer style dual pattern carb pad and then using the Edelbrock shim gasket to seal the carb to the enlarged plenum. What about the taper in the secondary bores? I have a mill and will be getting porting tools so I can do bulk removal and semi-precision fitting of parts together as well as the detail blending.

Help is definately appreciated. Thanks,

 

[dr_frankenstein]

I say run the adapter..... a 4 hole one.... If you get a decent carb bonnet which is fairly efficient at bending the air you shouldnt have any tuning issues. and any you might have can be tweeked out of the carb.

 

[CTX-SLPR]

Adapters run from a Trans-Adapt at ~$25 to a Hamburger unit at $132. Right around the Hamberger's unit the cost of the adapter starts equalling what a KB or Weiand intake runs on the used market.

Edelbrock, Trans-Adapt, and Proform all are ~$25, all are 0.850-0.875 so it's really just a question of is the Hamburger unit work the 5x price? The Edelbrock is the shortest so I think I'll toss it. The Trans-Adapt is the same height as the Hamburger unit so I guess I'd try it. Worth trying before I cut the intake up I guess.

 

[dr_frankenstein]

I think your over engineering a bit....

were not exactly shooting for every drop of power in an NA form.... so i think we can eliminate the fancy unit for the moment. If you have some good success or are right on the edge of actually making a record or an amazing pass, then by all means splurge for the goods and make the pass.

Lets drop the cheapo unit down on it, with some mild cleaning up with a dremel if it needs it and lets get the boost to the engine and see what she does. you only want, what........ 350 hp? Sounds like good fuel and 12lbs of boost with a junkyard NA motor. The goal isnt that far off even with only 200 or so cubes. Blow-thru boost is much more efficient then Draw-thru.

Think of it as bang for the buck....

 

[charlief1]

If you haven't read my post on modifying the 4.1 intake please do. It should help you get the most of of it but if you decide to get rid of the divider you'll need to do a little welding. On my first one I welded over the center EGR posrt which helped quite a bit and if you thread the heads on the outer EGR holes you can plug them pretty easily.

 

[mikemcvaney]

How much taller is the 4.1 compared to stock 3.8 turbo intake?

 

[CTX-SLPR]

Updated plan.

4.1L intake modified as a hybrid between Charlie's guide in the sticky and fitting to the underside of the 4 hole adapter. Holley Double Pumper (probably a 600) modified with a milled choke horn, Hanger 18 mods, and an "Air Seal" made by putting a fitting and channels in the adapter plate and feeding pre venturi boost into holes drilled into the throttle shaft bores.

Been reading up on boost refference power valves and I think I see what Dr Frankenstien is going on about with the CO2 powered valves. It's what the www.turboforums.com calls the "crutch" which is possitive pressure feed into the power valve to open it up under hobbs switch control. There looks like another alternative which is to basically "flip" the power valve around so that instead of being sucked open, it is blown open under boost. Will have to think/tinker with these ideas some but the more I read up, the less intimidated I feel by trying to set up the carb myself with a wideband and a selection of good tools.

 

[dr_frankenstein]

yea... i do something simular to the crutch.... but a little less to do with boost pressure and more fine tuning. since im draw thru, i dont really need the crutch per-say, but what i do like is i can control my powervalve. if you use a decent enough nitrous controller and solenoids, you can control the ramp, duration and timing of your powervalve. lots of things you can do to make a huge carb streetable.