Is there a verdict on using an adapter plate so that one could use a std 4bbl manifold. Do you lose anything by doing this? Any other possible disadvantages?

Mike

 

possible disadvatage is bad fuel distribution with certain intakes.

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-Tas
'89 Formula WS-6

305, TBI, auto, 14x3 chrome flat based open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

To be installed eventually far far far into the future: Yours if the price is right and I don't have to ship :
Hooker 1-5/8" 50 state legal headers, Dynomax 3" I pipe (PN 44063 and 43248), Catco 3" cat, and injector spacer.

Super GRK_Taz World
F-Body Dual Exaust
EFI & Intake Options
AOL IM: superGRtaz

[This message has been edited by Tas (edited September 17, 2001).]

 

Would it be ideal to mount the TB in the center of the adapter vs. rear mount or front mount? Which manifolds promote poor fuel distribution? Would a swirl bore design in the adapter promote better fuel distribution and more power/fuel economy? Thanks

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-Don't buy any wooden nickels

 

which intake?



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88 SC 305 TBI... for now

 

I guess the question is: does it matter which intake? Won't any "std" 4bbl intake have the same characteristics? Couldn't the argument be made that the TBI itself looks like a carb to the manifold? Does the manifold care about what is above the butterflys? As long as the TBI sprays out fuel that has the ability to atomize then whats the diff between the TBI manifolds and 4bbl manifolds? I'm not sure I understand why air/fuel sprayed from the TBI looks any different from air/fuel sprayed in via the venturi's in the carb to the motor? I'd be interested in your thoughts

Mike

 

To put this all into perspective, the TBI is usually a 2 barrel. The problem with this is that the fastest air will be at the rear of the TB unit because of the design of an opening blade! The spread bore intakes usually position the main bores closer to the middle. The square bore doesn't really matter because it was built for WOT anyways unless a 4 barrel TB unit is installed (TB blades face eachother so not all air at rear of intake). Also the fuel distribution can be a real major factor when running a TB on a single plane. Single plane intakes don't like spread bores in theory although....anyways, dual plane is always better at even distribution of air/fuel mix.
With a single plane intake most likely you'll want to position right in the middle. For a dual plane design you'll want it towards the front slightly.

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, Jon (350 TBI!)
91 Red My website

 

thx jon, maybe some background - might be on sacrilegious ground here, but... taking a 305/LG4 TBI w/T5 setup out of an 88 Camaro and dropping it in my 74 TR-6 british roadster, hence the Baby Cobra uname (and license plate). For those not old school, the AC Cobra was a lightweight 2 seat british roadster powered by 427 F*rd motors and ran like raped ape's. Had a power to weight ratio of about 7:1 or less depending on how the rat motors were built. The old british moto/trans combo weights at least if not more than the 305/t5 setup so the new V8 setup keeps my suspension balance intact. Not looking to do the Friday nite 1/4 thing, more stoplight to stoplight and freeway onramp suprises. bottom end torque is mucho importante for me vs HP. Looking at holley 670 TBI, dual plane intake (make/model unk), WP S/R Torquer or Sportsman heads, midrange Summit cam with block hugger headers (engine compartment clearance is an issue). I'm a programmer by trade so the geek factor of TBI works for me, as well as the keeping the hood stock for sleeper appeal. Going to keep it CA smog legal so engine component balance is a must. Target is 330hp/375tq based on simluations in Dyno2k, which gives me about 10:1 power to weight. But software being what it is I'll be happy to be in that neighborhood as long as its well mannered on the street. *Any* improvement from the 94hp 2.5 litre demon that currently sits inside the TR6 would be welcome.

I saw a picture of an autocad drawing that someone had done of an adapter plate on ftp://ftp.dyi-efi.org and thats what started all of this.

I'm hesitant to look towards the 4bbl holley TBI, 950 cfm is crazy overkill (drool, whine, snarl, pant) for this motor setup but you mentioned that 4bbl might be better behaved in fuel distribution when using an adapter plate. Is there a line of thought when it comes to 4bbl TBI?

Mike

 

I cant use a 14 inch air cleaner because the TB is centered over the back barrels. Other than that, this setup I have going is ausome.

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69 Chevelle 2dr hardtop blue, bench seats, 12 bolt w/3.73's muncie 4 speed. best 14.5@90

 

my thought on 4bbls, is that 4 injectors cost more $. and arent nessesary. i think a 2bbl correctly made, would have better throttle response, better low and high end power/torque than a 4bbl tbi. but, thats just my opinion.

 

I ran a two brl TBI on a cross fire base, and a Wieand 7525 (lopo G Team). Things were nice. The TBI limits you to some degree to about 340, and up till then things are just a matter of getting the right combo. I used a Comp cam 270, early vette AL heads, and it made for a decent street machine. The best times were mid 13s with the cross fire and dual TBs.
You will defintely lose some off idle response, but from 3K up things are alot better.
YMMV

 

I have a friend machining me one of those adapters in his spare time.
I have been looking at intakes that come on in the 1500 to 6000 rpm range.




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I think the Sun Visiors are still Stock,Anybody know were I can get some after market ones?

 

BbyCbra, Check out this post. They mention a holley 700cfm 4brl tbi and holley also has a 600cfm 4brl tbi. Might be worth looking into. https://www.thirdgen.org/messgboard/...ML/000037.html

 

steve8586iroc, saw that thread but it has a few more responses since the last time I looked in. I'll dig thru it again, thanks for the lead.

I think I'm going to go with a std 4bbl EGR manifold (need CA emissions) and a plate. I've been digging thru the diy-efi site and there is some good info in there. The TBI manifolds are pretty much just cast with the plate as part of the manifold so all should be good with using the plate - just need to figure out where to align it within the dual plane, in the front or the rear.

 

this is not true of the Edelbrock TBI intake, its only true of the Holley TBI intake. The Edelbrock TBI performer intake is totaly different than the carb performer. The Edelbrock TBI intake has round bores that go all the way down to the runners with a crossover passage. The rectangualr area under the TBI holds coolant to keep the intake charge hot so it can vaporise more.



------------------
-Tas
'89 Formula WS-6

305, TBI, auto, 14x3 chrome flat based open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

To be installed eventually far far far into the future: Yours if the price is right and I don't have to ship :
Hooker 1-5/8" 50 state legal headers, Dynomax 3" I pipe (PN 44063 and 43248), Catco 3" cat, and injector spacer.

Super GRK_Taz World
F-Body Dual Exaust
EFI & Intake Options
AOL IM: superGRtaz

 

If you take a look at the performance 2bbl intake manifolds, you will notice that many of them raise the carb much higher than the similar 4bbl intake. This is done to aid in distribution issues. Get the TB up as high as you can.

 

I don't think you have to worry about emmissions in a 27 yr old car in CA???

 

I'm confused why are you worried about comyfornia smog rules for a 1974 car?

 

I’m confused why your posting on a 2001 thread