Hello there, Well I am ever so much closer to my 355 Vortec TBI set up

from a 4.3TBI Swap in my S10,




This forum is really the only place to read up on TBI set ups,

I am using a edelbrock Performer EPS Vortec style manifold, I am also using one of DCTrumpets TBI Units, a 50mm 7.4L TBI UNIT

Well I know as stated from edelbrock, this specific intake is designed more for peak torque in the 3500RPM range from the runner design " using a edl sqr bore carb" I figured this would be a good intake for my vortec heads, and for the fact of TBI's torque, I am also using a Comp XE268H Cam as well

My question is that would this intake and engine combo benefit a crossover passage between each throttle body? Will this cause Vacumm problems?

I ask this because I have TBI Adapters to use with the carbed intake to convert it for my TBI, I was pondering if I should machine a crossover about 1" wide, centered between both bores, The spacers make it basically a 1" spacer so basically, I'll have a 1" square cut for the crossover?

I been dabating on just keeping it both 2 bores but since im about to install the plates just wondering if I would benifit from a cross passage,

I figured it would at least evenly distribute fuel to both intake planes, BUT wouldnt that defeat the reason for a dual plane?

 

If you ever noticed the GM TBI to Quadrajet Adaptor Spacer had the center open for a crossover. That is what I am using, but I never tried an adapter without a crossover. I would say if GM used it you probably should too. Just my opinion.

 

I have a Holley TBI manifold. Venturi's are seperated. Edelbrock does same for TBI manifold. As does GM Vortec for TBI. A crossover will add to plenum volume. Do we need more plenum volume?. Lack of crossover may help with velocity but hardly much.
Good Q. Another Q is one of two injector fires every DRP. Is it benefical to make sure better aligned TB to intake valve injector is the one that fires? Maybe not as all inj does is keep the intake runner plenum wet-wet.

 

That is a good concept, Injector firing at a specific rate, Whats BRp you said?

I am just worried about how my adapter sits on top of my intake, as you can see yes i got larger bores, but the intake walls kinda obstruct part of the bore, I figured between both spacers being about 1" that would ad more volumn hoping that may compensate.

Do you think that would HURT performance or would be not noticable?

Heres a few pics of what I am playing with...

I figured just try the 2 seperate bore spacer and use my center cut spacer down the road for "testing"

 

I doubt that small crossover will cause any troubles or big gains.

The intake manifold in your pic 1 does not look like a good match with the TBI TB bores.

It would be interesting to have that intake manifold with the adapter plates flow tested, with and without crossover.
Then compared with these flow# https://www.thirdgen.org/forums/tbi/...bi-3704-a.html.

 

Seems like i get mixed reviews on this one lol, I figured if i use a cutway in the middle it might compensate where the intake is choked down on the side walls, the open area might be beneficial at higher rpms.

does inject pulse really come into play on a tbi motor?

I noticed edelbrocks 4.3l tbi intake has a similar cutway like i want to try,

 

The stock intake that cam on my LO3 had a crossover from the factory and the engine did run wery well.

Having your intake set up, flow tested will give you a good idea of its efficiency.

Fuel pressure and fuel demand change the injector pulse width, in relation to the MAP rpm and probably some others.

 

DRP distributor reference pulse.

I wonder if a single plan such as Weiand Accellerator low profile would obstruct? If I was swapping manifolds and need to use adapter I might lean towards it instead.

 

Well I just decided to just install the two bore spacers as is of now, Maybe down the road I'll Try the xtra spacer I have and maybe have it cut in a full wide open passage and play with that, that way I can have a base to work with and somthing to compare to other than just using it from the get go.

heres a few installed shots!