ownor

iTrader: (5)

Hello there guys,

friend of mine has a 84 CFI Vette and the engine is out for a performance rebuild. we're planning to convert the car over to TBI and running an EBL in it.
so far we the outline is to use patriot 188cc freedom heads, somewhere around 10:1 CR, cam xfi280h but it's staying at flat tappet. prolly gonna run a reman'd & modded 2" BBC TBI from dctrumpet, so hopefully not limited in terms of TB airflow. anticipated power band with that combo would be somewhere peaking at or a hair over 6krpm with somewhere between 350-400hp(?), maybe shifting at 6.5k or so. tranny is being overhauled and have a 2500 stall put it, stock rear gears are 3.07 i think and no plans of digging in there just yet. car has long tube headers and half decent exhaust.

right now i'm looking at different options for the intake manifold.. the C4 is rather limited as far as hood clearance goes, so i was looking at the pro-jection manifold which is what our fellow member Ronny was running on his TBI C4 for quite some time. here is what he had to say about it:

so it seems the holley would be a good fit.. the spacers he mentions might be needed to clear the pod & lines, because the base of Holley's own TBI (the 2bbl 670cfm Projection TBI) is different and a stock TBI obviously wouldn't clear the TB base of the manifold without spacers. might be able to get away with just one spacer (.5"), not sure. the powerband is listed idle-6000rpm. (link: http://www.summitracing.com/int/part...make/chevrolet)

is the pro-jection gonna choke the engine, what do you think? could i relieve that with some hand-porting or is it still "too small" of an intake for those power/airflow goals?
also this one already has 2" bores so could save some money not needing a carb adapter nor needing additional boring.

i was also looking at the Weiand X-Celerator (link: http://www.summitracing.com/int/part...make/chevrolet, but that would require an adapter (reducing clearance and adding $) and also i'm not quite sure if i want to go with a single plane on this build, rpm range says 2-6.5krpm (for carbs). i know that guy and he's only gonna rev it up to peak every once in a while, so retaining some more low and mid torque would be more beneficial i think.

any input on this topic or additional input in general is appreciated!
thanks in advance

Fast355

iTrader: (2)

You can pickup a TBI adapter that is only 3/8" thick. Just make sure that the TBI bolts do not extend past the adapter when they are installed otherwise the adapter will distort causing a vacuum leak when the bolts come into contact with the intake and push the two apart.

I prefer single planes, but for your application a dual plane would probably be fine.

ownor

iTrader: (5)

Hey Fast,
thanks for your reply. I haven't specifically looked at adapters (we are talking about TBI-carb intake right?) yet, I figured I'd first decide on a manifold..
What do you think about using a TBI manifold such as the mentioned Pro-jection instead of a carb intake?

Fast355

iTrader: (2)

I am not a huge fan of the projection intake manifold. I tuned one and the air/fuel mixture was not very good between cylinders. Seemed like they had alot of variation with the TBI mounted as far forward as it was.

I also ran an edelbrock performer RPM with a holley projection adapter. With the projection adapter it had the same a/f distribution issues between cylinders. In my experience the TBI setup just runs better with the TBI in the middle of the manifold. Also likes smaller plenum areas like you would find on a 2bbl manifold or stock TBI manifold. With a 4bbl manifold you have to drastically increase your AE fuel to keep it from lean spiking on take off.





One of the better running setups was a set of ported 081 TPI heads, ZZ4 cam, edelbrock 3704 intake with a 1" open center spacer, 454 TBI and 85mm MAF setup.

ownor

iTrader: (5)

Hey Fast,

thanks for the insight. So you're saying both the Projection manifold as well as the Projection adapter you were using were giving you poor flow distribution.. May i ask how you go about diagnosing this?
You are mentioning 2bbl or stock TBI manifolds - in your opinion, what's a good choice to use with a 350+hp build then, when you need additional flow over stock or the performance TBI manifolds? I actually thought the Projection manifold was a kind of/similar to stock 2bbl TBI manifold..?

What do you think about the Weiand 7547 I mentioned? I was told by Summit that the height on that one is only Front 3.09", Rear 4.06" so there'd be plenty of space left even with a TBI to carb adapter.

One more:
I was talking to dctrumpet (TBIPARTS) and he confirmed his ported 46mm units flow the same as a big block 50mm unit (650cfm). Would you guys see any advantages in using one over the other?
Thanks

Fast355

iTrader: (2)

It will flow close, but the big block will still edge out the bored small block.

If you use a carb manifold, make sure that your adapter plate mounts the TBI in the center.

The problem I saw was easy to diagnose. Hot blistered spark plugs in some cylinders and carboned up in others.

ownor

iTrader: (5)

Hmm, assuming the claimed 650cfm on both are actual numbers, would you prefer one over the other?

On the carb manifold and adapter thing, not 100% sure how to tell about the center mounting of the TBI, but does that look like a good design in that regard?



i would think this would mount it quite in the center, but then i haven't had my hands on one of these things.

ex-x-fire

I have a truck tbi (holley) on my 84 vette, I've had the projection & smokey sy-1 intakes on my mild build (never dyno'd). The projection seemed to have good drivability & good low speed performance (& much more hp at higher rpms) over the cfi intake. The sy-1 traded that for strong mid range power, I could've gotten a better matching converter & rear gears for that intake but I never did. I switched back to the projection intake.

makaveli09

Yeah. That's a center mount TBI adaptor.

ownor

iTrader: (5)

thanks for your input.
on the projection intake, did you check your plugs for any indications as Fast355 gave? i'm actually avoiding the projection right now because of that and plan to go with the Weiand X-celerator single plane.
i've never heard about the SY1 but a quick google search shows me it's quite expensive to get one? strong mid range sounds good imho, but not at that price. so that's a "crossram" intake too, hu? what weight and gears and stall did you run in that vette then?

ex-x-fire

I ran a stock converter & 3.07 gears, most of the problem with that intake on my 84 is the stock ecm I was using. It moved a lot more air then any cfi/tbi intake out there.

ownor

iTrader: (5)

ah, i see the problem there with the stock ecm then, yeah. we were planning on using a 2500 stall and the same gears, hoping to make up some for those lame gears with that stall..