I currently have the Holley adapter that places the TB forward.

Where can I get an adapter that centers the TB over the intake plenum (Holley sauare pattern)?

P/N's and prices please.

Bill

 

I thought that the PAW adapter plate was centered and its something like $12. You might want to look into that, I'm not positive if it is centered though.

http://www.pawinc.com/

 

PAW sells the holley adapter for $12

 

So, do I need to make my own, or does someone make one?

Thanks!

 

turbo city????

 

Yeap, i believe the turbo city plate is centered, unlike the holley one.

 

I had heard that the Turbo City unit was for spreadbore manifolds.

Do they make two of them, one for square flange, and one for spreadbore? Went to the site and couldn't find the adapter.

 

When do you need it by? Reason being, I've got a bunch of things we're getting waterjet cut and I'm getting some stuff cut for myself. A square bore centered adaptor plate and mis other things, I could get back with you on the price if interested. I wouldn't mind tapping the holes while I'm at it. This is of course a couple weeks time.

 

Sounds interesting. PM me with a price. Bores need to be 2.2 inches vs 2.0, same center though.

 

Jon, I would be interested as well. Let me know. Thank you

 

What about modifying one of these?

http://store.summitracing.com/partde...part=sum-G1406

 

I guess you could, but I would imagine by the time you're done boring it out to match the 2" or 2.2" tbi at an angle, and drill the holes for the tbi bolts, it would have been much easier and cost efficient to just make your own.
Also, the 2bbl carb bore's seem to be closer than that of the tbi's judging from the picture, so properly boring it out could be kinda tricky.

 

Agreed.

I was thinking out loud again.

 

Would there be an issue with making a single opening vs 2 matching the bores?

If not, is there any benefit to retaining separate bores?

This will either be used on an open plenum manifold or one with a dropped divider and don't we want the ability to draw from both bores?

Bill

 

I don't really see why not. I really think the ability to draw from both bores is actually a good theory. You know how the holley adapter is made so you know what I'm talking about, in that the bores on the adapter only go about a 1/4" before it opens up, and leaving a gap underneath it that allows air to flow from both bores. Granted, it is restrictive in this particular setup, but let me tell yeah, even with a horrible knock problem and ESC timing retards, my engine is pulling incredibly strong at 5,500rpm. Haven't taken her past that yet, but WOW! I was never able to take her up to 90mph in third before!

Also, I think the only thing you would have to be careful with as far as leaving the adapter open is the passage circle in the pic. I'm not even sure if it is important or not, but I would think you would want to keep it sealed.

 

I would imagine a cut like this may work though. Sorry for the simplicity

 

When I bought a rebuild kit for my TB from CarQuest, there was a gasket in there with that exact shape. Don't know what the application is, as there were a bunch of gaskets included that I didn't need.

I saw in an ad for TD Performance different spacers now available for TB's. One of them has the single large opening. When I went to the website, I couldn't find the product. Can't remember what mag I saw it in either.

I believe you are correct with your comment about covering the passage indicated, though.

I currently am using the RPM Air Gap manifold and am sure that now I will have to go to a single plane that doesn't allow passing of air under the plenum. It's my understanding that TBI injection needs some heating in the intake to work properly. I drove my truck the other day and experienced icing on the throttle blades and it was a 50 degree day.

I also believe that the Holley adapter is causing my front 2 cylinders to run lean.

 

I've seen that gasket as well. And I think it was over at Howell's website that I saw the same open spacer that you're talking about.

I'm using the vortech RPM Air gap as well, so I'm sure you know about the open "gap" between the adapter and divider plate, thus allowing for access to both tbi bores per cylinder, albiet restricted, but still there. So far, I am really satisfied with the manifold, definetely pulling into higher rpms that the performer intake did not allow me to do I think it's a combo of the runner design, cooler charge, largr plenum(adapter plate is taller), and the "single plane effect". Unfortuantly, I have lost a lot of low end torque....I hope to get some of it back with proper chip tuning.

I'm not sure about the tbi needing to be warmed. I mean I guess if there has been good discussion on it and proof (your blades icing) then there could be grounds for concern. I haven't had problems yet, and was running her today in the 40* weather, but I guess we will see.

I would imagine it would be relatively easy to tap a coolent line into an adapter plate though. Maybe not the Holley one, but definetely a fabbed one. It would help heat the tbi, while a 3/8 gasket between the adapter plate and intake would keep the intake cool.

One last note: I think the adapter plate may be doing the same with mine as well as far as running the #1 and #2 cylinders lean. I am experiancing horrible ping/detonation and what I guess you could call a miss at anything over 2,600rpm, no matter how far I retard or advance base timing and with or with out the dummy knock sensor. My ignition should be pretty hooked up-a day old ignition module, msd blaster coil, MSD 6A, new 8.8 wires, new dis cap, and 5 plugs that are maybe a month old, and the other 3 maybe 6 months old. The 1.5 rockers are back on there and have been adjusted and re-adjusted. My only guess is that one or two of my cylinders are running horribly lean, or I have a seriously fowled plug.

 

The more I read about TBI, the more I believe I am on the right track.

I don't think I will necessarily need to actually heat the TB. I believe going away from the Air Gap type intake will solve the problem. I have an old single plane Holley Street Dominator that the plenum dips way down into the lifter valley. I will also remove the heat shield under the intake. This should warm the fuel mixture enough. If not, I can always install the EGR system and the appropriate intake gasket.

I also have a miss that starts around 4K RPM. I have the big cap DUI racing distributor with 8.5 MSD wires. No amount of fuel pressure increase will get rid of my white as snow front 2 spark plugs!

Walt Sherwin advised me to use this particular intake. Like a fool, I listened to carb guys and their logic and tried to apply it to TB, hence the Air Gap manifold. They don't pay a guy to be an engineer at GM to know nothing .

 

Just checked Howell's site.

They have the adapters for both spreadbore and holley patterns.

Their adapters are of the open design.

 

Wow!

I just remembered I may have the answer to my questions sitting at home on the shelf.

Way back when I started using this modified TB I have, I had the factory water donut modified for the 2.2 inch bores. Don't ask me why...............

Anyway, since my single plane is dual pattern, I can use the factory water donut I have to mount the TB.

In case you're wondering what the water donut is, my truck came from the factory with a spreadbore carb manifold with the water donut to mount the TB to it. Cooling system water was circulated thru the donut to prevent icing of the TB!

Guess I may be doing an intake swap this week.

Oh yeah. If anyone is interested in one of these "factory" TB to carb adapters, I have a few..........

 

454ss, do you have the link to those adapters? All I could find was this, and I'm guessing it's for the 1 11/16" bores, as it does not appear to angle in, as is needed with the 2" bore tbi's.

I'm actually pondering fabbing my own, especially since you have also confirmed the miss and spark plug problem. I am confident this stupid adapter plate is the culprit.

I'm going to try to stay with the RPM Airgap. I think it will work pretty good with my application-it matches my cam's powerband, and the port work on my heads should help match the cam and flow at higher rpms. More over, the darn vortec manifolds are so darn expensive, unfortuantly outta my price range to be able to experiment with. That, and single planes are still highly theorized with tbi. At this point, I really need to start to focus on upkeep, body work and suspension/chassis.

However, I think with yourself and Pablo running single planes with tbi, many questions will be answered and hopefully many doors opened. It will be interesting to see the end results, and I think it's safe to say we're all pulling for ya.

 

Forgot to post the pic.......my bad

 

Thanks for the kind words! Most of the people at the 454SS truck site have settled that with TBI, power can't be made beyond 4800 RPM.

As far as the adapter needing to have the bores angle in, this is how I got around that. Remember, my bores are 2.2 inches, not 2.0. Where the adapter meets the intake, I used a dremel and blended the intake to meet the adapter. Maybe not the best solution, but seemed right at the time.

On the previous note, I am converting from the 8747 ECM that came in the truck to the 16147060 PCM that came in the 91-93 SS pickups. Faster processing and a fellow member has written a program with extended RPM tables that go to 6.5K RPM!

The info I've gleaned from this site has been incredible.

As always, I will pass along my experiences.

Bill

 

Here's a quick and dirty solution:

Grab a cheapo spreadbore to Holley adapter at the local AutoBone, I'll send you one of my factory adapters, and boom, you're done!

 

You'll definetely have to let us know how that goes. I would imagine that coverting from a 8746 would be about the same. The slow a$$ 160 baud rate is horrible.
Darn it! I gave my spread bore adapter away!, otherwise I could do it with out a problem. Oh well, it was easy enough to fab up, and I think your idea will make for an easy and inexspensive solution. Even if it is sloppy looking, it's gotta beat the problems with the hooley adapter. TBI to spreadbore, then spreadbore to squarebore-it takes the hard part of fabbing you own out f the equation. I think I'm gonna have to give this a try....

 

Check your pm box.

 

I dunno if this will be any help to anyone anymore ,but if you check Z28Boy's website (z28boy.cz28.com) he has pictures of how he modified his square bore to accept a small adaptor, not like my gigantic holley one lol.

 

OK, the Holley adapter is off and the problems went away!

I rigged this all together with parts I had and could get locally to determine if the Holley adapter was the problem.

Installed a spreadbore to squarebore adapter and installed my factory water donut and TB on top of that.

Previously, I had a mid and upper RPM miss and my O2 readings were way rich, no matter how low I adjusted the fuel pressure.

Now I am showing lean at WOT, yet there is no miss, and pulls strong and smooth.

Too dark out to do plug cuts.

I need to go another route to get more fuel pressure at WOT. Currently, my reg won't allow more than 26, and now I am showing lean.

Didn't experience icing of the throttle blades either, but it was in the 60's today. Further testing will determine if I need to switch to a manifold with an exhaust crossover to allow some heating.

 

http://www.painlessperformance.com/catalogframe.htm


go to fuel injection accessories


Zac

 

Are there any adapters that are needed, but not made by anyone? I would be interested in making these if they are needed.

 

va454,
I am glad to hear you had success. Like you said, she may not look pretty, but it's getting the job done. Do you still plan on swapping to the single plane just out of curiousity?

As far as the fuel problem goes, there are two routes I would recommend. I am assume you have a high volume/pressure pump installed of course. The two options I know of are 1) replace the spring with a stronger one. I don't know of any places that sell actual springs for regualtors though, but people have talked about just using something you can pick up from home depot. It may take a few times to get it right, but a little trial and error never hurt. Just make sure you are not bottoming out the diaphram on the regulator. You'll know if you do when you get to a point where an 1/8 of a turn yields a 20 psi difference.

The other route is 2) ditch the stock regulator all together and find an inline regulator with a return line. I looked for a little while, and didn't have too much luck finding anything in the right psi range, but there has got to be something out there. Problem with running high fp with tbi is that tbi regulators won't go that high and mpfi afpr won't go that low.

Of course the other option is to burn a chip, but I can understand why that may be out of the question for the time being as you are swapping ecm's.

Also, when you get time I was wondering if you could post the theory on needing heat in the manifold. I am interested in it.

Good job and keep up the good work!

 

Though not in high numer demand, we need a 2" and a 2.2" tbi to squarebore adapter, with the bores being centered on the adapter, not at the front and actually overlapping the plenum like Holley's adapter does. The trick part is that the bores need to angle in to clear the plenum. An open adapter, like the drawing depicks a few posts up would probably be the most ideal.

 

Don't know how to explain the theory for heating with TBI fueling. I had read that somewhere, GM did it originally for some reason (other than emissions), and Walt Sherwin rec'd I do it, even when I go with the Vortech.

Heating may not be necessary, but I don't want to deal with issue of icing of the throttle blades.

Now that I am in a position to begin actually tuning and not chasing my tail, I will probably wait to evaluate the single plane. If I can supply enough air with the Air Gap and modified TB, it may not be necessary.

Good tip on the Home Depot spring! I do believe I am in fact bottoming out the spring. I'm sure it will be cheaper than buying the regulator from GM for the 94-95 454 trucks that is rated for 28-32 psi, just to get a spring. I can disassy and reassy the regulator in my sleep now, so spring swapping is not an issue.

If I can't get the right pressure with the GM reg, I will go with an external regulator of some sort.

Thanks for the encouragement!

 

Well, so much for rushed results.

Found out I wasn't going to WOT after moving the TB rearward.

Still got the intermittent miss at WOT above 4K.

Wondering if its my stupid 8747 and the fact that the scaling ends at ~4700?

I probably do need to get a decent adapter on and the 16147060 installed before proceeding with an intake swap, etc. The 7060 will provide me with much more data to analyze.

This may be an off the wall question, but could gutted cats cause some kind of reversion, etc. I've heard that gutted cats cause turbulence and should be sleeved.

Any truth to that?

 

Yes there is acually. Simply gutting a cat causes turbulance, not only because of any left over screen, but from I understand, because of the way the cat is designed it's self. It is much better to run a straight pipe through it-helps out flow while keeping the government somewhat of your back.....well at least in terms of vehicles

 

Also, that is really bad news about the adapter. Are your front two plugs still showing lean conditions?

I never really believed in the theory that because you are accelerating, the rear of the block gets more fuel. But maybe there is some trueth to it. If your front two plugs are still showing lean, then maybe attempting to angle the tbi ever so slightly up front would help. Just an idea though.

Also, I don't see why it would be your ecm if the problem starts at 4,000rpm. I can understand it doing it after 4,700rpm if that is as far as the charts go in the 7747 ecm.

Did you make any other changes after you installed the rpm airgap, i.e. rockers or ignition?

 

[QUOTE]Originally posted by r90camarors
Also, that is really bad news about the adapter. Are your front two plugs still showing lean conditions?


Did you make any other changes after you installed the rpm airgap, i.e. rockers or ignition? [/QUOTE

Haven't had a chance to do any plug cuts yet.

Had this problem once in a great while when running the TBI intake.

Thought it might be the small cap HEI and I had plans to switch to the DUI Racing big cap HEI anyway, so that went on. No improvement.

Actually, the duals and gutted cats were installed prior to the Air Gap.

Other changes were made to the driveline (tranny, converter, gears, driveshaft, and tires), but those shouldn't affect this problem.

 

How many people would want these? I will look into doing them if they are needed by more than just a couple people. Let me know. Also, is anyone local to me that could test it out? If not, that's ok, but preferred.

 

va454ss,

yeah, I was just making sure the problem was completely isolated.
I would guess your best bet would be to find out about those spark plugs and go from there. If they are still indicating lean, then I would still lean toward the adapter idea, and go on trying to figure something out, someway to supply those front to cylinders with fuel. However, if they seem to be ok, then it can only really be one of two things given your ignition setup is sound. 1) the ecm and or chip not corrisponding to your manifold change and rpm needs, or 2) back to the theory some heat is needed for proper atomization

 

Guess I'll grab a few more straws.................

 

Also, what about making the mounting pad have slotted holes, so the adapter could be postioned anywhere over the manifold opening?

 

Good idea! Now how many takers?

 

tell me how much and i'll take one.

i just found this thread because currently, im looking for the pattern i need to cut so that i can make my own TBI adapter.

my intake gaskets are starting to go, and rather then reuse the stock manifold, im going to use this single plane intake that i had used on my 400... but it has no EGR... so im not swapping until i get my EGR chip i made burned (this weekend hopefully)

then i just need the adapter plate and im set.

 

i just got off phone with howell eng. i have their adapter plate 1/2 inch. it is the plate for 2.00 inch dual TB or in my case a 1995 7.4L dual TB, on a weiand single plane. their application may be specific for holley, not sure. maybe this was stated but since i have not yet bolted up it appears the diameter width of the TB is greater than that of the top surface of the intake. my intake was shaved some what to allow more hood clearance and thinner at top lip due to shave. if i chamfer the intake top i will lose valuable mating gasket surface or have potential vac leak. the howell opening matches the TB exactly and of course is wider than the intake top. the air stream will flow down the TB venturi past the cut in plate and hit a ridge of about 3/16 on each side of top of intake. now is this a big deal? maybe not. howell seems to think it may not cause any issues. turbulence may not be the worst thing. the truck manifold of course is a perfect match but the hood clearance is issue with that. with my vette i think i have about 3/8 inch maybe 1/2 to bottom of hood. alternative is run one inch plate and allow angle taper in machine process BUT the clearance issue again. comments? OBTW the air cleaner is a perfect fit with 1/8 inch clearance over top of injector pod so no room to spare there.