I've got a Weiand Street Ram intake #7525 and an '87 GM 454 TBI unit. Does anyone here have any insight into the design of a 2bbl TBI - 4bbl carb adapter plate for this intake? More specifically where to put the holes and other design issues that affect distribution.

------------------
1988 T/A,
9" Ford, 3.50 gears, Auburn posi, 700r4 -w- 2100 converter
350 .060 over with forged 1 pc rms crank, and forged TRW pistons, 9.5:1 cr
Factory GM heads Pocket ported, 2.02/1.60 valves, back cut
Lunati roller 219/227, .479/.480, 112 LSA
Holley 700cfm 4bbl on TBI truck 7747 computer and chip by Howell-EFI
Edelbrock Performer EGR intake, Edelbrock TES and 3" cat

 

First off what carb pattern does this manifold have? If it's a square bore I think I would put it as centered as posible. I did mine that way using a 1/2" aluminum plate minimum. You could use a thicker one and radius the bottom side to clear the manifold (from the outside edge toward the inside edge of the plenum) and at the same time radius it front to back to give it a gentler transition to flow to all ports.

Steve

 

I think that you should make the bores under the TBI as long as possible(that fit under the hood) to prevent the blades from making the air and fuel favor one side of the engine over the other.

------------------
-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....

Soon to be installed:
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
EFI & Intake Options
AOL IM: superGRtaz

 

dan just make a square plate and center the holes over the bore. Youll need to cant the outer edges inward because the 454 is wider than the flange.. its a peice of cake to do i converted the turbo city adapter from 1 11/16 to 2"

just center it, the fuel distribution issues are adressed by spacing the injector pod upward and programming for minimum IAC counts

and thats just at idle so dont worry about it

 

I need to keep the height to a minimum for hood clearance so a tall spacer is out of the question. I've got a piece of 1/8" or so thick steel cut to shape... just waiting to drill the holes. The throttle blades will actually open fully w/o clearance issues in the center (the narrowest portion) of the intake.

Any idea why Holley offsets theirs? Any Idea about what kind of mods Traco did to theirs?


[This message has been edited by Dan W (edited April 16, 2001).]

[This message has been edited by Dan W (edited April 16, 2001).]

 

holley offset theirs to make it for the more allround user. Somebody who isnt going to be doing much modding to their tbi system. So they went for the economical quick fix of moving the tbi instead of pablos answer of fixing the injector pod problem.

I would center it also. I am thinking traco's is nearly identical to holleys or turbo city's. just an angle inwards to allow for the bores to clear. traco may have done some sort of drop into the manifold or something like that, to change plenum volume, and mess with flow and velocity a bit.

saw your pic. edit. dan if you would, send me the bolt pattern specs and opening if you could, maybe a rough scetch scan, so i can design an adapter for my tbi for that manifold design. thanks.


[This message has been edited by snflupigus (edited April 16, 2001).]

 

Just curious Dan, are you changing from the 4bbl to the 670 and why? Did you find the Traco article interesting? I liked reading it. I have some 1/4" plastic called delrin and was wondering if it would be better than the 3/8" thick aluminum adapter that I have made for my 350HO due to be installed in May? Good luck with your mods?

 

I would make sure if you plan on using a thin plate to make your adapter out of, to have enough threads to securely hold the tb in place. A 1/8" steel plate won't allow enough threads to keep the bolts holes from stripping out while you are trying to tighten the tb to the plate. I wouldn't go less than a 1/4" IMO.

Steve

 

DM91RS, I just want to test its capabilities... it wont be on there for long because I'm going to convert the intake to multi-point and the 2bbl is going on a 454 in a '69 truck. I'm also in the process of swapping heads... AFR 190's.

Steve... Nuts, bolts and perhaps a few tack welds.

 

I would advise against using delrin. Ive handled the stuff and it didnt seem particularly tough.

ANd I agree with what snf said

dan, the GMECM and DIYEFI archives are now searchable, look at the prom board. I found some interesting infor regarding the stock gmecm injector drivers running two pairs of holley injectors.

 

DO NOT center the TBI bores in the carb pad. They MUST be forward as much as possible!!! No ifs, ands, or butts...

IMO, just buy the Holley adapter plate. Nice piece, clean and easily trimmable to match the outer side of the carb platform.

 

I was hoping for a consensus

Fast, I've never been one to do as I was told without asking why first. Would you mind delving into the specifics.

My biggest concern is that since this is a single plane, cylinders 5&7 are next to each other in the firing order and not separated like in a dual plane. Distribution problems can occur between these two cylinders. My concern is that with the Throttle body at the front, these rear cylinders will see less mixture and perhaps amplify the distribution issue. Thoughts?

 

yes, fastbroker. please explain your opinion on this issue.

Mine would be that unless you are really trying to squeeze each and every possibile horsepower out of the engine, that the distribution problems are actually not bad enough to worry about durring normal driving and a few strip runs. seriously, whats a half an inch going to do for you?

 

Dan W. the AFR's should kick a##! Pablo, would phenolic material be any better or am I being needlessly conserned about heat transfer and would the air-gap manifolds help with manifold heat buildup? I would also like to hear about the best hole location for the adapter plate.

 

You could fab / buy a metal adapter and use a phenolic gasket. I think this Holley part may do what you want: 508-11 ...best call the tech line first and ask though. My 4bbl came from Holley with a phenolic gasket and the 2bbl Holley I just installed on another car came with the above part number.

 

Thanks Dan! I went to the Holley web-site and looked under fuel inj. service parts and acc. and was surprised to find photos to match part numbers. The 508-11 was the gasket that came with my 670 and it reduces the 2" bore to the standard. Did not think about using it since it's been so long since I bought the unit. I'll just take it to work and run a 2" end mill through it and use it on the .375 thick alum. adapter plate that I have already made. Thanks! Darrell M

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91 RS 305TBI T5 3:08 16" GTA'S 255 50 16 ZR'S

 

Ive run both adapters. THe holley adapter is a crutch. Ive done some dedicated plug reading and found once you seriously reduce iac counts (iac steps vs kpa at reset table does the trick) and space the injectors properly, you dont eally have much of a problem with the rear cyls being rich. My plugs front to rear look about the same. However there was a time when they didnt and it was the result of too much IAC opening.

when i had the holley adapter on the rear cyls still looked rich

 

The throttle blades "aim" the air/fuel mixture backwards towards the rear of the plenum. ie, the problem is not "rich rear cylinders", it is "lean front cylinders". This is made MUCH worse with the 2" TBI units, especially the Holleys, because the injector spray actually hits the blades, drips down them and is forced backwards by the inflowing air off the plates. If you have a forward bias, you will give more fuel to the front.

Not really a big deal, guys, but if you want the most, IMO, use a forward bias. Again, it's not the rear cylinder richness, it's lean condition in the front cylinders, which is MUCH worse...

 

Tomato, Tomahto

same ****, and at idle, its not particularly a huge concern

 

btw my front cyls were just fine.. I had it tuned 'that way'

you can go either way so if you are trying to sound smart I award you no points and may God have mercy on your soul

 

If you tune front cyls to be ok, rear will be rich... If you tune rear to be ok, front will be lean. take your pick. I got dyno tests to prove it... Nice try.

 

Yes, single plane Strip Dominator (big) and dual plane Air Gap tests, both intakes tested with carb/HEI AND with TBI on last engine dyno testing trip with XE250 cammed 350cid.

Nobody asked, nobody got...

 

what are the hp differences on the dyno. 5hp?

 

More like 25/18, lb-ft/hp respectively on BOTH manifolds. Or, deltas of about 6%/6% respectively, too. And, that's with the 1-11/16" TBI! I am sure that it will be worse with the 454's because the size of the blades is like a plain wing in the airflow... And I don't even want to discuss the Holley injector pattern. I could spray better between my front teeth...

If 6% is not worth your time and $60, don't get into PROM programming.


This stuff is a fact, guys... I am not the only one who know/preaches this. Why the arguements??? Run a HUGE 4bbl carb with the rear barrels disconnected (to negate the effect of the only two-barrel thing) and you'll see other odd-flow characteristics...

Ask an engine builder/dyno operator. They'll confirm.

[This message has been edited by FastBroker (edited April 19, 2001).]

 

Pablo,
Come on now, let the discussion happen.

Fast,
What you are saying makes sense at idle but at WOT when the blades are fully open... wouldn't you want them centered on the intake??? What type of adapter were you using for the dyno testing?

 

What are the dyno differance's between a reg. performer and the air gap rpm you are refering to?

 

Thank you for repeating what I said in different words.. "tune the front to be fine the rear will be rich" Now that i have controlled IAC counts, this is not a problem at idle or part throttle

at wot theres no paddling going on

This is real world tuning rather than on a big drum in a garage

 

BUT
I think either way will be adequate for your regular run of the mill small block. My setup works fine for me, and im sure the forward TB would work fine aswell. 'Specially on the generally tame motors we are talking about

[This message has been edited by Pablo (edited April 19, 2001).]

 

peak hp comes at wot, no?

so, if you tune your chip right, iac, and injector pulses at idle, then wouldnt you want it in the center. so that at wot, you have even distribution and peak flow and hp to all cylinders evenly, at wot.

if you are racing, or even daily agressive driving, how much do you care about how your hp is at 1/3 - 3/4 throttle.

so you shouldnt put in a lopey cam. because your idle would be bad.

 

thats why I said to make a tall spacer to negate the effect of the blades spitting the air and fuel to one side or the other.

 

Of course you guys are right for WOT operation. Unfortunately, for myself anyway, my TBI vehicle is a street driver. Aren't yours??? how much time do you think you actuall spend at WOT/90deg throttle opening while street driving??????? Not much... not much at all. I should have clarified that my comparion discusion was not at WOT/high rpm but at more moderate rpm levels and partial throttle settings, but I thought this was obvious because the plates are open at WOT and there is no effective diversion front or rear, as I believe Pablo mentioned... Only diversion at WOT is airflow/plenum diversion/turblence.

but yeah, for absolute WOT drage racing, you can go for the center. Just don't get mad if you notice that your daily driver with big cam (worse) runs like sheoot and you have tuning problems front to rear. BTW having the unit centered vs forward produced no repeatable differences in hp or torque at WOT and high rpm settings, only under high load (water brake dyno), part throttle settings that I was using for PROM work.

someone asked about tuning between two dual plane manifolds. Performer vs RPM AirGap? It was between single plane Strip Dominator (Holley, kinda like an Edelbrock Victor Jr.) vs dual plane Air gap. XE250 cam 1.6 RR's, Vortec heads.

Engine still not in Jeep, yet. Too tired from work to get to it... Please, enough guys. Sorry for the confusion. Just put ANY plate on and get it RUNNING like a banshee!!!

[This message has been edited by FastBroker (edited April 19, 2001).]

 

This is a great post. I'm glad nobody has said that the rear cylinders are rich because when the car is moving forward.... .
Check out my sig for what I've got. I checked the plugs and they're all running rich so I can't tell you for sure. I never thought about the blades directing air towards the rear, that's a good point.

------------------
, Jon (350 TBI! it's trenuous and efficacious while getting 23mpg highway with off the shelf eprom)
91 Red RS w/grey int, sq stereo (Alpine v12, kicker solo, MB quart premium etc)AIM: JPrevost

• Holley 670 TB unit w/ 1/2" spacer/adapter
• Edelbrock RPM vortec intake
• 350ho 330hp vortec crate motor
• 8" harm. balancer
• Stewart stage 2 water pump w/160 thermo
• SLP tri-y headers to full 3"
• Rebuilt trans w/ SLP shift kit
• Centerline 16x8's all around
• 36/24 mm sway bars
• Full poly bushings, even motor mounts
• SLP LCA and panhard
• Alston SFCs
• Edelbrock 3 point STB
• Global west steering brace aka wonderbar
• Eibach pro kit springs
• Bilstien high perf. struts and shocks
• All this and I still have AC

My websiteAny questions?

 

Tas, I'm with you about the spacer but there just isn't room on my car w/o a cowl hood.

Fast, Did you just say that its best for WOT to have the TB in the middle and a paragraph later say that there is no HP increase for having it there? You are confusing me again.

I understand that either placing the holes in front or middle will work... that minimizing IAC opening and optimizing fuel spray patterns help the situation. That placing the TB up front is good for part throttle but is probably not good for WOT. Everything sounds like a degree of compromise. I can already hear the TPI guys laughing.

Maybe the best situation would be to keep the TB in the middle and do some modifications to the adaptor and / or intake to make the distribution better at part throttle. If there is a way to do this w/o and performance compromise, I think this is it.

... Which brings us to the now out of business Traco. I’d like to explore the possibilities of a Traco type plate. I e-mailed Jim Jones the former proprietor of Traco... he now works for Calloway. The project was a long time ago and he couldn’t remember the specifics. So we are on our own unless we can come up with someone who paid for that package. or... anyone buddies with Marlin Davis? He is the original author of the article. Who knows, maybe he has pictures / details of the adapter or can put us in touch with the cars present owner.

What I’m thinking they did was weld a couple pieces of round or half round 2-2 ½” diameter x ½” – 1” long tubing to the underside of the plate. Thoughts?

 

Ya I've thought about adapters that send the TBI bores down into the plenum. If you got fancy, you could even make them adjustable in length. Take a TBI-carb adapter, machine the bores oversided, counter sink the lip. This way you can put in pipes with a top lip into the bore without them falling in. You can have adjustable lengths too.

------------------
-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....

Soon to be installed:
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
EFI & Intake Options
AOL IM: superGRtaz

[This message has been edited by Tas (edited April 20, 2001).]

 

for the record, my car with a centered spacer runs fine.. not like "sheeeoot". It idles so smoothly most people cant tell its cammed until i tell them(esp. warm idle..). I ran a holley carb on there and there was a definate definate hot rod lope (sounded mean though!)

 

but in my opinion run either frickin one. Id run the centered just because you can bolt it on and dont have to mess with the linkage or anything. When i had the holley adapter i had to make some linkage extensions for it to work right

 

I'm with ya. Just run one and go!!!

I am trying to stress that the differences I saw were at part-throtle settings, not WOT. In theory, you'd want the bores centered at WOT, I suppose... Just letting you guys know of my dyno testing/PROM work, mainly. Better forward for driveability, low-end torque, how's that? WOT, doesn't seem to matter. That said, what's wrong with a little more low-end torque and having the bores up front? That was my point, that's all. Honestly, most won't even know/feel the difference...

Have a nice weekend guys!!!

 

you too fast.

taz, just to let you know. that is an old concept and has been used plenty. i dont know if you were thinking it was a new idea or not. I studied up a bit on manifold and spacer design, while designing my tbi.

o and also taz. how hard a car leaves the line, does effect its fuel distribution. raw fuel that builds up inside a wet manifold like ours, will flow twards the back of the engine when acceleration occurs. with a lower plenum floor than the runners, this can be avoided, so that the raw fuel on the plenum floor doesnt run down thru the runners into the rear cylinders.

anyway, for my tbi, ive made the adapter in way that it will change plenum volume, . and i think it will give a nice little torque boost. I also think it will improve over all flow. I really cant wait to let you all see, but i have to.

I would also like to make note that this is another area where tbi wins the contest against carb. a carbs inadequate atomization at lower boosts signals, will yeild an even worse distribution problem than our tbis will if positioned in the center because our injectors atomize the fuel better. The more fuel you have atomized in the air, the less you need to worry about which way the blades are going, because the front runners will pull air from almost halfway down the oposite side of the manifolds runners. so even if the air is pointed to the back by the blades, the front cylinders wont have too much of a problem pulling what they need. now, the fuel that doesnt atomize, will be pointed down the rear runners, and flow down the rear runner walls.
this contradicts what was said earlier about the problem being lean fronts instead of rich rears. but that is tuning, like pablo said, tune the front to be normal, and the problem will be rich rears. tune the rears, yes, your problem will be lean fronts.

so now that ive thought way too much about this, i agree with fastbroker. it wont hurt anything to move it forward, even at wot, because like taz joked about, at WOT, will cause any raw, nonatomized fuel to flow twards the rear cylinders.

tune the rear, let the front suck what they need. move it foward till its a pain in the *** for your linkages, then leave it be. that should help your decision a little more dan.

 

I thought I said the "lean front, ok rear. ok front, rich rear" thing. Oh well. guess you guys can figure it out on your own.

Rain in CA today, eh, Tas?

[This message has been edited by FastBroker (edited April 20, 2001).]

 

lots'a big gray clouds but no rain yet. I got rained on a bit yesterday though.

 

Houses in the 94920 hood coming down quite a bit. Gonna have to step up to the next level of affordability at next fed ease...

Decided to go Spring-over on the Jeep for the Summer street/beach action(ie, 6 inches taller) i'll be sure to post pix when motor is in, axles are flipped, top is off and stainless stuff is installed. Might chop the rear off and add the rear of another Wrangler to make a custom 6-person wranger/SUV. Whattya think? It's been done and looks pretty cool. gotta do something different with this thing... 350 isn't different anymore. helped too many people convert... Have a TH350/Advance Adapter/NP231 23-spline t-case Chevy V-8 conversion package for sale. konw anyone who might be interested? $1000 takes it all: TH350 in GREAT shape w/custom valve body and B&M TransPak, converter, Advance Adapter t-case adapter, N231 t-case w/modified shifter, rear output slip-yoke for d-shaft, B&M Star Shifter, custom mounts to use the OEM Jeep cross member mounts.

email me if you like. Nothing like a 350/314, or a 350/350 or a 350/400 Wrangler...

later

 

check out my website for odd 4x4 pics. I got a 6x6 CJ in there, stretched SWB jeeps, bobtailed CJ8s.... I'm gonna lift mine soon but I dunno how, but this is interesting though ---> http://forums.jeepsunlimited.com/ubb...ML/003194.html

FB, you need to get AOL IM.

------------------
-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....

Soon to be installed:
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
EFI & Intake Options
AOL IM: superGRtaz

 

fastbroker you did say that, i was just restating.

btw, I think the extened jeep thing is cool. ive seen pics of stuff like that. or you could stretch the body laterally. so its wider like a hummer.

i mean, if youre gona be going for unique.

also btw, dan, tell us what you decide. and how it works out.

 

I'm about 10 minutes from installing my new AFR 190's and I thought I'd let you guys know what I found about the performer intake.

The upper plenum seems to have been having a distribution / atomization issue. All the upper runners are discolored, all plugs from upper plenum runners look black and all cylinders had more carbon build up. Exhaust valves from the lower plenum are light colored, valves from the upper plenum are black.

 

I would have bet money that the perfomer intake with a TBI adapter would have a "distribution / atomization issue." I spoken against this intake for TBI several times. I made a new Dual Exaust page. Its in my sig.

------------------
-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....

Soon to be installed:
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

 

Seems to me the upper side of the intake is rich. Why? Injector imbalance?

Seems a distribution problem would show as some black plugs and some white. Not all cylinders black.

 

I dont think so... but have no way to really prove it.

The plugs from that plenum's runners were black, the rest normal.

I bet this is something a spacer would fix.

 

Dan do you mean a taller spacer/adapter such as a 1/4" thick compared to a 1" thick one?

 

Wouldn't a distribution problem show up as different color plugs on the cylinders fead by the plenum in question?

It just seems odd that all the cylinders on one plenum would run richer than the other.

 

Ah, I see what you are saying Brent. I probably used distribution in the wrong context, sorry. I was referring to it in relationship to the other plenum that is yes, more or less spearated. The Gasket I'm using is about 1/4" thick (phenolic) so there is some opening between the plenums.


All the injectors are the same size...
Could it be this is a manifestation of running 4 injectors on 2 drivers? Maybe but why just one side? ...here are how the injectors are wired. I'll label the injectors by what driver they go to and then their position in the series circuit, either first or second.

LF D1/S1
LR D2/S2
RF D2/S1
RR D1/S1

I did have a problem with an injector not working when I first got the TB but replaced it and now they are all working fine. I've had the heads off since then and everything was cleaned up before they went back on.
Do you think it could be a puddling type of issue caused by the injector being that much closer to the floor of the upper plenum.