84 TBI question
Thread Starter
Pro
Joined: Oct 2006
Posts: 503
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From: Oxford Pa
84 TBI question
If I wanted to get them rebuilt who would be the best person to do it?
While I'm at it would it be worthwhile to change the intake, and which one would be the best choice.
1984 Automatic, 80,000 miles, stock except for Magna flow system.
While I'm at it would it be worthwhile to change the intake, and which one would be the best choice.
1984 Automatic, 80,000 miles, stock except for Magna flow system.
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
You really don't need to replace the intake. Just hone the living **** out of it.
The ports are about 1/2 the size they need to be.
Do a Forum search for Throttle Body Rebuild. There are shops that can upgrade them - bore them larger and do different injectors. Stuff like that.
Drop a note to CFI-EFI, I am sure he can help you.
The ports are about 1/2 the size they need to be.
Do a Forum search for Throttle Body Rebuild. There are shops that can upgrade them - bore them larger and do different injectors. Stuff like that.
Drop a note to CFI-EFI, I am sure he can help you.
Le Mans Master
Joined: Sep 2000
Posts: 6,303
Likes: 714
From: Bartlett IL
The Xfire manifold can be modded to support over 350hp. You can visit www.crossfire.webhop.net for additional information. If you're planning on a PFI manifold, that would require a new harness and ECM along with tuning.
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
GEt the bigger ones or have yours enlarged if you have the time and budget for it.
IIRC the stock ones flow 560~580 CFM. A little low on flow but with the 1/2 size intake port outlet in the manifold they're fine.
Soon as you start to relieve some of the restrictions in the intake system the TB's will be too small.
Get them fixed now and you'll be all set for some more mods later.
You may want to think about porting the manifold while you're waiting on the TB's to return home.
The stock CrossFire runs great but.... I got my butt handed to me a few months back by one of those danged Furd TunderNerd things.
I let him get a little run on me and then couldn't make up for it.
Another 50 hp would'a done it.
IIRC the stock ones flow 560~580 CFM. A little low on flow but with the 1/2 size intake port outlet in the manifold they're fine.
Soon as you start to relieve some of the restrictions in the intake system the TB's will be too small.
Get them fixed now and you'll be all set for some more mods later.
You may want to think about porting the manifold while you're waiting on the TB's to return home.
The stock CrossFire runs great but.... I got my butt handed to me a few months back by one of those danged Furd TunderNerd things.
I let him get a little run on me and then couldn't make up for it.
Another 50 hp would'a done it.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
IIRC the stock ones flow 560~580 CFM. A little low on flow but with the 1/2 size intake port outlet in the manifold they're fine.Soon as you start to relieve some of the restrictions in the intake system the TB's will be too small. Get them fixed now and you'll be all set for some more mods later.
You may want to think about porting the manifold while you're waiting on the TB's to return home.
You may want to think about porting the manifold while you're waiting on the TB's to return home.
I've witnessed a stock longblock CFI car go .6 faster in the 1/4 from nothing other than a HEAVILY ported intake. AFTER the intake was ported and those results were in, I bored the TB's for this person to 2.09". On a stock long block w/ported intake engine, the bored TB's made zero difference. I also bored the TB's on my CFI which featured a 400 long block, 224/234 cam, RR's, and heavily ported intake. On that combo the bored TB's MIGHT have made a 10th. I also made other changes at the same time so I'm not confident that the 10th I got was from the TB's.
The TB's aren't a restriction on a CFI motor that's anywhere near stock. Knowing what I know now, I wouldn't bore TB's until after I had heads, cam, heavily ported intake, headers...THEN maybe I'd consider boring the TB's. One way to find out if your combo is approaching that point is to put a vacuum guage on it, or a scan tool. Do a WOT run and watch the intake manifold pressure (vacuum). If you draw ANY vacuum, you could benefit from bigger TB's.
Last edited by Tom400CFI; Jan 13, 2007 at 05:27 PM.
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Le Mans Master
Joined: Sep 2000
Posts: 6,303
Likes: 714
From: Bartlett IL
If you didn't want to do any real mods I would suggest:
1. porting the manifold,
2. running // fuel lines with same size injectors in each TB.
You'll find that the motor runs significantly smoother.
3. 1.6 ratio rockers.
4. Port match the stock exhaust manifold and grind back the
AIR tubes in the primaries.
Nice car. Good torque. Just don't go picking on any LS or LT motors.
1. porting the manifold,
2. running // fuel lines with same size injectors in each TB.
You'll find that the motor runs significantly smoother.
3. 1.6 ratio rockers.
4. Port match the stock exhaust manifold and grind back the
AIR tubes in the primaries.
Nice car. Good torque. Just don't go picking on any LS or LT motors.
Thread Starter
Pro
Joined: Oct 2006
Posts: 503
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From: Oxford Pa
Feels like there might be some play in the TB shafts
Does "//" mean run two fuels lines?
If I change the rockers do I need new/different push rods?
I'm not neccessaryly looking to build a screamer, just some more pep and or to improve overall performance without major engine mods.
The weakest like appears to be with the TB and Manifold.
Does "//" mean run two fuels lines?
If I change the rockers do I need new/different push rods?
I'm not neccessaryly looking to build a screamer, just some more pep and or to improve overall performance without major engine mods.
The weakest like appears to be with the TB and Manifold.
Burning Brakes
Joined: Sep 2006
Posts: 1,202
Likes: 3
From: MD
You really don't need to bore the TBs any larger on an otherwise stock motor with a stock intake, ported or otherwise. Work up from your largest restriction. The intake is the largest. If the TB shafts are worn, have them rebushed at any good carb shop (getting a little tough to find these days). 1.6 rockers are a great way to quickly/cheaply get more flow out of your heads, but the intake is the absolute best place to start. Modify too much in the engine and you'll need to get into tuning which it sounds like you don't really want to do. My $.02
Le Mans Master
Joined: Sep 2000
Posts: 6,303
Likes: 714
From: Bartlett IL
Feels like there might be some play in the TB shafts
Does "//" mean run two fuels lines?
If I change the rockers do I need new/different push rods?
I'm not neccessaryly looking to build a screamer, just some more pep and or to improve overall performance without major engine mods.
The weakest like appears to be with the TB and Manifold.
Does "//" mean run two fuels lines?
If I change the rockers do I need new/different push rods?
I'm not neccessaryly looking to build a screamer, just some more pep and or to improve overall performance without major engine mods.
The weakest like appears to be with the TB and Manifold.
accumulator and regulator currently in the TBs. The reason the injectors on a Xfire are 62 and 66# is because there's about a .5psi drop in the FP between the front and back injectors. So GM compensated for the reduced FP by increasing the injector flow in the back. IMO, one of the major reasons why the A/F mixture distribution sucks in the Xfire manifold. This is a fairly low cost mod and most of it DIY. I think you'll find that the motor will run much more quietly. You'll hear the exhaust note but little engine noise when cruising assuming everything else is fine.
As for the rockers, the stock pushrods are fine. I would suggest at least a set of roller tip rockers to reduce friction and help with valve guide wear. You may even want to try 1.6 rockers on the intake and 1.5s on the exhaust first and see how you like it. I would also upgrade the Fuel Pump to an LT1 pump. Once you're hooked and get ambitious, get a HAM ECM adapter harness, swap out the stock ECM for an EBL from Dynamic EFI, and learn to tune.
Last edited by Dominic Sorresso; Jan 14, 2007 at 11:46 AM.
Thread Starter
Pro
Joined: Oct 2006
Posts: 503
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From: Oxford Pa
// means splitting the fuel line and feeding the TBs in parallel not in series as is stock. This will require an external FPR and blocking off the
accumulator and regulator currently in the TBs. The reason the injectors on a Xfire are 62 and 66# is because there's about a .5psi drop in the FP between the front and back injectors. So GM compensated for the reduced FP by increasing the injector flow in the back. IMO, one of the major reasons why the A/F mixture distribution sucks in the Xfire manifold. This is a fairly low cost mod and most of it DIY. I think you'll find that the motor will run much more quietly. You'll hear the exhaust note but little engine noise when cruising assuming everything else is fine.
As for the rockers, the stock pushrods are fine. I would suggest at least a set of roller tip rockers to reduce friction and help with valve guide wear. You may even want to try 1.6 rockers on the intake and 1.5s on the exhaust first and see how you like it. I would also upgrade the Fuel Pump to an LT1 pump. Once you're hooked and get ambitious, get a HAM ECM adapter harness, swap out the stock ECM for an EBL from Dynamic EFI, and learn to tune.
accumulator and regulator currently in the TBs. The reason the injectors on a Xfire are 62 and 66# is because there's about a .5psi drop in the FP between the front and back injectors. So GM compensated for the reduced FP by increasing the injector flow in the back. IMO, one of the major reasons why the A/F mixture distribution sucks in the Xfire manifold. This is a fairly low cost mod and most of it DIY. I think you'll find that the motor will run much more quietly. You'll hear the exhaust note but little engine noise when cruising assuming everything else is fine.
As for the rockers, the stock pushrods are fine. I would suggest at least a set of roller tip rockers to reduce friction and help with valve guide wear. You may even want to try 1.6 rockers on the intake and 1.5s on the exhaust first and see how you like it. I would also upgrade the Fuel Pump to an LT1 pump. Once you're hooked and get ambitious, get a HAM ECM adapter harness, swap out the stock ECM for an EBL from Dynamic EFI, and learn to tune.
Le Mans Master
Joined: Sep 2000
Posts: 6,303
Likes: 714
From: Bartlett IL
FPR is Fuel Pressure Regulator. I use one with a Vacuum Adjustable FP. That's the Aeromotive 13301. Not a cheap unit but for higher output motors where you really need to crank up the FP, you'll probably want to try varying the fuel pressure so idle can be controlled with a longer pulse width. But that's for later.
I currently use the Crower Stainless Full Roller Rockers, but had the CompCams Magnum roller tip rockers for a long time and like them a lot.
One other thing you might try is pulling out the diffuser plates under the TB and removing some of the material. I removed material from them and then bent the vanes a bit more vertical. If you're in colder climate you'll want to keep them for driveability.
I currently use the Crower Stainless Full Roller Rockers, but had the CompCams Magnum roller tip rockers for a long time and like them a lot.
One other thing you might try is pulling out the diffuser plates under the TB and removing some of the material. I removed material from them and then bent the vanes a bit more vertical. If you're in colder climate you'll want to keep them for driveability.
Thread Starter
Pro
Joined: Oct 2006
Posts: 503
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From: Oxford Pa
Great stuff! Thank you very much. I was getting ready to pull the valve covers anyway to repaint them, now I have a better reason to do so.
Do you have any pics of the fuel lines, and pressure regulator?
thanks again
Tom
Do you have any pics of the fuel lines, and pressure regulator?
thanks again
Tom
or this
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
The first part of this post isn't right (in my experience) the last sentence quoted is where you should start.
I've witnessed a stock longblock CFI car go .6 faster in the 1/4 from nothing other than a HEAVILY ported intake. AFTER the intake was ported and those results were in, I bored the TB's for this person to 2.09". On a stock long block w/ported intake engine, the bored TB's made zero difference. I also bored the TB's on my CFI which featured a 400 long block, 224/234 cam, RR's, and heavily ported intake. On that combo the bored TB's MIGHT have made a 10th. I also made other changes at the same time so I'm not confident that the 10th I got was from the TB's.
The TB's aren't a restriction on a CFI motor that's anywhere near stock. Knowing what I know now, I wouldn't bore TB's until after I had heads, cam, heavily ported intake, headers...THEN maybe I'd consider boring the TB's. One way to find out if your combo is approaching that point is to put a vacuum guage on it, or a scan tool. Do a WOT run and watch the intake manifold pressure (vacuum). If you draw ANY vacuum, you could benefit from bigger TB's.
I've witnessed a stock longblock CFI car go .6 faster in the 1/4 from nothing other than a HEAVILY ported intake. AFTER the intake was ported and those results were in, I bored the TB's for this person to 2.09". On a stock long block w/ported intake engine, the bored TB's made zero difference. I also bored the TB's on my CFI which featured a 400 long block, 224/234 cam, RR's, and heavily ported intake. On that combo the bored TB's MIGHT have made a 10th. I also made other changes at the same time so I'm not confident that the 10th I got was from the TB's.
The TB's aren't a restriction on a CFI motor that's anywhere near stock. Knowing what I know now, I wouldn't bore TB's until after I had heads, cam, heavily ported intake, headers...THEN maybe I'd consider boring the TB's. One way to find out if your combo is approaching that point is to put a vacuum guage on it, or a scan tool. Do a WOT run and watch the intake manifold pressure (vacuum). If you draw ANY vacuum, you could benefit from bigger TB's.
The only time there is none is when the engine is not running.
BTW, All of my previous post was correct.
The location of the restrictions in the CrossFire induction are well known.
The manifold outlets are HALF BLOCKED in a Crossfire intake.
The TB's are also a restriction @572 CFM.
Once these are 'fixed' the restriction will move to the valve ports.
Additional lift/duration can 'help' but the biggest 'help' will be heads with improved flow characteristics.
ALL of these together will be best.
It doesn't matter WHERE you start.... It's where you FINISH that counts the most.
Here's the flow info courtesy of CrossFire Injection site:
Throttle body flow numbers.
Stock (1.812") TB, two injector tower gaskets @13.6" - 286 CFM (each) total, 572 CFM together.
2" TB, two injector tower gaskets @13.6" - 333 CFM (each) total, 666 CFM together.
2.130" TB, two injector tower gaskets @13.6" - 379CFM (each) total, 758 CFM together.
Le Mans Master
Joined: Sep 2000
Posts: 6,303
Likes: 714
From: Bartlett IL
There will ALWAYS be SOME VACUMN in the intake of a normally aspirated engine.
The only time there is none is when the engine is not running.
Here's the flow info courtesy of CrossFire Injection site:
Throttle body flow numbers.
Stock (1.812") TB, two injector tower gaskets @13.6" - 286 CFM (each) total, 572 CFM together.
2" TB, two injector tower gaskets @13.6" - 333 CFM (each) total, 666 CFM together.
2.130" TB, two injector tower gaskets @13.6" - 379CFM (each) total, 758 CFM together.
The only time there is none is when the engine is not running.
Here's the flow info courtesy of CrossFire Injection site:
Throttle body flow numbers.
Stock (1.812") TB, two injector tower gaskets @13.6" - 286 CFM (each) total, 572 CFM together.
2" TB, two injector tower gaskets @13.6" - 333 CFM (each) total, 666 CFM together.
2.130" TB, two injector tower gaskets @13.6" - 379CFM (each) total, 758 CFM together.
Just as an illustration of the TBI flow, I run a set of 2.13" TBs/two gaskets on a stock block 350. With my port matched, EH'd Xfire manifold with 5/16" lid spacer, my kPa will drop from 97 at 3400rpm to 96 @ 5500rpm during a WOT run. The heads are 195cc TFS 23d with 64cc chambers. "Key on" MAP is usually 98 here in Chicagoland.
Thread Starter
Pro
Joined: Oct 2006
Posts: 503
Likes: 0
From: Oxford Pa
Sorry to be a pest
Injector tower gaskets?
First vette so I'm learning
Nice pics, the plumbimg looks good, need to keep the return lines functional also I see like on a mechanical FI.
I have used and setup many Hilborn Mechanical FI's on small block chevy's in Sprint Cars.
Injector tower gaskets?
First vette so I'm learning
Nice pics, the plumbimg looks good, need to keep the return lines functional also I see like on a mechanical FI.
I have used and setup many Hilborn Mechanical FI's on small block chevy's in Sprint Cars.