Up grading old motor - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 04-18-2008, 03:29 AM
Registered User
 
Join Date: Apr 2008
Location: Drakesville,Ia
Posts: 3
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Up grading old motor

I have to chage motor in my 88 chevy pickup. it has a 350 tbi, I have a older carb. motor, can i put the tbi intake on the older motor. Or would i have to chage heads also? And is there any thang else that i need to do to make this work? I know ill have to put a plate on the fuel pump hole.
Any input is greatly appreciated!!

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-18-2008, 03:43 AM
curtis73's Avatar
Hates: Liver. Loves: Diesel
 
Last wiki edit: How to find cheap parts
Last journal entry: 1999-2001: Getting it on the road
Last photo:
Join Date: Dec 2005
Location: Pittsburgh, PA
Age: 40
Posts: 5,128
Wiki Edits: 16

Thanks: 0
Thanked 2 Times in 2 Posts
The TBI intake's center bolt holes are a different angle than the older block. Some guys have had success with hogging out the holes for the other angle. You'll see what I mean when you compare the TBI intake to the older engine.

IMHO, the work it takes to put a TBI on another engine is much more than the benefits. The TBI is a pretty crappy setup. It doesn't use injectors, it uses nozzles that squirt liquid fuel. The TB only flows a very pathetic amount. You'll hear reports of 450+ cfms which is dry flow without the nozzles. With the nozzles installed it flows 380 cfms or so. The nozzles are known for leaks as well.

I would also never suggest putting TBI heads on anything. They are fine for a super low-power application that is done by 4000 rpms, but they are one of the worst flowing heads GM ever created. They are cast with a swirl vane in the intake port to try to increase turbulence, increase mileage, and reduce emissions. They do increase turbulence, but they failed miserably at the other two tasks. GM committed to the heads, then found they had to use horrifically tiny cams (161.7* intake duration) to meet emissions, and despite their 180-hp output, they struggle to make 13 mpg average.

Last edited by curtis73; 04-18-2008 at 03:50 AM.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 04-18-2008, 12:40 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,696
Wiki Edits: 0

Thanks: 3
Thanked 404 Times in 349 Posts
Quote:
Originally Posted by chevy4x4man
I have to chage motor in my 88 chevy pickup. it has a 350 tbi, I have a older carb. motor, can i put the tbi intake on the older motor. Or would i have to chage heads also? And is there any thang else that i need to do to make this work? I know ill have to put a plate on the fuel pump hole.
Any input is greatly appreciated!!
With a little effort yes.

1) The 88 has Throttle Body injection, no big deal if it works well don't mess with it. The center 4 bolts (2 on each side in the middle) have a different angle 72 degrees on the 88 heads and 90 degrees on the old motor's heads. either the heads can be interchanged or the center bolt holes on the intake egg shaped to move the angle of the center bolts. The bottom of the bolt head needs to fit flat against the intake, so you'll have to take a die grinder or a mill, if you have one, and dress this area so the bolt heads lie against a flat surface.

2) Your other big headache is the flywheel or flexplate assuming the old motor is a two piece seal type, it has to have the matching fly/flex as the bolt pattern to the crank is different between 1 or 2 piece seal cranks.

3) The injected engine uses a detonation sensor, there is no place to mount it on a carbed block without fabricating a bracket, often this is done by installing a 1/4 inch thick plate between the engine and its mount with a tapped hole for the sensor.

4) You already know about the fuel pump boss needing to be blocked off.

Bogie
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 04-18-2008, 01:14 PM
How fast is fast enough?
 
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 29
Posts: 8,702
Wiki Edits: 0

Thanks: 17
Thanked 284 Times in 264 Posts
I'd actually just recomend rebuilding your carb and spending some time tuning it. TBI is pretty much crap as stated. TPI on the other hand is great for engines looking for low RPM power and good milage. If you just want to stick with your computer controls go with the TBI, but there's really no other benifit from it.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 04-18-2008, 09:49 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,696
Wiki Edits: 0

Thanks: 3
Thanked 404 Times in 349 Posts
Quote:
Originally Posted by ap72
I'd actually just recomend rebuilding your carb and spending some time tuning it. TBI is pretty much crap as stated. TPI on the other hand is great for engines looking for low RPM power and good milage. If you just want to stick with your computer controls go with the TBI, but there's really no other benifit from it.
TBI is just fine, like anything else, you have to understand it. It's really not all that different from TPI, on these early models you can swap TBI and TPI computers back and forth it you want. The actualization is the same, just on TPI it fires 4 small injectors at a time switching from the left to the right bank and back again. On TBI it's doing the same thing just to a single large injector for each plane of a 180 degree manifold. Except for the LT1 and LT4, the TPI of the 1980s and 90s is not sequential in the sense of fueling one cylinder at a time. Since the TBI uses what is essentially the same computer, especially where Manifold Absolute Pressure (MAP) TPI systems are employed, it does not flow continuously, it is in high speed flutter, switching on and off one side then the other and back again much faster than the eye can see. The TBI intake manifold that many people disparage, does as good a job with wet flow as anyother 180 degree manifold with a carburetor can do. Certainly TPI is superior in flow management, but that applies against TBI or carburetors. Anybody who thinks this rocket science doesn't work, isn't paying attention. The power levels achieved with these modern injected engines matches and exceeds that of the muscle car days with less displacement, way less cam timing, and a lot less compression delivering 2 to 3 times the gas mileage and almost no emissions doing it.

If you need more flow than the TBI GM gave you, it's easy enough to lay your hands on one from a 454 or get a Holley 507-6 both deliver 670 CFM. Turbo City bores out 1&11/16s 400 CFM GM units to almost 2 inches which flows about 650 CFM. If you must go for more, multiple TBIs can be used, Holley packs a 900 CFM 4 barrel version. Retrotek makes a 750 CFM 4 barrel that looks like Holley/Barry Grant unit. On the cheap side, there is an injector riser available from most any speed shop that raises the injector head on GM TBI by a quarter inch or so which adds about 60 CFM with no other changes simply by getting the injectors above the air stream.

Carburetors are also rated in dry flow, so in the real world they don't deliver their rated flow as all air plus fuel. Fuel being denser than air reduces the amount of air flow by about 20%. But induction air flow is all Voodoo anyway, it's intended to compare one product against another. The numbers have nothing to do with their absolute abilities when bolted to an engine, least anybody thinks a fan sucking on the bottom of a carburetor has any similarity to what's going on inside their engine.


Bogie
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 04-24-2008, 11:11 AM
Registered User
 
Join Date: Sep 2005
Location: MA
Posts: 41
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by curtis73
IMHO, the work it takes to put a TBI on another engine is much more than the benefits.
Here's a justification for the work & benefit: TBI will give you excellent fuel economy, much better than a carb and certainly better over all operating conditions.

Quote:
The TBI is a pretty crappy setup.
Crappy by 2008 standards, perhaps. Not crappy because it uses computer controls, not crappy because it gives good emissions and economy, and especially not crappy because it's so easy to modofiy beyond what GM designed it for. And lastly, not crappy because it's a low-cost 2-injector version of a carb.

Quote:
It doesn't use injectors,
Yes it does. Larger lower pressure injectors to be sure, but solenoid-controlled injectors just the same.

Quote:
it uses nozzles that squirt liquid fuel.
Wrong. That's a better description of the poppet-valve style central fuel injection used on some of the L31 engines.

Quote:
The TB only flows a very pathetic amount.
False.

The bores on a v6 or sbc v8 TBI are 1 and 11/16 diameter. That's 42.9 mm per bore. On a big block v8 TBI, the bores are 2" (50.8 mm). On a similar vintage L98 TPI or LT1 sefi engine, the TB has 48 mm bores.... which is smaller than the bbc TBI. Airflow capability is proportional to area, and hence to the square of the bore diameters. So the flow proportion of these with the big block throttle body as the reference standard would be

0.713 for the v6 sbc v8
0.893 for the L98 or LT1 sefi v8
1.000 for the bb v8

Comparing the engine sizes by their displacements, again using the bbc 454 as the ref:

4.3 v6 (262 cid): 0.577
5.0 v8 (305 cid): 0.672
5.7 v8 (350 cid): 0.771
7.4 v8 (454 cid): 1.000

So the TBI bores are not undersized for their applied use (engine size), and if you looked the actual flow numbers (with or without the injectors in place) posted here:

http://www.fullsizechevy.com/forums/...i-airflow.html

you would see that they all flow more than enough air to support much more than the stock output. The v6 sbc v8 TBI, even with the 42.9 mm bores, can flow enough air to support more than 310 fwhp, and the bbc TBI can move enough air to support 430+ fwhp. Airflow through them is not the problem. Fuel flow was often thought to be the problem, because there are only two injectors.... but that's overcome by using either copcar 350 injectors, or raising the fuel pressure, or both. GM did exactly these things in the circa 1994-1995 454 SS when they used mid-sized injectors combined with 28-32 psi factory fuel pressure. So airflow is enough and so is fuel, so long as the owner can retune the ECM to suit the rest of the engine mods (cam, exhaust).

Quote:
You'll hear reports of 450+ cfms which is dry flow without the nozzles. With the nozzles installed it flows 380 cfms or so. The nozzles are known for leaks as well.
All injectors leak when they have clogged tips.
Your comparison of flow with/without the injectors is false. The injectors are aero-shaped and positioned far above the throttle plates, so they are not impeding the airflow anywhere near what you claim they are.

Quote:
I would also never suggest putting TBI heads on anything. ......
I would, and here's my reasons.

If you are retrofitting them, you can do a mild port cleanup. That means you can read this thread before you do:

http://www.thirdgen.org/techboard/tb...-headflow.html

They will also give you excellent torque at part throttle and street speeds, and excellent fuel economy, because they were originally designed for those things while used in fullsize cars and light trucks (such as your pickup).

They are far from the worst heads GM even made, and they are far from the worst flowing heads. They were an intermediate design point for GM between the years when they really didn't understand how to have low emissions, good fuel economy, AND good power. They bridged the years between open chamber, low compression-era smog heads, and the LT1/LSx heads. They share features with both, but the good outweighs the bad.

Many people have retrofitted TBI systems into earlier model cars, trucks, and motorhomes. And many others, especially those that lurk at Thirdgen.org have done a lot of work on showing how TBI can be used for street performance far beyond what many people believed. I don't think your needs go anywhere near that far as far as performance is concerned, so I don't think there is any good reason not to pursue this other than your own time & effort. HTH.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 04-24-2008, 11:58 AM
curtis73's Avatar
Hates: Liver. Loves: Diesel
 
Last wiki edit: How to find cheap parts
Last journal entry: 1999-2001: Getting it on the road
Last photo:
Join Date: Dec 2005
Location: Pittsburgh, PA
Age: 40
Posts: 5,128
Wiki Edits: 16

Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by oldbogie
Carburetors are also rated in dry flow, so in the real world they don't deliver their rated flow as all air plus fuel. Fuel being denser than air reduces the amount of air flow by about 20%. But induction air flow is all Voodoo anyway, it's intended to compare one product against another. The numbers have nothing to do with their absolute abilities when bolted to an engine, least anybody thinks a fan sucking on the bottom of a carburetor has any similarity to what's going on inside their engine.
Bogie

Wow... great post Bogie. I like it. I wanted to clarify one thing. When I posted my TBI flow numbers, I wasn't talking about dry and wet flow, I was saying that TBIs are rated high because they are flowed without the nozzles in place. Even if you dry flow it with the nozzles in place, the flow is much lower than the rating. Many sources say it flows 450, but that's with no nozzles in the way. With the nozzles in place, dry flow is more like 380cfm.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 04-24-2008, 12:44 PM
sbchevfreak's Avatar
Licenced Automotive Technician
 
Last photo:
Join Date: Feb 2004
Location: Land of big Easter eggs, Alberta
Age: 34
Posts: 1,604
Wiki Edits: 0

Thanks: 8
Thanked 9 Times in 9 Posts
Quote:
The injected engine uses a detonation sensor, there is no place to mount it on a carbed block without fabricating a bracket, often this is done by installing a 1/4 inch thick plate between the engine and its mount with a tapped hole for the sensor.
Actually, the knock sensor is screwed into the passenger side block drain, at the rear of the starter. Be careful no to overtighten it, it only needs to be snug.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 04-24-2008, 02:31 PM
Registered User
 
Join Date: Sep 2005
Location: MA
Posts: 41
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by curtis73
....I was saying that TBIs are rated high because they are flowed without the nozzles in place. Even if you dry flow it with the nozzles in place, the flow is much lower than the rating. Many sources say it flows 450, but that's with no nozzles in the way. With the nozzles in place, dry flow is more like 380cfm.
http://www.fullsizechevy.com/forums/...i-airflow.html

and many links within that thread.


Wet flow vs Dry flow:

http://www.thirdgen.org/techboard/tb...ow+measurement


Flow data with and without injectors

http://www.thirdgen.org/techboard/tb...ow+measurement

... summarized here for those who don't follow the links (per measurements by Ken73 at the Crossfire Vault). The single bore TB units from a Crossfire engine (82,84 Vette; 83-84 Fcar) are essentially half of a dual bore TBI, using the same bore diameters:

Stock single bore TB (42.8 mm or 1.68" inside diam bore)
one injector tower gasket @13.6"
285 CFM (each), 570 CFM together.

Stock single bore TB (42.8 mm or 1.68" inside diam bore)
two injector tower gaskets @13.6"
286 CFM (each), 572 CFM together.
This one, 572 CFM together, is the closest to a stock Fcar 2bore TBI, or Bcar TBI, or C/K/G truck.

Stock TB, injector tower REMOVED for study @13.6" - 288 CFM (each) total, 576 CFM together.

stock single bore TB bored to 2" inside diam
two injector tower gaskets @13.6"
333 CFM (each), 666 CFM together.

stock single bore TB bored to 2.130" inside diam
two injector tower gaskets @13.6"
379 CFM (each), 758 CFM together.

Holley dual bore 2" inside diam TB
670 cfm (their rating, unknown depression)

Notes

1. the extra injector tower gasket (stacking them vertically to raise the injectors) makes a slight difference on the 2" and 2.13 TBs, but makes almost no difference in airflow on the stock-size TB's. You'll have to find the orig posts on the CF Vault to see the before/after comparo of single v double gaskets.

2. Removing the injector tower means removing both the injectors and the injector mounting. There is almost no difference in airflow, so the injectors/tower really don't impede the airflow at all, contrary to what's often seen on TGO (and here on Hotrodders Bulletin board...).

So the above measurements refute a mythical "improvements" made by TGO TBI owners: raising the injector to increase airflow past the injector.

To compare other depressions (aka the pressure differential across the TB when it was flowed):

new_flow = old_flow*sqrt(newdp/olddp)

where newdp and olddp are the new and old depressions (depression is the height of the column of water used in the test manometer). Depression is a form of a pressure measurement, rather than a vacuum measurement -- so take care not to mix units of pressure and vacuum.

Lastly, more depression means more pressure difference and hence greater flow. The above equation is an approximation along a flow streamline, so it's useful but it's not perfect. HTH.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 04-24-2008, 11:55 PM
Registered User
 
Join Date: Apr 2008
Location: Drakesville,Ia
Posts: 3
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
sorry guys for starting a argument. all i whanted to know was if i could put a tbi on a older motor. becouse i'm to cheap to buy a new motor. i love my old truck, and the fuel milage. I don't race it or hot rod it. the biggest thang i with it anymore is my 14' flatbottem. Thank you for the info. on the tbi. What whould if any, hapin if i din't put the knock sensor back on? Thanks again, Ray
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 04-25-2008, 12:34 AM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,696
Wiki Edits: 0

Thanks: 3
Thanked 404 Times in 349 Posts
Quote:
Originally Posted by chevy4x4man
sorry guys for starting a argument. all i whanted to know was if i could put a tbi on a older motor. becouse i'm to cheap to buy a new motor. i love my old truck, and the fuel milage. I don't race it or hot rod it. the biggest thang i with it anymore is my 14' flatbottem. Thank you for the info. on the tbi. What whould if any, hapin if i din't put the knock sensor back on? Thanks again, Ray
Off hand I don't know what would happen if it weren't there never tried that. Just tape it up someplace quiet if you can't find a way to mount it, All it does is to cause the computer to retard or terminate the spark if it hears detonation or other similar loud sounds.

Truly, your biggest problems will be a flywheel or flexplate that will mount to the old engine's two piece seal crankshaft at one end and the clutch or torque converter at the other. Pretty much that means using the fly/flex original to the old engine if you have it as clutches and torque converter mounting hasn't changed. The other thing is getting your TBI intake onto the older heads if you use those instead of the Swirl-Ports. As I said some time back, the angle of the center four bolts is different in between the old and new heads. You can mix the newer intake with the older heads by egging the holes to allow bolt shank alignment. The other part is to provide a flat surface for the underside of the bolt head to lay against. You can accomplish that by grinding a new angle into the manifold surface, or use a spherical washer which you can hunt down on the web. These will adjust for the different angles between the surfaces to give the bolt head proper support.

You do need to take the cam into consideration, the old motor you want to use needs to have about the same cam timing as your TBI motor because TBI needs a new computer chip to accommodate anything more than about a 10% difference in cam timing.

Bogie
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Putting a Grand National Motor in a Cutlass ChrisMiddleron Engine 8 04-01-2011 08:54 PM
New Rebuilt Motor Will Not "Start newdad1 Electrical 8 03-29-2009 09:13 PM
The D.O.T. gonna gitcha. coldknock Hotrodders' Lounge 32 10-31-2007 06:33 AM
engine selection rphillips Engine 44 07-23-2007 04:09 PM
I need a new motor in my vw. 72superbug Engine 14 08-21-2003 01:55 PM


All times are GMT -6. The time now is 01:27 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.