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Old 02-18-2014, 09:09 PM
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JimN JimN is offline
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GM Big Block TBI fuel regulator spring?

I know someone who finally got tired of the carb on his '69 Coupe DeVille, so he's fitting it with a take-out TBI system. The old spring is toast and the ECM/injectors are old, so he'll be doing the cal and data acquisition himself. None of the sources he has used have a good part number and since he knows I worked with marine applications, he thought he'd ask me. Since the big block engines weren't TBI, I thought I would ask here, since we have several gearheads in the stew we call TeamTalk.

I'll post the throttle body part number when I get it. This friend is the one who worked at the Desert Proving Grounds- he's still in contact with a lot of his friends form the old days, so I'm extremely surprised they haven't found a number for this part.

Thanks in advance.
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Old 02-18-2014, 09:14 PM
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Why not find a regulator off of say a 90 gm truck 1 ton 454? They were throttle body.. Or did I miss the question? Sorry not exactly sure what your asking.
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Old 02-18-2014, 10:08 PM
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Originally Posted by clrussell View Post
Why not find a regulator off of say a 90 gm truck 1 ton 454? They were throttle body.. Or did I miss the question? Sorry not exactly sure what your asking.
He has a throttle body, but the spring is old and not right for the engine, which isn't really stock. The car was a test vehicle, used for tire and shock absorber testing. I'll see if he has any photos, but we call it 'The Road Warrior". The engineers opened the wheel wells, to make it easier to swap wheels/shocks, installed thermo-couples on EVERYTHING, a fuel cell, full roll cage, custom headers with side pipes, set gauges into the dash, removed the rear seat and did a nice job of re-upholstering the rear area and added a three-segment ballast box in place of the front bumper. The engine is the 500 c.i.d and when it's revved up, it freaking roars.

He was saying that originally, they used higher volume injectors, but changed to shorter pulse width and higher pressure. The problem is that the test data from that time isn't available and the engine he has isn't what they used in general production OR testing for TBI.

He worked in V8 Powertrain Development, but not at that time and he doesn't have the on-hand parts inventory that was such a luxury when he was there.
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Old 02-19-2014, 05:37 AM
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O ok, I think I understand now. The car sounds pretty cool! I know a couple of local guys that do tuning on the throttle body rigs, I'll ask them if it's something they might know about
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Old 02-19-2014, 09:10 AM
Roman Roman is offline
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Hmmm, an interesting post.
If he is in Powertrain development, he should be able to get his hands on some equipment from buddies. Problem for an engine that old is all the equipment GM might still have lying around on the shelves might be too new. Never know though.

If hes been out fo the game for a while, and hes a bit of a nerd (engineer so must be), tell him to google "MegaSquirt". He can build one himself, or buy a semi-built one.

So for somethign like a BBC and he is using a mechanical distributor, version 1 should be sufficient and cheap ($150-200) since all you need to control is fuel. The only hard part will be how to obtain your wideband fuel readings. Unlike cars, you cant just drill a hole in your downpipe and install your wb02 sensor since boats have liquid cooled exhausts. It think this will be the hardest challenge to overcome. You will also need to wire up a few extra sensors like crank position, intake air charge, mass air flow, map, throttle position. Those off the top of my head would be best to have. The more the better, but I wouldnt go with less than that. Those ones should be fairly easy. This is actually a sort of invloved project. It can easily be done on the cheap if you can do some simple custom fab (intake and wideband sensor aside), and wiring. Its fun though when its done and working properly.

Also tell him marine engines run rich of stoic, unlike the automotive counterparts. Im not sure why, but they probably do for a reason, and I would assume its due to exhasut heat generation with the heavy loads the engine sees.


Side note. When I find the right boat, Ive actually wanted to do somethign similar (nothing I own that has an engine is stock, including weed eater, and lawnmower. They are both port matched to clean up casting and improve airflow). I was thinking something like an mp112 or m90 blower, with a set of ported heads and maybe an intercooler, all controlled by a megasquirt controller.

Last edited by Roman; 02-19-2014 at 09:28 AM.
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Old 02-19-2014, 10:12 AM
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What kind of pressure is he looking to run? On a 500 cid I would guess something near 18 psi so a stock spring might not get him there.

What is a take-out TBI system?
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Old 02-19-2014, 10:22 AM
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Quote:
Originally Posted by Roman View Post
Hmmm, an interesting post.
If he is in Powertrain development, he should be able to get his hands on some equipment from buddies. Problem for an engine that old is all the equipment GM might still have lying around on the shelves might be too new. Never know though.

If hes been out fo the game for a while, and hes a bit of a nerd (engineer so must be), tell him to google "Mega Squirt". He can build one himself, or buy a semi-built one.

So for somethign like a BBC and he is using a distributor, version 1 should be sufficient and cheap ($150-200) since all you need to control is fuel. The only hard part will be how to obtain your wideband fuel readings. Unlike cars, you cant just drill a hole in your downpipe and install your wb02 sensor since boats have liquid cooled exhausts. It hink this will be the hardest challenge to overcome.

Also tell him marine engines run rich of stoic, unlike the automotive counterparts. Im not sure why, but they probably do for a reason, and I would assume its due to exhasut heat generation with the heavy loads the engine sees.


Side note. When I find the right boat, Ive actually wanted to do somethign similar (nothing i own that has an engine is stock, including weed eater, and lawnmower). I was thinking something like an mp112 or m90 blower, with a set of ported heads, all controlled with megasquirt.
He was in their V8 Powertrain development, until they decided to move the plant. He put up a building with 5 units and opened his own shop, servicing cars/trucks, having done service on his own for decades. GM opened a smaller test facility in Yuma and he's going there in early April, so he may be able to resume some connections. I think he still knows a few people with shops that have dyno facilities, too.

But this is different- it's not initial development, which would be easier because the engine would be on a frame in a dyno room and seeing the results in real time/running hard would show success/failure. I think it would be easier if it was a production engine, too- this wasn't, but I don't know the specifics of what makes it different. Also, he's not putting it on for high performance, he wants the TBI because it starts when you turn the key and he's tired of the carb, even though it always passed emission tests. He doesn't drive the car a lot, which means the carb goes dry and getting it to fire has become annoying.

Marine engines run richer because they would eat the exhaust system if the temperatures were similar to what's present on a car or truck, run at high RPM.
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Old 02-19-2014, 10:40 AM
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Originally Posted by CantRepeat View Post
What kind of pressure is he looking to run? On a 500 cid I would guess something near 18 psi so a stock spring might not get him there.

What is a take-out TBI system?
I haven't seen which pump he's using, or what the pressure is.

'Take-out' is removed from an engine so some other fuel system can be installed on the engine. I don't know all of the details.
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Old 02-19-2014, 12:34 PM
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I think i totally missed what this thread was about lol.

I thought you had a friend, who use to work at GM, who had a modified 500ci BB, that was looking to get it running on fuel injection to use in a boat since he didnt want a carb.

I know nothing about tbi other than the basics of how it works. Best of luck to ya!
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Old 02-19-2014, 03:02 PM
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How about these: http://www.ebay.com/itm/GM-Throttle-...item3a89a96197

Also, could just call Jeg's and get an adjustible fuel pressure regulator: http://www.jegs.com/i/JET-Performanc...64#moreDetails
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