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Fuel injection for the 400...options?

MattK

MattK

1/2 ton status
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I wanna run fuel injection on the 400 small block in my Blazer. It currently has a Holley 750 on it that runs beautifully well on the street, but when I get off camber, climbing, etc it will flood and run poorly for a while after that.
I don't know any exact specs on it, but several people that have heard it run tell me it sounds like it's got a mild cam in it.
What options do I have for injecting my rig?
I'd like to keep cost down as I don't need anything exotic, but I would prefer to not lose any of the power I currently have with the Holley 750 up top.
 
I had a 90 GMC that had a nicely built 406. Used all the stock parts off the TBI onto the 406. Ran friggin' awesome. Easiest way is to get an entire harness/ECM off an 87-89 K-5, 90-91 will work too, just they have a full electric speedo, possible other stuff too, but never messed with one.
 
The easiest way to cure the off-camber problems is to swap on a truck carb (Quadrajet).

The easiest and cheapest FI will be a junkyard TBI system.

If you can get the intake, injectors, sensors that bolt on, Megasquirt can be used to run anything.
 
b454rat said:
I had a 90 GMC that had a nicely built 406. Used all the stock parts off the TBI onto the 406. Ran friggin' awesome. Easiest way is to get an entire harness/ECM off an 87-89 K-5, 90-91 will work too, just they have a full electric speedo, possible other stuff too, but never messed with one.
Click to expand...

Did you have to do anything with the TBI setup to flow enough for a built 406? My motor isn't built by any means, but I would imagine 50 extra cubes would call for some sort of tweaking.

Blue85 said:
The easiest way to cure the off-camber problems is to swap on a truck carb (Quadrajet).

The easiest and cheapest FI will be a junkyard TBI system.

If you can get the intake, injectors, sensors that bolt on, Megasquirt can be used to run anything.
Click to expand...


So megasquirt would be something I'd need to alter the setup of a 350 TBI for a 400 cid engine?
 
Nope didn't do anything to it. I put 7-8k on it before I sold it. I replaced every panel on it when I got it, then get hit again, had enough of that and sold it. Dipsh!t I sold it to blew it up from smoking the tires EVERYWHERE. I never had any issues with the way it ran, never spit sputtered nothing.
 
If you FI your truck you will need to know what kind of cam is in it. also other mods like compression ratio. heads ect. Weather you go with a junkyard TBI or aftermarket Fuel injection you have to have the engine /cam specs so you have a starting point to tune it or burn a chip.
IMO if you want to keep costs down and have a great off road /street truck. Just go with Hillbilly Injection... Put a Q-jet back on it. GM really did know what they were doing.
Best all around truck carb ever made
 
Hmmmm I appreciate the info guys. I'll consider going back with a qjet. My only beef with it is my old qjet did the same kinda stuff.

Thanks!
 
If you want to keep the Holley there is a thread here in the garage now "How to tune a carb for the hills" Good info there for making a Holley work better off road. i have worked over many Holley's for off road. you cam make them run acceptable off road. But i gave up on them a long time ago and used Q-jets on all my trucks. I have ran Q-jets on fords, jeeps, and of course chevys. They always worked best for me.
You coulld also look into a Holly truck avenger carb. They around $450. They work much better than regular holleys offroad. Most people here that use them like them once they get them tuned.
 
C3H8
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you can yank the fi system off of any sbc. if it's late model you just have to drill the center 2 holes on each side of the intake at a different angle. You can make or by washers that will be angled to fit right. Then go to http://www.howellefi.com
They can burn a chip however you want it. Then they'll keep reburning it until it's right.
 
MattK said:
So megasquirt would be something I'd need to alter the setup of a 350 TBI for a 400 cid engine?
Click to expand...

Megasquirt is a stand-alone engine management system. It would replace the ECU in whatever system you were running. The advantage is that it can be tuned to run anything (and is very low cost + open source). The disadvantage is that is has to be tuned from scratch to run anything. I know I've posted some info on it before. It's not for everybody, I know.
 
I'm going to throw in here that it may be questionable to throw a 350 throttle body on a 400. At the very least, you would have to tune it. At worst, new injectors and BBC or bored out 350 throttle body. Throttle body is just going to depend on how much a 400 needs, and what the 350 throttle body can flow.

There is no getting around tuning. If you increase the displacement of the engine, and don't tune, or at least make the effort by upping the fuel pressure (which isn't the right fix, but is better than nothing) then you run the very real risk of burning your motor up.

This has been covered before, so I'm not going to get in depth.
 
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