305 Fuel Injection on 400?

47convert · November 20, 2009, 05:54:48 PM

I'm thinking about building a street/occasional drag race late model ElCamino and I have a real good 400 Cu.in. small block Chevy and a set of late 305 heads and the multi port injection from a Camaro. I know about drilling the heads for the steam holes but I'm wondering if this injection would work. I'd buy one of the aftermarket harnesses for it but will it supply enough fuel to the 400 especially considering it would make frequent passes down the track.

enjenjo · November 20, 2009, 06:28:17 PM

yes it will work. You may want to consider a larger throttle body, they are available from several sources. there are several companies that will supply you with a new chip for the larger engine. You definitely want bigger injectors. Summit has a good deal on them, no big deal to change, no recalibration needed in most cases. If you want more air flow, there are larger runners available too. Depending on how radical the motor is, and the amount of fuel needed, you may have to go to a high volume fuel rail, but that would be a big horse motor. But by then you will be outside the parameters of the computer too.

The only difference between a 305 injection and a 350 injection is the injector Lb. per hour rating of the injectors.

wayne petty · November 20, 2009, 06:44:13 PM

without going into if it will work on not...

installing larger displacement motors under a stock gm fuel system will work with a few pitfalls..

since during most street driving the system is in closed loop... setting the fuel ratio with oxygen sensors feedback....

during acceleration and heavy engine loads like WOT ... at certain levels... the system falls out of closed loop and reverts to open loop... open loop is where the system runs on preprogrammed graphs...

the acceleration enrichment graphs are set for a certain cubic inch with a set amount of injector flow...

usually one can get around this by going to larger flow injectors... this gets rid of the flat spots off idle... and when you kick passing gear in..

i would think that what you are doing may work... but i would think that installing a stand alone wide band oxygen sensor and display would be a good back up... to make sure the system does not go too lean without your knowing about it..

tomslik · November 20, 2009, 06:45:22 PM

i'd use the 400 heads, the 305's are gonna raise the compression so much that you're not gonna like the results on pump gas...

47convert · November 21, 2009, 02:50:35 AM

Quote from: "tomslik"i'd use the 400 heads, the 305's are gonna raise the compression so much that you're not gonna like the results on pump gas...

Ahhh, I was wondering about that. I was thinking these 305 heads were a different bolt pattern, where the intake bolts on - Obviously I haven't taken anything apart yet, but I guess I'm thinking about the Vortec heads. This won't be a real high horsepower engine - I just want to run somewhere in the 12s, maybe ow 12s, but I thought I'd work up to that slowly. Thanx for the info. I need tosell my 66 ElCamino first then get started on this newer one. The 66 is just too nice to race.

kb426 · November 21, 2009, 08:36:00 AM

That Elcamino is one of my favorite body styles.

tomslik · November 21, 2009, 10:05:28 AM

Quote from: "47convert"
Quote from: "tomslik"i'd use the 400 heads, the 305's are gonna raise the compression so much that you're not gonna like the results on pump gas...

Ahhh, I was wondering about that. I was thinking these 305 heads were a different bolt pattern, where the intake bolts on - Obviously I haven't taken anything apart yet, but I guess I'm thinking about the Vortec heads. This won't be a real high horsepower engine - I just want to run somewhere in the 12s, maybe ow 12s, but I thought I'd work up to that slowly. Thanx for the info. I need tosell my 66 ElCamino first then get started on this newer one. The 66 is just too nice to race.

you'll have to redrill the center 4 bolts as they are at a different angles but it can be done.
vortec heads are a different matter....and i beleive there's a different lower intake available to do it.
THAT would be worthwhile!

nice elke,btw but too nice to race!?!?!
wouldn't stop me;)

Dr Flowgood · November 21, 2009, 11:36:20 PM

Are you talking about bolting a TPI system on from the late 80's -early 90's camaro or vette?
The TPI system falls on its face at about 4500 rpm on a 305 or 350 so on a 400 it will be lower yet. it will make good torque down low but just run out of steam at higher rpm no mater how big the throttle body is because the runners are small and long. and any system will need to be reprogrammed to work well when swapping it to a 400. An LT1 efi intake and throttle body can be modified to work on a ols school sbc and it will support the higher rpms and make more power to meet your goals on the somewhat cheap compared to aftermarket stuff.

Ditto on the 305 heads bumping the compression up . The 350 vortec heads from a 96 thru 2000 truck will make 30 or 40 hp more than any of the old school factory heads will, so kick that around (note: Vortecs take a different intake than a conventional sbc) The aftermarket efi stuff is easier to tune but cost more usually

Doug