lift .480 .480 duration 274/274 cam with OE fuel injection

[Reptoid Overlords]

I've seen a few threads regarding aftermarket cams running OE fuel injection.  I'd like to briefly revisit the topic.

What would the drawbacks be to running a .480 .480 274/274 cam with my stock fuel injection?

My engine is an F54 stock internals with .080 shaved P79 with stock cam and valve train.  I would replace all necessary valve train components to meet new cam requirements. 

 

Thanks for input . I know it's a kind of old topic, but I value current experience here the most.

 

 

Edited April 24, 2020 by Reptoid Overlords

[Zed Head]

I think that main problem is that a bigger cam is designed to flow more air at high RPM, which requires more fuel than the factory system is designed to provide.  So you end up with the dilemma of tweaking your system, through the AFM spring or an adjustable FPR or bigger injectors, to provide the fuel the cam needs at high air flow, causing rich running at lower air flow rates, or leaving it tuned to run well at low air flow rates and go lean at the high end.  

Basically, there will be a range of throttle position and RPM where it will run like crap.  But it might make more power.

[madkaw]

Chickenman has done it I think , but he doesn’t get on here much anymore . Take the leap to programmable ECU - let the force be with you

[Reptoid Overlords]

As of now, my EFI system is functioning properly.  I drive the car almost every day, and I realize that I am modifying and potentially make an otherwise good running engine run poorly, as stated, at certain RPM's.  I almost feel that while expensive, the FAST EFI kit might be a good thing in this case.  I can remove all of my stock components, unmodified, and store them.  This is a future possibility for sure.  I'm in the process of buying a house, so I'll likely be broke 'till the end of time.

[Jeff G 78]

I tried it - twice.  The first time was circa 1997 with a L28 at 9.83:1 CR and a street cam.  The engine was fresh and the car ran like crap.  It had low power, wouldn't idle and was simply a disaster.  Since the engine was new and the EFI a bit untested, I removed the cam and related components and returned the engine to a stock cam.  It ran great and I was able to enjoy the car.  The performance cam sat on a shelf for a decade or so.  My Z was running great and was well-sorted, so I figured that I would try again.  I installed the same cam and related parts back into the engine and got the same result.  I tried to tune it, but it didn't make enough vacuum to keep the L-Jet happy.  I once again pulled the cam springs and rockers and went back to stock.  

I then installed that cam into my SU carbed L28 racecar and it runs like a dream.  It was everything I had hoped for in my street car.  Both engines are very similar other than the fuel systems.  

You can try it, but many have the same results as me.  L-Jet simply doesn't like low vacuum.

 

For reference, my cam is a Web Racing Grind 91 with .450 lift and 260 duration

Edited April 24, 2020 by Jeff G 78
Added cam specs

[Reptoid Overlords]

Thank you guys for the input.  I have my original N42/N47 engine from my '80ZX disassembled and on the stand.  Once all my house stuff gets in order I was thinking of installing flat tops in it.  Better yet having a shop balance them to a lightened flywheel.  That head could use a new valve train anyway, might as well install a bit hotter cam and have it on deck for future use.  That motor can produce similar compression to my .80 shaved P79 currently running in the car, and I can leave the perfectly good running engine alone.  

 

 

[Reptoid Overlords]

If I  wanted to run programmable EFI say, Megasquirt's MS3 EVO, would I also be best served to run a wideband o2 (I have pre o2 ECM)and aftermarket ignition system such as the Crane XR3000?  It's a bit over my head, but it hasn't stopped me in the past.  The reason I'm considering going nuts on this stuff is because while my engine runs wonderfully, I just don't think I'm getting the full potential of the high compression modification.  I'm running NGK lower heat range plugs with my distributor advance base timing at 10 degrees and no advance.   Haven't had time to modify it.  Pump 92 octane fuel.  I've gotten it so that it doesn't ping under heavy load. 

https://datsunspirit.com/shop/megasquirt-ms3-pro-with-8-wiring-harness/

https://whiteheadperformance.com/product/fast-crane-xr3000-electronic-ignition-kit-datsun-240z-260z-280z-280zx/

[Zed Head]

That MS3 system should have its own spark "drivers".  You shouldn't need any aftermarket system for the spark side.

Looks like it will do a lot of stuff.  Lots of race car features.  It's a huge jump from no distributor timing advance at all.  Did you mean no vacuum advance or no advance at all?  Your distributor should have, at least, centrifugal advance.  You can see that with your timing light.

https://www.diyautotune.com/product/ms3pro-evo-standalone-engine-management-system/

[Reptoid Overlords]

2 hours ago, Zed Head said:

Did you mean no vacuum advance or no advance at all? 

 

I meant to say no vacuum advance.  Wasn't paying attention to what I was typing.  With Vacuum advance, It will ping under load.  I am trying to work out a fuel delivery system that will communicate with the ignition system to deliver optimum performance with a bit more cam.  It'll be a rabbit hole but one I think I can climb out of.