Thread: 3.5lt EFI vs Carby Engine

EFI heads from memory have a small notch where the injector sprays into the port. Shouldn't be hard to file a replacement notch. The cam profile is different, just use an EFI cam in the rebuild. The valve sizes may be smaller depending on the year of your engine. Sourcing a pair of EFI heads shouldn't cause any problems.

I believe early 3.5 blocks were built with less cast webbing around the crank case so are a little weaker for heavy duty use.

Agree,you can even just stick some rags into the manifold and cut the notches in situ if you like.
I have actually fitted Federal injection to a 77, but it was hardly worth the effort and cost.
Otherwise they are identical except for the cam.
Regards Philip A

what about compression ratio's are they different and if so does it matter, im not really up on the differences, but i will be by the time i finish reading about it i will be

Originally Posted by Kevin B

what about compression ratio's are they different and if so does it matter, im not really up on the differences, but i will be by the time i finish reading about it i will be

Depends what the motor came out of, most were 8.13:1 but there was a hi comp 3.5 that was release with the TF727 auto in 83-85 (9.35:1 ) but then when back to 8.13:1 with the introduction of EFI in late 86.
The hi comp would be better.

thanks, i will see what it is when i pick it up saturday, as i said im planning a full rebuild, which includes sending the block to be crack tested and any other tests to check its condition as well as the heads, if these come back fine then i will replace everything inside, i know there are some that will say why bother just get a 4.6 and use that but i dont want to i want to use a 3.5 and just swap it over with mine when done, pop into the local RTA and swap the engine numbers over as opposed to having a engineering certificate for a bigger engine, if this part is incorrect maybe someone can correclty inform me,

thanks all

Be aware that an earlier model engine may not be legal in a later model vehicle as it hasn't been emission certified. It's not that the engine is different in any specific way (other than the correct camshaft) but you could strike issues with your RTA. I'd check with them as to how much difference it makes at inspection time. It might be easier to track down an EFI 3.5/3.9 donk. The engine number would need to be in the same or later series as the original.

Failing that have the block shaved and restamp your existing engine number back on, no-one needs to know anything then.

Originally Posted by bee utey

Be aware that an earlier model engine may not be legal in a later model vehicle as it hasn't been emission certified. It's not that the engine is different in any specific way (other than the correct camshaft) but you could strike issues with your RTA. I'd check with them as to how much difference it makes at inspection time. It might be easier to track down an EFI 3.5/3.9 donk. The engine number would need to be in the same or later series as the original.

Failing that have the block shaved and restamp your existing engine number back on, no-one needs to know anything then.

Thanks Bee, im sure you have done this before, would you see any trouble even if the engine met Emmision standards when tested..

i Have been reading lots and lots on here over the last few days, Oh there will be some Questions, might have tio start its own thread to document and add pictures of the build process from start to finish...