I currently have a S5 NA motor in my car. The rear rotor popped and I came across a cheap S4 NA motor that I want to swap into my car. Given that I don't actually have much wiring to do on my car (carb'd, not efi), would I just be able to swap over the shortblock and everything hook right up? i.e. manifolds, water pump, rad hoses, etc.

 

i don't see why not. but thats a step down imo. since your carb i see it being pretty easy. execpt did you have the electronic omp. if you did then you gotta put the s5 fron cover on the s4 block to keep the omp working.

then again im not sure about your set up since as far as i knew all s5's were efi.

 

If he's Carb'd instead of EFI then it's an aftermarket intake. Which brand of intake are you running?

Properly tuned Carb'd setups can provide significant power gains on an NA. Were you talking about the S5 to S4 engine? If so, then the majority of the extra power comes from the intake, which is being swapped onto the car anyway. The S5 makes slightly higher compression, but with any amount of tuning the difference is negligible.

 

You can run the s4 block but you're going to have to swap over all your s4 stuff over as far as front cover and filler neck and such so the rad hoses will fit. But otherwise you're golden, do it!

I'd reccomend premixing now if you don't already, unless you want to swap the S4 OMP over as well. ( I don't know how that goes, I been premixing since baby Jesus' time)

 

I'm running a Jaytech manifold to a holley carb.

So all I would need to do is swap the front cover from the S4 motor to my S5? Besides that, it should be pretty much plug and play, correct?

 

To be honest, it should fit perfectly fine without swapping the front cover. The radiator and water pump fittings are in the exact same position with the exception of the water pump inlet, which is off by about 5 degrees, but it doesn't make much of a difference if you cut your rad hose right. The filler neck on his S4 block is going to require a radiator cap holder thing without the pressure outlet like this:

and a fixed radiator cap and everything else can be uses with the stock S5 setup. Just fill from the right driver's side, not the thermostat housing area.

The S4 omp uses a mechanical lever attached to the linkages on the front of the throttle body. If you swap ECUs, then it would be pretty easy. If not, you have to keep the S5 electric OMP plugged in and either run the S4 mechanical or just block it off like the rest of the sane world.

 

Well, swapping ECU's would be nice, but I don't have one. :P The car is a full carb'd setup.

Engine shots:

 

Oh yes, I forgot.. no TB. ****..

OMP blockoff on the S4, swap the intakes, keep the S5 omp plugged in, clean everything while you're at it, and I can't think of any other differences off the top of my head.

 

you can't swap ECU's like that. The S4 chassis harness won't plug into the S5 ecu. Block off the OMP regardless, and swap the front cover. Give me a minute I'll search my thread I had awhile back when I was trying to swap an S5 into my old S4

 

Yeah, you would need a new harness too. I apologize for not explicitly stating that.

 

yeah saying to swap the front cover i was thinking about the omp set up. but since your carbed do you premix or do you have the omp hooked up? thats the only reason i was saying to swap front covers so he could still run the s5 omp. and yes jmkogut i was talking about the high compression of the s5 to the s4 as being a step down. i wouldn't do the swap in my opinion. but i am on the other hand a efi guy so don't know if it is much of a difference with a carb set up.

 

Take what applies from this tech, obviously since you're carbed not all of it is going to apply.

http://www.rotaryresurrection.com/2n...o_s4_swap.html

 

I have the stock OMP hooked up. Haven't had any issues with it so I see no reason to remove it. Would it be better in the end to take it off anyway?

 

It does make a difference, it's far easier to tune a carb'd rx-7 vs an efi rx-7 without an aftermarket ECU.

It basically takes a screwdriver and an AFR meter. The problem is carburetors are finicky bitches. At least they seem that way to me. I personally would prefer a standalone EMS + EFI anyday.

I personally wouldn't really care to swap that much. The difference between a well running S5 motor and a well running S4 motor is negligible. Possibly a slight noticeable difference. The only thing that could deter me is the difficulty of bastardizing the two generations. I would go S4 to S5, just not S5 to S4.

 

I'll have to look at the FSM to be sure, but I'm positive you can't hook up your S5 OMP to an S4 front cover. The easiest (and possibly better route) is just to get a blockoff plate and premix. Otherwise you'll most likely have to swap front covers.

 

thats what i was saying......wasn't it?

 

Block the OMP and premix.

 

You can't hook up an S5 OMP to an S4 at all....


S4 front cover AND OMP goes on S5 block

Did you read that link I posted?

 

Well, as much as I'd love to do that, a S5 motor for me is like $800. On the other hand, a friend of mine just did a turbo swap and is selling me his old S4 motor for $300 so I'd rather go that route. Plus, unless I'm mistaken, the S4 rotors have lower compression, making them better for doing a 6-port boosted setup in the future.

 

oh hey if its the cheaper route do it all i was stating was personal preference. i would do it too if i got a good deal.

and your going from carbed to boosted? im not a carb guy so i don't know but can you boost a carbed setup or do you need to go to efi.

 

Well. I'm just aiming for the S4 motor for the lower compression. I plan on converting it back to efi eventually with a microtech or haltech so I can run a blow-through setup (assuming I decide not to keep the stock TB)