I just bought a 1987 mazda rx7 needs engine work should i fix the rotary turbo or put in a 350 camaro engine in it im looking for speed.

 

For speed? I'd say rotary. For traffic light drag racing, I'd say V8. Of course racing on the street is stupid. Where were you thinking of driving fast?

 

The rotary engine in Jeff's avatar would be kewl. If you do a V8, please spend the money and get one of the new 4 valve per cylinder aluminum block/head engines please.

 

and don't get a fake v8 nuttin but 350 or higher plz

 

OK, your title reads 305, but your post reads 350. Anyway, the 305 was phased out of the Camaro, so you can probably figure out how good it was.

Looking for speed? What does that mean? Even a Yugo engine would get you to 70mph. The FC can travel over 190mph with 400hp, but if you try that on the street, you are going to be dead meat if you hit even a slight bump or pot hole.

 

thats the kind of speed im talkin about.....i wanna experience 250 mph someday

 

i would go with rotary, cause you can go pretty fast with it and i think one reason for getting a rx7 is for the rotary...........

 

why would u think about not a rotary, into a rotary? sorry to butt in, but I would think it to be a waste of time, putting in something that would have a rotary walk all over it.

 

So a rotary in my rx7 would be faster the a 350 cararo engine in it for street racing.

 

no... but everyone else will tell you otherwise.

 

Street racing? Oh geez... better put a V8 in it.

 

The 305 was junk emissions-era crap, the 350 also was junk emissions-era crap. If you have to build a Chevy then build a 327 - the absolute best small block Chevy ever. The bore to stroke relationship was good, the rod length/stroke ratio was PERFECT 1.75 (3.25" stroke / 5.7" rod), the displacement to valve area was perfect, etc.

The next best thing would be to build a 302 - a 327 block with a 283 crank, or if you're lucky you can find a later 283 and bore it waaay out to 4" (late 283's were built on 327 castings so they have enough metal). 302's were in the original Z/28s, the real ones from '67 to '69. Of course, you'd have to *build* it likewise... no torque until 3000, then sings to the end of the tach. Basically like a mean ported rotary but twice as large.

In short - 350s are trash smog era piles of junk with too much stroke, 305's are even worse because they had the 350's stroke but a way tiny valve area-crimping bore, and almost all of them had internals made of compressed cheese. Might as well do it right and build a *real* small block - a 327.

 

lol, maybe he'd have better luck stroking a 350 out to 383 or whatever the kids are doing these days? Yeesh!

I've noticed a few '68 307s had a whine at idle. How much do you know about the 307, and how it compares to the two versions of the 327 available in say a '68 Impala? I think one was good for power, and the other was good for mileage. They had differing torque and HP specs.

 

The 307 was the opposite of a 302.

Where the 302 was a 327 bore with a 283 stroke, the 307 was a 283 bore with a 327 stroke. Of course almost all 327's and all 283's were small-bearing blocks and internals, while 307's and 350's and the like were large bearing. But you could put a 307 crank in a 350 and make a 327.... waitaminute, '68 307? That'd make it small-journal. Didn't know they made any of those...

There were many different 327's made. Power, mileage, it all depends on how the engine came from the factory.

 

My dad's '68 Impala had a 307. From memory, the engine options were the 250 inline 6, 307, 327 economy, 327 power, and the 396 big block. I think you're right that the 307 had small journals. It was a two bolt main block, and had a two barrel carb and a two speed tranny.

Over the years I've seen and heard other 307s run, and I think all of them had that same whine. It could have been the clutchless fan though.

 

You can also take a 350, do the 383 stroker thing, then bore it out to a 400. Put a blower on it, run 10psi and have 600+hp with more torque. Unfortunately, what it would cost you to build that motor with F.I. would be about 5-10X as much as building a decent 13B-REW motor with a single turbo and stand-alone making low 400's. After that, speed is dependant upon your gearbox, traction, and what's in front of you...oh yeah, and the potential to crash or get caught.

 

Throw yourself off a Building. It will end with same results.

 

ahahah i wanna go like horizontally at 250 mph not vertically

 

i want to turn at 240 mph

 

Why not just start with a 400 to begin with? I mean, first you're taking a 400 crank, machining down the main journals so it'll fit into a 350 block, then you're putting an eighth-inch overbore on the 350? Assuming you even have enough metal in the bores to do that, it'd be a ton weaker than just starting out with a 400 in the first place. Lots more expensive, too.

 

If you don't care if it would be a v8 or a rotary, i would say put a v8 in there and save yourself some money and patience. Trust me, you are going to be a lot happier with a 350 rather than a stock rotary, even a turbo (unless it's twin turbo of course). Yes, you can make a rotary go faster but you are going to have to spend more money and in the end find yourself with more problems.
I'm not trying to bring rotaries down but just being open minded here. I'm still sticking with mine for now.

 

Open mindedness is good thing.

I often think about the different engine swaps that can be done. I keep looking into my '85s engine bay and think how cool it'd be to have a lil' 289 putting around under there. And I look under my friend's 240Z hood and think, hmm, *maybe* a two rotor (have 12A will swap!) would fit down between the firewall and the front crossmember and the firewall wouldn't even have to get cut for tranny clearance, and a new front mount plate could be fabbed to use the stock L24 engine's motor mounts.

But then the L series six kicks ***, and it'd be a shame to waste it. Heavy, but beautiful mid range torque and bolletproof. Hmm, maybe it would look just as good as a small block Ford, under the hood of the FB...

 

Or a straight six in an FB? How would it weigh-in with a 289-400 or a 20B? All NA of course (to keep the weight of the 20B down).

 

Becasue they are starting to get hard to come by, and the 4 bolt mains are REALLY hard to come by now, although the 2 bolt might be a better start since you could machine it for 4 bolt and have it splayed ~10-15*.

Ideally Peejay is right start with a 400, My best bet is to go with a 400 block toss in a large journal 327 or 350 crank and a little bore and BAM 350/377 respectively, which are both big revving motors.

PeeJay I think you are a little biased againt the 350/355's I have seen many tach 7k+ on shifts for multiple years and still run fine making huge amounts of power. Altough if they were 400 based they would make sizably more. The 350 has such an insane aftermarket call Jegs or Summit and goto town. You want to biggy size the headers? Would you like nitrous with that intake?

Yes you can work with the 305, but you are better off selling it and buying almost another v8.

BTW peejay you ever heard of a ford, 289 with 5.4" rod giving a 2.0 R/S ratio. You know what has to be done, do I have to get some pistons with raised wrist pins ALA 347? or what. sorry to go off tangent but thought you were fond of the old blue oval

 

For speed, LS-1 aluminum V8 would be my choice. For a cool car, a built rotary would work better with the RX-7 and be easier to do.