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Old 02-06-2006, 01:47 PM
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Help Need To Decide On Engine For My Car

I have a 1984 Mazda Rx7, thats going to be swapped over to sbc soon, only problem is I cant decide which engine to use. I'll prolly go with a WC T-5 for now and soft shift it until I can afford the T-56.

The car will under 2500 lbs fully swapped and will be running only a 26x8" slick for the time being until I do the narrowed 8.8, the weight ratio is just about 50/50, stock rear is solid with a 4 link setup.

A 406 would be a blast but that torque might make hooking up not very much fun.

I thought about a GM 302, lot less torque but still good HP.

377? 383? The ole 350? 327? What would you do?

Appreciate the input.


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Old 02-06-2006, 01:56 PM
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I like the sbc 302 idea with some 4.56 or so gears. Im not really sure but i dont think that t-5 would live very long behind a big torque monster engine like the 406 or even a 383, but i think your car would be the s*it with a 302 built up good. just my thoughts Jake
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Old 02-06-2006, 02:04 PM
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we used 26 inch M/T ET Drags on a 75 Vega with a 400, 200cc dart II heads, forged pistons, 234 244 duration @ .050 cam, Holley 800 spread bore, on a old edelbrock scorpion intake, TH350 tranny, 3500 stall, 4.56 gears with moroso brute diff. 350 horse big shot nitrous kit, it had a basic slapper bar rear set up, never had a issue with it hooking. a guy we raced against installed a 350 into a RX7, never got it to hook on street tires, so he used a leaf spring system to tub it, not only did it look cool with those 31 inch tall 16 inch wide steam roller meats under it, it hooked hard with little burn out.
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Old 02-06-2006, 02:57 PM
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the sbc 302 is a high reving engine something you should look at due to your light will find if you haven;t notice the engine will situp quite high on this fab'in a dumble hump oil pan would help
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Old 02-06-2006, 05:00 PM
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Personally I would build the 406 and if you have trouble hooking it up, work on the suspension or in the worst case scenario, feather it a little off the line. If you are looking at a good short stroke combo, a 377 is a nice, but I have also heard of people making a 392 out of a de stroked 406 that has worked well. I am not too much of a fan of destroked drag motors. I had a 358 destroked 406 in a 3000 lb 69 firebird running a 100 shot that made 600 hp on motor and ran a 6.29 in the 1/8th. That was not a bad time for that setup, but I am currently switching to a 434 for the added torque and hp. The 434 will be faster and alot more fun on the street. You had to wind the 358 up to 5500 RPM before it started to make any power. That along with a glide did not make for a very snappy street car. It was still really fast, but I had a vortec headed 355 in a 72 nova that had instant power no matter where you were in the power band. That was alot of fun.

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Old 02-06-2006, 06:01 PM
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My stepdad had an 81 Mazda rx7, tubbed, powerglide, 4.56 gears and a 300 (maybe) horse sbc.
Ran real nice, but coulda used a little more umph.
If its for a street car, Id build a nice 350 with a decent bottom end, forged pistons, good intake n carb and stuff a 125-175 shot of nitrous and be done.
Less money in the build, good power. HG
I was built with the body of a God! To bad it was buddah.

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Old 02-07-2006, 08:29 AM
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The sbc to RX7 is a great swap. Here are a couple pics of my '79 with a 307 and 350 trans which I finished back in '95. I ran the 307 simply because it's what I had, not because of its desirability. Just two notes on the swap. The sb and trans slide into the RX7 with almost no body modifications at all. Just a few good whacks on the transmission tunnel here and there with "the big tool". I used the stock motor mounts with a 2" spacer made from 2x4 rectangular tubing to get the motor up to the correct height. The transmission mount was simply a mating up of the RX7 crossmember and the mounting hardware from the original car (a Buick Regal).

The only negative I encountered with the swap is the additional weight on the front suspension. Without a spring/shock swap of some kind, it will not handle anywhere near as well as with the rotary. I sold mine before coming up with a remedy so unfortunately do not have any suggestions...except to note that you'll need to do face that challenge. Oh, and you will also be faced with a significant hood clearance problem. I cut down an aftermarket air cleaned to about 1" tall - because I wanted to have a real "sleeper" appearance.

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Old 02-07-2006, 09:44 AM
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If money isn't a huge issue- the more cubes the better. I would probably go with a 383 for cooling reasons ( I know 400 guys are going to have a fit over that). If you feel its too much torque for you just lower the gear ratio out back. You may just have to live with a 180 top speed that's all.
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