Never mind my horrid spelling. I recently aquired a 74 Repu with a bad engine. It has a FC N/A transmission installed to a stock driveshaft, diff, ect.

I just pulled the engine and am about to tear it down. It appears that the flywheel is the stock 33lb? repu flywheel and PP setup. I know it has the stock 9.2 comp rotors.

When I get down and dirty with this thing I would like to replace the Flywheel PP combo with a lighter set. Is there any stock FB or FC flywheel that will work with the repu rotors and front counterwieght?

If not I may just go with a s5 N/A rotating assymbly. If I did this would I need to swap anything other than the front counterwieght, rotors, and flywheel? Is there any reason this swap wouldn't work or be a good idea?

Thanks,
Steve

 

1. Yes. REPU has the heavy 11.5lb 13b rotors. As does the GSL-SE. You can use a GSL-SE flywheel.

2. Also need to swap S5 e-shaft. This would be a good idea, but the heavier rotors make good torque.

I would reccomend a Racing Beat aluminum flywheel. I have one, and with the stock 74 4.625 R&P that motor really revs up quick YO!!!!

 

That engine has a Cosmo/RX-4 215mm clutch and flywheel. The REPU came stock with a 225mm assembly, but also has a funky offset so no other models are compatible. I think the flywheel itself is also 33lbs, but I never weighed one when I had the chance... maybe I'll get another opportunity in a week or two.

I thought the '85 and earlier eccentric shafts were better than 2nd gen stuff because there is no idiotic oil pellet to worry about. They're supposedly stronger too since there is more metal. This metal is in the rotational center of the shaft so it doesn't add to rotating mass, if you're worried about that sort of thing.

I can't remember what rearend gearing that truck has, but I'd honestly recommend against the aluminum flywheel in an REPU environment. My friend and I've tried it with the stock flywheel, Cosmo/RX-4 flywheel, GSL-SE flywheel, and RB's light steel and aluminum flywheels in 215 and 225mm sizes. Light steel is best for performance and the GSL-SE is better for light towing duties. Having said that, my daily driver REPU has a stock flywheel and it does fine for heavy towing and is even ok for daily driving. If the engine is strong and thge clutch fan is in good shape, it will still rev up ok with a stock flywheel (don't ask me how I know, hehe). You can also do healthy burnouts. Actually, back in the day, that truck you just picked up could roast 'em off somethin' proper. For a time, it was the quickest truck in our local area too.

I'd recommend keeping the RX-4/Cosmo flywheel if the disk doesn't have too much wear. They're quite valuable since as well since R5 and earlier 13Bs all came stock with compatible rotors. If it does have more wear than you're comfortable with, you should look for a GSL-SE combo to take advantage of its lighter weight (27lbs) and 225mm clutch size. If you must go with an aftermarket flywheel, get the RB light steel and 225mm clutch. It'll rev up quick and still retain a little rotating mass for towing. Your burnouts will suffer though. By the way, my friend tows a 1st gen race car on a decently sized trailer with a light steel flywheel in his REPU. The truck also has a supercharger, which boosts the torque curve up in the lower revs. In other words, it scews the comparison I'm trying to make in this thread, and probably should be ignored.

Of course you can do whatever you want, but keep in mind what the truck will be used for. Towing a jetski is easy enough, but towing a car, or a car on a trailer is always easier with anything but aluminum.

By the way, congrats on getting the truck. Have fun.

 

Thanks for the valuable input guys! I just got done tearing the motor apart. Almost everything is salvageable. Rotorhousings are next to perfect and it looks like everything else just needs to be cleaned good. There is some rust in the engine as the truck sat outside with no hood or carb on it for who knows how long. Just water falling into the intake manifold and draining straight into the engine :/

The truck is now in storage and I will be rebuilding the engine soon (within a couple weeks). The interior is out and getting cleaned. Still don't know what I am going to do about the top.

Here is what I think happened after tearing down and inspecting the engine.

-One of the rotors spun a berring and that clogged the oil injection in the eshaft leading to oil starvation and some scarring on one of the rotor housings. There was alot of berring metal smashed in the eshaft.
-The main pully nut crush washer was not aligned when tightend down so that may have been it. I don't know for sure.

AS FOR THE FLYWHEEL: the clutch looks like it has been abused. I think the best thing to go with would be the SE flywheel if it is indeed 27lbs. That would give me alot more options with aftermarket clutchs and PP's, quicker revving, and still maintain mass for towing.

PORTING: the streetport on it looks nice... but I think it could go bigger.

On the exhaust side... man those stock ports are small. Those are definately getting opened up. I am thinking just porting down on the exhaust ports. Or would porting up a little not hurt the torque that much?

I will get some pics up if I am not to lazy!

 

13bpower, I really like the wheels that are on your truck, If you decide you want something different, let me know before you get rid of those. Thanks, Charles

 

You'll want to keep an eye on the clutch fan once the engine is running. It was a bit stiff for my taste last time I saw the truck run. I don't know if it's a stocker or from a 1st gen, but my red truck's stock clutch got really stiff and leaked a little oil so I threw in a 1st gen clutch and fan assembly. It was a nice improvement and no more belt slippage. By the way, the famed dual belt alternator pulley did not prevent one or both belts from squealing.

The GSL-SE flywheel ought to work out well. Look into the Street Strip pressure plate from Racing Beat and either the Street Strip disk or the HD Street Strip Disk. The HD version has some sort of glue in the marcels preventing them from being springy. Clutch engagement is more abrupt (may be kinda weird for towing).

As for the intake ports, you may not want to go much bigger. It'd be fine to runs someting in there to clean out the rust, but don't smooth them. Leave them slightly rough (ask Rx7Carl). I've got a set of mild ports (little larger than stock '74 size) on my white truck and it's got a slightly lumpy idle from a '77 Hitachi carb. The high end is ok, but I'd imagine a Holley or whatever would idle worse but gain more top end power.

Porting down would open the exhaust ports too soon and hurt torque. They shouldn't go much lower than they already are. If you have any T2 or NA FC rotor housings sitting around, you could compare the ports. The GSL-SE rotor housings in your engine may have larger ports than my R5 housings, but when I compared mine to a T2 housing, I noticed that the opening of the ports were the same but the closing was vastly different. Since the housings were going into a truck and I wasn't running a turbo, I ported a nice round closing edge with a nice 2mm Ito bevel, and the engine ought to have long apex seal life.

Again, I don't have any GSL-SE rotor housings here to look at, but it's a safe bet to port up and/or down until the ports are the same size as stock T2 ports (or a slightly rounded variation thereof).