Dyno sheet

Dyno graph

This past winter, I tore down my engine, for some new rings and bearings. With about 400 passes on my engine, it was time. At first I was just going to pull the bottom end apart to do a freshen on the bearings only, but after discussing things with my engine builder, Jack Michula of Jax Racing Engines, I decided that a complete teardown with a hone and new rings was a good idea. This gave me the opportunity to install main studs and reline hone for more lower end durability. It turns out that this was a good call, because in the process, the crank and rods were magnafluxed, and a hairline crack in the #1 main journal was found. I replaced the crank and had the works rebalanced, and reassembled the engine (rebuild process can be found here).

I arrived at R & R Performance in Spring Lake Park at about 8am. We got everything hooked up by 9:30, and filled the carb, etc. Fired up the engine and after about 10 seconds, we were still not getting oil pressure. Took out the distributor, and tried turning the pump with a socket and ratchet. Plenty of resistance. Then Ron the dyno guy noticed the fitting for the oil pressure was screwed quite a ways into the extension piece, and figured that maybe the fitting was sealing the pressure off. So we put in a different fitting, and the oil pressure immediately jumped to 60 PSI. Phew, disaster averted.

We did the first checkout pull after running the engine for about 15 minutes just to let everything get seated (old cam was reused so no valve spring games this time). We noticed smoke coming from the passenger side of the engine. Turns out there's oil coming from the inside of the bellhousing somewhere and is getting flung by the flywheel onto the exhaust. I'll have to check this later. We shielded the oil leak, and continued.

The horsepower was down some from last time, so we started investigating. First we noticed the rear of the carb was lean. Ahhh, I put jet extensions in, I remembered. According to Ron, that usually reduces the effective jet size by three, so we jetted the rear of the carb up. The mix came back to normal, but there really wasn't any more power. So we decided to set the lash on the rockers. The exhaust rockers were as wide as .037. Once we tightened these down to .026 where they're supposed to be, all of a sudden the power started coming on. That change alone was probably worth 10 HP across the board.

Next came the spacer checks. It turns out the 4 hole tapered diamond spacer was worth another 5 HP. With a small timing change we were now at 515 HP.

Due to the funky headers a Mustang requires, my long tubes didn't make the dyno last time. Because the VicJr heads have the small ford exhaust pattern, we had to use the 1 5/8" long tube dyno headers. Well, due to some changes Ron had made to the dyno setup, he gained some more clearance back there and we could use the BBK's that I'd brought with. Of course with a 2 hole flat plate on the collector, there wasn't any exhaust adapters that he had that would fit normally, so we took the studs out, use one bolt on one of the holes, and vice gripped the other side to hold the standard triangle adapter on. This was to be the last pull.

The engine was making great power, then at 6800 RPM, the vice grip decided it had enough of this abuse and let go. The result was a sudden increase in loudness and some big flames coming out of the collector. We decided we'd had enough fun for a day. But the result was 522 HP at 6800 RPM.

Also, during testing we pulled to 7000 a couple of times, and the engine sounded like it was breaking up a little. I don't know if my valve springs are getting weak, or if the ignition needs some work.

In any case, I'm a happy guy. I'll fix my oil leak whereever it turns out to be, and talk to my engine guy about the possibility of needing new valvesprings (those were reused from last year too, they're now going on their third season).

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