[alfabender]

I took my GTV race car with a freshly built engine to the AROSC time trial at Willow Springs this weekend and after a mostly good weekend the engine threw a rod toward the end of the final race. Here are some details and some questions:

- The engine had the following components:
Ported head
Weber 45s
10.5 mm "race" cams
Stock rods
Stock type pistons from a 1750 engine--makes the displacement something like 1650 and raises the compression a bit. I calculated the compression, taking into account head height, at around 10.5
All components balanced
Block was race prepped (cross drilled etc).
Spruell oil pan baffle

Note: This is the third engine I've run with this exact specification, in fact the same head and cams, but this time with a fresh valve job and carbs. I've run them to 8000 rpm before.

When I arrived at the track Saturday morning the engine only had tuneup time on it. So I took it easy, first going to 6000 rpm for a session, then 6500, then 7000, and finally during the race I bumped it up to 7500.

I checked the oil between sessions and it was so clean you could hardly see it on the dipstick, without any drop in level.

Also, the engine never came close to overheating.

What I noticed as I ran to higher revs was that the engine didn't seem as rev happy or strong at high revs, especially compared to the other 1600s I had before.

Finally, during the last race, the engine blew. Here's the sequence: I ran it to the rev limiter (7500 rpm) at two places on the track. I was racing closely with two competitors. On the 6th lap of the race I was running at 7500 down the front straight just before Turn 1, and as I came out of the turn I noticed a significant loss of power. The engine got weaker so I waved my competitors by and slowed down, hoping to get back to the pits. At Turn 8 I noticed a lot of smoke and bad smells and noises so I coasted back to the pits. When I got out of the car to inspect, and the smoke cleared, I found two holes in the block, one on either side, lined up with #2 piston.

Here's one theory of what happened: The engine was built with its tolerances too tight, which prevented high revving and robbed power. (Another theory is that the cross drilling was not done correctly--we'll learn that at teardown.) Either way, when I tried to run it to 7500 rpm it starved for oil in the #2 main bearing and spun the bearing, which later in the same lap seized and threw the rod.

Questions:

- What is the practical maximum for a 1600 race engine (I had thought 8000 or 8200 rpm).
- What does it take to run a 1600 engine at 8000 rpm?
- Does my theory sound right, or are there other theories of what happened?
- Is there any risk to an engine by running it up to the rev limiter--some shock due to the sudden loss of spark?

Actions I have are: (1) check the tachometer again to make sure it's correct--I can't do that till another engine is in the car, but I think I did that once or twice already and it was good to within 200 rpm, and (2) tear the engine down to see if there are any clues.

Doug Bender