One more chance for the big block

Enjoying this thread. I have not been on here for months. I run Sprint sit up Enduro with Championship Enduro series. I have not made a race this year but plan to be at Blackhawk in August. Over the past five years I have broken my share of parts running the BBC engines. I believe I have learned where the weak spots are and now have a formula to build a very reliable and strong big block.. Currently running a Honda block 390 with +.020 piston and long rod. Stock valve sizes with Comp cams springs at 50lbs on seat. Gage roller rockers, chromoly pushrods and Dyno 356 cam. Carb is Tillotson HR181 on methanol. Also use a ARC flywheel and PVL ignition. I turn it up to 7200 all day. My dyno maxes out at 35 HP. This engine will overdrive the dyno so I know its a good engine. My Bully 4 disc works great. I weigh in at 460 lbs on the kart with a full 2 gallons of fuel.

I did break a connecting rod once but know I swap rod bolts every other race weekend. No more failures - knock on wood!

I also ran several different oils. My favorite is still FHS 62R. Make sure to get a full 32 ozs. in the crankcase when using a billet side plate. Troubles are gone. This thing is a lot of fun. I only wish there were more big guys making the switch to big block power. It makes an old fat guy really smile :)
 
Finally got the alcohol big block apart. Looks like a few of the side cover allen bolts backed out and the engine began leaking oil. Luckily my brother who was driving pulled off to the side of the track and shut it off. Going to install a new gasket and regular bolts, wire them and go on to Savannah.

We were running this engine at about 6700 rpm, but it's not looking good to do that for a 30 minute road race. Will take three teeth out of the rear sprocket which should get us closer to 6K. We will adjust according to the stopwatch from there.
 
Ran the alcohol Honda GX 390 at Daytona this year. Dropped the rear sprocket from 50 teeth to 43. The rpm stayed almost the same 6600 vs 6700, and the lap times dropped 5 seconds. Zero issues with the engine all weekend. The kart did chew up a rear sprocket during practice and we had a small issue with the intake manifold. Pulled very hard out of the turns and kicked out that deep boom-boom-boom sound. So fun to hear it go into turn three while we were standing on pit lane. No plans to do anything different for the Savannah race. Just glad I didnt have bring it home in a leaky box.
 
Spring Savannah race went without incident on Saturday. Took third in Open Sprint.
Sunday was different. The engine quit after 4 laps. Took it apart today, here are a few pictures.
 

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I have had similar issues when racing clones on asphalt sprint tracks on an open clone class, always by the end of the races, like last 2 laps. I could even hear the change of pitch some time before it broke, loss of performance, overheat, etc. No other visible issues or parts braking, always the rod.
 
Spring Savannah race went without incident on Saturday. Took third in Open Sprint.
Sunday was different. The engine quit after 4 laps. Took it apart today, here are a few pictures.
Did you change the oil after the saturday show? I would suspect it was going south saturday
 
possible oil drain back issue? But i wouldn't think so if it made it 30minutes the first day. The world formulas have a cross over from the v/c to the crank case to aid in this. Jody mentioned the pin size being the issue. Any reason you couldnt turn it down? or does that leave to little of overlap and make for a weak crank?
 
possible oil drain back issue? But i wouldn't think so if it made it 30minutes the first day. The world formulas have a cross over from the v/c to the crank case to aid in this. Jody mentioned the pin size being the issue. Any reason you couldnt turn it down? or does that leave to little of overlap and make for a weak crank?
Never really thought about turning it down. Will begin the rebuild sometime this millennium whenever parts are available again.
 
Ran the VC460 big block this weekend at Savannah. Turned 1:30 lap times all day long. Clutch stayed cool, the rod held together and it pulled like a freight train. Very high fun factor. The Honda crf450r kart was a beast. Leading Open Sprint until it broke an axle on lap 8.
 
I recall the standard Superkart axle is 35 mm. I can't remember how our Anderson's axle was keyed, but we never had any issues with them. Of course our CR250 had a little less grunt, but still, that's quite a failure! I assume you're using 428 chain?
Try to get a hold of Andy Kiker or Johnnie West. They might have a fix for that.
Sounds like fun.....other then the breaking stuff part!!
Clark.
 
I recall the standard Superkart axle is 35 mm. I can't remember how our Anderson's axle was keyed, but we never had any issues with them. Of course our CR250 had a little less grunt, but still, that's quite a failure! I assume you're using 428 chain?
Try to get a hold of Andy Kiker or Johnnie West. They might have a fix for that.
Sounds like fun.....other then the breaking stuff part!!
Clark.
It's a 50mm shifter axle. I'm welding in another inner sleeve and going from a "medium" to a "medium-hard" axle. You guessed the chain correctly, it's a 428.
We had a garage next door to Johnny West at Daytona. Super nice guy and quite the character!
Ya that crf450r is a thumper, love that boom-boom-boom
 
The one race that I actually got to race our 250 (my Son had to go on vacation with his wife's family:cool:) I remember following a 450 in practice. The thing was sooo loud, I couldn't even hear my own motor!!
 
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