max rpm someone has run stock crank & rods at "for a while"

just curious what the documented top end is for these motors with the stock rods and crank

I've been to 8300 for a while and my new cams have more duration so hopefully will be going beyond that to justify the cost of the indy car springs and custom Ti retainers that got made without my "okay" . . sigh.

thanks,

Sean

 

Rods and crank will hold together fine. I have a Factory Daytona Comp engine apart now that still has the OE rods in it after all these years albeit 3 did not pass crack testing. Off the shelf rod assembly used in both the Daytona and the 308 with nothing done to them before heading to the race track.

Dave

 

Someone here mentioned a (2nd order?) harmonic frequency exists around 8500 rpm. If true, it may be wise to stay continuously above or below it rather than to keep passing through it on every shift.

After Mark (mk e) said he saw a chunk of flywheel/clutch embedded in the dash of a 308 (no one was in the car when it broke), I would really like having something more substantial between me and the engine besides a sheet of carpet covered aluminum. If I were considering taking the engine above 8000 it wouldnt even be a question. I would securly fasten a panel of heavy sheet steel around the clutch housing.

 

Good point, a "scattershield" would be a good idea.

 

thanks Dave . . what was the top RPM of those motors? any idea how many hrs you'd go before tear down for magnaflux running like that?

 

good point on the scattershield .. . speaking of harmonics, etc. . . any thoughts on not running a harmonic balancer? . . someone mentioned the newer motors don't have one?

8450 rpm will sound pretty good at every shift . . . would one of the newer style harmonic balancers (fluid or clutch) help with this 2nd order harmonic or maybe not worry for now? You know at 8300 it did feel like something was starting to shake a bit back there.

Thanks,

Sean

 

8800 RPM but as with any race engine you know there are a dozen over revs per weekend when the heat of the battle overrides common sense.

If crack tested good, balanced to a half a gram, polished and shot peaned I would consider them OK for a couple of seasons between re-tests under race conditions using civilized CR's.

With the cost of gaskets and the effort required to remove and tear down, the cost related to bringing them to a race prepped state, Carrillo's can be justified in very short order and eliminate any concern. With Carrillo's in place your maintaince would be isolated to the top end and the lump could stay in place for a long time. Rev range could be substantially increased with the bottom end built that way which would open up a world of possibilities related to induction, cams, porting.....

This is how I build my mule test engines allowing me to make various changes to the top end where all of the power gains are with no concerns to the bottom. Hard pill to swallow but far cheaper than buying blocks and heads for the 308's! Ask me how I know that after buying 3 to make one for my own car. The rods in the Comp. Daytona engine lasted 30+ years with no failures but with the now irreplaceable status of that engine assy it would be irresponsible to use anything less than the best.

It all boils down to your budget (ya RIGHT! With a race car?!) and if you are feeling lucky. The stock units are really a very nice piece but are getting a little long in the tooth for your stated purpose.

Dave

 

thanks Dave that's some sound advice.

any thoughts on using copper head gaskets and being able to re-use them? .. . it's not to difficult for me to cut the wire groove in the sleeves since I bore them on my lathe .. . can you get the water jackets to seal or is that why I've been told they can be a pain? . . one guy told me to just throw some block sealer in there if I have issues but don't leave it in there.


thanks,

Sean

 

I prefer to Cooper rings and O-rings but that alone can get quite expensive. If you are willing to cut down a little of the liner protution then I would do a shim steel head gasket. I ran an old TR-3 wet liner full race engine (contridiction in terms when using the term full race and a 3 main English tractor engine in the same sentence) at 14.5:1 @ 7200. It worked fine for many years so long as I limited the liner height to under .002" above the block. I was able to get about 10-15 head removals to one gasket.
My carbed 308 engine will be O-ringed if I can get the mill set up with new DRO's in time.

 

thanks again Dave .. I think is what the Cometic gaskets are perhaps? . . was told to watch the liner protrusion and could re-use them.

or do you mean literally just a steel shim for a head gasket . . .like something I could just make?

thanks,

Sean

 

Thats what I did. Four coats of copper coat on each side, and thin copper wire around the liner and back on it would go at the track.

Dave

 

I'll run my car around 9300 rpm's for five or six minutes at a time... but no longer than that. Any more and you are just looking for trouble. Oh, while I have you here... anyone want to buy my car?



Gene




P.S. When I read the subject line I immediately thought... who would admit to this?