I had a build done about a year ago. I had 10:5.1 pistons. 585 G cams 103 plus heads . I service it regular and take care of my bike. I do a lot of touring and I enjoy the power, but i don't hotrod it a lot. So what should I expect out of my build in millage before a rebuild ?

 

A lot of factors play into this. How clean were the parts at assembly, how close were tolerance adhered to? Your motor could last 100K or 10K it all really depends on how well it was put together, and the only person who knows that is the one that did the assembly. Generally speaking when you increase lift on the cam, compression of the motor, you will wear things out faster. I know this isn't much help, but its what I know.

 

Well I know other guys that have the same build and one has 11500 miles and he says his is still strong. I've got 34000 on mine and it has great CCP. I really don't see why a engine would wear out faster if you have the right equipment made for high lift cams and compression.

 

You built it to hot rod,go for it! My 124" was built in 02,and it regularly sees the rev limiter.The seasons are just too short here in the NorthEast to waste a minute not having fun.

 

As said, a lot depends on the quality of the build. A lot depends on how it's treated.

I don't believe that a "built" engine will last as long as stock. Increased compression = increased internal heat. Increased power = increased stress. Heat and stress = wear.

Ever notice how the tank on your air compressor gets real hot if you run it awhile, but the same air coming out of a blow tip can actually ice up the tip of the blow gun? That's the basic principle of how air conditioning (or a heat pump) works.

When you compress a fluid (air is a fluid) it heats it. When you decompress it, it cools. The more you compress it (increased compression,) the hotter it gets.

That said, increasing cam overlap and changing cam lobe timing can reduce the effective compression and compensate for some heat. That's why some racing engines need very high theoretical compression. They "lose" some compression to long valve open timing and overlap. I don't know the specs on your cam, but if it's ground for lower rpm torque, you aren't losing much effective compression.

I'd be danged sure that engine wasn't running lean. It gets much of its cooling from the incoming fuel charge (which has just vaporized and therefore cooled) and a lean engine runs hot.

Some would say that hp = heat and heat = wear and in a way that's correct imho. Certainly increased stresses from increased compression and increased power = wear.

Assuming a well-built engine, the #1 enemy is heat. I'd read the plugs for mixture, and put an oil temp gauge on it. If it is lean and/or hot, for sure I'd add a cooler and enrich the mixture.

A richer mixture also helps avoid destructive detonation which can occur with higher temps and higher compression. I'd watch my plugs for detonation by looking for tiny bits of metal sticking to the plugs.

You can't put 5# of chit in a 1# box, and you can pull only so much HP from each inch of displacement, especially in an air cooled engine. That said, if it's a non-radical and quality build, and if you get the mixture right and otherwise take good care of it, it should last a good long time but no way of saying how long.

$.02

PS I said air is a fluid. I didn't say it's a liquid.

 

01 Ultra, 124" Zipper built in HD cases, Baker 6 spd.
When we would ride with other baggers, we ALWAYS took less juice at the pump, than the 'stock' ones, we were riding with.
THAT was an added bennie. It wasn't built for 'economy', jus' turned out that way.
That was puilling 70 - 80 mph. NOW, if we were running solo, and out in SoDak, throw the mileage out the window, HOW FAST CAN I CROSS THE STATE????? Yes, it would bury the speedo, and still be pullin'. BEST we ever did? Little over 5 1/2 hours, Rapid to Sioux Falls, 2 gas stops. YOU figure it out.

 

I took heat as a contributing factor and adjusted accordingly. I use mobile 1 and an under the frame oil cooler. My engine has never seen 230 degrees. It stays at a normal temp, unlike the new harleys running from 230 to 280 degrees. I actually get great gas millage sense the new mapping. If an engine is built for power with the right components , I would think i could get at least 150K out of it.
I thought maybe there would be someone with a build that could give a idea how many miles these motors with mods can take.

 

I believe you, for sure.

You know, back in my youth (waaaaay back ) we used to buy 55 - 57 Chevys. The V8's would get better gas mileage than the straight 6's (235's) for some reason. That was especially true on the hwy, and assuming the cars had the same tranny and rear end ratio.

I always figured it was because you had to put the pedal to the metal and run the guts out of the 6 while the 265/283 V8's were loafing.

But then, what would I know? I just know it's true.

PS A 57 VW Bug would get at best 27 mpg hwy. You had to run the guts out of it. A 57 Chevy with the power pack (4 bbl, bigger valves, etc) 283, stick and overdrive would break 20 mpg hwy, m/l. A 57 Vette with an even more powerful 283 and a 308 rear end would easily break 20 mpg. Go figure.

 

I talked to my service manager about it yesterday and he said i might want to start getting it checked out after 50K. Might want to redo the top end . His mechanic said they rebuild top ends on thumpers after 40 to 50K . I ask then why didnt you tell me this before you did the build ? I would of left my engine alone !!!!! And now there telling me not to use synthetic oil.

 

total miles 348... figure 30 - 35 minutes per stop for everyone to top up on fluids and stretch... average speed somewhere between 75 and 80...

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