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Author Topic:   When do you replace engine parts/freshen?
maxrpm
Dirt Roller

Total posts: 6
posted April 04, 2005 08:21 PM  
When you freshen up a engine, I do mine every 20 nights. When should you change the valves, rod bolts, roller lifters. I guess is there a life span on these parts or ???

ARR
Dirt Full Roller

Total posts: 68
posted April 04, 2005 09:45 PM  
As far as rod bolts go, if they were properly torqed to specs they should last for a long time. We race about 25 races a year and turn about 6500 rpms. We have had the same rod bolts in for 2 seasons going on 3. The manufacture will have certain specs on rod bolt stretch, you should find this info and check it or have it checked. If the bolts are stretched out of specs replace them.

[This message has been edited by ARR (edited April 04, 2005).]

[This message has been edited by ARR (edited April 04, 2005).]

[This message has been edited by ARR (edited April 04, 2005).]

Istock66
unregistered Total posts: 68
posted April 04, 2005 10:10 PM           send a private message to ARR   Edit/Delete Message   Reply w/QuoteBBBBBB
I have 2 scenarios.

1. When I ran pavement I freshened my weekly race motor after two seasons. With 35 to 100 lap mains it easily had a total of 4000 laps, some half mile some quarter probably more.(75-140 laps a night with practice)

2. Here on dirt in Iowa I know of guys freshening after 25 nights, some even less. A night here is 4 practice, 6-8 heat,15 main. So 30 laps a night.

Thats only 750 laps, why freshen that?? That would be less than 6 of my pavement nights!!

Also I ran open carb rules on pavement and every thing here is 2 barrel.

rico 08
Dirt Forum Champ
Total posts: 1139
posted April 05, 2005 06:39 AM  
two seasons?....wow,i don't recall that ever working around here.I tried to reuse my 13 race old main bearings and now i've lost some oil pressure over last year(won't do that again)
one thing i've noticed is some teams replacing the cast cranks every other year,while the forged crank users getting 3-5 years out of one.
as far as rollers,i'd replace the roller lifters every couple years..they may look ok but i've seen them turn sideways when worn and really cause havoc.

Istock66
unregistered Total posts: 1139
posted April 05, 2005 07:15 AM           send a private message to rico 08   Edit/Delete Message   Reply w/QuoteBBBBBB
Thats what Im wondering? Why freshen after 20 races.

I have claimer motors I would want to freshen after 20 races but mainly because they are unbalanced.

But a balanced assembly I would think could run for years in a dirt car with the limited laps we do??

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted April 05, 2005 07:46 AM  
With our mod we shoot for 25 nights, or roughly 1000 laps. Now that being said we did run close to 35 last year and engine looked great. First thing to wear out will prob be rings or valve springs. If you check your valve springs regularly and replace them if needed during the season then do a leakdown on the motor and keep track of ring wear that should be a good indication of when to freshen it, barring any unforseen disasters.

On dirt I think you need to freshen more often because of the dirt itself. No matter how hard you try it will get some inside and that is harder on the rings and bearings etc.

The other thing for us is the fact that we dont want to get 10 races into the year and have to freshen the motor. Its a lot easier to do in the off season. We usually get 25-30 nights a year so it works out good to just freshen every year.

148mod
Dirt Newbie

Total posts: 1
posted April 05, 2005 02:21 PM  
But what about valves, I run manley severe duty. Should I get 3 or 4 seasons? The engines have always looked great at 20 nights.

zeroracing
Dirt Forum Champ
Total posts: 1876
posted April 05, 2005 02:36 PM  
Depends on what you run, how hard you run it, how often you change oil.

Our little motor is a 355 flat top, solid cam, kevko pan, eagle i beam rods, trw pistons.
we ran it i think 3 seasons took it apart and replaced the bearings, timing chain, and the rings. then ran it this last season, took it partially apart and NO problems. So no new parts.

We turn it about 7200 most nights and as high as 8000 for a race.

Also valve springs should be replaced every season almost, check them often with a cheap checker to look for one going soft, that is an early warning sign.
If you turn 6500 or less then check the springs, and over 6500-7700 every season at least, and 7700+ mid season changes may be needed.

i agree with 66 unless your turning it like 7700+ you should get more than one season out of a motor.

Xtreme12x
Dirt Forum Champ
Total posts: 874
posted April 05, 2005 04:35 PM  
Rings and bearings are cheap...
Racing on dirt like someone else stated, you need to freshen more often. The main thing is Compression, the more compression the sooner you'll want to freshen it with bearings. On 9-1 Motors we see 40 races before we freshen with rings, bearings, springs, gaskets... on the 13-1 and 14-1 motors we race maybe 15 nights

maxrpm
Dirt Roller

Total posts: 6
posted April 06, 2005 09:09 PM  
Thanks for all your help!

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