new forged or shotpeened rods

[cosmo]

OK, I don't even need to talk about the pros of forged rods, but one of the cons is they are about $700. Would getting the stock rods shotpeened be good enough for 300whp or less? Not to mention it would be cheeper. I don't have major goals, but 275-300 is eventually what I want to end up with.

Discuss

[erich]

Leave the rods alone. 275-300 hp is no problem for the stock ones.I'm running 260-270 crank and I'm gonig to upgrade this weekend to about 350! Other people on the board have put down more on stock rods, if you search you should be able to find out who.The only thing the stock rods won;t let you do is to raise the redline. The force on the rods goes up with the square or the RPMs so if the stock redline is OK (and it is unless you are going to change the cams and inkake plenum) then the stock rods should be fine.

[cosmo]

I had plans on getting some cams(JWT 248/248 I think?) and maybe that Greddy IM(will someone please find out if it fits?)and doing the entire valvetrain. So they probably wouldn't hold up then would they?

But I'm willing to forgo the cams and IM if it means getting forged rods. Or is shotpeen the answer?

[TrunkMonkey]

oem rods are forged and shotpeened from the factory. the only thing on the bottom end that you might condsider upgrading is the pistons.

-demetrius

[Silent Drifter]

I have the same goal as you 300rwhp, all im changing is pistons to forged an probally '99 Altima piston rings.

[cosmo]

Yeah, pistons were a given.

Hmm...well I've successfully trimmed about $2000 from my project in a weeks span. Dammit I'm on a roll.

[vwluv10338]

My internet is down so I am not on my computer but I have a good link that might help. It is all about building turbo sr20de's for sentra se-r's. In the article I believe they just upgrade to det rods because they said they have never seen one fail. I mean with all the shops now pushing over 450whp obviously they can take it. Now I know people will say, sure they can take it but for how long. If you have the engine apart I would use the stock rods and have the rotating assembly balanced and micropolish the crank and that kind of stuff. I will find the article whenever my internet get up again.

Eric

[vwluv10338]

http://www.se-r.net/car_info/e....html

check out the rods section

[Projex240]

I really like this post. Most of the time when stock rods break its from drivetrain ABUSE.by this I mean downshifting from 5th to 3rd without double-clutching, and letting the motor slow itself down using rpms. When this happens, most of the time, its not the rods themselves that break, its the rod BOLTS that go and then the rods end up throught the block.When rebuilding a motor, I would have the rods magnafluxed to check for any stress fractures that would cause them to fail later. If at that time they are still good, just shotpeen them again for good measure...the whole process cost me only 200 bucks.

[Nathan]

The stock rods look so small...after seeing the thrown rod out of my old engine I couldn't risk an engine on those things

[SingleCamSam]

Quote »by this I mean downshifting from 5th to 3rd without double-clutching[/quote]

Now why would you waste time double clutching a transmission that uses synchros?

[Projex240]

Double clutching takes some of the strain off the motor when you downshift. If youve ever tried to downshift and just let off the clutch with giving any throttle, the car lurches and slows down HARD. THIS IS BAD! This is exactly what causes stress on the rods. Instead of getting pressure from above, they are stretching due to the crank spinning faster than the rear wheels should be. When the motor slows itself down by doing this it puts great stress on the motor. Tach out 1st and then without shifting or using the clutch, let off the throttle...itll slow itself down. Thats too much stress on the factory rod bolts. Double clutching allows the driver to control how fast the rpms rise and drop between downshifts. Syncros only help the car go into gear smoother and without grinding.

[SingleCamSam]

I was under the impression that the whole purpose of syncros was to automatically match the speeds of the engine and transmission before the shift actually occurs, thus eliminating the need for double clutching like a Dog-box?

[TrunkMonkey]

I was under the impression that the whole purpose of syncros was to automatically match the speeds of the engine and transmission before the shift actually occurs, thus eliminating the need for double clutching like a Dog-box?

it is.

i've always wondered why people double clutch when rev matching is easier, smoother, takes less time to do, and is just as effective.

i say save the double clutching for the big rigs.

-demetrius

[C-Kwik]

Double clutching takes some of the strain off the motor when you downshift. If youve ever tried to downshift and just let off the clutch with giving any throttle, the car lurches and slows down HARD. THIS IS BAD! This is exactly what causes stress on the rods. Instead of getting pressure from above, they are stretching due to the crank spinning faster than the rear wheels should be. When the motor slows itself down by doing this it puts great stress on the motor. Tach out 1st and then without shifting or using the clutch, let off the throttle...itll slow itself down. Thats too much stress on the factory rod bolts. Double clutching allows the driver to control how fast the rpms rise and drop between downshifts. Syncros only help the car go into gear smoother and without grinding.

Uhh? The highest stress on a rod actually occurs on the exhaust stroke at TDC when there is no resistance to the piston flying off other than the rod holding it in. Partilcularly at higher RPM's. The lurch you feel is more because of the heavy flywheel trying to maintain the speed of the motor while the car slows down. Get a lighter flywheel and you'll find the crank will match speed with much less violence.

And double-clutching does nothing for matching speeds. The reason double clutching was used was because before the use of syncros, the dog gears had nothing else to assist in matching the speeds of the gears when the clutch is pressed in. For example, if you had no syncros and you put your car on the top of a hill. Put in the clutch and allowed it to roll down. The gears attached to the driveshaft would spin relative to the shaft speed. But the gears attached to the clutch disc would not be spinning. They to throw the car in gear and because of the difference in speeds, you'll grind. If you were to let out the clutch breifly with the motor running, this would cause the clutch disc to turn which would then turn the gears attached to it. This allows smoother engagement of the gears since now both gears are moving. But since the clutch is still in when you are engaging gears, it does nothing for the crank. There is no resistance at this point on the crank until you pull the clutch back out.

The lurch you describe comes from the fact that the flywheel or engine speed is different than the input shaft or clutch disc speed. Say at 50 mph in 2nd gear, you'ld probably be getting close to redline. But if your vehicle is travelling 50 mph and you are in second, but your clutch is pressed in and the motor is at idle, guess what happens when the clutch pedal is released. There will be nearly a 5000 RPM difference in speed between the flywheel and the clutch disc. So now the car has to slow down and the engine has to speed up to meet somewhere in the middle.

If what you are saying was true, those who speed shift(without letting off gas) would have cranks or rods breaking all the time. Poor rev matching would lead to transmission failure before it led to engine failure. And you'ld still need to produce quite a shock to the gears repeatedly to cause that. Double clutching does nothing to buffer the shock when a clutch is released with too much of an RPM difference between the flywheel and clutch disc.

[C-Kwik]

I was under the impression that the whole purpose of syncros was to automatically match the speeds of the engine and transmission before the shift actually occurs, thus eliminating the need for double clutching like a Dog-box?

No. It only matches the speed between the dog gear and the receiver gear allowing them to engage. Does nothing for mismatched speeds of a flywheel and clutch disc. Racing Dog gear engagement boxes just use a looser tolerance between the dog gear and the receiver so it is easier to get in even if the speeds are different. But they do make a clunk when engaged and require a quick deliberate movement so double clutching is not necessary. Dog boxes with tolerances similar to a transmission with syncros(doubt they exist much anymore) need to be double clutched.

[MECPInstaller]

i have a real bad feeling about this i think i'm going to sound like a dumbass but just curious how exactly do you double clutch sorry only owned a 5 speed for about 2 months

[Nathan]

depress clutch, shift out of gear...let out clutch. Depress clutch again, shift into next gear, let out clutch.