66deuce

iTrader: (1)

ok,so we all know that with a good dual spring,you can run an aggressive XER or similar lobe and have good spring life.but,how much harder are they on the valve seats? how long before the seats are pounded out,or how many miles between valve jobs?this would be on a street car that sees the strip a few times a year,not an all out drag car.just wondering as i haven't seen this discussed too much.

Cstraub

iTrader: (1)

Once spring pressure drops 20% from installed pressure on the seat you better change them. This is when the valve tends to bounce on the seat and power drops. Anyone going very aggressive on cam profile needs to solid roller. This way adequate spring pressure can be used and possible lifter failure can be avoided.

Chris

SPANKY LS1

iTrader: (24)

You're talking about springs, right?

Shawn

JCMGTO

What are you considering an aggressive cam profile? Exceeding what specs? Deciding on a cam right now and just wondering. Looking at XE-R 224/230 581/588 114LSA.

Cstraub

iTrader: (1)

Yes, change the springs. The valve spring is the most critcal part in an engine. That $6 part or $30 part can destroy an engine. The hyd roller is a valve spring nightmare due to the fact it is heavy as hell and you are limited to how much seat pressure you can apply to it to control its inertia before you overcome and collapse the hyd valving.

As I have stated time and time again the hyd roller is wonderful for making power in pushrod engines under 6K rpm. It is a nightmare for making power above or for extended runs over 4K rpm. If you don't believe me as Mercury Marine.

It's not my place to comment on what is aggressive and what is not. My advice is you better go with good valve springs and make sure the keeper does not move in the valve groove up and down.

Chris

SPANKY LS1

iTrader: (24)

He asked about valve seat longevity.

Shawn

66deuce

iTrader: (1)

i was just wondering how much harder an XER type lobe is on the valve seats,not the springs.i know you won't go 100,000 miles or whatever like a stock or mild cam.just wondering how many miles people are getting on their motors between valve jobs with the more aggressive cam profiles.

66deuce

iTrader: (1)

i was talking about the valve seats.but thanks for the advice on the springs.

Cstraub

iTrader: (1)

Let me put this in simple terms:
aggressive lobe + heavy hyd roller lifter= very hard on valve spring life.

Valve spring gets weak + rpm = valve bouncing on seat

bouncing valve + continued running = cup valve and beaten seat possible cracking.

So as I said, if you don't monitor the seat pressure of the valve spring then you will beat the SEATS out of the head.

Chris

66deuce

iTrader: (1)

ok,i get what your saying.but assuming proper spring selection and pressure,and no valve float,isn't a more aggressive cam profile harder on the valve seats than a stock or mild grind?

Cstraub

iTrader: (1)

No. In a perfect world they are not harder on seats, but the world is not perfect. If you go aggressive just monitor the SPRING pressure. I have seen Sportsman 2 heads that were hyd cam engines where the seats are beat all to hell do to lack of seat pressure.

Chris

66deuce

iTrader: (1)

yeah,i know the havoc a weak or mismatched spring can cause.i just thought that a more aggessive cam would be harder on the seats no matter what.but from what your saying,the proper spring pressure will control the lifters and valves so as not to pound out the seats,no matter what grind you are using.thanks for clearing that up.

Cstraub

iTrader: (1)

your welcome.