How important is a valve job?

[OffshoreDrilling]

Ive got some SI stainless valves that I am about to toss into my ported 3500 heads. So far I have only pulled out one valve and it looks like they could be seated much better.

Is there anything to gain/lose from doing or not doing a valve job? I would imagine burning oil and a slight loss of compression.

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[bikrboy128]

it would be a waste not to. as long as they are out, might as well get 'em done.

 

[MuffHugger]

R&R Engineering in Addison, IL (630) 628-1545.

 

[M@]

SI valves are AWFUL, the necks of the valves fail very often, and will tank your entire motor in the process...

Many a 3800 has met its end due to SI valve failures.

 

[madscientist]

ask crawlin thats who worked on mine

 

[2TonGTP]

Its about as important as giving the wrap around when u stick in her corn hole.

 

[CrawlinTBSS]

its all about the seal. a good seal with keep good compression and power in the engine. valves dont come cut to fit your seats perfectly thats why you install new seats and cut the valve to match the seat then vacuum test then. we recommend vavle job when doing any of that stuff. pm me if you need anything.

 

[OffshoreDrilling]

pm'ed

I cant wait to finish up this junk ass motor so I can talk some shit already.

 

[M@]

Valve jobs are important for low-lift flow, not for sealing.

If there are sealing issues, a simple valve lapping will fix that. Valve jobs are to optimize the angles at which the gases are entering and exiting the chambers. Angles on the intake to keep good fuel atomization, and radius on the exhaust for maximal flow.

 

[M@]

pm'ed

I cant wait to finish up this junk ass motor so I can talk some shit already.

if your cheap valves last long enough to make numbers worth talking shit about...

 

[OffshoreDrilling]

if your cheap valves last long enough to make numbers worth talking shit about...

Are you talking about in the intense stage 3 heads?

Not to sound like a nuthugging ricer and trying to talk my shit up, but in the 60 degree v6 community, I have yet to hear of problems with these valves.

 

[M@]

Are you talking about in the intense stage 3 heads?

Not to sound like a nuthugging ricer and trying to talk my shit up, but in the 60 degree v6 community, I have yet to hear of problems with these valves.

Nope, has nothing to do with any vendor, or anyone's heads.

SI valves have had a 75% failure rate in the cars I've had experience with them in. A friend in Minnesota lost his entire motor and one head due to an SI valve failure.

Another guy has had several of them fail (why he continued to run the SI's I don't begin to know) each time taking out the bottom end and one head with it.

The stems on the SI valves are thinned for increased flow, but that makes them no longer adequate to provide the fatigue life needed for a street driven motor. They might, MIGHT, last in a strip-only car that sees very limited run times, but I've seen these things fail even in strip only cars when cylinder temps/pressures are very high. Honestly, on a completely NA motor that sees very little mileage, they might be alright, but on a blown or sprayed car, I would absolutely never use these valves. They're inexpensive, that's seriously their only strong suit. The faces of these valves suck for flow, and the heads come off like crazy...they're just crappy valves, ask any real machine shop. I told my machinist that I used to run SI valves and he seriously laughed.
Get some Manleys, Ferreas, or just stock GM's. I run stock GM valves (LS1/5.3 valves).