So I was talking with our head porter a while back and we were talking about how great the flow potential was on a VQ head... I asked if he really thought there was much need for portwork at all on an FI street motor and he said that it wasn't so much the portwork but the guides that needed to be addressed... he said the stock exhaust valve guides get brittle and fall apart under the increased heat from boost... I hadn't heard of people complaining about this on the forums so I thought this might just be something that comes up only at CRAZY egt levels like those required to make 1500hp (which is the world he mainly works in)...

Well, I just got off the phone with a valvetrain engineer at Ferrea and when I ran this by him he confirmed that this was a major problem. He surprised me by saying that even on a street car, with a bolt-on turbo kit, guys are having their guides fall apart in 6-8 months... they will last "a year if you are lucky" he said...

I'm not try to get everybody in a panic here, I'm just looking to open a discussion on this... have people been seeing this problem after extended run time with the bolt-on turbo kits on stock motors? has anybody even been checking?

From what I've heard now from these two reputable, knowledgeable sources, I wouldn't even consider doing FI without swapping out the exhaust guides, but I'm always curious to gather more information...

Jeff

 

i have not heard of anything but I never did check mine after all my abuse. I had a good year of all boost and never had any symptons so I am not sure how I feel about that.

Perhaps just by porting the exhaust ports and making the valve guides flush will solve the problem... or would that make it worse? But I would think having less surface area of the guide in the actual exhaust stream may help?

We will all know very soon! We have enough built engine cars running around now that if a problem comes up, then surely it will effect many of us this year. At this point I dont know if I would alarm anyone putting on FI.

 

Ive put 50k miles of 400whp on my boosted VQ30DE and no valve guide problems.

 

My machinist carefully examined the head, and found everything in very good shape.

I would change the guides when doing full blown head work. Cams, retainers, guides, valves..etc.