PRC 285s or 265s?
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Teching In
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From: Virginia Beach
PRC 285s or 265s? I've got a 07 Z06 that's a daily driver that I bought new. It now has 87K miles on it. The warranty's now expired and I'm a bit paranoid about the exhaust valve drop problem that's plaqued the LS7 since it's birth.
So... It's time to take care of the valve issue and step on it a bit at the same time. As of now, pending a leak-down test and a "heads off" cylinder inspection, I intend on keeping it N/A. Asssuming a good bottom end I intend on doing heads, FAST 102, Nick Williams 102 TB and a cam swap. With all the problems surrounding the OEM heads I intend on using new heads. R&R-ing the stock heads isn't an option, IMO. The factory (uncoated) titanium intake valve are not compatable with Bronze/manganese guides as they're not coated and will wear them out prematurely. It you add the price of new titanium intakes to the cost of head refurishment you're knocking at the door of new heads costs. So, I'm going with new heads.
Here's my quandry... TSP recommends the 265s for a N/A stock stroke 427 build. But... depending on the bottom end, I may go boosted or stroked. My question is, will the 285s work OK with the stock stroke N/A build or do I HAVE TOO go with the 265s? I'm going to buy the heads in advance of everything else. I don't want to get stuck with too small heads if I end up going stroked or boosted.
Everyone's thoughts???
So... It's time to take care of the valve issue and step on it a bit at the same time. As of now, pending a leak-down test and a "heads off" cylinder inspection, I intend on keeping it N/A. Asssuming a good bottom end I intend on doing heads, FAST 102, Nick Williams 102 TB and a cam swap. With all the problems surrounding the OEM heads I intend on using new heads. R&R-ing the stock heads isn't an option, IMO. The factory (uncoated) titanium intake valve are not compatable with Bronze/manganese guides as they're not coated and will wear them out prematurely. It you add the price of new titanium intakes to the cost of head refurishment you're knocking at the door of new heads costs. So, I'm going with new heads.
Here's my quandry... TSP recommends the 265s for a N/A stock stroke 427 build. But... depending on the bottom end, I may go boosted or stroked. My question is, will the 285s work OK with the stock stroke N/A build or do I HAVE TOO go with the 265s? I'm going to buy the heads in advance of everything else. I don't want to get stuck with too small heads if I end up going stroked or boosted.
Everyone's thoughts???
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Teching In
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From: Virginia Beach
It's not just the exhaust valves but the Ti intakes too that require replacement. The stems on the factory intakes are not compatable with bronze guides. The will wear the guides rapidly. If you add the price of new intakes, +/- $1100, then new heads are as cheap as an OEM head refurb.
What's the price difference? 285's might make your low end power suffer some on the Stock cubes and make it a little harder to tune, but I don't see it being a horrible problem if any at all.
If the price difference is significant, get the 265's and later on have them opened up to 285's if that need arises.
If the price difference is significant, get the 265's and later on have them opened up to 285's if that need arises.
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I just talked to Manley, who custom makes the titanium intake valves for the PRC 285s and 265s. They said their Ti intake valves are intended for racing only and WILL NOT last on the street. They said to get the Ti intakes to last on the street then the valve heads need to be DEL coated, as well as coating the valve stems (which they do). They do sometimes apply that coating to the heads of their custom valves. They didn't know if TSP's custom Ti valves had that done.
Does anyone with the Ti intake PRCs know if the intake valve heads are coated? I talked to TSP and they didn't know. I guess this would apply to all the aftermarket heads with titanium intake valves.
Does anyone with the Ti intake PRCs know if the intake valve heads are coated? I talked to TSP and they didn't know. I guess this would apply to all the aftermarket heads with titanium intake valves.
All of the titanium valves we use for the LS7 heads are coated.
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So if you had a choice Matt which would you do PRC 265s with the ti valves/SS exhaust or reworking the stock heads with tumble polished ti valves/SS exhaust which would you do?
Stock motor just bolt ons with a baby cam in the future
Stock motor just bolt ons with a baby cam in the future
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I am betting he'd say if the budget allows it, go PRC aftermarket castings.
It's not just the exhaust valves but the Ti intakes too that require replacement. The stems on the factory intakes are not compatable with bronze guides. The will wear the guides rapidly. If you add the price of new intakes, +/- $1100, then new heads are as cheap as an OEM head refurb.
Thread Starter
Teching In
Joined: Sep 2012
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From: Virginia Beach
Thread Starter
Teching In
Joined: Sep 2012
Posts: 23
Likes: 0
From: Virginia Beach
It could be as late as January before The actual work's done. It depends if I do it myself (January) or I sub it out (sooner). With two on-going carreers "space available" is hard to find...
I was waiting until GM makes a statement on the boards before I buy the heads and final stuff (I know, pie in the sky hopes...).
I was waiting until GM makes a statement on the boards before I buy the heads and final stuff (I know, pie in the sky hopes...).
