Quench area question

[ViperC]

After reading a lot and learning more about LS engines and quench I did a quick search for Vipers and quench and didn't find much information. In the LS world, a tight quench seems to be very important for many reasons, including detonation protection, combustion, and efficiency. It doesn't appear to be as important for Vipers, with stock motor builds having pistons deep in the hole and a pretty wide quench area. So is quench not as important with Vipers? I know quench between .035" and .040" seem to be the sweet spot for LS naturally aspirated builds, but Vipers seem to be .060-.080"+. So what's the deal? Should we be using thinner head gaskets and/or decking our blocks to tighten up the quench? Are we leaving power on the table? Thanks.

[Camfab]

Combustion design is just as important on the Viper engine as it is in an other engine package. The Gen II heads are the equivalent of a old school small block Chevy head. They are a full design evolution backwards from an LS engine. Gen IV and above heads are on par with LS technology. Personally I dumped the GEN II heads for Striker heads some 10 years ago. Greg Good can likely do miracles with the old heads. If you have the cash, Arrow Racing, sells a kit to retrofit GEN IV+ heads onto a GEN II. If I didn't already have my set up, I'd do that in a heartbeat.

[ViperC]

Combustion design is just as important on the Viper engine as it is in an other engine package. The Gen II heads are the equivalent of a old school small block Chevy head. They are a full design evolution backwards from an LS engine. Gen IV and above heads are on par with LS technology. Personally I dumped the GEN II heads for Striker heads some 10 years ago. Greg Good can likely do miracles with the old heads. If you have the cash, Arrow Racing, sells a kit to retrofit GEN IV+ heads onto a GEN II. If I didn't already have my set up, I'd do that in a heartbeat.

What mods have to be made to the Gen 4 heads to fit a Gen 2? I know there are some issues with the power steering pump bracket, but what about the head casting itself? I think the bolt holes might have to be enlarged to 1/2" but I'm not sure.

[dave6666]

Dan Lesser also does a Gen 4 head conversion. I also recall some discussion with him on the subject that the true JM Stryker heads (not the JM stock casting CNC heads that people call Strykers) are an equivalent to the Gen 4 casting basically. So if you have the real (actual...) Strykers, you are already there. I would knock them off your wish list.

BTW, since JM was pushed out of that business years ago there are others that have picked things up where he no longer is. Don't know if that's just the CNC work he did on the OEM castings or the the aftermarket castings (Strykers...). But, as logic might lead to define, why look up that mess trying to make one more "one-off" pairs of Strykers when you can just go down the street and get the G4 heads. Short of the CNC work he did on the OEM castings, I think his legend is history.

[ViperC]

Dan Lesser also does a Gen 4 head conversion. I also recall some discussion with him on the subject that the true JM Stryker heads (not the JM stock casting CNC heads that people call Strykers) are an equivalent to the Gen 4 casting basically. So if you have the real (actual...) Strykers, you are already there. I would knock them off your wish list.

BTW, since JM was pushed out of that business years ago there are others that have picked things up where he no longer is. Don't know if that's just the CNC work he did on the OEM castings or the the aftermarket castings (Strykers...). But, as logic might lead to define, why look up that mess trying to make one more "one-off" pairs of Strykers when you can just go down the street and get the G4 heads. Short of the CNC work he did on the OEM castings, I think his legend is history.

Regardless of what type upgraded head you may use, Stryker or Gen 4, it still doesn't take care of the huge quench area that Gen 2 and probably other Gen Vipers have. A stock piston is .035" in the hole. Add the thinnest MLS head gasket you can get, which is .027" I believe, and that makes your quench an astronomical .062", which is effectively no quench at all. I just want to know if for the best performance I must reduce the quench to an acceptable level, is it "really" that important, or are the other ways around it?

[Camfab]

As an FYI I did reduce the distance by using a thinner Cometic head gasket. This was recommended to me by Jeff Mory's as I was looking for extra compression without changing the stock pistons. I have the real Striker castings not the CNC stock heads. The Strikers had much thicker decks, better cooling, and completely revised chambers. I want to say valve angles and positioning was changed as well but I can't remember the particulars right now. Anyway as Dave noted, the Gen IV head package is the way to go as it is essentially a copy of the Striker head. It offers the benefits of the Strikers with the availability of the Gen V intake which is a huge leap in design. As a cheaper alternative you can run the dragpak manifold which was part of the original Gen III to IV swap kit. You also get the later style injectors, harness and all the parts necessary.
So to return to your original question, yes tighening up the quench is important, but your really just polishing a turd.

[Camfab]

Just to drive home how bad the GEN II castings are vs the newer options. I picked up 200+ crankshaft hp (150+ rwhp) by simply swapping heads and a cam. I have an OEM non ported intake, stock throttle bodies and ALL emmisions intact. Power and torque were increased off idle all the way to the top. If you've ever built an engine you know that simply doesn't happen. You run a bigger cam, you're going to lose bottom end and make gains on top. Not here, massive increase in power across the board. Bottom line, swap the heads.

[ViperC]

As an FYI I did reduce the distance by using a thinner Cometic head gasket. This was recommended to me by Jeff Mory's as I was looking for extra compression without changing the stock pistons. I have the real Striker castings not the CNC stock heads. The Strikers had much thicker decks, better cooling, and completely revised chambers. I want to say valve angles and positioning was changed as well but I can't remember the particulars right now. Anyway as Dave noted, the Gen IV head package is the way to go as it is essentially a copy of the Striker head. It offers the benefits of the Strikers with the availability of the Gen V intake which is a huge leap in design. As a cheaper alternative you can run the dragpak manifold which was part of the original Gen III to IV swap kit. You also get the later style injectors, harness and all the parts necessary.
So to return to your original question, yes tighening up the quench is important, but your really just polishing a turd.

I understand using Gen 4 heads or Strykers over stock Gen 2 castings. In fact, I have a set of used Gen 4 heads in bedroom as we speak. It still leaves the quench issue. New pistons, decking the block, and/or thinner head gaskets are all a way to do that, or at least a combination of them. I am just curious how important is a tight quench. Is it worth new pistons or decking the block?

[Camfab]

Gen IV heads in the bedroom, now that's a guy with his priorities straight . As far as new pistons, just for the sake of tightening up the quench, I guess if cash is available. If it were me and I was thinking about a full rebuild, then yes. If all was perfect, tolerance wise in the short block, then no. The other question is what are your goals. I stayed eutectic because I didn't see the need to go forged when forced induction was not in the cards.

[ViperC]

Gen IV heads in the bedroom, now that's a guy with his priorities straight . As far as new pistons, just for the sake of tightening up the quench, I guess if cash is available. If it were me and I was thinking about a full rebuild, then yes. If all was perfect, tolerance wise in the short block, then no. The other question is what are your goals. I stayed eutectic because I didn't see the need to go forged when forced induction was not in the cards.

I am just pursuing perfection, that's all lol

[ViperC]

Gen IV heads in the bedroom, now that's a guy with his priorities straight . As far as new pistons, just for the sake of tightening up the quench, I guess if cash is available. If it were me and I was thinking about a full rebuild, then yes. If all was perfect, tolerance wise in the short block, then no. The other question is what are your goals. I stayed eutectic because I didn't see the need to go forged when forced induction was not in the cards.

Really I just want a high compression NA build that will make big HP. I am trying to keep a stock bottom end as well, but want to address the quench issue. Decking the block would be an option, but new pistons would probably be a better idea but would be counter to maintaining a stock bottom end.

[Viper Specialty]

What mods have to be made to the Gen 4 heads to fit a Gen 2? I know there are some issues with the power steering pump bracket, but what about the head casting itself? I think the bolt holes might have to be enlarged to 1/2" but I'm not sure.

Its a whole package, and multiple processes. For what its worth, actually do your homework on what it REALLY takes to do the job. If I had a dollar for every customer who shit bricks over the price of the VS-X700 package we offer, went and did it themselves.... and them came back later and said "what the hell was I thinking?!?" I would have... lots of dollars. LOL

All of the small details, labor, tuning, wiring, hardware, exhaust, intake, cam/timing, finishing, etc is always conveniently omitted from the calculations in everyone's head. They seem to mentally stop at the heads, manifold, covers, rockers, and machine work.










This is what professionally done looks like.


To answer the original topic, yes, quench matters. And no, a non-effective quench does not make a difference... ineffective is ineffective. If you don't have a good rotating assembly and a properly machined block, you don't want to chase an effective quench... you will end up running your pistons into the head deck at high RPM. Ideal is .035 +/- with steel rods.

All of that said, if you aren't running a high power application with either very high compression or forced induction, its not a paramount type thing. Its something you build for if you are doing the job anyway.

[ViperC]

Its a whole package, and multiple processes. For what its worth, actually do your homework on what it REALLY takes to do the job. If I had a dollar for every customer who shit bricks over the price of the VS-X700 package we offer, went and did it themselves.... and them came back later and said "what the hell was I thinking?!?" I would have... lots of dollars. LOL

All of the small details, labor, tuning, wiring, hardware, exhaust, intake, cam/timing, finishing, etc is always conveniently omitted from the calculations in everyone's head. They seem to mentally stop at the heads, manifold, covers, rockers, and machine work.










This is what professionally done looks like.


To answer the original topic, yes, quench matters. And no, a non-effective quench does not make a difference. If you don't have a good rotating assembly and a properly machined block, you don't want to chase an effective quench... you will end up running your pistons into the deck at high RPM. Ideal is .035 +/- with steel rods.

All of that said, if you aren't running a high power application with either very high compression or forced induction, its not a paramount type thing. Its something you build for if you are doing the job anyway.

Thanks. That's the type of answer I was looking for.