so, collecting parts for a build, just wanted to make sure i am able to rev to 8000 safely. will a single spring valvetrain kit be enough, say BC valves, springs, and retainers? or will i need some dual springs like the supertech springs, valves, and retainers? the bottom end will be fully built with forged pistons and rods. i will have everything balanced but just need to make a decision right now on what valvetrain i should go with. thanks

i did search around quite a bit, but found no good evidence one way or the other. seems like one guy is fine with nismo springs up to 8400rpm, and the next guy is having his valves contact his pistons due to valve float at 8000rpm with nismo springs. maybe the second one wasnt balanced as well, idk, just looking for some solid guidance on which valvetrain to go with.

 

i should also say i have BC stage 2 cams

 

Engine balance has nothing to do with valve float

You need to ask your machinist these questions and provide him with the various specs on your intended build. He will tell you if it's physically possible for contact to occur given the specifics of your components. Unless somehere here has your exact engine, all you're going to get are random guesses

As an aside, given your other components (most notably your headers), I wouldn't stress over very high rpm use, as you are going to be significantly limited in that arena.

 

problem is that no engine builder in my area has much experience with the vq35de, so i am doing all i can to get as much info on here as possible. maybe power up to 8000 will fall off some, but the intent is to at least have the capability to rev that high for track use, it will be useful to be able to hold a gear with a little more rpm vs shifting, whether im still making power or not. not to mention, id like to have the heads built for the future when maybe i will do other mods to increase power that high. either way, im not really convinced that the headers will be the restriction up there. with a cutout and some gasket matching, i think it will pull pretty high.

so, anyone else?

 

it has nothing to do with knowing a VQ or not...it's all math, and any engine builder worth using can evaluate the specs of what you are using and tell you if it is/is not at risk. If they can't, find someone who can

You are not likely to make power to 8k IMHO, but thats a whole different discussion. Even moreso since you're using cats. If power falls off by any meaningful number, which will be revealed on the dyno, there is zero point in revving it past that point unless torque remains at least flat. A proper final drive for the track(s) you're running will let you manipulate the output curve of the engine for the conditions it's being used. You can calculate the right final drive for the application through some track mapping/datalogging sessions.

An exhaust cutout pre-cat (like at the header) is going to kill your midrange torque fwiw and make it a very, very peaky engine if using a shorty type header (even on a proper set of longtubes I would expect some losses), not to mention, likely far too loud for any track sanctioned events. Post cat, I can't see any real point in, but I've never tried it first hand to know for sure

 

ok, now that my build has been picked apart, is there anyone that knows the answer to my original question

 

I wasn't trying to pick your build apart, but rather just to point out that you're worrying about something you don't really need to worry about. I think I did answer it...if you're machinist can't, or isn't willing to answer whether 2 parts you are considering using, may come in contact with one another at a certain point, you would really be well served to find a different machinist. If it grenades itself, it's his a$$ on the line at the end of the day

In and of itself, a BC stage 2 cam and a Wiseco off the shelf 11:1 piston should not have any interference issues. That cam will do just fine with BC's spring kit - BC designed them to work together. A dual spring would need either a very high rpm ceiling, or a very aggressive cam, to be in the mix.

 

Cutout would be at the beginning of the midpipe. The point being to bypass the remaining stock muffler.

So are the BC springs good to 8000 or only about 7500? Or what do you consider "very high"?

 

does BC not answer their phones? why not ask the people that make the parts??

Alberto only has single springs and revs his 8000+ all the time. I'm sure there are alot of other ppl revving to 8000 with single springs as well

 

FAil written on this..

who will be doing the "building"