I figured this would be the more appropiate forum as there are not yet a whole lot of boosted VQ35's.

Feel free to move if it is in the wrong forum.

We know that stock VQ30 are capable of revving to @ least 7200 w/ out modification.

Now can the same be done with a VQ35 with built bottom end with stock heads and boost?

Or do the heads NEED to worked to accomplish this safely without harm to the engine?

Thanks.

 

We shall see... I'll be experimenting with a built 3.5 bottom end with stock 3.5 heads with my boost setup. I do have the ability to raise the Rev limit up with EU but since I sold my JWT Valve springs, I don't plan on seeing anything more than 7k.

The stock 3.5 heads flow better than the 3.0's and in theory, with the modified 3.5 IM, it should push the powerband to the right enough to benefit with the higher rev limit but we really haven't seen an actually dyno to see how much exactly. With stock 3.5 tho, it would be il-advised to rev a boosted setup higher than stock.

 

So reving to 7k with boost and stock heads with a built bottom end should be okay? I don't want to rev that high with stock heads only to damage the engine.

 

The weak spot on the 3.5s is the bottom end. Connecting rods but mostly the rod bolts are what have the tendency to give out. Replace those with ARP rod bolts and it should give you some peice of mind.

But because of the long stroke Im not sure if it would be a good idea to rev passed stock redline on boost. NA it can take it no problem w/o ARPs to 7100-7300 (SR20DEN's redline IIRC), but under the pressure of boost dunno.

This is just speculation however, no one here has really tried to boost a 3.5 AND go with a higher redline to the best of my knowledge. Experimentation is how we find out things ... but I doubt many people would want to experiment this subject on their car, as most people here use it as their daily driver, plus the expense of an engine if it blows :-X

 

Definitively do ARP rod bolts.

 

I think several are going to 7500 with the ARPs. I would definitely recommend them if going over 6500, and it wouldn't hurt if you are boosted anyway with the stock red line.

You might want to check in some of the Z/G boards and see what kind of foolishness their engines are handling and what they say the limit is.

If you are just running fairly low amounts of boost, and/or are properly tuned then I can see going to 7200 or so, but after that it is probably uncharted territory for those rods.

 

Why would boost be any harder on the rod bolts? RPM is RPM on the rod bolts since they are on the bottom and hold the rod on the up stroke. Boost doesn't add any force on the up stroke correct? Boost would be harder on the main caps for the crank, which are plenty beefy. If the stock rod bolts will handle 7100rpm on N/A 350z's, then they should handle that much on a boosted engine too, given their job...

 

I guess the question would be why would you need to? Depending on what type of boost you plan to run, I would guess that one would reach peak hp/torque before redline. But I guess if you run a big turbo, it might not reach peak boost until later in the rpm band. Not sure why you would want to do this though.

 

With bigger turbos or peak HP/TQ is higher, you would definitely want a higher rev to make the most out of it. Higher rev allows you to potentially shift right into heart of your powerband. Even if you have a your power peaks near stock, if the right side of the powerband is flattens out unlike a 3.0 dyno curve, it would be beneficial too; more time spend in power...

 

I understand that. Just not sure why would one design it that way when a bigger turbo usually means more rpm lag. I would think one would try sizing a turbo so it would peak under the redline so one wouldn't have to run such high piston speeds to get the most out of the engine.

 

Some may complain about wheel spin especially FWD, so they go bigger on the size to "combat" the quick spool/tire spin. Its really a personal perference and the style of driving that they do. OR maybe they just like to say I can rev it up to 8k and I'm boosted

 

If I am capable of making power up to 7k why not take advantage of it? I could careless about anything else.

I just want to make sure that I cover the bases. I really don't want to build the heads if its not needed.

 

You dont need valve springs till mid 7k's. Completely stock heads and cams are perfectly fine to 7200. Its boost thats an issue above 6600. 7000 on a boosted stock block is pushing it even with ARP rod bolts.

 

So then if a boosted stock block is pushing it a 7000. Then what about with a built short block?

 

Before we get into all that, what are your power goals and what's your budget like?

 

This is already in the works...trust me you shall see soon.

 

I wasn't asking to know your "secrets". That's not really my concern.


My questions were completely serious, BTW. Projected power goals and how much you're willing to spend on the build-up have everything to do with how high it will be able to rev under boost reliably. Then there's the issue of actually making power up there. How high you rev should be based on where you make power, not just to say that you can.

 

Sorry man didn't mean to come off any other way. I know there alot of newbies that ask similar questions and I just wanted to clairfy I am not of them

I noticed that it has already been edited but I was never inquiring about the stock block.

Yes, as I mentioned previously I am not looking to say "oh I can rev to 7k". I plan to actually make power to justify the need for a higher limiter. Plus there are times (i.e. Road Racing, etc.) that it would be nice to have the extra revs. Get what im saying, so its not all about power per say.

Secondly, I suppose I should just rephrase my question:

Can I safely rev to 7k rpm with stock heads and a built short block w/ High Boost? Or do I need to build these heads.

JP

 

That's a definite yes as long as stock cams are being used.