Hi folks - I'm neck deep in an R53 build posted here. I've removed the cylinder head and will be reinstalling a ported one, as well as a ported intake and supercharger + horns and a mild but upgraded street cam (Newman PH 1/2). I'll also be running a 17% pulley and other intake and exhaust upgrades, plus of course high flow injectors and a tune.

So here's my question: I'm taking my head to a machine shop for a build - are oversized valves worth the extra cost given my set up? If so, what should I consider that's reasonably priced? (I started by looking at these). And more important, what effect would this have on MPG (I don't want 10 mpg as the expense for more HP!) and more importantly CEL codes? I have an emissions inspection in June so want to be careful not to screw things up. Also, my overall goal is spirited daily driver for rare but occasional track use that can go tens of thousands of miles without serious work.

I'm eager to get this done, but figure it's worth an ask of the board if folks have any thoughts - or even better first hand knowledge? I'll continue to dig in the forums but hope there's fresh perspectives out there as well. Truly appreciate your thoughts!!

 

I was looking to see if there was any actual "scientific" data out there to assist in your decision. All I've found so far is lots of folks on various forums, you tube, etc. basically stating the same thing. Stock valves can do the same as large valves if you crank the boost. Sadly, we're sort of limited in our ability to do so and the ability to compensate for the increased heat generated by the higher boost - unless you're maybe spraying meth or alcohol. So, I'm thinking that with the current other upgrades (e.g. cam, springs, etc.) you might come out ahead.

Again, not really sure at this point but I'll keep hunting around.

There was some drama on this sort of stuff a while back (between RMW and Thumper): (not sure the resolution)- still interesting to read.

https://www.northamericanmotoring.co...er-tpr2-3.html

 

Yep, that thread was a lot of emotion and not super helpful, and I've gone down a rabbit hole searching around. For instance, I found the Thumper TPR-2 - their midrange offering and the max recommended for street driving - uses the same size valves as those linked above but that, of the three offered, it's been retired for some reason and notably "MPG isn't your brother": https://www.thumperheads.com/r53.php

It's remains quite unclear for a prospective $400 investment on valves, and my takeaway is most folks on this board bought a Thumper or RMW rather than try it themselves. Then again, I'm willing to save a thousand or even double that to try it myself and forgo the best of the best. And I'm eager to splurge on a dyno when all said and done for the tune and to compare the results.

Thanks for looking around; I'll give it another day or two and proceed with the port and polish job I have but the OEM valves.

 

Check out this guy.

In the first few minutes he does talk about larger valves and boost. This was a live-stream so no dyno but he does have some cool stuff if you are interested.

I really like that he has some expertise and tests his theories on the dyno. While his stuff is mostly LS related, I think the basic principles apply.

 

Thanks, so pehaps I just LS Swap the mini? I'll check out those vids!

 

Larger valves only really benefit your power potential if accompanied with port work.

The factory JCW head is basically a stock head with a slightly larger exhaust valve, and it creates more power, but that is only in conjunction with the smaller pulley as well. And since many have met or beat JCW numbers with just a pulley change, it stands to reason that the valve size alone has minimal advantages.

Besides most people not wanting to dive into the technical aspects of head work when it comes to valve sizing, the reason most of us went the "simply purchase a head" route, is the porting. Remember the ports don't just need to be larger, there is also shaping involved, and very few have the time, patience, money and skill, to do the experimental leg work involved in porting the head of a low volume/demand engine.

Bottom line, I wouldn't worry about the larger valves, unless your going to attempt porting.

 

Thanks for the perspectives - I've learned a lot the past few days on just how many variables are at play when it comes to head work. And it seems that TPR2rT works great for your set up, what a sweet ride!

 

Funny. Someone actually did that. There's video on youtube somewhere. I was not properly set up and was relatively gutless.

 

A stock rebuilt head will set you back up to $1,100. Way wants $2,400 for a stock JCW head. Thumper's TPR-2 head is evidently so expensive they won't even list a price online. Question to ask yourself: Are larger exhaust valves going to add enough power to justify the HP per $ cost?

 

^^ Actually, the Thumper website shows the TPR1 @ $1295, the TPR2 as "retired", and the TPR2R @ $2195--- not that any of this is relevant as Outlandish already has a ported head in hand and plans on adding a cam as well, hence the reason to consider these last little pieces to finish it out.

 

This was fun, but I landed with the stock valves and went to the machine shop with the new rocker caps and my Newman Cam today. I can't find indication of a massive HP improvement (if much of any) with larger valves and my state of mods - e.g. no massive turbo - and to your point @cooper48 why spend money on speculation?

Based on continued readthough on posts on cylinder heads, I'll still claim success even bringing up this topic without judgment and drama, particularly since it's a hand-ported (very nicely, IMO) effort and not some CNC machined masterpiece that costs more than the price of my ride. And in the end, I do know that Miniman Adam's R53 with the same port work to the head, intake manifold, supercharger (plus a whole lot of additional mods) but no change on the valves was one of the fastest cars I've riden in. Dynos don't lie and I can't wait to see what it tells me.