I was just reading about the HKS forged piston and rod set. I think HKS kind screwed themselves with this kit.
Firstly, the whole point of this kit was to be able to fit it without having to balnce anything in the engine because the weight of the pistons is the same as stock, and the weight distribution of the rods is the same as stock. But here's the stupid part, the pistons are 95.7 bore, and the stock bore is 95.5, so your going to have to get the block sent of to be bored out 0.2mm. If you've got your engine appart already, then it does't take much more effort to get the crank balanced!
Second, if your going to make forged rods for forced induction, i would try and make them a bit beefier, because the HKS ones look almost like stock! HKS website in Japan, claims their good for about 500 ps, isn't that just a little bit more than what the stock ones hold?
Sounds like HKS screwed up there in my opinion. What do you guys reckon?

 

95.7 mm bore is gives the engine a better balance with the stock crank. so there is nothing wrong there. Unless you are doing stroker kit you dont really wanna do full max bore with the stock crank
IF you are building your engine you will have to get it machined anyways jsut like most pistons in the market for the vq currently anyways
2, basides the look the pistons come with some very good rings which is where a lot of the strength is...
IN any case this is a good setup for the balanced mid level FI build of a full n/a race engine.
I dont think they screwed up based on the points you raised. The fact that they are not so beffier and they are lighter is because they aim at allowing you to raise the rev limiter too.
YOu do sleeves with this setup and it can be pretty bad ***

the only thing that sucks for US peeps is ovbiously the price.

 

I don't understand what you mean by giving the engine a better balance. Your still going to have to bore the cylinder, even if it is only a small amount. So what i'm saying is that if your going to bore the cylinder, it won't take much more to balance the crank at the same time.
I suppose what i'm trying to get at, is that is HKS put so much effort into get the weight and balance of the piston/rod, to not have to balance the crank, then why not also make it stock bore, so it make them virtually a bolt on opperation?
Don't get me wrong, by no means am i saying that HKS is crap and doesn't know how to do things, i'm just saying, that if your going to do forged internals then make them to withstand more than just 500 ps, and just have the crank balanced whilst your getting the cylinder bored out.
Don't you think?

Oh, and i was referring to the rods being beefier, not the pistons.

 

The only way to ensure the clearances are correct is to have a slight overbore. No way could they put out a stock bore kit and have it have any sort of real success on the street.

 

I agree with you Zivman, all i'm saying, is that if they went through the effort of making them balanced, then maybe find a way where you don't have to bore the cylinder. I know you can install stock bore pistons without overboring, but it just isn't recomended, but still possible.

 

not really possible.

If you were to have a brand new block that you were putting them into, it may be possible. Even then, you would need to measure cylinder specs and match to the pistons

 

If you don't find it necessary to do the proper machine work prior to rebuilding the engine, you shouldn't take it apart and rebuild it period..

You might as well reuse you old rod and main bearings as well and your old headgasket too while you're at it.

 

I don't really understand your concern, if you have the engine down to the level of disassembly required to replace rods and pistons you should get it balanced anyway you will have to have it at the machine shop for bearings anyway, you will be spending a lot of money already what is a couple of hundred bucks to do the rest of the job right. If they are making so that the weights are close to stock is to help you in balancing and reduce the amount of material needed to be removed from the crank to balance it, also if you are building the engine you want it balanced anyway, those guys balance it way more than the stock factory does so you can rev higher without concern.

As for the bore size, most people will be rebuilding a used block so it is always advisable to machine it 20 over to get a clean smooth surface to break in your new rings on, they are not doing anything different than any other rod or piston manufacturer, the benefit from them I guess is that you are buying a complete set of rods and pistons rather than getting different manufacturers and they do quality stuff.

 

I agree with you. If a was going to rebuild my engine, then i would just balance the crank and bore out the cylinder. I don't think anyone is reading what i'm writing. If HKS is making forged parts, then why not make them hold more than 500ps. That is what i'm trying to get at!
If were going to have to bore the cylinder, and as westpak says, perhaps balance the crank only a little bit, then what is the benefit of making forged internals that don't hold more than 500ps, because it sure as hell isn't saving money!

 

thansk for replaying westpak and Zivman, ovbiously the OP need to do a lil more reserach how engine build work with the VQ. A light overbore is needed on teh block to get it to best balance ratio... that is the strength of the supra engine, other than being stronger in internals it comes perfectly balance from factory, thats why they can run 700-750whp on stock block

"advisable to machine it 20 over to get a clean smooth surface to break in your new rings on"
i couldnt agree more...


Only think i said is the price on this is a lil steep but then again this pistons and rods are designed to work together so they are not bad at all....jsut for the US its too expensive

 

I do find it necessary, and if i was going to build my engine, then i would most definitaley bore and balance!

 

Oh please, don't lecture me. I know exactly what is necessary when doing a build. All i'm trying to do is discuss the benefits of this set, and try to understand why they didn't make them hold more power

 

beacuse the range tat thsi handle is enough for a mild fi build that cna rev quit high because the internals besies being forged they are also lightwheight
The rings are very nice on those pistons, the Connecting Rod Bolt is custom to the specs of this setup which gives it good strength too.....
again the price is not nice... but this are not design to have a 1500whp motor......the 500 ps that each too btw you gotta X6

 

they are not designed for it... its design to have a 350whp high rev n/a engine....or a 500-550(maybe 600) whp high rev FI build.
and besides how beffy they are there are other things that make this setup strong too like the rigns and rod connecting bolt which looks bigger than most applications.

 

Good point, where did you see that? I looked on the website and didn't see any details as to power, let me know and I will ask our rep as well for more info as I know someone here already interested. I know their parts may be pricey but their quality is great, I am running their headgasket as well as the Fcon.

 

Its on the japanese site, give me a minute and i'll get it for you.

 

Ok, if you go to hks-power.co.jp, and on the tab on the left go to engine, and scroll down until you see the picture of the VQ35 internals and click on it you will see at the top it says 500ps. I used google translate to put it in english:

* Merit - While strengthening the weak point 500PS and 7200rpm as a supposition, considering the total cost which becomes necessary for the whole [chiyun], it has become the kit design which held down price. - The forging piston compression ratio 9.0 (G/K t=0.7mm) makes [rokonpu] specification, corresponds to supercharger [chiyun]. - As for the connecting rod using the private I section forging material. As for the balance taking of the V6 crank the private jig becomes necessary, but weight balance of the small end large end by the fact that it makes genuine similar, without processing the genuine crank you install and I section connecting rod set it is possible. - The connecting rod small end can consider strength, because tilt processing is not done, cannot use with the genuine piston. Please use with the HKS forging piston and set. - High intensity volt/bolt is adopted to connecting rod volt/bolt.

 

Trust me it is possible. NOT RECOMMENDED, but still possible. I have rebuilt countless Yamaha outboard engines (4 cylinder and V6) with new pistons and without borring the cylinders, only honing them, and there still running strong today. And marine engines get used and abused all day long, not to mention there harsh environment.

 

I don't think its 500 per piston/rod, that would make them able to withstand 3000 ps. I somehow doubt that.

 

???