bonkas Posted November 9, 2017 Share Posted November 9, 2017 Hey Guys, I need your thoughts on some new forged pistons I had arrive today for my 4g63 build. I put the order through the Ross piston agent here in NZ as they were recommended to my by local engine builders and also a few friends. My specific instructions were that I needed to save weight where I can as I am looking at spinning much higher RPM, Need a 10cc dome to obtain the CR I want and 1mm oversize. My head got measured up and specs of new valves, potential lift/duration etc and the order was placed. What I got back was not what I expected... They only contain a 7cc dome (they machined a 10cc dome but with the valve pockets this has come down to 7cc) They are identical/pretty close to the original - no weight savings as far as I can tell My calipers are not with me at the moment but they appear to be 1mm oversize - Th is correct as I asked for 1mm oversize. There is a significant weight difference - 363g Stock 445g Forged The few people I have shown the pistons who build race engines for a living have referred them to a "lawnmower piston". This has gotten me a bit down on the big plans I had as these pistons cost me a pretty penny and at this point I just want to give up on the whole project as everything revolved around these pistons. It really comes down to 2 questions... Will these still be suitable for higher RPM. I was hoping 8-9k but higher would be a bonus. Is the weight difference anything to be concerned about? Here are some pics: Quote Link to comment Share on other sites More sharing options...
Mr Vapour Posted November 9, 2017 Share Posted November 9, 2017 When I was selling ross pistons, anything custom like this required a schematic drawing. Did you provide one? Have they just supplied you shelf pistons with machined pockets.? I would be walking them back in with a copy of the communication you had with them and ask them if they fell what you ordered is what you received. Quote Link to comment Share on other sites More sharing options...
RUNAMUCK Posted November 9, 2017 Share Posted November 9, 2017 Someone once mentioned to me that ross slugs were heavy. Nothing further to add. 1 Quote Link to comment Share on other sites More sharing options...
Yowzer Posted November 9, 2017 Share Posted November 9, 2017 How specific were you? Did you tell them you wanted them lighter than the factory 360g? Those pistons look like they'd handle a tonne of boost happily though. 1 Quote Link to comment Share on other sites More sharing options...
Roman Posted November 9, 2017 Share Posted November 9, 2017 This is going to be an NA build right? How much is that 3cc going to change your compression ratio? It's not going to make or break your engine in my opinion. But, it comes back down to the correspondence that you had with them initially. If they gave them to you 1mm oversized compared to what you asked for, I'd be sending them back. 1 Quote Link to comment Share on other sites More sharing options...
Roman Posted November 9, 2017 Share Posted November 9, 2017 Not busting your balls here, but curious as to why you chose to start with a 3 valve head when there's a common 4 valve head available that I'd imagine is a better starting point? Like you might not make power to 8-9k anyway. (again to reiterate... Not criticising just curious) Quote Link to comment Share on other sites More sharing options...
Yowzer Posted November 9, 2017 Share Posted November 9, 2017 Make 'em beefy, machine down if the strength isn't required perhaps? Quote Link to comment Share on other sites More sharing options...
fuel Posted November 9, 2017 Share Posted November 9, 2017 8 hours ago, Roman said: Not busting your balls here, but curious as to why you chose to start with a 3 valve head when there's a common 4 valve head available that I'd imagine is a better starting point? Like you might not make power to 8-9k anyway. (again to reiterate... Not criticising just curious) It's not even a three valve head he's using - the SOHC 8V 4G63 has the exhaust valves not symmetrical - so cylinders 1 & 2 and 3 & 4 are grouped together. The piston has both cut outs machined/cast to accommodate all cylinders. This is also why the Sirius DASH 3x2 12V engine has 4 valve reliefs on the pistons too. Quote Link to comment Share on other sites More sharing options...
fuel Posted November 9, 2017 Share Posted November 9, 2017 also, as I've said before - a SOHC 8V 4G63 especially with its stock bore/stroke & rod/stroke ratio doesn't lend for high revs. Combined with a heavy bottom end they are best for low/mid range torque and strength which comes in handy for turbo applications. I would look at finding a 4G64 block which has the 86.5mm bore, possibly bore it out to 87 or 87.5mm if you're daring (probably do-able with N/A but not for turbo), and then fit the 4G63 88mm crank instead of the 4G64 100mm crank, and then fit off the shelf long rods and potentially pistons with the wrist pin height increased. This would bring the bore/stroke almost square and most importantly the rod/stroke ratio is much much better than stock that revs better and has less harmonic vibration. 9 Quote Link to comment Share on other sites More sharing options...
mjrstar Posted November 9, 2017 Share Posted November 9, 2017 1 hour ago, fuel said: . I would look at finding a 4G64 block which has the 86.5mm bore, possibly bore it out to 87 or 87.5mm if you're daring (probably do-able with N/A but not for turbo), I wouldn't push it to 87.5 even for NA. if you want to pull 8000-9000 rpm reliably a 4g63 is not your best option, have you considered a 2zz,13bt, 4g92 mivec, K20 etc.. / barra conversion 5 Quote Link to comment Share on other sites More sharing options...
Roman Posted November 9, 2017 Share Posted November 9, 2017 2 hours ago, fuel said: also, as I've said before - a SOHC 8V 4G63 especially with its stock bore/stroke & rod/stroke ratio doesn't lend for high revs. Combined with a heavy bottom end they are best for low/mid range torque and strength which comes in handy for turbo applications. I would look at finding a 4G64 block which has the 86.5mm bore, possibly bore it out to 87 or 87.5mm if you're daring (probably do-able with N/A but not for turbo), and then fit the 4G63 88mm crank instead of the 4G64 100mm crank, and then fit off the shelf long rods and potentially pistons with the wrist pin height increased. This would bring the bore/stroke almost square and most importantly the rod/stroke ratio is much much better than stock that revs better and has less harmonic vibration. God I love reading your Mitsi posts. 4 Quote Link to comment Share on other sites More sharing options...
bonkas Posted November 10, 2017 Author Share Posted November 10, 2017 Sorry I was not very clear in my initial post.... I ordered the pistons 1mm oversize as I am increasing the bore size. @fuel I chose to keep what i've got (SOHC 8V 4G63) because that's what I have and to see what I could make of it, I am well aware of other options but wanted the experience of the build/modifying process and wasnt shooting for huge numbers but doing what I could with what i have. Your advise is always spot on and informative, even if I dont follow it haha... before I started the build you did advise a different head but I wanted to go ahead with what i had. @nzed No I didnt weigh with the pin as it never got sent back to me! so I dont have one to measure with I was hoping it didnt weigh enough to matter a huge amount. Will track one down and measure again, I do understand this will skew my weights. The total weight of the rod, piston and pin wont be too much different drom stock as my new forged rods are ~150 grams lighter than stock but I was really aiming for a lighter assembly. @Roman I had sent a few emails but got no reply so most discussion was over the phone (This guy is oldschool), I was pretty specific about weight savings and the dome I wanted. The head for the engine was in Christchurch having work done and the Piston Agent/Engineer was also located in Christchurch so he took a look at my head and took all required measurements to put through the order, I had no expertise in this regards so left this up to him. I am confident I can make up the 3cc after the head and block are decked when ready to be put together anyway. 3 Quote Link to comment Share on other sites More sharing options...
Roman Posted November 10, 2017 Share Posted November 10, 2017 Oh man engine builds are exciting. (Even if stuff never goes to plan) Look forward to seeing this come together. Stick at it! 1 Quote Link to comment Share on other sites More sharing options...
Testament Posted November 12, 2017 Share Posted November 12, 2017 Did you fill out the ross spec sheet form yourself? or send your specific instructions in an email or letter? did you see what the agent filled out and sent to ross? http://www.rosspistons.com/wp-content/uploads/2016/08/Order-Form.pdf my guess would be the fault is with the agent as im pretty sure ross would have required that form and made to meet that spec. But if you don't have any of those things in written form the agent could be real a dick about it if they are and old hat belligerent barry im the race parts guy and I know best kind of crowd. the dome size is not that big of an issue but +1mm and 30% heavier than the stock piston is not really acceptable if you asked for lightweight n/a for high rpm and stock bore. Quote Link to comment Share on other sites More sharing options...
bonkas Posted November 14, 2017 Author Share Posted November 14, 2017 On 11/13/2017 at 09:14, Testament said: my guess would be the fault is with the agent as im pretty sure ross would have required that form and made to meet that spec. But if you don't have any of those things in written form the agent could be real a dick about it if they are and old hat belligerent barry im the race parts guy and I know best kind of crowd. the dome size is not that big of an issue but +1mm and 30% heavier than the stock piston is not really acceptable if you asked for lightweight n/a for high rpm and stock bore. That is exactly the problem, sent numerous email but received no useful replies due to "I hate the computer, I dont go near them, my wife does the computer stuff" so everything was organised over the phone. I can imagine having a hard time convincing him of anything so I have not yet contacted him about it. The dome size is something I can get around bu decking the block and a head skim and modifying the pistons to suit - The reason I ordered custom pistons in the first place was so all this could have been avoided. I did order 1mm oversize, this is the only chinese whispers that got through correct to the manufacturer.. I should edit my initial post. 1 Quote Link to comment Share on other sites More sharing options...
Mark_Fleming Posted December 8, 2017 Share Posted December 8, 2017 lighter wrist pins are available.... Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted December 9, 2017 Share Posted December 9, 2017 This is exactly why doing everything in writing is so great. Humans are good at making mistakes.. Quote Link to comment Share on other sites More sharing options...
bonkas Posted December 21, 2017 Author Share Posted December 21, 2017 Turns out it has ended up not too bad. With the new rods, gudgeon pins etc the whole piston assembly ends up lighter than the old gear so a little win there. Also with the new valves which have gone into the head, this has decreased the chamber volume and my compression ratio has raised beyond what I wanted (10.8 instead of 10.5) it's getting a little high and I want to run regular pump gas. Good thing I didn't get the original 10cc dome I asked for or the CR will be way way high. 3 Quote Link to comment Share on other sites More sharing options...
Roman Posted December 24, 2017 Share Posted December 24, 2017 If youve got big cams then high cr should be fine/needed? Do you know what dynamic CR is with that cam. Quote Link to comment Share on other sites More sharing options...
fuel Posted December 24, 2017 Share Posted December 24, 2017 I think 10.8:1 instead of 10.5:1 isn't going to make much of a difference, it will mostly come down to the tune and the specifics of the fuel delivery. Engine/cylinder head temp, injector spray pattern, fuel and spark timing etc will all have more influence on knock/pinking than a 0.3 increase in CR. 1 Quote Link to comment Share on other sites More sharing options...
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