neo vvl head

[The Doc]

Btcc cars and rally cars both had 54c heads and under homoglation rules could not be drastically modified, if the spring rates of the valve were correct and the correct installed heights used of them with good cams and correct shimming there is no reason why the shims can fall off , if all of the above is not done correctly or the parts have become worn and side thrust is introduced then you will have failure of rockers and or shims will break.
Also another point to mention is if revved to high of you have some other cause of valve float then you will throw rockers, some drag gtir and primera engines have been known to rev to 8.8-9k rpm with out issue on stock rocker designs too.

 

[The Doc]

54c cylinder heads are solid lifters as standard FYI .

 

[vpulsar]

99.9% of people on here would have no need what's so ever it's just a waste of money, I can understand how a couple of you might like to rev to silly levels to get the best out of your big turbo's but most of us wont gain anything to speak of, My head is getting a bit of a clean up some HKS cams and a Billet turbo that should be everything I need to put a grin on my face. I never rev my cars past 7k I don't like all the noise I prefer the low down grunt, I definitely don't want to spend another £2500 on something I wont ever get the benefit of.

But it's a good thread and shows what is possible.



Rob

 

[The Doc]

There are no limits to what is possible on anything, man would never have got to the moon if there was limits!

the issues we had in this country is false information with the gtir from people who could not build reliable cars, they then blamed the car when it was there lack of ability at fault.

 

[The Doc]

There are other things that I am able to enlighten people on with the cylinder head designs,rocker types and the like and it is surprising that what and how much is actually standard parts on other models.

 

[vpulsar]

they then blamed the car when it was there lack of ability at fault.

I've seen so many cars ruined by so called tuners like DP and co.

 

[Empty Pockets]

Never knew that Doc, So why are all the stories of thrown rockers out there at 7-7.5k rpm, i've read a few and i'm not talking about feeler shimmed jobbies.. Why are 99.9% of the cars limited/cut at 7-7.5k, even all the 500bhp fresh built one's rev to 7-7.5k, are they specced wrong head wise, can't recall any over that apart from Sams Tomie headed 2.2 which went 8k ? How would you spec a gtir head to rev to 8.5k reliably, and what sort of longevity would you expect, i thought solid lifters were renown for needing adjusting constantly, not ideal for a road car ?

 

[The Doc]

The race engines had hollow cams and no oil spray bars for less chance of the cam and rocker picking up (better oil flow), also the last variant of the sr20 had roller rockers and they are interchangeable with the correct cams (cam design is a whole new story) , but basically good uprated valve springs correctly set up with the right cams and the top end will go to 8.5k rpm, as for solid lifters needing to be checked reset often again a false assumption...yamaha's r1 has 25,000 mile service intervals on the valve train and that revs to 14.5 k rpm.....so a gtir with a properly shimmed head and regular oil changes should do at least 50,000 before needing checking, my own car I had before had 97,000 miles on it with a very good service history and that did not need shimming when checked by myself.

As for why are the cars at the moment not revving higher than 7.5k rpm that are making 500 +bhp! maybe because they are making a lot of torque and using wider ratios to make use of the power! I know red readings car is geared to do over 200mph.

 

[Empty Pockets]

Why would wider gear ratios impede rpm, you'd just have a higher top speed, why shorten your powerband unless it's unsafe or there's no power there ? Maybe it was an application specific problem , i remember my bro was warned off solid lifters on his 4g63 for the above reasons, and that guy does know his onions (unlike me).. So basically you're saying just a well built head will safely run 8.5k all day, which really asks the question why nobody does.. can nobody build a good head ? I know the GTiR's a cheapskate car, people would rather pay 200 quid to the bloke with a dremal than 1k to the guy with 30yrs experience, but surely they can't all be specced/built wrong ? Surely setting the nose and seat pressures is common practice for a good builder, i know when my bro had his cnc Rick wood head done they went through about 36 Ferria beehive springs just to get an equal pound set to start with, so what's the problem, is it really just a case of nobody can build a head ?? lol

 

[nismo gti-r]

Double guide conversion on rockers should also help.
proper valve springs matched to cam profile is a must.
i have been revving mine at 8000 for many many years without issues...
My dad's primera p10 gt with sr20de hydraulic lifter engine has seen 340000km and hit the rev limit at 7500 or 7800 rpm(don t remember) soooo many times and never had a problem.
Of course the ve head is better, hut gtir head is pretty good too

 

[The Doc]

If you have longer ratios and high torque and horsepower you don't need to rev an engine, that is all down to the tune and the width of the available power spread vs what you are doing with the car., we are diverting from the question.

People have built proper cylinder heads, they just don't post on here or i think you have answered your own question, no body has bothered to or been able to build a good head....well except nissan, as nismo gtir has said.

will post more on this tomorrow as I am tired.

 

[Empty Pockets]

Of course you don't need to, but if it's still making power you'll be slower shortshifting, so why would you if it's safe to rev high, especially as high hp is generally at the expense of lag, it makes no sense to me to unnecessarily shorten your powerband, if it made 500 at 7.k what would it make at 8k if it was built well enough to do so, a gt30-35 isn't done at 500bhp and 7krpm. Anywho, thanks for the info, it seems i've been scaremongered into keeping low revs, if i end up keeping my engine i'll try 8-8.5k, i know it's been built well, pressures set etc so in theory it should be capable.

 

[Makaveli_se7en]

Of course you don't need to, but if it's still making power you'll be slower shortshifting, so why would you if it's safe to rev high, especially as high hp is generally at the expense of lag, it makes no sense to me to unnecessarily shorten your powerband, if it made 500 at 7.k what would it make at 8k if it was built well enough to do so, a gt30-35 isn't done at 500bhp and 7krpm. Anywho, thanks for the info, it seems i've been scaremongered into keeping low revs, if i end up keeping my engine i'll try 8-8.5k, i know it's been built well, pressures set etc so in theory it should be capable.

Russ, the thing you'll need to look at with going over 8k is not the top end but the peak piston speeds. They'll be high as you're on a stroked crank. This is why I've gone over-square on an overbore so I can rev to 9k

 

[Empty Pockets]

Russ, the thing you'll need to look at with going over 8k is not the top end but the peak piston speeds. They'll be high as you're on a stroked crank. This is why I've gone over-square on an overbore so I can rev to 9k

Don't worry about that mate, i'm sure my r/r is ok for 8.5k, and i'm sure the hks silvia ran the kit at 9k iirc ? What's the length of a standard rod dude ?

 

[Makaveli_se7en]

Standard rods are 136.3mm is memory serves me correctly.

 

[Empty Pockets]

Cheers Ed, Also, i'd of thought the peak safe ps will change with the weight and strength of components used, pin height etc, i reckon ps would be the least of my worries revving to 8.5k, although i doubt i'd have the gonnads to try anyway. All good info though, just wondering why these 2ltrs are all done at 7.5k if they're capable of more, oh, and why Rob doesn't like long powerbands...... lol

 

[warpspeed]

This is great! don't get discussions like this on other sites.....;-)

 

[vpulsar]

oh, and why Rob doesn't like long powerbands...... lol

In the past I've had a lot of lazy V8 engine'd cars mate and I really like my power low down that's why I've chosen a small fast spooling turbo this time, One of the most fun cars I've ever driven was my brothers old VW motor sport G60 golf, That had instant power but could still push my skyline down the M3 at over 160 mph, These days I don't want to be doing much more than a 100 mph so getting to that point as quickly and quietly as possible is my aim lol.

But you guys can have all your Honda revs if you like, in fact why don't you stick a turbo charged Honda engine in the R job jobbed lol


Rob

 

[warpspeed]

Don't you start swearing now! :-D

 

[Empty Pockets]

In the past I've had a lot of lazy V8 engine'd cars mate and I really like my power low down that's why I've chosen a small fast spooling turbo this time, One of the most fun cars I've ever driven was my brothers old VW motor sport G60 golf, That had instant power but could still push my skyline down the M3 at over 160 mph, These days I don't want to be doing much more than a 100 mph so getting to that point as quickly and quietly as possible is my aim lol. But you guys can have all your Honda revs if you like, in fact why don't you stick a turbo charged Honda engine in the R job jobbed lol Rob

I'm only messing with you mate,and i don't think anyone's saying 'do it like this or it's rubbish', using Docs superbike analogy, I just pictured you in attack mode on an R1 granny shifting at 10k, shouting to anything that overtakes you 'I don't like big powerbands, they're pointless' lol