Oversize Valves - The easy way out

[Adam.Findlay]

OVERSIZE VALVES

A bit more prodding into evo compatibility on my part has turned up evo valve similaritys

Evo Inlet Valve
- Diameter = 34mm
-Length = 110mm
-Stem diameter = 6.6mm

Evo Exhaust Valve
-Diameter = 30.5mm
-Length = 110mm
-Stem diameter = 6.6mm

followed by 6A13TT valve measurements

6A13TT Inlet Valve
- Diameter = 33mm
-Length = 104.8mm
-Stem diameter = 6mm

6A13TT Exhaust Valve
-Diameter = 28.2mm
-Length = 104.8mm
-Stem diameter = 6mm

This Possibly means 6A13TT heads can take evo or aftermarket evo titanium or billet valves with a re work of the valve seat and chainging the valve guides to accept the bigger valve stem of the 4G63T valves.

the inlet evo valve fits easily within the standard 6A13TT valve seat so only a regrind of the valve seat and valve guides would be needed on the inlet side. however on the exhaust side it is a tighter fit but I think it is possible in the limits of the stock valve seat. I Still have to take the head into a cylinder head specalist to get their opinion on the matter.

If We can use evo valve guides with evo valves. that means we can use aftermarket evo dual valve springs. dual valve springs require their own special retainer and due to our engines having the 4G93T valve stem size, we cannot use 4G63T retainers on our standard valves. Main reason for pushing to use evo stuff is easy aftermarket support to easily make the heads safer to rev higher without valve float aswell as making the heads breath better throughout the rev range, helping with Volumetric Efficency therefore more power

there is also aproxx 5mm difference in length between 4G63T and 6A13TT valves, however this should be taken up by the lash adjuster, especially if used in conjunction with a cam regrind as the cam regrind makes the base circle of the cam lobe smaller to get larger lift from the cam. see here ----http://www.clubvr4.com/forum/showthread.php?60575-EOI-Aftermarket-cam-grinds-and-Valve-spring-group-buy&p=675147#post675147

Pictures of valves compared next to eachother are featured in the above linked thread.

[Spetz]

Being a turbo car I think it is important to have the exhaust flowing very freely. Judging by the intake and exhaust valve disparity in the 6A13TT I would say it would be very beneficial to use larger exhaust valves.
However, jumping 6mm to use Evo valvetrain? I think you would run into complications

[Adam.Findlay]

yes i do beleive it to be inportant to get the exhaust gasses flowing as fast as possible but cannot neglect the inlet valves either,
where did a mention there being a 6mm difference in size. the largest size difference was in the stem length of 5mm longer with the evo valve but as i mentioned if used in conjunction with the reground cams i have been looking into in the thread linked above the ground down cam lobe in combination with the hydrauluc lifter should more then compensate for this change.

[Gowf]

6mm is a fair bit to have removed from the entirety of the cams... Also would you physically have room for larger exhaust valves in the 6a13 heads or are you going to start to get interference issues. Do you know what the level of overlap is on the standard cams? The reason for saying this is that after talking with Kev (HPRulz), he was of the impression that you would srtuggle to get anything bigger in there without serious reworking of the head. He did work for a company that make cylinder heads, and did make those for the TVR speed 12 I believe.

On the other hand if you can prove it works its a significant step forward and its this level of boundary pushing that I like

[Adam.Findlay]

Yip i understand all of this so far i have just done measurements of corresponding parts, i will be taking the valves and head into the cylinder head specalist. im not 100 percent confident that it will all work but the evo valves will definatly fit within the stock vr4 seats so that with a bit of port work will gain a bit more flow.
its just a matter of getting the tool to knock out a valve guide and test fit a evo guide and then see if the extra stem length is doable or not. the possibility of grinding a few mm off the end of the evo stem is there also!

[Gowf]

I do agree, it would be easier to machine the valves than the cam. You're bang on with the port work though, there is so much metal that can be removed. I keep meaning to start to do mine, but just never get round to it.... I cant see me ever finishing this new engine build any time soon, esp when people keep offering me 5.7 chevys

[Adam.Findlay]

ha yeah well if you read the linked thread above (bottom of first post) I am looking at getting a local christchurch business to regrind my stock cams to get 264 duration and 10.5mm lift. that will already reduce the size of the cam lobes base circle so any extra material that needs to be lost can be lost off the end of the valve stem

[Spetz]

It depends on the power level you're trying to achieve to be honest.
The inlet valves seem fine in size and to be honest considering you are forcing air in I think the higher velocity of air would yield better results than the possible restriction.
With the exhaust valves I meant that with 5mm oversize in diameter you will need to adjust the port sizes etc to match and the head design may not allow you this.
I also think that it is important to mention that bigger is not always better and in things like turbo applications I think in many cases people get carried away and overdo things which in the end make their car either slower or at the very least less drivable. For example many people use huge intercooler piping when in reality something smaller would give better response and better torque.

[Adam.Findlay]

no if you re read the measurements the exhaust valves are 2.3mm bigger in DIAMETER not in radius 5mm oversize valves would be hugely excessive IMHO you always want the inlet bigger then the exhaust because the pressure of the piston forcing the exhaust out will almost always be higher then any amount of boost you are trying to push into the cylinder,
and yes I fully understand the tradeoff's of flow in total volume vs inlet charge velocity.
to get you up to speed with my plans i intend to build and engine supporting 2 GT2860RS turbos and getting as much powerband from those turbos as possible so trying to acheive 10,000rpm, stock ports valves although may be close will be getting close to if not exceeding their maximum flow

[Spetz]

I don't understand, your first post stated that the Evo exhaust valve diameter is 34mm and the 6A13TT exhaust valve diameter is 28.2mm?

Also 10,000rpm in my opinion is not achievable because of the hydraulic lash adjusters.
You would be much better off using the MIVEC heads which have solid lifters and you can use 2 cam lobes to both help spool the turbos and also be able to make power at 10,000rpm + the MIVEC heads should, with accompanying modifications, be safe to rev that high, 900rpm more than standard to be exact anyway

[Adam.Findlay]

haha oh wow doesnt that make me look like a idiot, typo there the evo exhaust valve is 30.5mm

[Adam.Findlay]

not intrested in doing a mivec conversion as going to a 2 litre head will further restrict flow (theoreticly i dont know the port sizes)
there are the haters out there but Im mainly doing it because i want to not because its the easiest option. I am aware that the lifters have a high chance of colapsing with a agressive valve spring and cam but i will tackle that problem when i get there. anyways back to the thread topic of oversized valves. just need a valve guide remover. might try and fabricate one this weekend

[Spetz]

I agree with you and applaud your effort but the problem is too often people start something with so much enthusiasm but somewhere down the line interest is lost and so is motivation, especially on something which will clearly pose a substantial challenge.
Nonetheless I am very interested in this build so please do keep us posted.
Have you considered building the bottom end first and all accompanying mods and leaving the heads last? That is how I plan to do it however I am building an atmospheric engine

[Adam.Findlay]

yes i have all parts planned out i do hope it all does not become to overwhelming but as i have a spare engine to build up instead of constantly taking the working motor in and out of my wagon that takes alot of the stress off things.

my build thread here
-http://www.clubvr4.com/forum/showthread.php?54099-And-it-begins-the-6A13TT-tear-down-and-build-up-thread!!&highlight=6a13t+teardown

thread about cams here
-http://www.clubvr4.com/forum/showthread.php?60575-EOI-Aftermarket-cam-grinds-and-Valve-spring-group-buy&highlight=6a13tt+teardown+and

info about forged cranks
-http://www.clubvr4.com/forum/showthread.php?59315-Forged-Cranks-interest-and-information&highlight=forged+cranks

[Spetz]

Thanks Adam I have glanced over your build thread and the cam gear stuff.
I have searched for 4G93T cam gears and they are indeed cheap but are they any good?
Also, with your dealings about regrinding the cams, did you price the possibility of billet cams? I recall in Australia I spoke to tighe cams and was quoted $1,700 AUD for billet MIVEC cams

[psbarham]

having spent many many hours playing with various heads over the years i do beleive you are pissing in the wind with the 6a13 heads without spending some serious cash.

There isn't enough room in the combustion chamber with increased lift and duration on the cams to get much more than 1.5-2mm + inlet valves in there, there is an option though, ofset valve guides, and some serious valve seat work.

Also i think with the valves themselves, it would be easier and cheaper to get a local engineer to make some custom stainless ones made up to suit.

[Spetz]

psbarham, can you comment on the MIVEC heads at all?


Adam, as much as it saddens me to say, I think you have to set more realistic goals to save yourself from wasting lots of money and save yourself from disappointment.
I say this from experience, because I too at some stage wanted to be different, and do something that hasn't been done, and show the other car manufacturers what Mitsuishi etc can do, but the sad fact is as time goes by you star realizing that you could have spent half the money and been twice as fast. And yes in the excitement of the moment this may not mean much but it is something that in due time will hold grave value.

I was reading the post about the forged cranks, and the owner of the 600hp FTO himself said that pushing more hp was not possible. And he made a decision that it would be more financially viable to cut his losses on his 6A13TT build and use a 4G63T. So, it was more financially viable to lose out on his megabuck 6A13 build AND build a 1,000hp Evo motor than it was to extract another 30% more power.

I hope you do not misunderstand me in any way, I am simply giving you my advice from being in a similar stage around your age (I read you are 21 in another thread).

[Kenneth]

6a13
Inlet Valve area = 33.20% of bore area (+1mm in valve diameter (Evo valves) will boost inlet valve area to 35.24% of bore area)
Exhaust valve area = 24.24% of bore area

4G63
Inlet Valve area = 32.00% of bore area
Exhaust valve area = 25.75% of bore area


Yes, bigger is better. However since the job of the valve is to allow the cylinder to fill, I feel you should be paying more attention to the valve area in relation to the cylinder bore.
Compared to 4g63, 6a13 also has a shorter stroke, resulting in less piston speed for any RPM which will result in less suction on the valve.

The 6a13 is very good at the RPM it is tuned to. The intake is tuned to around 4000 RPM and that shows. I did a model of boost vs torque (from a number of dyno plots) and the only way I could get a good model was to run VE of ~110% at ~4000 RPM. There is no wonder that Gareth had a HUGE torque curve with TD04s.

I don't see (in terms of the cylinders) why the 6a13 cannot run very well at decent RPM, provided that the work is done on the inlet and outlet to support it. You are definitely peeing into the wind if you were to use the standard intake and expect to rev high.

Here is a interesting comparison
Suzuki Hayabusa
Bore 81
Stroke 63
Inlet Valve 33mm
Exhaust Valve 27.5

Peak power 9500–9750 rpm

[Adam.Findlay]

Thanks Adam I have glanced over your build thread and the cam gear stuff.
I have searched for 4G93T cam gears and they are indeed cheap but are they any good?
Also, with your dealings about regrinding the cams, did you price the possibility of billet cams? I recall in Australia I spoke to tighe cams and was quoted $1,700 AUD for billet MIVEC cams

didnt bother looking at billett ones as regrinding stock cams will give more then enough lift and duration

having spent many many hours playing with various heads over the years i do beleive you are pissing in the wind with the 6a13 heads without spending some serious cash.

There isn't enough room in the combustion chamber with increased lift and duration on the cams to get much more than 1.5-2mm + inlet valves in there, there is an option though, ofset valve guides, and some serious valve seat work.

Also i think with the valves themselves, it would be easier and cheaper to get a local engineer to make some custom stainless ones made up to suit.

have priced custom valves from the local cylinder head specalist and at $40 per valve and 24 valves it adds up pretty fast, and you still have to add head maching ontop of that so easier to buy 1.5 sets of evo valves @ ~$270 USD a set and get 1.5 sets of evo valve guides ~$80USD a set

psbarham, can you comment on the MIVEC heads at all?


Adam, as much as it saddens me to say, I think you have to set more realistic goals to save yourself from wasting lots of money and save yourself from disappointment.
I say this from experience, because I too at some stage wanted to be different, and do something that hasn't been done, and show the other car manufacturers what Mitsuishi etc can do, but the sad fact is as time goes by you star realizing that you could have spent half the money and been twice as fast. And yes in the excitement of the moment this may not mean much but it is something that in due time will hold grave value.

I was reading the post about the forged cranks, and the owner of the 600hp FTO himself said that pushing more hp was not possible. And he made a decision that it would be more financially viable to cut his losses on his 6A13TT build and use a 4G63T. So, it was more financially viable to lose out on his megabuck 6A13 build AND build a 1,000hp Evo motor than it was to extract another 30% more power.

I hope you do not misunderstand me in any way, I am simply giving you my advice from being in a similar stage around your age (I read you are 21 in another thread).

I understand all this and yes I am young but (without sounding cocky here) consider myself pretty clued up on engines and the like, being a mechanical engineer student I have developing materials know how.
as I said they are just "goals". I will be more then happy to settle for 500hp if the stock crank cannot handle more, with when I finish my degree and get a propper paying job i can afford extravigant parts such as forged cranks and the likes. but for now i can live with scale back the build for cost purposes, in saying that I am in no rush I have an open ended timeframe to complete my project.

Richard or ZENTAC does have in my opinion (hope I dont get flamed for this) a bit of a jaded opinion on the 6A13tt, yes he had a forged shortblock and bigger cams with a huge turbo, but he also used standard valves with standard plenum so he didnt really fully explore the limits although he did highlight some weaknesses while he was at it. must have just hit the 600 number and given up.

but the main point of most of these threads is for the greater good of the club, finding different more cost effective ways of modifing the 6A13TT for anyone who is willing to take on such extensive modification. hopefully be able to keep up to some of the 1jz/rb26(25) guys

[Adam.Findlay]

6a13
Inlet Valve area = 33.20% of bore area (+1mm in valve diameter (Evo valves) will boost inlet valve area to 35.24% of bore area)
Exhaust valve area = 24.24% of bore area

4G63
Inlet Valve area = 32.00% of bore area
Exhaust valve area = 25.75% of bore area


Yes, bigger is better. However since the job of the valve is to allow the cylinder to fill, I feel you should be paying more attention to the valve area in relation to the cylinder bore.
Compared to 4g63, 6a13 also has a shorter stroke, resulting in less piston speed for any RPM which will result in less suction on the valve.

The 6a13 is very good at the RPM it is tuned to. The intake is tuned to around 4000 RPM and that shows. I did a model of boost vs torque (from a number of dyno plots) and the only way I could get a good model was to run VE of ~110% at ~4000 RPM. There is no wonder that Gareth had a HUGE torque curve with TD04s.

I don't see (in terms of the cylinders) why the 6a13 cannot run very well at decent RPM, provided that the work is done on the inlet and outlet to support it. You are definitely peeing into the wind if you were to use the standard intake and expect to rev high.

Here is a interesting comparison
Suzuki Hayabusa
Bore 81
Stroke 63
Inlet Valve 33mm
Exhaust Valve 27.5

Peak power 9500–9750 rpm

/banana
very intresting. as I have mentioned with bigger turbos comes lag which is unavoidable, so to keep the same 4500-5000rpm power band the peak torque and horsepower figures will need to be shifted to the right. same ammount of useable power just up much higher
i do think that the evo exhaust valves will be a bit too big but a +1mm on the inlet cant be to bad especially to support my dream of 10krpm