Larger Valves

[Drfatz]

I am about to start opening up the engine and checking the internals as well as resetting the valve clearances etc. It was suggested to me by John at WC to installer larger intake valves from the later 4 pots. Has anyone done this before and know what is involved? Also, is this even worth doing?

-Graham

[andydclements]

I am about to start opening up the engine and checking the internals as well as resetting the valve clearances etc. It was suggested to me by John at WC to installer larger intake valves from the later 4 pots. Has anyone done this before and know what is involved? Also, is this even worth doing?

-Graham

I bought a gas flowed engine recently, looks pretty good, got the gas flow reading plot etc, they didn't increase the inlet valve size, but did open the ports up a lot - not a great deal all the way along, but there is an area where thr flow is quite restricted, so it may be getting the ports re-worked would give more than just larger valves.

I guess the good point to updating to larger valves from a later engine would be the weight of them. If they're made from a better, lighter material they'll be less prone to bouncing or floating at high engine speed, was that the reasoning for the suggested change?

Andy

[Artie]

I am about to start opening up the engine and checking the internals as well as resetting the valve clearances etc. It was suggested to me by John at WC to installer larger intake valves from the later 4 pots. Has anyone done this before and know what is involved? Also, is this even worth doing?

-Graham

Graham,

My head has been rebuilt with the Sport 300 intake valves(same as S4s) and the later head gasket, I'm not really sure the mod is that effective until a larger turbo and gasket matched piping/inlet opening is fitted. Worth doing I am sure whilst everything is apart, more flow means more power down the road especially if you fit better pistons/rods, turbo etc, which I am assuming most of us will do at some point. The head is really the weakest link in these engines according to most experts.

Artie

[mwmackenzie]

I have larger inlet valves and fully flowed head and 107 cam, vernier pulleys a t35 hybrid turbo etc etc... Alluminium carbide coated piston crowns everything that spins has been ballanced, 680cc injectors, water injection, charge cooler, DTA ECU and other bits and bobs... Not sure of the results yet as it's still not ready.. Should be in the next couple of weeks though... hourah!! I'll keep you posted on how it drives and what knid of power i manage to get... Hoping for circa 350bhp with a whack of torque too......

[t70]

I may be talking out of my butt..a but a boosted engine generally responds better to bigger exhaust valves rather than intake. The reasoning is due to pressure differantials between the exhaust pressure in the cylinder and atmospheric vs atmospheric vs cylinder vacuum. That's why an intake valve is larger than an exhaust valve... This however, all changes when you add boost... the exhaust valve has to approach the same size as the exhaust valve as boost pressure increases because now the intake pressure is greater than atmospheric and the manifold back pressure is a bit greater than on a naturally aspirated engine but not by as much as the increase at the intake size...

[Drfatz]

I figured this would cause some debate. Well the valves are $380 for a set of 8 and then I would have to get the head machined. I plan on installing the nice turbo from WC as well as a HUGE chargecooler and some up rated injectors and a new ECM. I am looking to put 350 hp down at the wheels, so are the valves really worth it considering the other upgrades?

[Vulcan Grey]

I figured this would cause some debate. Well the valves are $380 for a set of 8 and then I would have to get the head machined. I plan on installing the nice turbo from WC as well as a HUGE chargecooler and some up rated injectors and a new ECM. I am looking to put 350 hp down at the wheels, so are the valves really worth it considering the other upgrades?

The larger intake valves were used in the S4s and Sport 300.

IMO the risk of machining the head correctly may not be worth it... would not be worth it to me.

In my experience the Lotus 910 head is very difficult to machine correctly, due to it's irregular surfaces and very little clamping area. To machine it correctly would require a fixture that locates off the cam tower surfaces. Something that most machinishts would not do.

I had two machinists distort and taper my head doing a routine skimming operation. The second one did it even after I told him what the problem is. A distorted tapered head will cause the belt to run towards the edge of the cams and may cause premature failure or a really annoying whine sound.

The valve seats are the same from the SE-S4s, but they are cut differently on the S4s and Sport 300 intake seats. The intake Valves are different as well.

Head diameter - inlet - s4 3 5 . 4 7 - 35.65 mm (1 .396 - 1.404 in)

- S4S & Sport 300 3 6 . 3 7 - 36.63 mm (1.432 - 1.442 in)

lnlet fhroat diameter:

S4 & GT3=31 mm

S4S & Sport 300 = 32 mm

inlet valve seat gauge.

S4 & GT3 = 33.53 mm

S4S & Sport 300 = 34.68 mm

S4S & Sport 300 bored inlet throat

inlet valve seat width = 2.0 mm

Then Lotus always marks the RH rear end of the cylinder head with "S300"

[Artie]

The larger intake valves were used in the S4s and Sport 300.

IMO the risk of machining the head correctly may not be worth it... would not be worth it to me.

In my experience the Lotus 910 head is very difficult to machine correctly, due to it's irregular surfaces and very little clamping area. To machine it correctly would require a fixture that locates off the cam tower surfaces. Something that most machinishts would not do.

I had two machinists distort and taper my head doing a routine skimming operation. The second one did it even after I told him what the problem is. A distorted tapered head will cause the belt to run towards the edge of the cams and may cause premature failure or a really annoying whine sound.

The valve seats are the same from the SE-S4s, but they are cut differently on the S4s and Sport 300 intake seats. The intake Valves are different as well.

Head diameter - inlet - s4 3 5 . 4 7 - 35.65 mm (1 .396 - 1.404 in)

- S4S & Sport 300 3 6 . 3 7 - 36.63 mm (1.432 - 1.442 in)

lnlet fhroat diameter:

S4 & GT3=31 mm

S4S & Sport 300 = 32 mm

inlet valve seat gauge.

S4 & GT3 = 33.53 mm

S4S & Sport 300 = 34.68 mm

S4S & Sport 300 bored inlet throat

inlet valve seat width = 2.0 mm

Then Lotus always marks the RH rear end of the cylinder head with "S300"

Ahh! That was your annoying whine Travis? I remember reading that in your blog last year some time! Makes perfect sense. So you had the head re remachined and they messed it up again?

Artie

[t70]

Interesting about the machining... It's good to know if i have to plane mine in the future. The other thing a guy could do is put 0.5mm over size valves in and do some mile port work with a gasket match and probably be just as effective if not more so. If you do 0.5mm over-size valves, you can use your original seats, therefore you wouldn't need to do any machine work on the head. Port work is not that hard to do and I can scan the instructions on how to build your own flow-bench. I build my own and ported my 5mge supra head from 185 cfm stock to 252 cfm with no more than a 10 cfm difference from worst to best port. Here's a pic or two of my flow bench:

and then some port work too....

The flow bench cost me about $300 CDN... works like a charm.

Additionally, if you gasket match and polish your exhaust ports with as high a grit sandpaper as you can, you should get a decent improvement.... and also polish your cylinder head dome... don't forget to round off any rough edges. Then in order to make sure you're exactly the same on each dome, just use a piece of glass with a hole in it and use oil as a seal on your valves and glass to head area. All you have to do then is fill it with water using a graduated pipet.. as long as each cylinder head dome is equal, you're fine... and you can crank up the boost a bit more without risk of detonation (due to the fact that there are no "sharp edges" to get hot and cause pre-ignition)...

[Paula&Marcus]

Hi Graham,

The S4S/S300 head really is a nice one, indeed.

But IMHO its not worth upgrading. Actually you hardly will feel any difference. 1mm more inlet diameter on a blown engine is hardly noticable.

The HP-difference the S4S/S300 shows is solely due to the fact that the S4S and S300 runs 0.25 bar more boost and uses a bigger turbo intake and turbine.

Cheers

Marcus

www.PUKesprit.de

I am about to start opening up the engine and checking the internals as well as resetting the valve clearances etc. It was suggested to me by John at WC to installer larger intake valves from the later 4 pots. Has anyone done this before and know what is involved? Also, is this even worth doing?

-Graham

[Esprit Aviation]

This may be pointless, but just playing devil's advocate for a moment. After reading another post on aerodynamics, the golf ball came up in the discussion. We all know the dimples are there to reduce drag ( I presume to enable more 'laminar' flow around the ball). Obviously it works better than a smooth polished ball.

Can we therefor apply the same theory to an evenly rough casting surface as opposed to polished? I am not talking bigger ports here, just surface treatment. This assumes there are no gross chunks of casting sticking out, etc.

OK, lets take it a step further. With today's technology, why not manufacture all intake and exhaust tubes, runners, pipes, etc., w/ dimples inside, like on the golf ball??

Got any ideas?

Cheers, Lee

Edited February 1, 2007 by Esprit Aviation

[Paul93Lotus]

I think that analogy is flawed when it comes to increasing air flow within an engine. I imagine the dimples are fine for a moving projectile through still air, but not for air moving through a dimpled passage. Kind of like 1+2=3 but not 3+2=1. The intention is to increase flow, not introduce turbulence.

I think going with the S4S valves would be a waste of money especially when you could use that money for porting by someone who is an expert. I'd be curious to know the flow between the two set ups. I imagine it is not much to warrant the effort.

[Drfatz]

Well thank you all for your input! Weighing all of the advice I have decided not to put in the larger valves. However, Otis' flow bench looks rather intriguing and I may have to venture down that road to help match ports and improve flow. B)

[t70]

The dimples do more than just create less drag. I am fairly confident that the dimples are more for stability than anything else... The dimples create a low pressure zone around the outside of the ball. This low pressure zone makes it so that the air doesn't have anything to grab ahold of and make the ball curve un-naturally.

I don't think ports will have the same effect... infact I'm quite certain it won't. When porting a head you generally "polish" the intake port with a 45 or 60 grit sandpaper (not smoother) in order to create enough turbulence to keep the fuel from pooling against the side of the port wall. Other than that, you want the ports to be as smooth as possible on the exhaust side. The other reason for a mild grit on the intake is to keep the air from flowing perfectly straight. If it flowed perfectly straight and smooth, you would end up effectively "dumping" a poorly atomized pile of fuel that wasn't properly mixed with the air, into the cylinder. This would cause massive fuel consumption and higher risk of detonation due to the unpredictable burn patterns and resultant afr in the cylinder...

Just my 2 cents

oh and as another note... Increasing flow and valve size isn't particularly to increase horsepower directly in the case of a boosted engine. It's purpose is more to create a more efficient flow into the cylinder at higher pressure. So, that is why you can increase boost pressure on that engine.... It's the same logic as to why i heavily over-ported the head on my supra... it's only to function well as a boosted engine.. the amount of flow that i have in that head is completely useless as a naturally aspirated engine.

Edited February 1, 2007 by Mark T-C

[Esprit Aviation]

Otis,

Good points. I suppose your Supra is rather speedy!

Cheers, Lee

[t70]

well... it's not turbocharged yet... but it's actually surprisingly driveable in NA trim. It's got a VERY flat torque curve (seat of the pants dyno) from 2000rpm to 6000rpm. The main reason for the flat curve though is my ecu can't be tuned and all i can change is the afm spring tension and rheostat position so my afr under full throttle sits at about 12.2. Fairly torquey but not optimal. Doesn't really matter though... once it's boosted I expect about 500hp at 15-17lbs of boost.

[Squelch]

I don't get on here often but this thread was brought to my attention, so I thought I should chime in...

Firstly, WC Engineering did not recommend UPGRADING to the larger intake valves.

The statement was during a phone conversation, that if any of the intake valves needed replacement, then you might as well replace all the intake valves larger S4s ones.

Reasons for this,

1. They are available

2. You only need to machine the seats, not replace them, a very simple job for almost any machine shop.

As for exhaust valves, yes larger ones would help on a turbocharged engine, more so than larger intake valves, but can anyone (other than a few friends in the Chicago area) tell the list where to get oversized exhaust valves for the 910 engine?

Also, what the oversized exhaust replacements made of??? (Hint: ring finger)

And how much they cost?? (Ouch)

WC Engineering has made a reputation for first class quality work, and has made a great effort for provide help and advice to fellow Lotus enthusiasts, even those that haven't used our services or our products. We will strive to continue this course of action to help the marquee.

However finding our comments and helpful advice taken out of context, and then to be criticized by others is disheartening at best.

I'll go back under an Esprit now...

John Welch

WC Engineering LLC

[Artie]

I don't get on here often but this thread was brought to my attention, so I thought I should chime in...

Firstly, WC Engineering did not recommend UPGRADING to the larger intake valves.

The statement was during a phone conversation, that if any of the intake valves needed replacement, then you might as well replace all the intake valves larger S4s ones.

Reasons for this,

1. They are available

2. You only need to machine the seats, not replace them, a very simple job for almost any machine shop.

As for exhaust valves, yes larger ones would help on a turbocharged engine, more so than larger intake valves, but can anyone (other than a few friends in the Chicago area) tell the list where to get oversized exhaust valves for the 910 engine?

Also, what the oversized exhaust replacements made of??? (Hint: ring finger)

And how much they cost?? (Ouch)

WC Engineering has made a reputation for first class quality work, and has made a great effort for provide help and advice to fellow Lotus enthusiasts, even those that haven't used our services or our products. We will strive to continue this course of action to help the marquee.

However finding our comments and helpful advice taken out of context, and then to be criticized by others is disheartening at best.

I'll go back under an Esprit now...

John Welch

WC Engineering LLC

John,

I hope that no one has taken your advice out of context but mostly I SURELY hope no one criticized you and what you do, I for one have never seen or heard anyone criticize you or what you offer our small community, you are truly a pioneer and an asset to all of us, especially those of us willing to undertake complicated projects on these cars. I hold what you have done for me in the highest regard, and know first hand your level of expertise and willingness to offer help and advice, with or without payment. So let me be the first to apologize if this is the case!

Artie

[Vulcan Grey]

Hey John,

There goes my reading comprehension again... I hadn't even noticed he mentioned you in the original post.

Of course it doesn't matter, cause I was only giving my opinion whether it was worth it to me (IMO). Hope I was clear about not downing someone elses idea, even if it was out of context.

Oh and I was trying to relate the issues that I have been through trying to find a local machinist that won't screw up a Lotus head, so that they may be informed before they decide to get theirs machined.

Oh, and I do know a local machinist that'll cram in the wrong size valve seat.... I think it might have been off his Chevy...

[t70]

I am feeling the same way about the whole issue of unintentional insult. I had no intentions of offending anybody... just giving my two cents with regards to my understanding of engine building and tuning. The last thing on my mind is to hurt anybody or offend anybody. As for the valves... I have a few sources for custom valves and I can look into it for you.. They will probably be swirl polished stainless valves. I wouldn't expect to be able to fit 1mm oversize on a 4 valve head on the exhaust side.. but if it is possible --- that would be great. So If all that is necessary is a seat grind then i'll source that size.. If somebody could supply me with all the valve stats (stem length/diameter/retainer height etc..) Then I may be able to get some made. My supra valves were only $100 canadian for 12 (6 exhaust, six intake) and they were more or less custom (very short production run)

I guess the end result is if I can find them.. I'll find out a minimum order number and if we can have a large enough group purchase to get the price down... we'll do it.. yeah?

[sanj]

As for exhaust valves, yes larger ones would help on a turbocharged engine, more so than larger intake valves, but can anyone (other than a few friends in the Chicago area) tell the list where to get oversized exhaust valves for the 910 engine?

Also, what the oversized exhaust replacements made of??? (Hint: ring finger)

Hmmm, exhaust valves to match my exhaust pipes...yummy. How much? B)

[Drfatz]

John,

My apologies. I thought you had suggested while I had the head apart to install larger intake valves. I guess I misinterpreted your advice to only do that if the valves are damaged. I absolutely did not mean to offend anyone In the end I have decided to do general maintenance on the head and reset the valves while it is off the car and leave the current valves in place.

-Graham

[Pete_Inno]

I plan on installing the nice turbo from WC as well as a HUGE chargecooler ....

Where are you getting the huge chargecooler? I assume that you will be using a more powerful chargecooler pump. Sounds like a mod I'd like to do.

Pete

[Artie]

Where are you getting the huge chargecooler? I assume that you will be using a more powerful chargecooler pump. Sounds like a mod I'd like to do.

Pete

From my correspondence with Graham(Drfatz) he will have a custom CC made! When he accomplishes this task I will probably have his fabricator do the same for ME!

Artie

[Drfatz]

Indeed you are correct Artie. I am looking into ordering a custom charge cooler from one of the various manufactures out there that produce these things for drag racing. It is going to require me to massage my setup a little so that everything fits, but in the end I will have a large charge cooler for much less then the price of a Lotus one! Also I will be installing an electric pump and plugging the mechanical pump hole in my block. I will be sure to keep everyone updated as to my progess.

From my correspondence with Graham(Drfatz) he will have a custom CC made! When he accomplishes this task I will probably have his fabricator do the same for ME!

Artie