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Peter H.

Porting Cylinder Heads - is it worth it?

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I'm thinking of getting my engine (1988 2.2 HC N/A 63,000 miles and currently generating 143hp at the flywheel) professionally reconditioned this winter. I've spoken to Mike at Lotusbits and Steve Williams Lotus, but I still have a bit of a dilemma.

I'm thinking a standard rebuild will hopefully get the engine nearer 170hp (right?). So the dilemma is.....is it also worth getting the cylinder head ported while the engine is out?

Its a pricey additional thing to get done and I know it needs a new inlet manifold to go with it. So I wondered if anyone had any opinions or first hand experience of getting this done.....or even what sort of performance gains they experienced?

If its 10-15hp improvement, I probably would not bother.....but if it is +20hp, then perhaps its worth it?

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I think you should see at least that 20hp, perhaps even 30 if you altered the exhaust manifold. One of my Excels has a flowed head and standard exhaust manifold and the power delivery is noticeably different from my standard Excel.

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I'd love to see some data/templates/dyno sheets on ported heads on the 2.2.  I cleaned the out rough casting finish and made sure the runner was smooth going into the valve seat before a multi angle valve cut on mine,  but I did not want to change port shape or size without more guidance.  But I've got a turbo to push past some amount of head issues.

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all I have done (myself, easy diy job)  is make sure the ports are in line with the manifold  (port matching)  apparently so many are not, usually just a few mill (1-3) using a piece of paper to draw both sides and see where they aren't in line. then clean the ports from casting debris.  only polish the exhaust side as the inlet side benefits from a matt finish. (the wet parts in the mixture release easier from a matt than from a polished port)  al this can be done yourself, and make up for a good improvement but it does not give you the max that can be.  

apparently Mike his 4-2-1 exhaust is a big improvement in mid range (where it counts on the road) 

why do you need another inlet when porting the head?  as far as I know it's  the shorter the ports the less for midrange (but good for top)  

 

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I think that what Peter means is, the inlet manifold has to be ported as well as the head and Lotusbits supply them ported rather than take the existing and have them machined then returned. The ideal inlet is off something like a 911 used in the Talbots as they had the shorter tracts.

 

Thomas.

My engine was dynoed and was showing over 200 (if I recall correctly).

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I gas flowed the twin cam head on my Europa many years ago after reading this by David Vizzard, a very well known tuner of the time.

Simply use the carb spacers as a template to open the inlet ports & the exhaust manifold gaskets similarly.

I also reshaped the valve seats & heads to increase air flow.

I mounted a rotary file in an electric drill for working on the alluminium head & changed to a grind stone for the valve seats & heads. I also opened out the cast iron exhaust manifold.

The effect was very noticeable for little effort & money. 😀


Cheers,

John W

http://jonwatkins.co.uk

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Many thanks for the input guys. I think I am currently sitting at 60/40 in favour of doing this.

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I'd say, look at it as a cheap way to move from NA performance to near-turbo performance. The NA Turbos were 210-215 hp and had lag (as with all single turbos), whereas you could get 200+ for just the cost of porting & flowing the head & rebuild costs (labour + gaskets etc). Is that now closer to 95/05 in favour?

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1 hour ago, andydclements said:

 whereas you could get 200+ for just the cost of porting & flowing the head & rebuild costs (labour + gaskets etc). Is that now closer to 95/05 in favour?

That's a 27% increase, I doubt if you'd manage that without changing cam shafts & re jetting the carbs.

I'd think a 10% to 15% would be more likely, which is 180 to 190 BHP but still worth it. ☺


Cheers,

John W

http://jonwatkins.co.uk

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Isn't the standard HC N/A car around 175HP, therefore a 15% increase would put it around the 200+HP Andy mentions

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On 21/09/2019 at 07:27, jonwat said:

I gas flowed the twin cam head on my Europa many years ago after reading this by David Vizzard, a very well known tuner of the time.

Simply use the carb spacers as a template to open the inlet ports & the exhaust manifold gaskets similarly.

I also reshaped the valve seats & heads to increase air flow.

I mounted a rotary file in an electric drill for working on the alluminium head & changed to a grind stone for the valve seats & heads. I also opened out the cast iron exhaust manifold.

The effect was very noticeable for little effort & money. 😀

Like John, I did this on the head of my very early Elan TC to good effect as there was striking mismatch between carb centres and the inlet ports. I'd be quite surprised if Lotus were producing 90x series engine components with that sort of defect but who knows? DV has a distinguished record in working engines over with plenty to say regarding the lovely, classic TC. A number of factors indicate that the modern engine series likely had ports and valves rather larger than optimal, illustrated most tellingly in how much the torque band thickened when spec changed to 2.2 from 2 litre. It is always vital to performance that the valve seats and adjacent regions of the ports are of correct form so there's that even if enlarged valves aren't warranted, and the inlet to head match absolutely should be checked.

I believe the HC is rated at 172 in the Esprit, and runs 104 inlet, 107 exhaust cams on 104 MOP green dot pulleys. Well regarded engine tuning software I tinker with indicates a very streetable 210 HP is to be had using those cams  if valves/ports and both inlet and exhaust side tracts are optimal. I have found exhaust cam MOP at 110 - 114 seems beneficial if that tract can be made optimal. Interested in hearing what Mike will specify, also Garry Kemp is a noted specialist worth speaking with.

Cheers 

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2 hours ago, jonwat said:

That's a 27% increase, I doubt if you'd manage that without changing cam shafts & re jetting the carbs.

I'd think a 10% to 15% would be more likely, which is 180 to 190 BHP but still worth it. ☺

No, not 27%. 200 from what was 180 is an increase of 11.11% It's starting from a HC NA so starting at 180.

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24 minutes ago, andydclements said:

No, not 27%. 200 from what was 180 is an increase of 11.11% It's starting from a HC NA so starting at 180.

My mistake, espritworld quotes 172BHP so 200BHP would be an increase of 16%, still a bit of a stretch for porting & polishing though. 😯


Cheers,

John W

http://jonwatkins.co.uk

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Somewhere I've got a dyno from a ported and polished Excel at 210, so even given the different exhaust configuration on an Esprit I'd think 200 is equivalent.

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3 hours ago, jonwat said:

My mistake, espritworld quotes 172BHP so 200BHP would be an increase of 16%, still a bit of a stretch for porting & polishing though. 😯

Dont forget, or underestimate, the significans of the turbos higher torque. 

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17 hours ago, gvy said:

When I got my engine out in 2014 , I portmatched in and outletports. I used the gasket between manifold and head. I Placed the gasket on the head and with a marker I could indicate the opening. and I did the same on the manifold. After that I could take material away until ports in the head, the gasket and the manifold were identical, so portmatched for optimal flow.

You'd be surprised how much difference there is on the openings

Geert,

Did you open out the carb ends of the inlet manifold? If not it's worth doing as they can be quite a bit smaller than the O ring spacer.  Also, if your O rings have constrictions on them they're only there to aid emmissions & it's worthwhile removing them as they restrict flow, although you'll need a lathe to do it.

For some unknown reason the first Lotus, twin cam 8 valve cylinder heads had the inlet manifold cast with it (see pic) so the only inlet port matching possible was to open them out to fit the spacers. Made adifference though. 😊

Check your spacers are flat & have not been distorted through overtightening by placing them on top of each & looking for rocking.

 

090908053922-europa08_orig.jpg


Cheers,

John W

http://jonwatkins.co.uk

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