Discussion
It is a nice job. This head was done by Oli and Karl at NMS. It sits atop Oli's Escort engine. It probably made around 430 bhp when it gained the class mile record at Bruntingthorpe in 2007ish. I believe it still holds the record to this day, it hit 174 mph.
I looked at it the other day in their workshops. They think the same as myself and Dave Gollan with regard to power increases in stages with the CVH. It is nice to see some interest in such an old and little used (it would seem) head these days. We do one or two standard class tweak up heads but I cannot remember the last time we did a fully ported one. We do a few insert fits for NMS and made a batch of guides for them but there seems less general interest these days.
Some folk express alarm that we grind the bosses down. On most heads we would not do this. However, the CVH is an exception. The guides may well be the longest used in cylinder heads so the guide length left is still longer than most guides I can think of. The valve seat to guide is still a safe distance and less than a fair few heads that have shorter guides to boot.
On a happier note with CVH heads, Oli is trying to get the engine rebuilt in time for the RSOC National Day at Donnington, weekend of 27th August. We may get to run it on our rollers if Oli runs out of time to bed it in on the road.
Peter
I looked at it the other day in their workshops. They think the same as myself and Dave Gollan with regard to power increases in stages with the CVH. It is nice to see some interest in such an old and little used (it would seem) head these days. We do one or two standard class tweak up heads but I cannot remember the last time we did a fully ported one. We do a few insert fits for NMS and made a batch of guides for them but there seems less general interest these days.
Some folk express alarm that we grind the bosses down. On most heads we would not do this. However, the CVH is an exception. The guides may well be the longest used in cylinder heads so the guide length left is still longer than most guides I can think of. The valve seat to guide is still a safe distance and less than a fair few heads that have shorter guides to boot.
On a happier note with CVH heads, Oli is trying to get the engine rebuilt in time for the RSOC National Day at Donnington, weekend of 27th August. We may get to run it on our rollers if Oli runs out of time to bed it in on the road.
Peter
The thing is, if I may say as an amateur engine bod [and proud of it], I have been often told that"modern" heads are just not worth the time and expense for any fetling, power comes from "using up" what ever longevity reserve was written into the engine control software....
But is this actually the case? are modern heads really that good??
I have one example in 20v four pot turbo configuration sitting on the drive {where a "proper" four valve setup would in theory provide higher flow}do the manufacturers produce heads that do the business now, without the need for the practice of the arcane art????
If the answer is a resounding YES, how boring is that!!
The cvh head is ripe for fetling as can be seen from above!!!
But is this actually the case? are modern heads really that good??
I have one example in 20v four pot turbo configuration sitting on the drive {where a "proper" four valve setup would in theory provide higher flow}do the manufacturers produce heads that do the business now, without the need for the practice of the arcane art????
If the answer is a resounding YES, how boring is that!!
The cvh head is ripe for fetling as can be seen from above!!!
Edited by Kccv23highliftcam on Saturday 28th July 00:03
I think we are thread drifting a little.
If the valves are large enough already, gains from fettling 4/5 valve set ups will be far more marginal than the good old 2v heads we are familiar with.
I tend to tell folk we can smooth out the (usually) poor area where the valve inserts are fitted and tend to have steps either from insert to port, port to insert or both and gain a little power and some smoothness, icing on the cake stuff rather than great chunks of cake!
Some 4v heads work well with increasing valve size/s and they tend to make good improvements but they are a rarity.
Overall the multi valve heads tend to have such good valve time area that it is hard to gain significant amounts from porting usually need head/cam/cr/induction and exhaust work to make a bigly difference to my way thinking.
Peter
If the valves are large enough already, gains from fettling 4/5 valve set ups will be far more marginal than the good old 2v heads we are familiar with.
I tend to tell folk we can smooth out the (usually) poor area where the valve inserts are fitted and tend to have steps either from insert to port, port to insert or both and gain a little power and some smoothness, icing on the cake stuff rather than great chunks of cake!
Some 4v heads work well with increasing valve size/s and they tend to make good improvements but they are a rarity.
Overall the multi valve heads tend to have such good valve time area that it is hard to gain significant amounts from porting usually need head/cam/cr/induction and exhaust work to make a bigly difference to my way thinking.
Peter
The simple fact is that the easy (N/A) gains have gone.
Back in the day, a typical 2l 8v would wheeze out 50bhp/litre, so even mild improvements would net large power gains.
Today, when factory engines make upwards of 80 bhp/litre even for a "low tune" engine, there is just not that much left to be gained. So you put in a massive amount of expensive, time consuming, work, and find just say 20bhp. Compared to forced induction, where the same amount of tuning work would double the engines output!
Back in the day, a typical 2l 8v would wheeze out 50bhp/litre, so even mild improvements would net large power gains.
Today, when factory engines make upwards of 80 bhp/litre even for a "low tune" engine, there is just not that much left to be gained. So you put in a massive amount of expensive, time consuming, work, and find just say 20bhp. Compared to forced induction, where the same amount of tuning work would double the engines output!
Seeing the post re the S2000 engine reminded me we have been testing a Honda S2000 for a customer. The epitome of development of 4v per cylinder in road use guise? In 5th gear it pulled cleanly from 1300 rpm to the 9000+ rev limit. The engine was standard apart from an aftermarket exhaust system. Wheelpower was 212.8bhp and wheel torque 151 lbs/ft, flywheel approximation 250.1 bhp and 174 lbs ft torque. Absolutely stunning! I wonder what they can make in race trim?
Peter
Peter
people thought the m3 was fully developed when it had the highest specific torque of any NA production engine and 114 h p/ L back in early 2000's. with bolt ons people have been able to increase performance from 280 whp to 340 whp and torque 235 wtq to 250 wtq.
with opened engines the gains are further as the cylinder head can be made to flow 10-15% better with someone who knows what they doing
with opened engines the gains are further as the cylinder head can be made to flow 10-15% better with someone who knows what they doing
Edited by Inline__engine on Monday 30th July 11:19
PeterBurgess said:
Seeing the post re the S2000 engine reminded me we have been testing a Honda S2000 for a customer. The epitome of development of 4v per cylinder in road use guise? In 5th gear it pulled cleanly from 1300 rpm to the 9000+ rev limit. The engine was standard apart from an aftermarket exhaust system. Wheelpower was 212.8bhp and wheel torque 151 lbs/ft, flywheel approximation 250.1 bhp and 174 lbs ft torque. Absolutely stunning! I wonder what they can make in race trim?
Peter
Is it coincidence that the first torque peak is at almost exactly half the RPM of the second peak?Peter
PeterBurgess said:
Seeing the post re the S2000 engine reminded me we have been testing a Honda S2000 for a customer. The epitome of development of 4v per cylinder in road use guise? In 5th gear it pulled cleanly from 1300 rpm to the 9000+ rev limit. The engine was standard apart from an aftermarket exhaust system. Wheelpower was 212.8bhp and wheel torque 151 lbs/ft, flywheel approximation 250.1 bhp and 174 lbs ft torque. Absolutely stunning! I wonder what they can make in race trim?
Peter
You should see one of their factory forged pistons and the clearances they run, that would give you something to think about. They run tighter bore clearance than you'll do on most cast pistons.Peter
It's right there in the top ten best production engines ever built.
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