12 replies to this topic

[Shooter63]

This is something that bugs me and as I get older I've found a lot more things bug me, on with the story, if I wanted to buy a set of modified heads for a SBC,BBC,SBF,BBF,Hemi etc I can go on line and there are hundreds of companies all listing that there heads flow X cfm at X lift, they are proud of what they are achieving. Recently I've contacted a few companies over here and asked the question " what do your heads flow at X lift" the standard answer is " I can't tell you that, that's classified " Now I'm not sure if they think they have some how changed the laws of physics or fluild dynamics but there isn't any magic in head modifying, its just a god awful job work wise which is why people pay the money, are we expected to divy up the cash because they say there heads are better than someone else's, a little bit of proof would go a long way
A classic example, I've been following a guy on YouTube who has been cutting different valve angles in the head and showing the changes on his flow bench, he tells you what angles you should use for what lift cam, all for free, all in the open, no nose tapping etc, wouldn't it be nice if guys over here would do the same, although in fairness a certain Mr Vizard did write a book explaining exactly how to get the most out of a A series head and perhaps that's the problem, people are not matching what he achieved.
I'm off to sit in the Freezer now

Shooter

[Spider]

I think you'll find most companies don't say not for fear of letting some world secret out, but that in fact, they don't know because their heads haven't been tested on a flow bench.

Turbo Phil is one guy though who is UK based and does have a 'open house' manner. He really seems to know his stuff and he tests what he does.

One last ling I'll add here, and I'm sure you're already well on to it, while CFM is a factor there's much much more to it than just flow.

[Ethel]

Yes chasing CFM could be just as meaningless as chasing peak BHP.

 

Part of the fun is taking on those judgement calls yourself, but it does help having machinists who'll enter in to that discussion with you.

[Shooter63]

Yup I fully aware of what's needed and not, in a former life I was involved with what would now be called The World Superbike series when manufactures still left a bit in the pot regarding head flow etc, now they do it all for you with very little to be gained in that department, there are still newish ideas coming out that work but on the whole nothing new since the 80s, it's just the secretive nature over here that gets me, if the yanks were into the A series like their big v8's they would be plastering the media with there achievements. If your interested in this sort of stuff, block flexure is a good subject

Shooter

[DeadSquare]

People like Iskenderian, 50 years ago, used to give a wealth of information about their cam, valve and head profiles.

 

"Tuning" an engine for power is many parts of a single entity, but divided into two parts, before the valve head and past the valve head.

 

Before the valve, a tapered tube is the ideal, most easily achieved with fuel injection, but the ideal taper is often not attainable.

 

A radius on the valve head and the valve seat is effective, but does not retain its profile for long.

 

Past the valve head is where the magic happens, and anyone who has ground the combustion chamber into the perfect shape with a "philosopher's stone", isn't going to share what they know with "Muggles".

[Ethel]

He wasn't asking to learn their spells, though: just for some indication of how good their magic was.

 

I suspect they either don't know the answer, or didn't want to give a promise they might be held to. Not unreasonably, as Spider & other have said.

[Shooter63]

People like Iskenderian, 50 years ago, used to give a wealth of information about their cam, valve and head profiles.
 
"Tuning" an engine for power is many parts of a single entity, but divided into two parts, before the valve head and past the valve head.
 
Before the valve, a tapered tube is the ideal, most easily achieved with fuel injection, but the ideal taper is often not attainable.
 
A radius on the valve head and the valve seat is effective, but does not retain its profile for long.
 
Past the valve head is where the magic happens, and anyone who has ground the combustion chamber into the perfect shape with a "philosopher's stone", isn't going to share what they know with "Muggles".

Here's a few for you
Chamber 36 degree cut back
Short side radius as large as possible
Valve seats at our lifts 45 degree with extra cuts below and above, air will turn 15 degrees happily although 30 degree valve seats show gain at lower lifts this was used by Buick in the 1950's
Valve seat width around 55 thou on both inlet and exhaust, you can use a percentage but on our size valves if works out about the same
Dimpling is new ish and has shown to work in certain areas, mainly the short side floor to bring that into play at higher lifts and the same with the long side behind the valve stem
30 degree back cut on the valves


Nothing is unknown now and that's why I don't understand why UK head porters are so secretive

Shooter

[mab01uk]

Back in the 1980's when I was roving editor of David Vizard's 'Mini Tech News' he wanted to do some flow bench comparison tests on several of the leading UK tuning companies modified A-series cylinder heads and publish articles on the results, as he was already doing in the USA for various American V8 engines. However before investing time and money in setting up a fairly expensive workshop test plan he needed an agreement from at least one of the UK's leading car tuning and modification magazines to publish and of course pay him for his research. Despite his efforts to get the go ahead none of the UK magazines seemed interested in publishing any resulting articles....at the time it was thought this was possibly due to the risk of them losing regular advertising revenue if DV listed any companies with poor performing heads....

 

Also at the time I was using a cylinder head modified by Mini 7 Champion the late Chris Tyrrell whose workshop in Leatherhead was local to me and whose A-series heads at the time were used by many of the leading front runners in Mini racing. David Vizard invited Chris Tyrrell as a small independent to take part in some flow bench testing but despite his heads being proven to perform in motor sport, he declined on the basis of not wanting to give any 'secrets' away and not needing any more business than he already had queued up in his order book!

Edited by mab01uk, 17 July 2022 - 04:11 PM.

[PoolGuy]

Another thing to take into account is the variability of A series heads, no one can guarantee that all their 12g940 heads will flow the same. There are companies in the uk that are fully cnc working their A series heads, and while they're in the minority at the moment, I'm fairly sure that they know what the heads are flowing.

 

The long and the short of it is that you have to find a company that you trust and you're confident will supply you with the head that you want and is suitable for your requirements. IMO, that's much more important than buying an 'off the shelf' head that someone has randomly classified as stage 3.

[stuart bowes]

I was going to ask this at some point, is there actually a standardised rating system for stage 1, 2, 3 etc? or is it that each company does various levels of work and they number them in an arbitrary system that is not directly comparable with other companies

 

I see it often, people listing their engine specs, they say it's stage 2 tuned, and so on, but what does that really mean?  unless you say who 'staged' it and a full list of all the components you've used

 

it strikes me that a lot of it is basically bragging rights anyway when we're talking about road cars, unless you're hunting down an extra few tenths of a second around brands hatch in a race series of course.  not that there's anything wrong with that of course, each to their own hobby and all that

Edited by stuart bowes, 17 July 2022 - 07:02 PM.

[Spider]

The same level of secrecy around some firm's special cam shaft grinds falls in to this same rabbit hole. I get that they don't necessarily want to give away their profile shape, but the total lack of basic numbers turns me away. It's folly of them if they are worried about another firm copying their secret, as only very basic equipment is needed, which more home engine builders have, so for another grinder to measure and copy would be a 'snap' - if they had the desire to do so.

 

 

I was going to ask this at some point, is there actually a standardised rating system for stage 1, 2, 3 etc? or is it that each company does various levels of work and they number them in an arbitrary system that is not directly comparable with other companies

 

I see it often, people listing their engine specs, they say it's stage 2 tuned, and so on, but what does that really mean?  unless you say who 'staged' it and a full list of all the components you've used

 

I included a post about this in this discussion just the other week;-

 

https://www.theminif...of-the-factory/

 

Post #17

 

[sonscar]

Most talk is of BHP,but give me a good torque spread any day for a road car.I realise that one is a calculation from the other but no flat spots and torque from 2k to as far as you can get it wins for me.Older gent speaking here,Steve..

[Spider]

Most talk is of BHP,but give me a good torque spread any day for a road car.I realise that one is a calculation from the other but no flat spots and torque from 2k to as far as you can get it wins for me.Older gent speaking here,Steve..

 

I agree here. It's where often the car with 70 HP is 'real life' faster than the car with 110 HP and is usually easier / more relaxing to drive.