Flow testing of head.

[Keith Clements]

Julian has had extensive flow testing done on our racing heads.
He has managed to double the flow rate over the standard head with some interesting comparisons between Harry's and his cylinder heads.
We are now looking at the inlet track trying out various carbs so I have started making some adapters.

[RichardMc]

As it would happen I've just cut a cylinder head in half to have a look. Not much room in there but there are some obvious gains to be had. The rear of the inlet valve seat is very compromised and if you follow the work of David Vizard (love or hate him) a massive restriction. I'm going to do a write up and post it on here once I've got some more detailed measurements but once you cut one in half the problem is obvious. I'm going to try and split the ports at the same time, McAuley the Elder thinks it's a mad idea, he's probably right.

I can't get the image posts to work (see windscreen thread) but here are the direct links.

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[RichardMc]

PowerPoint Presentation.pdf

(568.39 KiB) Downloaded 17 times

This is a quick and simple mock-up showing the problem areas and suggested solutions. If anyone decides to follow this guide you are doing so at your own risk, the casting between the ports and the water jacket is only 1/4" at best. Gains can be made by shaping the valve guides but be aware that the exhaust guide helps cool the valve stem, if it gets too hot it will fail. I have a piston shaped paper weight to prove this!
Americans call this "bowl hogging" and it's quite common on cast iron heads from the 50's and 60's.

I've got a few jobs to do first but when I get round to cutting this 'test' head I'll post some updates. I might be able to get it on a flow bench but I'll have to stick the two halves back together.

The Powerpoint presentation is attached so the following is not required.
https://c-head-1.tiiny.site/ This should be a link to a PDF showing the idea, if you only see one page try zooming out or just download it from the "export" button on the top right of the task bar.

[Keith Clements]

Julian Crossley has done extensive tests on a Jowett head with professional race gas flow equipment. The results were counter intuitive!

I will prompt him to see if he can write it up.

The heads we have for Harry's new race engine were tested at the same time but not modified. They were quite good, but I do not have the quantitative results. From memory, the predictions suggest about 50% improvement on standard on Harry's and 100% on the new design. However, that is with special Piper cam and different valve gear. Interestingly, widening the valve size has an optimum.

[RichardMc]

Thanks Keith, would be great if Julian can do a short article to let us know what his findings were.

[AmilcarJohn]

If it is of interest, I have pictures of a sectioned head which is remarkably similar to the one shown by Richard. It would seem that the cores didn't move too much, which is reassuring.

It would be interesting to have more detail on the improved designs being tested.

[RichardMc]

Anyone fancy a Twin Port Jupiter head? I've been playing with the one I cut in half to see if it was possible, the answer is yes!
Two slightly overlapped 30mm bores just clear the water jacket and pushrod tubes, it isn't pretty but this was half a day in the workshop with a hole saw, grinder and pillar drill. As a proof of concept it works quite well. I did pinch the idea from Colin Chapman and his early Ford engines.

[AmilcarJohn]

Fascinating to see this is possible. Have you thought about the carb/manifold yet? I guess a twin choke would be most efficient, but not really a period modification.

[RichardMc]

The VW guys use twin 40 IDF carbs, there are quite a few manifolds that go from 40mm to 32mm to match the Type 1 twin port heads. I'm going to make an adaptor plate that goes from the shape I have to twin 32mm VW spacing. The VW manifolds are about £100 a pair from China and the copy IDF's are about £100 each. That should get me a dual / twin 40 setup. Last time I looked at a copy of the race regs for classics you specifically can't increase the number of chokes but I'm planning on doing sprints and hillclimb and I doubt anyone will care. If they do I just get bumped into the modified class but still get a day out.

[Keith Clements]

Frank Wooley tried a similar experiment.
Successfully fitting a carburettor to it would be a challenge. Perhaps some theoretical fluid dynamics would see what performance gains could be obtained.

[RichardMc]

I know Frank very well, between Geoff Mc, Frank and Mike Smailes I think they probably experimented with every possible tuning mod going. It was quite some education when I was younger. For the sake of a couple of hundred quid I'm just going to give it a go and see how it works out, I'm expecting low teens to the gallon. If it doesn't work I can always swap back to standard heads, bung a couple of Del FRD 32's on and save everyone else a load of effort. I’ve still got the paint and electrics to finish first so it might be a couple of months before I get to throwing an engine together, I’ve got all the bits but they are not necessarily in the right order (for those of you who remember Morecambe and Wise).

[Chris Spencer]

With regards to others especially owners of race cars / race engines that have invested financially pretty heavily into research / specialist parts manufacture in order to gain the maximum output from their cars - Please don't expect them to come forward and divulge all the information that they have learnt through the research process - They have personally undertook such commitment to gain a racing advantage - Its highly unlikely that will want to share the information with anyone that would directly compete against them. Whilst on the surface it may appear petty & selfish - far from it - You wouldn't expect McLaren to go sharing the technical information of their engines with Ferrari - I appreciate that we all need to work together for the larger cause but in racing circles its a very different scenario.

[David Kemp]

I love your work, always was curious how far you could port our heads. A dyno test would be interesting.
Dont ignore the exhaust ports Brian Holmes in Oz straightened his & had special manifolds cast. Gave his car more omph. As an ex speedcar driver I trust it was power he felt not noise..
On power of our engines, my understanding was breathing was fine it was simply the crankcases could not run more than 125hp before cracking?