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MG MGB Technical - flow question

Here's another item to keep this post running...
Grassroots Motorsports had an article in SEP. 02 about "Benchless Head Porting" (begins p79). The article has some very useful info for Do It Yourself people, and explains flow properties in simple terms. He covers intake and exhaust ports, and he has his own set of "five golden rules" of head porting. There is even a section for identifying restrictions.

The author is David Vizard, not exactly a newcomer to the MG scene. His article covers the fundamentals, as well as how particular setups may vary from the norm. Very slick work. Now I wish (hint) a knowledgable individual (hint) would post directions for making a "torque ram tube" (hint, hint) as done for the A-series engine. I could imagine a racing cam pulling from 1.5k rpm hmmm... Cheers, O. Jibril
O. Jibril

Hiya

I am not sure the 'torque ram tube' is all that new, I found an old Practical Motorist with a smallish Classified advert in the back for a 'white' tubed torque ram set up for A series sold somewhere up North(UK)I seem to remember.

I have spent a lot of hours setting a K&N version on the rolling road....it is very, very tight with its fuel requirements. When I am setting up a single SU I am happy to grind the needle if it is too weak. With the Torque ram tube, the mixture was weak all the time....I ground the needle half a dozen times, when to my horror the mixture went from weak (as in wouldn't pull the skin off a rice pudding!) to too rich. Assuming I had messed up the needle profile, I started again with another needle....same result...suddenly goes too rich...I tried yet another needle...same end result. The setup was on an otherwise standard Mini 1000 and the owner could never get the car to run right from when he had bought it with the ram tube on. After 4 hours or so I suggested the owner put a standard setup on......he nipped round to our local breakers yard and bought a standard needle and air filter assembly....once fitted the engine ran sweetly and smoothly.

Personally, I reckon there is more bhp out on the road when one gets the underbonnet induction temperature down.....1% bhp increase for every 3 degrees C temp drop.

Cooling the fuel helps too...I have seen a 10% bhp increase with a Peugeot 205 efi car fitted with an underbonnet fuel tank when we ran out of fuel and had to put fresh fuel in!....I understand that some of the manufacturers tend to cool the intake fuel for testing.....very effective for increasing bhp, but maybe not so realistic? Reminds me of the God Old Bad Old Days when allowances for bearing losses and oil pump friction etc was added to the bhp figure...and the exhaust was extracted at a lower pressure....a bit like a supercharger in reverse? All good for the bhp figures.

Peter
Peter Burgess

Any chance of a summary not being a Grassroots reader.

Just following Peter's post- there is an interesting article along similar lines.

http://www.minimania.com/MM/Induction_system___Improvements__initial_testers_1289.htm

Peter whats your view on ceramic coating or insulation wrap for manifolds.

From frosty Surrey

Paul
Paul

Hi Paul


Ceramic coating...

Should be good if it stays on....however, say it stays on the crown of a piston....where will the heat be rejected that usually travels down through the crown....some still has to be rejected as heat...my horrible guess is the rings and ring lands will take a real hammering. It is something I have not been involved with apart from ceramic sealing cracked TR4 heads.

Exhaust wrap.....

I am not convinced of the effectiveness of heat wrap...Keeping the exhaust isolated from the inlet manifold/induction system is great....use a physical barrier. Keeping the heat in the exhaust system could lead to extra heat being trapped in the cylinder head, reducing efficiency...in the same way that I understand stainless steel exhaust manifolds tend to keep the heat in the head. I have had two negative experiences with heat wrap....

1) MGB standard race car with heat wrap....after the end of the season the engine was replaced with next years' engine...only the owner rang up to say the new head was faulty as the studs didn't line up with the manifold ( standard CI)....after much head scratching ( :) ) it transpired that the manifold had warped by some 1/4 of an inch or so.....we wondered where the extra heat 'lived' under running conditions.No heat wrap from then on!

2) Ford Capri 2.1 Pinto with twin 45 Webers, hairy cam and monster cylinder head.....belonging to a friend...we relayed the story about the MGB ex manifold....bravely, our friend ripped off the wrap (about £30 worth!)....result 4 bhp increase, which seems to be attributed to removing the heat wrap. The engine is a x-flow so no heat was being saved from direct contact with the inlet manifold as in the MGB scenario, the benefit of having a cooler underbonnet area was more than wiped out by whatever was happening inside the head with the reduced heat rejection.

Overall, I get the feeling we can cause more problems than we cure with using heat wrap.

Peter


Peter Burgess

This thread was discussed on 05/01/2003

MG MGB Technical index

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