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How come they are so inefficient?

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J

JCSH

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This has been bothering me for some while now. How come the 3 litre engines are so inefficient? they produce far too much heat for their own good I'm sure we all agree, they only do 20 mpg and yet the whole car weighs SO very little, surely something is wrong here. Something that can perhaps be made right...? SO, some questions to ponder..
How is the fuel being wasted?
is the combustion shape so very bad?
Are the inlet outlet tracts so poorly designed?
Are SU carbs that bad at metering fuel?
Is the exhaust manifold such a bad design?
What else can be wrong?
I would really like to get 30 mpg from this car. If my old M3 can get 35mpg at a steady 100 mpg (and it weighed 1.3 tons) then surely we can squeeze a bit more efficiency out of this mill, even without FI.
 
Hi,

You have touched on several topics;

" They produce far too much heat "
Perhaps but the real " heat " problem with our cars is that they
cannot transfer/get rid of the heat that they do produce. If you cannot transfer heat efficiently, then any engine will get too hot for it's own good.

" Is the combustion shape very bad "
This has been discussed in the past on the forum. Others will put in their two cents. The shape/ flow design of the combustion chambers and ports in the head " leave much to be desired ".
Also the valves are not being opened to their full potential with the existing rocker arms. You can buy after market rocker arm assemblies that open the valves to their full potential. This is also discussed in old posts on the forum.

" Is the exhaust manifold a bad design "
Yes. If you do nothing but install headers you can get an instant increase of 50 hp in engine performance. This is also discussed in the forum and someone posted screen shots of the dyno outputs as proof.

Ed
 
edk, yes i agree on the headers contributing horse power and would add that ceramic coated headers also reduce localised heat, im looking for a set for my car (bj7) befor i do the engine istall, any recommendations?, thanks, anthony7777
 
The Healey engine would need to be re-conceived as an aluminum DOHC 4-valve head, modern pistons, very tight tolerances so lightweight hi-mileage oils could be run. Electric fan--no mechanical fan. Computerized fuel injection. Really great intake, headers & larger bore exhaust. Maybe an electric water pump.

Seems like it has a way to go to get to where the M3 is.

Personally, my guess is the bad flow, heavy pistons, bigger tolerances requiring older oils, heavy steel fan, tiny 1-1/4" exhaust pipes--it all adds up to a lot of friction, hence bad gas mileage.

FWIW--my weber-carbureted 1600 Alfa GTV got around 23 mpg on a trip. A 2100 lb car with 125 hp. The healey is not at all out of line for cars of the day.

BTW--my 29D car was getting around 17mpg until I switched to HD8s--am hopeful it will get better with them, than the HD6s.
 
anthony7777 said:
edk, yes i agree on the headers contributing horse power and would add that ceramic coated headers also reduce localised heat, <span style="font-weight: bold">im looking for a set for my car (bj7) befor i do the engine istall, any recommendations?</span>, thanks, anthony7777
Click to expand...
Al(?) Kirk at Kirk Racing www.kirkracing.com has been making headers for our cars forever; he made the set I bought in the late 70s from Jon Peter's Sports & Classics, and I bought a replacement set directly from him about ten (10) years ago.

jh_headers.JPG
 
I bought my Kirk headers directly from them a year and a half ago and at that time Kirk told me they no longer made them because they had had returns due to fitting problems. My pair had been returned by someone who'd not been able to fit them.

I was able to fit the pair with a few tweaks, but no particular problem and offered to do a free photo essay they could send along with the headers but Kirk expressed no interest.

Hopefully they'll make them to order if folks ask for them.

IMHO--50 hp is _way_ too much to expect from just adding headers. When I added the headers, Monza exhaust and DMD intake, though, I felt a genuine difference in seat-of-the pants acceleration.
 
JCSH,

Dido to all the above. On the topic of headers, from performance, heat transfer and weight reduction their're a must. Now here's the straight talk. Vintage racing a 6-cylinder Healey I've found here's a lot of crap out there for our cars, (poorly made and engineered equipment). Founding Team Healey PDX member and veteran vintage racer Richard Mayor discovered this nearly 25 years ago preparing his ultra light, ultra fast big Healey. Unhappy with the available headers on the market, he partnered with a NASCAR fabricator to design and build a special 1-off pair. Richard kept his custom jig and still produces a small number of the best designed and built race proven headers for the 6-cylinder
Healey. They should be ceramic coated for better heat transfer and with any installation of headers into a small engine bay, it takes patience, patience, patience.

Dougie,

Richard's Email:mayorrichard@hotmail.com
 
Re: Headers for Healeys. What do the header users use to mate the headers to a (more-or-less) stock Healey exhaust? Since the exhaust is fixed-mounted (instead of hanging), do you use some flex tubing to allow for the engine vibrations? I would think bolting rigid downpipes to a pretty rigid exhaust system would cause problems eventually.
 
randy, thanks ive been trying to contact him no luck thus far, no word yet on the other "shocking" deal im working on, ill be in touch if/when i get word.
 
Hi Bob,
First I'll say welcome. I see you registered back in '07, but such a flurry of posting today.
grin.gif
The list has definitely been slow the past few days.

Dave Russell has recommended stainless flex hose in the past. What I did was scrap the stock hangers and made more flexible ones. So the exhaust pipes will move more with the engine. I made the mounting points underneath the pipes so the hanger can be as long as possible from the frame without the pipes hanging lower than stock.
 
steveg said:
I bought my Kirk headers directly from them a year and a half ago and at that time Kirk told me they no longer made them because they had had returns due to fitting problems. My pair had been returned by someone who'd not been able to fit them.
Click to expand...

I had two small issues with my Denis Welsh headers. The rear single flange didn't line up with the head, so the heat wrench was required. The rear header also hit the heatshield on the footwell. I had to notch out a small section for clearance.
steveg said:
IMHO--50 hp is _way_ too much to expect from just adding headers. When I added the headers, Monza exhaust and DMD intake, though, I felt a genuine difference in seat-of-the pants acceleration.
Click to expand...
I agree, that kind of gain needs the entire system massaged from intake to exhaust tip.

When I get my car done Steve, we need to go break the law and see who's car is faster. :laugh:
 
Bob_Spidell said:
Re: Headers for Healeys. What do the header users use to mate the headers to a (more-or-less) stock Healey exhaust? Since the exhaust is fixed-mounted (instead of hanging), do you use some flex tubing to allow for the engine vibrations? I would think bolting rigid downpipes to a pretty rigid exhaust system would cause problems eventually.
Click to expand...
exh_003.jpg


More pictures at: www.rfdm.com/gallery/album78
 
Greg,
I think your car is likely faster as you have a rebuilt engine with aluminum head. I'm guessing but I bet you have a cam, too, which my 29D has the stock cam.

As for the 3x carbs--no offense meant, but who knows if they're really better?

Do you have headers? How about the exhaust? IMHO--the Bell 1.5" would be the minimum--the Monza is as I recall 1.75" all the way out. I think the stock 1.25" strangles the other breathing work.

I've seen the Richard Mayer headers and they are superb. Pictures on my gallery:
https://www.pbase.com/stevegerow
 
Hi Steve,
In all honestly, I'm not the most skilled driver (practice would help
grin.gif
), and I really don't care if I win any races. I think it's great fun to flog these cars on windy roads just for the fun of it. The sound of two or more Healeys roaring through the canyons would be quite a sound. My engine may have a few goodies in it, but I wouldn't sell your car short. I know you've done suspension mods that probably make it a blast to drive.
 
I had bought a set of Headers from a Healey specialist in the N.E. back in the seventies. I believe they came from PAECO in Alabama. Anyone rememeber them? PAECO had Healey engines in (I believe), five different stages with the full racing engine, Stage #5, referred to as "God Awfull".

The Headers had a raised portion around the flange that had to be dround flush before they fit. Also, the thickness of the flange was thinner than the intake manifold but after fabricating a special washer the rest of the installation was a piec of cake. No clearance problems.
Patrick
 
Steve,

Richard is a good pal of mine and I enjoyed your pictures of his wonderfully designed and manufactured headers. Tri-carb. is much better on the top end whether SU 2" HD8's or Webers. Twin 2" SU carbs. have a slight advantage in mid range torque. Over an entire race track however, a well tuned tri-carb. system has a big advantage. I custom built my exhaust system from Richard's headers down. I run twin 2.25" mandril bent angles into a 2.25" to 4" oval y-reducer then into a low profile Spin-Tech "NASCAR" muffler with twin 4" oval 90 degree angles exiting at the rear door. The whole system is 1/2 from the back side of the floor board and runs parallel with the chassis. The headers and the whole exhaust system is coated with a thermo ceramic coating to reduce heat emissions. Ten hp improvement on the dyno at the rear wheel with the install.

Dougie

HORSE POWER IS GOOD, BUT TORQUE IS BETTER
 
U MUST B DEF IN YER LEFT EAR!

:crazyeyes:

But any race car painted Florida Green has my vote!!! nice.
 
Ear plugs baby,

The sound rocks and when the cam comes on..............ooooooowwwwweeeeee!

Dougie
 
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