(Jan 2 2000 12:50AM) Jim Marlett RE: Good flowing heads Whether something is 'worth the extra cash' is a pretty personal issue. All I can tell you is that the majority of drag race engines say Offenhauser on the heads. What you can't tell is how much, if any, grinder work is done on them. Navarro high domes are increasing in popularity. What is the application? If it is a street engine, I don't think you will feel a big seat of the pants difference unless your seat is really sensitive. If it is a competition engine, the very fastest design their own heads. Also, I would be curious myself to know if anyone on this list has actually used Navarro, Motor City or Baron heads.
Lars Brandow (Jan 2 2000 12:55PM) RE: Good flowing heads As i understand it, its that the MCF heads are machined around the sparkplug area. To clear the plug sortof, since aftermarket heads usually are thicker. And they sort of burrie the spark plug. Then are the heads machined around the valve area, to improve the breathing. i think they call it undercutting. A couple of years ago MCF offered to do this on a set of Offenhauser that a friend of mine planned to buy from them. So i think the MCF 'technology' can be applied on most heads..What i understand is breathing more important then compression ratio..
Jim Marlett (Jan 2 2000 2:14PM) RE: Good flowing heads Lars, Motor City Flathead has started casting their own heads and marketing them under their own name. The combustion chambers don't look exactly like the modified Offys. The TV show mentioned elswhere today shows a set of their heads and you can see them pictured in Mike Davidson's 'Street Flathead' book (sorry about the book reference, Steve). The ones on TV didn't look like the same configuration as the ones in the book. Maybe it's the difference between how they do their blower heads vs naturally aspirated heads or a difference in lighting.
Steve M (Jan 2 2000 4:56PM) RE: Good flowing heads I recieved a catalogue from Tony Baron and in the catalogue the cylinder heads had CNC machined combustion chambers.According to Mr Baron the heads he sell come in two styles (full race and street) and are capable of producing 200 mph horsepower.Not to long ago Hotrod covered the construction of a very custom flatty and in the buildup they used Baron heads.They also reconfigured the combustion chamber to the motor`s specs.I did read a book written by an Australian fellow and he experimented with Kong heads also reconfiguring the chambers.I am sort of on a quest for maximum horsepower without exotic welding or machining.The parts have to be there and work well.Thanks for your input Mr Marlett and perhaps we should talk more about a subject that is becoming very dear to my heart.Thanks again, Steve M
Dave F. (Jan 2 2000 9:31PM) Head prep To broaden the discussion on heads a bit more.... Now that Jim, and others, have helped me make the decision to go with the Offy 425 heads, are the Offy 425 heads good enough right out of the box for most street applications? Or is it still advisable to have some prep work done after they arrive? Somewhere in the past I read the advice that on the aftermarket heads it is usually necessary to grind open up the area about the spark plug to prevent spark shrouding. Is this really necessary, and if so, to what degree? Several years ago, after hearing about 'spark shrouding', I checked the Offy 350 heads on my coupes '51 Merc engine while I had them off for a thread repair. I did find the Champion H-10, and the comparable Autolite 216, to be 1.5 to 2 threads short of fitting flush with the surface of the combustion chamber. I then went through about a dozen different plug brands and numbers to see if I could find a plug of the right heat range where the base would set flush with the surface of the combustion chamber. I found that the Denzo W20FS fit the Offy 350 heads perfectly. (The Denzo chart indicated the same heat range as the Autolite 216.) I've ran those plugs for several years now and they seem to work quite well. Recently I checked an old set of warped Edlebrock heads (F8.0 M8.5) with a Champion H-10 plug and found the same thing. However, I also found that the Autolite 411 fit the Edlebrock heads perfectly. I don't know if the heat range of the 411 is comparible to the 216, but the problem is the 411 is special order only. Anyone have thoughts/knowledge on the matter?
SOPP(Jan 2 2000 10:40PM) RE: Head prep I don't know if anyone else has had this problem, but, I've broken lots of champion plugs in lots of different heads, particulary aluminum. They seem to tighten themselves after propper insallation with a torque wrench. Sometimes as much as 2 to 3 times the install torque to remove. Never had this type trouble with any other brand plug. I've not been able to figure out why this is happening so I now buy only ABC plugs(Anything But Champion). just my 2 cents worth, Sopp.
Jim Marlett (Jan 2 2000 11:18PM) RE: Head prep Again I want to preface my remarks with the fact that I am regurgitating what I have read and heard and it is from very little first hand experience. I expect whatever plugs worked in your 350s would work in the 425s as long as the tip doesn't hit a valve. There is an illustration of the Motor City unshrouding in Frank Oddo's book. I've seen others that just have what looks like about a 30-45 degree 'funnel' cutting off the extra exposed threads. An important part of this excercise is getting rid of the sharp unused thread edges to prevent preignition. Also, just to confuse things, if your block is relieved and you want low rpm torque rather than high rpm horsepower, you may want to consider 400 heads. Too bad they aren't cheap enough to try out a couple of combinations to see what you prefer.
billk (Jan 2 2000 11:50PM) RE: Head prep Sopp, are you using anti-sieze(?sp) on the plug threads?
SOPP (Jan 3 2000 12:03AM) RE: Head prep No, I've never used anti-sieze but I understant that it is a good idea. Will use next time I change a set of plugs. Never broke anything but Champions when taking plugs out though.
Arrowsmith (Jan 3 2000 12:44AM) RE: Head prep I'm running 400 heads. where the round part above the pistons goes to the part valve above the valves there was a sharp edge that I smoothed. So the compression should be around 9 to 1 so far it seems to be working alright
rumble seat (Jan 3 2000 4:53PM) RE: Head prep Dave F. The Champion L series plug may be what you’re looking for, The L series plug is a 4 stroke plug and has a l/2 inch reach according to Champion, but you’ll find they’re just shy of 1/2 inch. BUT when screwed in they’re flush with the bottom of the threads on both Edelbrocks and Offenhausers. They’re not an extended tip plug. The L86C is the same heat range as an H10 according to Champion R&D. The L90C is one step hotter and is the hottest plug Champion makes with 1/2 inch reach. I run L90C in my flathead a/c the lousy gas we're getting. The L86C's foul too quick. Be sure to use anti-seize a/c plating on plugs tend to make the plugs 'weld' themselves to aluminum and you could easily strip threads when you pull them.. rumble seat