Hey, here's what I've been doing lately.
While having a good hard look at the log head, and milling over indepedent runner carb systems like triple Holley 2300's and the like, I started looking at more modern systems.
I've always liked the simplicity of the log 144-250 engines. They are very strong, very reliable engines that suffer from a restrictive intake runner design. So I looked at what I could do to build a good flowing log head without cutting the log off and welding a plate to it, like what the old guys used to do in Australia in the 60's and early 70's, before 2V's and Cross-flows.
So the idea I've come up with is to use the stock log head, and build a jig which allows the log to still remain in place, but get some savage modifications. This involves the following four things.
1. The drilling of 12 pilot holes, indexed in position against the two casting plugs at end of each extremity of the beloved log intake. 6 are for the Bosch/Siemens injectors used in GM 3800 engines. The other 6 are for half a dozen stub stacks or trumpets, which area as big as they can possibly be, 40 mm in internal diameter.
Each of these holes is enlarged die grinder, and then finished by plung drilling using a tungstan carbide boring bar.
2. These holes are then tapped with a die to allow the bosses of the injector to be placed in the heads intake runners. (There is also a pre located pod for the extruded aluminum fuel rail, which holds the injectors in place)
3. The six 40 mm ID intake trumpets are screwed into the intake manifold, with no slides or throttles at all.
4. The real good part is that there is no throttle slides at all. This is a MAP driven system, which runs off two throttle bodies mounted adjacent the groups of each group three intake trumpets. Hence the Twinductionâ„¢ label. These are mounted on a combined upper plenumb, reminiceint of the Rover 3500 Vitesse/ Holden SS Group A 'Walkinshaw' efforts which used twin throttle body set-ups in there homologation Group A forms in the late 1980's. This allows a range of existing Delco P4 (Melcal or Calpak units from GM 3800 V6's)/ EEC / Haltech / Motec / Zyteck /SDS/ Megasquirt engine management systems to work.
I favor the Delco P4 in this part of the world, as it is not saddled with some of the nasty dual pulse ingition set-ups which make post 96 Aussie 4.0 liter sixes such a beggar to tune with big cams. It also offers the opportunity to run a distributor-less ignition system, making more space for a supercharger of some kind on the left hand side of the engine.
Advantages:-
1. This set-up allows the intake manifolding to be optimised for peak power. Don't expect Tunned EFI-style low-end grunt, there isn't the space for long sweeping 4.9/5.0/5.8 EFI-style runners.
2. It will allow sequential or bank fire EFI to be used with a minimum of hassle, and will produce the best fuel mapping for anyone wanting to really work that Log headed anachronisim in to a Log-Burning normally aspirated, supercharged, or turboed small six.
3. The good later heads, with good size valves and induction hardened seats or hardened inserts, can be use. No 2V heads needed.
Once I get the critical dimensions sorted out, and a 200 buck produced, I'll spill the beans on how it all goes together.
While having a good hard look at the log head, and milling over indepedent runner carb systems like triple Holley 2300's and the like, I started looking at more modern systems.
I've always liked the simplicity of the log 144-250 engines. They are very strong, very reliable engines that suffer from a restrictive intake runner design. So I looked at what I could do to build a good flowing log head without cutting the log off and welding a plate to it, like what the old guys used to do in Australia in the 60's and early 70's, before 2V's and Cross-flows.
So the idea I've come up with is to use the stock log head, and build a jig which allows the log to still remain in place, but get some savage modifications. This involves the following four things.
1. The drilling of 12 pilot holes, indexed in position against the two casting plugs at end of each extremity of the beloved log intake. 6 are for the Bosch/Siemens injectors used in GM 3800 engines. The other 6 are for half a dozen stub stacks or trumpets, which area as big as they can possibly be, 40 mm in internal diameter.
Each of these holes is enlarged die grinder, and then finished by plung drilling using a tungstan carbide boring bar.
2. These holes are then tapped with a die to allow the bosses of the injector to be placed in the heads intake runners. (There is also a pre located pod for the extruded aluminum fuel rail, which holds the injectors in place)
3. The six 40 mm ID intake trumpets are screwed into the intake manifold, with no slides or throttles at all.
4. The real good part is that there is no throttle slides at all. This is a MAP driven system, which runs off two throttle bodies mounted adjacent the groups of each group three intake trumpets. Hence the Twinductionâ„¢ label. These are mounted on a combined upper plenumb, reminiceint of the Rover 3500 Vitesse/ Holden SS Group A 'Walkinshaw' efforts which used twin throttle body set-ups in there homologation Group A forms in the late 1980's. This allows a range of existing Delco P4 (Melcal or Calpak units from GM 3800 V6's)/ EEC / Haltech / Motec / Zyteck /SDS/ Megasquirt engine management systems to work.
I favor the Delco P4 in this part of the world, as it is not saddled with some of the nasty dual pulse ingition set-ups which make post 96 Aussie 4.0 liter sixes such a beggar to tune with big cams. It also offers the opportunity to run a distributor-less ignition system, making more space for a supercharger of some kind on the left hand side of the engine.
Advantages:-
1. This set-up allows the intake manifolding to be optimised for peak power. Don't expect Tunned EFI-style low-end grunt, there isn't the space for long sweeping 4.9/5.0/5.8 EFI-style runners.
2. It will allow sequential or bank fire EFI to be used with a minimum of hassle, and will produce the best fuel mapping for anyone wanting to really work that Log headed anachronisim in to a Log-Burning normally aspirated, supercharged, or turboed small six.
3. The good later heads, with good size valves and induction hardened seats or hardened inserts, can be use. No 2V heads needed.
Once I get the critical dimensions sorted out, and a 200 buck produced, I'll spill the beans on how it all goes together.