Hot Rod Forum banner
1 - 8 of 8 Posts

·
Registered
Joined
·
15,315 Posts
No unfortunately this would lean down everybody it’s been tried again and again. This is endemic to in lines and is largely the result of cheap and poorly thought out from a mixture perspective manifolding.

The only halfway decent approach was that of the Chrysler inline slant 6 which lengthened the individual runners and joined them to a plenum. This is especially true of the Ram Chargers 4 bbl slant 6 of the early 1960’s which embarrassed a lot of V8’s of the era,,,but cubic inches is what sells performance cars, not performance. None of the GM or Ford aftermarket intakes for those respective engines come close. My response here is use the Ram Charger Slant 6 intake as your model and buy some flat steel or aluminum for flange and box construction and some tube and start building.

The other alternative is port injection on a conventional intake. Not a cure all because of the sharp turns the air flow has to make but from a mixture by cylinder standpoint a quantum improvement.

Log style manifolds on a normally aspirated engine whether an inline or a V block have never worked for crap with a carb and this has been tried again and again without anything that looks like success in spite of the mighty claims made about them. The lack of runner length and of a flow managing plenum combined with abrupt direction changes always leads to uneven mixture ratios and cylinder volumetric filling. Much the same can be said for cross rams. The log of an inline simply acts as a large plenum allowing fuel condensation along its path, hence the massive use of exhaust heating, while right angle turns always result in flow separation on the inside turn which eventually leads to reducing the effective area of the runner and because of the differences in weights of fuel molecules to those of air ends up flinging the fuel out of suspension with the air flow so that it enters the cylinder as a liquid. This usually just flows through without burning in the cylinder or burning too late to add any power which itself derives from the heat of the expanded gases trapped in the cylinder. So if it doesn’t burn by about 15 degrees ATDC it adds nothing to power. Such a cylinder may actually show lean on an AFR while by weight of the constituents the mixture may be correct as all the AFR gauge measures is free oxygen in the exhaust so while the fuel may be there if it didn’t burn there will be an excess of free oxygen. So a big part of using an AFR is to insure the fuel delivered is mixed with the available air and is consumed by flame by 15 degrees After Top Dead Center is not necessarily a measure of the ingredients going in. This starts to speak to combustion chamber shapes inclusive of the piston crown and compression ratio. Here as with V8’s engines the chamber shape that is best is a model of the L31 Vortec. The best piston crown shape is a flat top or a D dish consistent with a squish/quench clearance of between .035 and .045 inch. These factors do a whole lot in getting the mixtures constituent parts mixed and in the case of the fuel atomized so there is a lot of fine surface area available for the chemical reaction of combustion. This is a standard across all engine designs, PERIOD! If you don’t have this you’re leaving power on the table while increasing fuel burnt for power achieved and increasing emissions. All that AIR stuff that the manufactures hang on the engine is to burn the fuel in the exhaust that didn’t burn in the cylinder. Well Bunky, if it didn’t burn in the cylinder’s first 15 degrees of downstroke, you paid for the gas and got no power out of it.

Compression ratio also comes to bear on this the Compensated or Dynamic needs not to be under 8 to 1 with an iron head. Typically manufacturers overstate their Static by a full ratio so the Dynamic seldom comes close to this minimum.

The answer is American inline 6’s don’t get a lot of design love and to make power and gain efficiency need a lot of basic engineering help which they respond to in larger measure than V8’s where much engineering love is devoted compared to the inlines.

Merry Christmas, Bogie
 

·
Registered
Joined
·
4,426 Posts

Offenhauser 5414 is the solution, just need a couple more carbs. Also minimizes the intake heat dilemma.
 

·
Registered
Joined
·
185 Posts
If money isn't an issue, 6 or 8(straght 8) Weber side draft carbs for that ole school look, And tuning headache of trying to keep 6-8 carbs in tune with each other.
I did see a rat rod a few years ago, with a Pontiac OHC inline six, with what looked like headers tubing for each port with a 1 barrel carb for each port . He built a cover that matched the engines valve cover to cover the carb bodies.
 
1 - 8 of 8 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top