300 Six Compression Ratio, Intakes, Heads, etc

[1986F150Six]

Jonathan:

I agree, that is one tall OD ratio, and it explains why David can cruise at such low RPM and yet have good MPH.

If I could pursue my dream [had enough money and talent?], I would raise compression, lightly port and polish [clean valve pockets, etc.] the head, install either F.I. exhaust manifolds or H.D. [preferable] exhaust manifold with a free flowing exhaust and find an Edelbrock 1 barrel intake manifold to use with my present carburetor.

Hmmm? I might even try an adapter and install a 32/36 Weber carburetor.

This would be to further the quest for best gas mileage.

 

[Gary Lewis]

Jonathan:

I agree, that is one tall OD ratio, and it explains why David can cruise at such low RPM and yet have good MPH.

If I could pursue my dream [had enough money and talent?], I would raise compression, lightly port and polish [clean valve pockets, etc.] the head, install either F.I. exhaust manifolds or H.D. [preferable] exhaust manifold with a free flowing exhaust and find an Edelbrock 1 barrel intake manifold to use with my present carburetor.

Hmmm? I might even try an adapter and install a 32/36 Weber carburetor.

This would be to further the quest for best gas mileage.

I think a compression ratio boost would give you the biggest MPG improvement, followed by a better intake manifold. Compression helps efficiency, and an even distribution of the air/fuel mix allows you to tune the ratio to get the best economy. And I doubt that the spider of an intake from the factory can have even distribution.

It would be interesting to put a wide-band AFR meter on the individual exhausts for a 300 and see how poor the distribution is. Then you'd know if you are fighting a losing battle tuning the carb - whatever carb it is. My guess is that the end cylinders are way off from the center cylinders, so aren't contributing to the efficiency of the engine as they should be. And, if I'm right, it won't make a whole lot of difference what carb you have.

Having said that, I believe that having a split manifold with two small carbs would significantly improve the distribution and let you tune the carb much more precisely.

But, that's just my guess with no empirical data. Perhaps the Frenchtown Flyer knows?

[1986F150Six]

But, that's just my guess with no empirical data. Perhaps the Frenchtown Flyer knows?

I hope I am not misquoting him, but a number of years ago, he attributed the broad [desirable] torque curve to the poor intake and exhaust manifolds! I believe what he meant was that at any given RPM range [probably ~1200-2000 RPMs], a couple of the cylinders were at their peak, so as some "came on" and others "dropped off" in efficiency, the torque band was widened.

 

[Gary Lewis]

But, that's just my guess with no empirical data. Perhaps the Frenchtown Flyer knows?

I hope I am not misquoting him, but a number of years ago, he attributed the broad [desirable] torque curve to the poor intake and exhaust manifolds! I believe what he meant was that at any given RPM range [probably ~1200-2000 RPMs], a couple of the cylinders were at their peak, so as some "came on" and others "dropped off" in efficiency, the torque band was widened.

Probably true, but an engine is most efficient at its torque peak. So, I would guess that the more pronounced that torque peak the better the efficiency when operating at it. Conversely, a broad torque peak would reduce the efficiency at that torque peak.

[Ford F834]

Jonathan:

I agree, that is one tall OD ratio, and it explains why David can cruise at such low RPM and yet have good MPH.

If I could pursue my dream [had enough money and talent?], I would raise compression, lightly port and polish [clean valve pockets, etc.] the head, install either F.I. exhaust manifolds or H.D. [preferable] exhaust manifold with a free flowing exhaust and find an Edelbrock 1 barrel intake manifold to use with my present carburetor.

Hmmm? I might even try an adapter and install a 32/36 Weber carburetor.

This would be to further the quest for best gas mileage.

David, is this the intake? Looks like it would even out the carb to cylinder distance quite a bit, yet is still for 1 bbl.

I agree that raising compression would help with efficiency, but what about cam/valve timing? Is there a profile and timing set that could help build cylinder pressure and hold gear at lower rpm? I know most performance parts are geared towards maximum power but the rock crawler crowd must create demand for low end torque parts...

[1986F150Six]

David, is this the intake? Looks like it would even out the carb to cylinder distance quite a bit, yet is still for 1 bbl.

I agree that raising compression would help with efficiency, but what about cam/valve timing? Is there a profile and timing set that could help build cylinder pressure and hold gear at lower rpm? I know most performance parts are geared towards maximum power but the rock crawler crowd must create demand for low end torque parts...

Yes, Jonathan, that is the manifold. The runner diameters are reportedly smaller with smoother bends [radii?] when compared to the factory log intake manifold. This was to enhance lower speed power [gas mileage] rather than higher speed power like a 4 barrel intake [i.e. Clifford or Offenhauser].

Regarding the camshaft: looking at the 1982 Ford Specification Sheet as provided by Gary, it is noted that a "reduced overlap camshaft" was used in all 300 engines with all manual transmissions & 2.47 or 2.75 rear axles - 49 states only.

[1986F150Six]

Having said that, I believe that having a split manifold with two small carbs would significantly improve the distribution and let you tune the carb much more precisely.

How about a split manifold with three small [stock] carburetors? This was made using three middle sections from a stock intake manifold.

https://www.jalopyjournal.com/forum/attachments/int3x108-jpg.3824400/

 

[85lebaront2]

Having said that, I believe that having a split manifold with two small carbs would significantly improve the distribution and let you tune the carb much more precisely.

How about a split manifold with three small [stock] carburetors? This was made using three middle sections from a stock intake manifold.

https://www.jalopyjournal.com/forum/attachments/int3x108-jpg.3824400/

The trick on that would be if you can make them progressive, i.e. center, then ends. I helped a friend years ago with a 240 engine build a setup using dual Holley/Weber progressive two barrels. It ran great, but then so did the kid's who worked for me Chevy 250 with dual Stromberg 4A1 carbs.

The front/rear firing order on an in-line six lends itself to a front-rear carb setup where the intake sequence is 1,3,2 front and 6,4,5 rear or if you think about it, center to ends alternating. Many European and Japanese in-lines used dual carbs with excellent performance and economy.

If you split the carbs front and rear, you have two 150 ci engines, the Holley/Webers are commonly a 32/36 size with 32/36 being the throttle sizes in millimeters. Pinto engines were 140 ci. The Pinto carbs used (a) removable jets for both main and idle circuits (b) mechanical secondaries and © hot water chokes. We used a Clifford manifold and a pair of adapters to take the Pinto carbs to the small square bolt pattern on the intake. We made two plates for the "hot spots" under the carbs and ran the heater circuit through there, teed both chokes in parallel and then to the heater and back to the water pump. A bypass valve was put in so the heater flow could be shut off in warm weather.

[Gary Lewis]

Ok, I apparently have the calculator perfected and no one can find anything whatsoever to suggest.

That being the case, now let's go back to the 300 six intake discussion. I've been thinking about the multi-carb setup with a progressive linkage. It seems to me that if you are trying to fine tune the AFR, and if the loooong intake is causing cylinder-to-cylinder differences, then the best way to fix that would be with two or three smaller carbs - but not with progressive linkage.

I say that because progressive linkage runs off the center carb until more power is needed. But that puts you right back where you started from with one carb and a long manifold. So, it would seem to me that several little carbs with a linear linkage would be better. In other words, run two 3-cylinder engines or three 2-cylinder engines, each with their own carb.

But, having said all of that, why not go with the later EFI setup? However, I don't know if the 300 ever came with EEC-V, mass air flow, and SEFI. If it didn't it wouldn't be that difficult to convert it.

[85lebaront2]

Ok, I apparently have the calculator perfected and no one can find anything whatsoever to suggest.

That being the case, now let's go back to the 300 six intake discussion. I've been thinking about the multi-carb setup with a progressive linkage. It seems to me that if you are trying to fine tune the AFR, and if the loooong intake is causing cylinder-to-cylinder differences, then the best way to fix that would be with two or three smaller carbs - but not with progressive linkage.

I say that because progressive linkage runs off the center carb until more power is needed. But that puts you right back where you started from with one carb and a long manifold. So, it would seem to me that several little carbs with a linear linkage would be better. In other words, run two 3-cylinder engines or three 2-cylinder engines, each with their own carb.

But, having said all of that, why not go with the later EFI setup? However, I don't know if the 300 ever came with EEC-V, mass air flow, and SEFI. If it didn't it wouldn't be that difficult to convert it.

Of, first, my internet was out from 1800 yesterday until 1030 today so I couldn't see let alone comment.

On the multiple carb 6, dual progressive 2 barrels (Pinto Holley/Webers) work quite well, have water heated automatic chokes and are designed to mount sideways on the engine. This essentially works as 2 3 cyl engines sharing a common distributor. Many European cars (Mercedes-Benz, BMW) some domestic Japanese cars (Nissan Maxima, Toyota Crown) used similar setups, and I suspect some of the early Australian Barra engines may have had something on the same order.

A single 4 barrel in the center worked well on the Chrysler Slant 6 due to the long runners, other examples, Pontiac Sprint OHC 215/230 used a sideways facing Quadrajet, Mercedes-Benz 280C and S before switching to injection, used a Solex 4A1 (Quadrajet copy) but it used a very peculiar intake, carb was mounted like it was on a V8, the manifold was split so each pair of barrels (primary and secondary) fed 3 cyls. It was not a real efficient design, and coupled with the total lack of power enrichment made for a real POS as far as running. Low throttle acceleration was abysmal, WOT decent at the expense of poor fuel economy.

If you go to 3 carbs, the manifold should allow for each to primarily feed a pair of cyls, good examples of that are, early Corvette, 3 Carter YH side drafts, Jaguar E-type 3.8/4.2L, 3 SU HD8s. Both of these were synchronized, meaning all 3 carbs opened together. There was a kit for the old Falcon/Comet/Mustang in-lines that put 3 stock carbs on the integral log manifold, these did run as a progressive system, 1 then 3 as that gave the best distribution. Best 3 carb system, 3 40 or 45DCOE Webers, wicked sound, lots of power.

EFI, 1996 300 had MAF/SEFI and some 1995 CA spec engines, but that would have been EEC-IV which is in the EFI pinouts, I have just added the 1996 4.9L pinouts and before I send you the updates will add the 5.0L and 5.8L 1996 information.