Just a heads up there is a set of 920 heads for sale on for a bodies only now. Any idea what the combustion chamber size on those is?

I have a pair of nice 920s in the attic I think the chambers were 58CC but it has been a long time and going strictly by memory on that. Maybe I could find some cheap 1.6 or 1.7 shaft rockers and a long runner MPI intake for LA heads... better yet could I buy a TBI with 8 injectors and just extend the existing wires to pulse them? I really think TBI is the best for an MPG project, the last mass produced engine sold in the USA with TBI got 50+ MPG.

TBI can be “spot on” if the intake manifold is “spot on” dividing air flow to each cylinder equally.

Since most TBI has 2 injectors or more,
that tells you it is hard to divide to each cylinder runner equally.

Having sequential multi point fuel injection SMPI seems good,
but should not each fuel injector be of slightly different flow rate to “put the icing on the cake”
since it is nearly impossible to make all intake runners flow equally?

Modern SMPI with equal flow rate injectors are said to typically be 8% off from best to worst air to fuel ratio deviation result.

Those heads on a roller/magnum tweener 318 block with the kegger and your 92 obd1 might be an interesting combo. Might help you get another 1pt of compression you mentioned you wanted depending on how much the heads could be cut.

OK so I got to thinking about this, pulled those heads from the attic and CCd them at 64 CC and can easily take .080 off before getting close to the valve, I could even throw in some old 1.88s and still mill .070. The PR pinch is wider than a magnum head and has a hole drilled for it instead of the raw casting like the magnum so it could be opened even more... from past experience I know I will have to slot the PR hole larger side to side to fit a roller cam motor (or go flat tappet) but that will not restrict the pinch width. I would just need to figure out how to drill the bolt holes for the kegger (backwards jig?)and find pushrods, rockers, 1.88s...


Just filling and eyeballing the level till it just barely covered the intake valve gives me 52 CC chambers. Plugging that into KB calculator with .030 quench gives me 12.2 compression. Maybe I can find flat valves to get a tiny bit more....

I need a math genius to double check my math but I figure I need to retard the cam timing about 20 degrees to keep cylinder pressure similar to the motor I ran in that 1500 ram. This would also allow the exhaust another 20 degree push on the crank. This is the cam specs I found for the 92 cam, (I am gonna assume the 98 cam was close enough to the same it wouldn't really matter).

Intake valve diameter 1.925 inches
Cam design type: mild hydraulic roller
Intake valve timing:
......Lobe centerline 115.5
......Advertised duration 251 degrees
......Opens btdc 10 degrees
......Closes abdc 61
.....maximum lobe lift 0.27 inches
.....rocker arm ratio 1.6
.....gross intake valve lift 0.432
Exhaust Valve diameter 1.625 inches
.....Lobe centerline 109.5
.....Advertised duration 261
.....Opens bbdc 60 degrees
.....closes atdc 21
.....maximum ex lobe lift 0.27
.....rocker arm ratio 1.6
.....gross exhaust valve lift 0.432


Going from 10.2 compression to 12.2 compression and retarding the cam timing 20* gives me a bump from 8.3 dynamic to 8.5 dynamic if I am right.

I found a hughes 9001 cam in the attic I forgot about, can't find specs butt I think it was pretty small

1994-1995 iron V10 camshaft specs might be a clue to the best fuel economy.

In their SAE paper Chrysler engineers proudly stated that this new bigger ”towing” engine was more than 10% better BSFC than the GM 454 V8

Since there has been a clear trend from 180 on up to 207+ coolant temperatures think about experimenting there.
Since there is good older evidence that 140 - 160 is best for peak high rpm power,
those higher coolant temps were adopted to increase fuel economy at lower cruise rpms.

5.7 engine’s variable valve timing would allow “dialing in” the highest tolerable dynamic compression ratio.
A “de-stroked” 5.7 with a longer connecting rod would have “superior leverage” with a less torque robbing rod to crank angle.

I already run a 205 t-stat in all my magnum powered trucks, I can't find any higher.

The rod stroke ratio is over 1.85 in a 318, the 5.7 is just over 1.74, to match the 318 it would need about 3.35 stroke witch is too much to gain (lose?) from offset grinding and using stock bearing undersizes so then I need different rods probably a chevy 2.0 size, then custom pistons and balancing. I have a set of 6.25" 2.1" journal chevy rods (I think there are bearings to use with a 2.0 journal in these larger rods) but it would still need custom pistons balancing and the machine work to destroke it and I should probably buy a steel 6.1 crank to replace the 5.7 cast crank if turning it down that much.

Like I said I could easily build a late 5.7 with early 5.7 pistons with stuff I have laying around, it would be very easy to fine tune a tight quench (around .030) and very high compression (12.5ish) as the pistons are taller and have a larger dome and MDS would be sweet for this also so the actual engine it'self would be the easy part, the rotating mass is waaaay lighter than an old 318... I really would love to run a new hemi but man the installation kit stuff is very expensive, $900 headers, $150, motor mounts, $2000+ engine control, custom AC lines, PS lines, coolant hoses... and so far nobody has volunteered parts or money, sticking with the magnum I can re-use a ton of stuff.

HRD does the 205 thermostat help mileage or is it an emissions thing? I have always run a 180 stat as I don't like running on the edge of overheating all the time. Atlanta asphalt in the summer sitting in traffic is like an oven.

The hughes cam you found- is it a 9704? That is the current baby roller cam they offer for 318's. IIRC they started similar grinds at number 9701.

I just use it for hotter heat and a little better MPG, I don't really concern myself with emissions.

a 205 T-stat doesn't fully open until 210 or 215 degrees, so the engine will usually run a couple [?] degrees hotter sitting in traffic.
this is where a factory designed cooling fan/shroud assembly works very well keeping the temperature in check.
these days, i prefer a factory setup over any aftermarket item, although others have had success using what the aftermarket offers.
just my experience and opinion.
your mileage will vary.

I run a dual electric fan setup from a Dodge Intrepid in my B1500. OEM part from a donor. It along with the aftermarket 3 row rad do a much better job at cooling than the OEM set up ever did.

I am not interested in any chinese electrical parts though. My experience has been I am better off setting the money on fire and saving the aggravation of having to replace them again in the next month or so.

My temp barely gets to 205* on a hot day, it only actually runs a couple degrees warmer than a 195*.

I second the use of OE electric fans, those aftermarket ones barely do anything. I have found that I can run around without any fan on most rigs and never get hot as long as it don't sit and idle at the drive thru or anything.

185 thermostats have been the specified rating since at least the 40's. Nothing to do with economy, everything to do with decreased engine wear not to mention oil sludging.

In fact a well know MOPAR engine builder told me to not leave the line (with aluminum heads) till the temp was 210 degrees so to build heat into them. The difference was 3 tenths in the eight, from 160 to 210 degrees

A 180 thermostat doesn't being to open until 3 or so degrees of its rated temp- so 177. Full open temp is 15-20 degrees above the rated temp. Most engine wear happens on startup and is not because of a 180 vs 205 thermostat.

You would be wrong. Go peruse the image I attached to my prior post. Begins opening at 157-162 degrees, fully open at 183-187 degrees. Uses the same thermostat as the pre-79 v8's and the values were confirmed this last weekend with my IR gun.

The rated temperature is the fully open temperature.

You reference a paper that shows a temp for the beginning of opening at about 160 degrees, and fully opened at 180. That is a 160 stat.

IR guns are notoriously inaccurate. Not sure how you could get a temp on the thermostat itself through the housing anyway.


https://knowhow.napaonline.com/temperature-control-engine-thermostat-testing-tips-and-
tricks/#:~:text=The%20rating%20listed%20on%20the,180%2C%20so%20177%20to%20183.

"The rating listed on the thermostat is the point at which the device begins to open. This is not the full open temperature, which is typically 15-20 degrees above the listed temp. For example, a 180 degree thermostat begins to open within three degrees of 180, so 177 to 183."



https://www.aa1car.com/library/thermostat_diagnose_replace.htm


"Most late model thermostats are calibrated top open around 195 to 200 degrees F. The thermostat should be fully open about 20 degrees F higher than its rated temperature for maximum flow, and should maintain engine temperature in the 200 to 230 degree range."

I should not have mentioned thermostats, since replies wandered off topic from Super duper MPG.
Sorry Dave.