All I know was it sure did sound sweet blastin away from the light in Bellview with the straight pipes!!

You scared that Mustang GT

Just drove to memphis and broke it up into 4 parts.

100 miles at 65 I got 29 mpg twice.

100 miles at 75-80 I gon 25 mpg

the 4th 100 mile trip was cut short when a brand new U-joint broke

I did put on the electronic ignition before leaving and hooked up the vacume advance witch definately was helping. It was a lot easier to maintain a steady speed and was more responsive when I was cruising and needed to go up a hill. Idle smoothed out like glass with the electronic ign.

It does definately want another gear (OD)in the tranny, it is turning nearly 3000 at 80.

Wow! Those are some really good numbers! Maybe you should pass some of your knowledge on to Chrysler.While I might not understand all the theory and such behind your build, I sure can appreciate your results!

too bad you're not made of money....I'd like to see comparisons with a small, fast ramp hydraulic (say a voodoo 60400) and the 273 solid in it, with both the 302 heads you're running and magnum heads....

it'd be interesting to see both mileage and performance numbers (be it RWHP/TQ or 1/4 mile times).....

I calculated your compression, assuming a 63cc head, 0 deck, 5cc valve reliefs and .039" gasket at about 9.6:1...what kind of gas does it run on? 87? 89? 92?


then it'd be interesting to see the same induction (heads, cams) comparisons on a 0 deck, flat top 360 short block, and what gas it would run on (it would be ~10.7:1 comp)

Anyone have numbers on what an electric water pump frees up?

Sounds like if you had the overdrive you would be in the 30s, or getting your current 65mph mileage at 80mph.

I forgot to mention I did a comp test with it warmed up and all plugs reoved throttle open and it was 160-165 psi. I was expecting a bit more with that little cam and high comp. I might get brave and try some mopar thin composite gaskets. My pistons are .005 below deck so it would bring up comp, give a little tighter quench and reduce crevice volume. I have not tried anything but 93 octane, it says it has ethenol on the pump but I don't know the %.

As for the highway miledge dropping off, I had a couple hundred pounds of tools in the trunck raising the front a couple inches from static Also I do beleive bringing the rpms down will help the higher speed mpg. It is running almost twice where the tq peak should be. I really had to keep my foot in it to cruise at 80, the wind drag wasn't that bad because it would coast in neutral just fine, it is engine brakeing very hard and that leads me to beleive a taller gear would help. Also if WOT peak efficency is at tq peak than cruising part throttle peak efficency would be at some RPM point lower than that.

Patrick if money was no problem I really would have been running a 273 with custom flat top pistons, no valve releifs, a custom solid roller and some magnums with 1.88 valves and seat inserts and epoxy to funnel the Air fuel in. I would also be running a offy dual port intake and probably some custom headers to promote low rpm tq.

I found a new 195 t-stat in my cabinet so I may try that soon. I am running a 180 right now. I have an electric fan and never need to use it unless I am waiting in line at the bank

The w-pump is belt driven, I would expect a gain from an electric one but it would be very small and not worth the complication IMO.

As for teaching the OEMs something, they have to know everything I am doing, nothing fancy (yet)just applying common sense and fixing what they screwed up, heck I don't even have efi

OK...I wasn't going to go here...but I gotta. If I was going to replicate this build, starting with a roller block, what kind of specs/numbers should I be looking at out of the cam???

Dave, I hear ya, but I personally doubt the 45 fewer CID would have a super significant effect on economy, especially if you used a fast rate roller hydraulic in a roller teen block. you're probably fine with the .030-.033" quench the MP gaskets will provide, especially since I doubt this engine is/will be revved past 5k.

4speeds, if it were me, I'd slightly sacrafice mileage for power and use something like this cam, with mag heads, since they flow so much better than the 302's, and I doubt they'd have much hit in economy.

http://store.summitracing.com/partdetail.asp?part=LUN%2D60710&autoview=sku

if you were more economy minded, I'd go with something like this:
http://www.hughesengines.com/partDetail.asp?partID=11409&eTypeID=1

I wouldn't choose that one because it specs out nearly identical to a factory roller cam, which you can usually pick up brand new for about 1/4 the cost of that crane one.....

Great numbers Dave. I'm building a larger version of this engine (408) with magnum heads and an overdrive trany. With the kind of numbers you have achieved I'm sure I'll be in the 20's for mileage

Now ditch that 904 for an aluminum OD four speed and break 30 mpg. Or maybe a 5 speed out of a Dakota.

Out of curiosity, do you know the lobe specs on that 273 cam?

I think with the OD I will gain some MPG at higher speeds, mabey another 2 mpg I am hopeing.

My theory on the 408 is with a .69 OD it will consume the same amount of air/fuel mix as a 281 inch motor set up like mine without OD so you might get a touch better MPG with a very mild 408 and an OD. My stroker that I will build when I get time and money will be a 416 and with mag heads and whatever I learn from this combo I should still get high 20s with the OD.

I just heard from the driveshaft shop and they said my shaft is trash and they want $230 to make me a new one. It might be sitting for a while

Bummer about the driveshaft. If my 408 get 25 MPG I'll be I'll be driving that thing all the time!!

If you drive it like it won't get 25 mpg

What's the rest of your build?

Yeah, I know it won't do too well with my foot in it. Here is my set up. Roller block with .506 lift, 114 lobe seperation. Duration intake 216. Duration exhaust 224. M-1 Dual plane intake good for 0 to 5000RPM. 10.2 to 1 static compression using Wiesco 20cc dish pistons set to .005 above deck. Magnum heads cleaned up and intake bowls opened. I'm getting 155 PSI cranking compression with this combo at 5000 ft. I just put a 650 Holley carb on it and the response is great( on the run stand anyway). Still need to do alot of tuning once it's in the car but so far it's looking real good. Engine is internally balanced. I did use the cheap chinese cast crank and I beam rods but it all went together well.Hope it don't blow up!! Will be running a .70 overdrive trany. All this in a 71 Duster.