273 mileage build ideas

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toypar

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I am in the process of gathering up parts for a V8 swap in a 4 cylinder jeep I have. I have a 40,000 mile 66 273 I used to have in a Toyota pickup years ago. I had installed a 340 cam and valve springs and ended up spinning a rod bearing. Pulled it out and installed a 318. Anyway...

This jeep I have has a 4 cyl, I could swap a 4.0l six in it, but looking at the stock specs of a 2v 273 it produces max torque at 1600 RPM where as the 4.0l produces it at around 3500. HP and torque and weight are very close between the 273 and 4.0l.

I don't really want a powerhouse, just something to idle around and cruise decent. I really want to build is engine to get the best mileage possible. I am thinking probably putting back to stock down to the solid camshaft and 2v would be ideal. (Solid might get better mileage due to lower friction on the valvetrain over hyd???)

I have had no luck finding a solid replacement cam, and looking at engine specs with the 235hp 273 cam shows peak torque at 4000!! I believe that is to high for my application.

Any suggestions to another cam, intake or carburetor combo for an efficient engine??
 
I have looked at that thread, lots of good info. I believe he used a stock 273 2v cam and heads if I'm not mistaken. Now just finding a stock cam in decent shape is the dilemma. I have even thought about a SP2P and a Thermoquad, Or a 2v Rochester (Similar to a Quadrajet, just cut in half)

Yes the gears are steep at 4.10s, but it will have the same five speed as a 90s dakota, and possibly 31-33 inch tires.
 
toypar said:
I have looked at that thread, lots of good info. I believe he used a stock 273 2v cam and heads if I'm not mistaken. Now just finding a stock cam in decent shape is the dilemma. I have even thought about a SP2P and a Thermoquad, Or a 2v Rochester (Similar to a Quadrajet, just cut in half)

Yes the gears are steep at 4.10s, but it will have the same five speed as a 90s dakota, and possibly 31-33 inch tires.
Click to expand...

Hah, I have a stock 273 cam that had 79k miles. I didn't pay much attention when I put it on the shelf but I think it was in good shape.
 
You could probably just use a later model flat tappet 318 cam, pretty similar specs and hydraulic lifters..just a thought.
 
If you have a useable core, Oregon Cam can regrind it to factory specs for either 2 bbl or 4 bbl solid lifter. They have patterns for both. They quoted me $80 a few years ago, but shipping both ways hurts.

In my 1965 273, I changed to a hydraulic cam w/ Rhoads "leak-down" lifters. I used the common "RV/Torquer" cam (~$120 w/ lifters on ebay) which despite the name has a bit more valve lift (0.422/0.444) than even the factory HiPo 4 bbl cam, but the Rhoads lifters make it act small at low rpm for better mileage. The adjustable lifters make setting lifter pre-load easy. PM me if interested in an extra set of Rhoads lifters I have (far below list price).

I never read that a solid cam has less friction than hydraulic. I think you need a roller cam, like Magnum engines to get less friction. I read those give 8% better mileage, but suspect more due to an aggressive cam profile than less friction.
 
273(4.5L) V8 would have better out put than a similar size 6 cylinder cause more overall head flow 8 ports vs 6 ports, the 6's ports would have to flow 33% more than the 8's to equal out. 273 bore size is an advantage where hurts high end HP but for efficency gives a more complete burn. I'd go with 9:1CR, performer intake with 600 Carb, High lift 256ish cam and 340/360 manifolds or headers and a good valve job and pocket porting couldn't hurt.
 
Never thought of Oregon Cam grinding. I should give him a call. My dad has drag raced with the owner for years.

I have never looked into Rhoads lifters. I don't know much about them. I will do some research.

There probably isn't much to be gained in mileage with a roller cam with a factory profile cam. I am sure the money for roller lifters could be spent on something else that would give a bigger gain. Although the piece of mind of not getting a flat cam with today's oils would be nice.

I think I will scrap the 2v idea and just go with a performer, with either a Thermoquad, 450 economaster, or possibly be a mileage Guinea pig for the New street demon.

I have a nice set of 340 exhaust manifolds, but king of hate to use them on a jeep. I was thinking magnum manifolds or find/build a set of 1.5 inch headers.

I wouldn't mind playing around a little higher compression, tight quench and water injection. I just need to realize the vehicle it is going in is like a wind sail going down the road. I would be happy if I could get around 18 mpg in town and 22 mpg on the highway at 65.

My first idea was to put a 1.9 TDI out of a VW. But after pricing a donor vehicle and adapters, that would buy about 5-6 years worth of fuel. THis small block swap is pretty much free.
 
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