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Which engine 283 or350

2K views 14 replies 8 participants last post by  newjpguy 
#1 ·
Not a hotrod but a conversion,I would like to replace my AMC304, 2brl thats in my CJ7,with either a 283[ which I have on hand] or a 350[don't have]. The transmission is a TH400, with a 3.50 gear ratio, tire size 31.10/5.15. For fuel milage and cost of conversion, my question is, would there be enough hp from 283 to pwr this unit or should i just get a dealer 350 dropin. The 283 would need a rebuild, so it could get some of the modifications that were posted by Nairb on jan 5 2003[engines]. The pwr band of 283 is right for this gear and tire combo also.Thanks, need help to make a decision.
 
#3 ·
:D

I suggest buying a new crate 350 from GM. They are in the $1200 range here at my dealer. I just rebuilt the little 283 Chevrolet in my 40 Ford coupe. It has been in the 40 since 1957 so I felt it deserved to be redone and put back.......almost like a matching numbers kind of deal. I spent MORE money rebuilding the 283 than the cost of a new 350 crate engine :(

That's OK because I knew that would be the case. The stock 40 transmission and rear end are better suited to the 283.

1)The 350 will have hardened valve seats (unleaded fuels) and the 283 does not.

2) The 350 has a warranty

3) Depending on which 283 you have......the 350 has a better rear main seal

4)The 350 is worth more $$$ used

5) The 350 will make more bottom end HorsePower (which should be desirable in CJ7)

6) SOME 283's (57-early58) do not have side motor mounts and starter mounting provisions needed for most conversions.



You already have 304 inches....why go back to 283?
350 all the way..........


.
 
#6 ·
I'd find a 401 out of an old Waggoneer :D

Some of the first Jeep V8's were 265 and 283 Chevy swap-ins. However these were the FLatfender Jeeps which were a fair amount lighter than your 7.

Look around. Do you see any CJ-7's with 283 in them? Mostly you are going to see the 350, and sometimes a 383.

283 was a great little engine in the smaller cars of the day (Early Corvette :eek: ), but nowadays, 350 is pretty much the bottom of the performance spectrum.
 
#8 ·
I am what you would call a GM man, but I do stray a bit. 304 is worn, hard on fuel, and I feel not as dependable as a GM. I have a GM TH400 case which should mate sbc to the transfer[guts should be same,tail same, just bellhousing change]. Thanks tossing ideas
 
#9 ·
Guts are NOT the same. You most likely have the Borg Warner Quadratrac transfer case which doesn't actually have an input shaft per-se. The output on the tranny (coarse 9 or 10 spline) sticks all the way through the transfer case to the output shaft.

If you're going to use the GM 400, your best bet is chuck the Quadratrac case in favor of a GM unit, or another Jeep case (LIke the Dana 300) using an adapter.
 
#12 ·
Veing an AMC kind of guy, I find it laughable that the 304 is less reliable than a Chevy, Ford, etc. But I'm not biased. That a Chevy is more reliable than any other long made engine design is the same. I don't see a reliablilty problem with any of the V-8s design by the US makers. It's all in how careful you are rebuilding. The 304 is as reliable as a 350 Chevy as long as it is taken care off. The only issues the AMC engines have are similar to the problems other US made V-8s have -- the oiling system wasn't designed for sustained high rpm use (constantly over 5,000 rpm -- I'm not talking about occasional "blips" of short duration). AMC uses an oil pump similar to a Buick -- built into the timing cover. It just has to be set up right. Rather than check clearance as described in repair manual, use a gasket on hte pum cover and plastigage between cover and end of gears, and tighten it all down. Gasket thickness varies, and end clearance is critical for proper oil pressure. Check clearance around the gears too. A new timing cover will set you back $250 or so, but if the engine has been properly maintained it shouldn't be a problem. The heads on the AMC are hands down better than stock Chevy heads. The AMCs flow much more, even the 304 heads. All AMC heads have the same size ports, but the 304 uses smaller valves than the 360/401. 401s or 68-70 390s are the best as they have forged cranks and rods from the factory, but if you need more power the 360 from a late model Jeep will be an easy bolt in to the CJ. All external block dimensions are the same for all 67 and later AMC V-8s. Everything larger than a 304 uses bigger valves, but don't try 360 heads on a 304. The bore would need notching for the valves, and shrouding negates any possible gain. 360s are plentiful -- almost every Wagoneer you see will have one, and they were made through 1991. The fuel system sucks -- 2V carb with lots of pollution control crap on it. Best bet is to get a TBI system for it and throw all the crap away, or a good 600-650 cfm 4V if it's off road only. If you have to buy an engine to rebuild, or buy a rebuilt engine, that's your best bet. The AMC 360 will have every bit the power of a Chevy 350, and usually more low end torque (with stock cam anyway). The heads are comparable to Chevy LT-1 units. If you considered having to replace or heavily port the stock Chevy heads to meet the specs of the AMCs, it's cheaper to build the AMC (vs. run of the mill Chevy 350). Fewer parts choices with the AMC, but cost to build isn't much more than a Chevy if you're buying all new, comparable parts for both.
 
#15 ·
Sorry driving GM 30+ years got spoiled, this is my first AMC. 304-2,th400w vacuumlock, runs like a top,leaks oil, antifreeze, and blowby. Not impressed with Ford electrics, and 10 miles per gal fuel consumpsion[ coffee cup on breather- hardly a shimmer though?]. I do have a 360-2,th400wlowrange setup from Cherokee,but I figured maybe harder on fuel.If I can't modify tranny the way I was hoping for I may have to reinstal AMC.Doing complete rebuild glass body and all, replacement of transfer and tranny were not counted on. Still tearing jeep apart, so I've got time to search the info needed to improve fuel mileage in an AMC. Thank you very much for your input, it really helps.
 
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