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post #1 of (permalink) Old 06-18-2006, 04:16 PM Thread Starter
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AMC 304

I pulled an AMC 304 from a junkyard CJ5 over a month ago for my CJ7. Got some money saved up to start rebuilding the thing.
Never built an engine before. I want to keep it cheap and stock.
Ready to take the block and heads to a machine shop this week.
Anyone have a good link to a site for rebuilding engines or where to get replacement parts for AMC.
Also, what parts definitely need to be replaced? Thanks.
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post #2 of (permalink) Old 06-18-2006, 06:15 PM
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Re: AMC 304

I rebuilt a 304 for my jeep a few years ago for around $1200. Jeepchick got the jeep hot and melted a couple pistons. For some odd reason the rebuilder told me that the first bore size for AMCs was .020 over instead of the more standard .030 like chevy. I might have gone more if I knew at the time the 304 had such a thick block and could handle a bigger bore. New pistons, rings, ground the crank, new cam, lifters ect. Also had the heads done at the same time. Your rebuilder should be able to get any parts for your 304. Mine had to dig out an old dusty AMC book that had everything needed for the rebuild. That was about 8 or 9 years ago and the motor still runs great. I'm ready to move on now. I have a 360 waiting for a rebuild. Ye-Haaa!
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post #3 of (permalink) Old 06-18-2006, 06:45 PM
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Re: AMC 304

NAPA will have all the parts you need. I rebuilt mine a few months ago. I agree that the cost will be in the $1000-1200 range though.
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post #4 of (permalink) Old 06-18-2006, 06:49 PM
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Re: AMC 304

I got all the parts for my 360 from Interstate Motor Supply in Danville. Good parts (crank, bearings, timing chain, cover, oil pump gear...) good price and great customer service.
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post #5 of (permalink) Old 06-20-2006, 08:58 AM
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Re: AMC 304

I did this for a living for several years, but internet advice is worth exactly what you pay for it...

No compromise here,...

1. Fel-Pro Gasket Set.
2. Clevite 77 engine bearing set.
These two things alone will save you more energy, effort & aggravation than anything else.

Always check your engine bearings, pistons & rings when they come in.
Things are often put in the wrong boxes, or broken when the come in, so pre assembly inspection is vital.

Decide what piston you are going to use.
Your common choices are Cast, Hypereutectic , and Forged.

Cast are just that and nothing more. Cast aluminum.

Hypereutectic are cast pistons with increased heat and abuse (detonation, overheating, ect.) resistance.

Forged pistons are a forged billet machined down into a piston.
They are VERY strong and can be very expensive.

With extensive use, we have found Hypereutectic pistons hold up just as well as forged in common usage.
Forged would be better in a racing situation, but Hypereutectic does fine in most stock or mildly built applications.

Do not allow a cold assembly of piston & rod!
Cast iron rods don't take kindly to having a cold piston wrist pin shoved through a too small hole!
The cast iron rod small end has to be heated before the piston wrist pin is installed or cracks will result! (This should be common sense, but you would be surprised how many install cold!)

You will also need to pick a piston ring type.

Most rings are ductile iron.
Just cast iron with a high nickel content.

The next step up is Molybdenum rings.
Chromium and molybdenum are added to cast iron to make the ring harder on the outside edge, giving the piston better bore seal.

Stainless steel.
Gapless and stainless steel 'endless' type rings are very good for alternative fuels, like alcohol, propane, ect.
Expensive and difficult to install correctly.
Add nothing to low RPM stock type engines.

Ductile Iron, Chrome-Molly, and Stainless steel rings all require different bore finishes, so you must decide before block machining.
'Molly' rings require a much finer finish on cylinder walls or the coating will be chipped off.

Connecting rods.
290, 304, 360 AMC engines were never offered with forged steel crankshafts or forged steel connecting rods.

DO NOT let anyone talk you into larger rod bolts!
The steel rod bolt is already many times stronger than the cast iron connecting rod, so removing (and weakening) the cast iron connecting rod further by removing material for larger rod bolts is a stupid idea!

Always check the rods for crack before doing anything else to them...
Use a good set of rod bolts, (1st choice is SPS, 2nd is ARP, 3rd is Milodon), STOCK SIZE and resize the rod bores.
Never reuse factory AMC rod bolts. Do a search here and you can find the horror stories about stock rod bolt & nut failure when reused.

Cast iron rods should ALWAYS be in a rod vice or rod clamp when removing or installing rod bolts, and a large end resize is mandatory after rod bolts are replaced.

Crankshafts were cast iron, but not nodular cast iron, so there are no special requirements for machining or polishing the crank.
Rolled fillets on the crank require correct bearing relief placement, but that's the only 'Gotcha'.

A quality main cap & head bolt set are cheap insurance against failure.

Cam Shaft & Supporting Gear...

Cam bearings are often incorrectly installed in AMC engines.
The cam bearing oil gallery comes into the cam bore at an angle, and most people cover, or at least partially cover the oil gallery hole with the cam bearing.
AMC doesn't deliver great amounts of oil to the rear of the engine anyway, and blocking the oil to the camshaft is a REALLY BAD IDEA!

Cam & Lifter sets are always a good idea. Edelbrock makes a good cam and lifter set that are matched and will fit into stock engines without modification.

There is a big difference between a 'Timing Set' (timing chain & sprockets)
--And yes, when it handles a chain it's a sprocket, not a 'gear'...--
A 'Roller Timing Chain', and a 'True Double Roller Timing Chain"
A 'True Double Roller Timing Chain' is the way to go.

The timing chain in an AMC engine doesn't get much lubricant, and real rollers help a lot.
Edelbrock sells a very reasonably priced True Double Roller timing set that is correctly machined for AMC engines.

You will also want to acquire a new distributor drive gear, as well as the distributor gear it's self.
Both of these will have substantial wear and will need to be replaced.
The distributor/oil pump drive gear attaches to the end of the cam shaft, and is not part of the cam shaft like other engines have.

You will also need to locate a fresh fuel pump eccentric if you are using a mechanical fuel pump.
It's also bolted to the end of the camshaft and will need to be replaced.

Oil To The Internal Accessories!

You may want to take this time to do things like an external or internal oiler to the front of the engine for the accessory drives (distributor drive, timing set, fuel pump drive eccentric).
It's as simple as drilling and tapping a hole or two and/or adding an oil line.
Will add decades to the effective usefulness of your distributor drive gear, fuel pump eccentric and timing set.
There have been at least two front end oilers developed on this BBS, and I'm sure there are more.

You may also want your machine shop to add an internal oiler in the lifter valley.
This is a couple of fittings and some heavy oil line to feed extra oil to the back of the block.
The rear of an AMC engine is starved for oil, and adding this extra line will greatly relieve that problem.

Do a search or ask LEVE for his vast knowledge of stored files around here and I'm sure he'll come up with the articles and posts.

More for the asking, just let me know...
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post #6 of (permalink) Old 06-20-2006, 11:34 PM
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Re: AMC 304

^^^ "the V8 Gospel" according to AMC ^^^
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post #7 of (permalink) Old 06-21-2006, 05:03 PM
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Re: AMC 304

I don't know about "Gospel", but I've seen a lot of AMC engines go south because of a few small quirks that weren't taken care of properly.
If I were you, I'd do both of the oil upgrades. The others are optional at your discretion, but recommended...

The AMC V-8 engine gets little or no oil pressure to the rear main bearings and cam bearings.
A simple feed line installed in the lifter valley will do wonders for this problem.
Around $30 and easy for a machine shop to install.
Try here, and enter, "Oil Line Kit" or "MOKV8".

A simple oil line added to the front of the engine will give a constant oil supply to the timing set, distributor drive gears and the fuel pump eccentric.
This is noting more than a couple of fittings, couple of feet of oil line, and a mig welder tip.
The hardest part about the install is drilling and tapping the front cover.
This will also cost around $30.

An alternate version of the front end accessory drive oiler is available, but must be done before final assembly of the engine.
This cost nothing but a drill, tap and mig welder tip.

Oil pump upgrades are always a good idea with an AMC engine.
There are several types of oil pump 'upgrades', from just using new gears to using a new front timing cover housing with an iron insert in the oil pump housing. (which works very well by the way, but is about $500)
I suggest you don't buy an 'economy' oil pump kit. Stick with a name brand, quality piece.
You get what you pay for, and if you want $20 worth of oil pump, that's exactly what you will get!

Using roller tipped rockers (not necessarily full roller rockers, but rollers on the valve stem top) will free up a little horsepower, but more importantly will reduce the amount of oil needed at the top end, and will reduce the stress on the valve stem and valve guides.
The new roller tipped rockers are about the same price as a good quality stock replacement rocker arm.
This will also give you adjustable rockers instead of the fixed rockers that like to make so much noise in AMC engines.

Using roller tipped rockers or full roller rockers will require the drilling and tapping of the rocker support towers.
Drill and tap for a 3/8" stud and you can use any of the aftermarket self aligning roller tipped rockers...

AMC used a very good flowing head design. Actually excellent for the time period.
A better intake manifold than the stock low rise, cast iron design is a good source of cheap horsepower and torque, cuts down on weight and helps shed engine heat.
Don't try the race car types, they don't start working until after you have reached your RPM limit.
Edelbrock Performer (not the RPM Performer does very well on low rpm & daily driving applications even with a two barrel carb.
This particular intake has all of the fittings for your vacuum hardware and the exhaust gas ports for your emissions stuff.

Headers should be given consideration.
Most people buy what ever is cheapest. Not a good idea when you are going to be banging around on them.
A set with thick flanges will be a very good idea.
Keep your headers inside the frame. Exhaust shop bill will be a little more for bending pipes, but you won't be tearing them off like you will if they are outside the frame rails...
Full exhaust and good mufflers are always appreciated by people you ride with.
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