Engine Rebuild / Performance / Heads / Cam / Etc
I created this thread to get some opinions on rebuilding the AMC 360 in my beast. I'll give some background on what led to needing it, as I think everyone will find it interesting.
For anyone following my rebuild thread (see my sig) you'll know I just did an 1,100 mile trip from Boise, ID to Sierra Vista, AZ. She ran well till about half way, where I figured the heat, altitude, ignition timing, and maybe a still-suspect lifter/cam lobe on #1 cylinder were making it run rough. Turns out none of those was the issue.
I popped off the air cleaner assembly to begin diagnosis and was met with a ton of oil soaked into the air filter and drowned insects:
PXL_20220615_001841059 by Robert Stone, on Flickr
The oil in the air cleaner told me I had a major cylinder compression leak into the crankcase forcing oil up into the breather tube, so I decided to take out all the plugs to localize the problem.
I discovered both the #5 (3rd back on driver side) and #8 (furthest back on passenger side) plugs just bashed and mangled. Great, the Jeep had turned into a V-6!
#5 electrodes almost touching:
PXL_20220615_004615686 by Robert Stone, on Flickr
#8 electrodes touching and porcelain missing:
PXL_20220615_011313746 by Robert Stone, on Flickr
Knowing bashed plugs come from debris in the cylinder, I decided to scope them both. Behold, I have missing bits from the piston crown and cratering in other areas. Pic shows the cylinder in top right with crown damage, and mirror image seen on cylinder wall in bottom left:
PXL_20220615_020847107 by Robert Stone, on Flickr
I'm thinking it ran hot/lean/bad at some point, caused the breakage to those 2 piston crowns, and the bits bashed the plugs. I know it started running rougher and hotter than normal near Las Vegas, but I blamed that on the weather and altitude at the time. I now know those 2 dead cylinders were causing the rough and hot running.
The only cause of the damage I can point to is when the engine stopped running on the highway 3 different times during the cold weather part of the trip in NV @ 7,000ft. Oddly, it never cut out in sweltering Las Vegas or throughout the hot AZ portion of the trip, so I wasn't sure if it was the Howell kit, or something else that caused the engine to just die completely in the cold weather. Oddly, I never heard any pre-detonation or any other warnings before it cut out those 3 times. Engine just quit suddenly, so I pulled over and restarted the engine without any issues.
So now that I know the reasons for the poor running, I replaced the 2 bad plugs and drove it around the neighborhood well enough, but she's obviously ready for a rebuild soon.
Odometer shows 246k miles on it, no idea how many the engine has on it.
This is where I'd like some input on rebuild options. I know BJ's / S&J do full long-block builds, but I'm really leaning toward keeping the rebuild local to me. I found a great engine shop in Huachuca City and am thinking about giving him the block to check, and if good, to rebuild the short-block for me, which would include dunking/cleaning, boring, align honing, squaring, crank machining/balancing, and full short-block assembly will be $2,000-2,500 depending on some variables and my long-block desires.
I'm also wanting to do some performance upgrades, but not sure on best bang for the buck. Something near 300HP or more would be nice.
That said, are Edelbrock heads a worthy upgrade over the stock dogleg heads?
I've read that a good RV-type cam/lifters, and 4bbl intake, combined with good headers, will really improve HP/TQ with the stock dogleg heads, so not really sure Edelbrock heads are even worth the coin beyond weight savings and some improved airflow. Maybe if I factor in the dogleg head rebuild costs the Eddies will still pencil out.
Can the dogleg heads be ported and polished to improve flow and performance, and if so, who can do the job well? I see BJ's offers a port and polish for $450 on their long-block page...
What else besides those big ticket items already mentioned do I need upgrade to hopefully double that sickly ~150 stock HP rating?
I'll stick with EFI, but will upgrade from the ancient Howell kit to a Holley Sniper or Edelbrock ProFlo 4 SEFI system I can easily monitor on my cell phone.
looks like typical detonation damage.
Given your goal I say do an LS swap or similar.
You're going to drop a crapload of coin on all new edelbrock stuff to update a 60's era engine design. Add in cost rebuild 360 and it's a no brainer.
I get the keep it AMC but a modern drivetrain will be way better in every way.
More hp, better driveability, cheaper widely available parts, increased fuel economy, etc.
Yeah, those 2 pistons were pretty well cratered in other areas I didn't bother to take pics of. Unfortunate for sure. No idea if they were already pretty bad off before the trip and the stress of towing a heavy trailer 1100 miles just exacerbated it, or if something went squirrelly with the Howell kit that then caused it (again, I have no history on the engine beyond what I've done). The beast never shut off again even after it started running rough near Las Vegas though, just crapped out in the snowy weather a few hours into the tip.
I'm going to stay away from the non-factory swap just to keep it simple. I'm not much of a purist anymore, but the ease of troubleshooting and later selling a stockish-engined vehicle takes a lot of guesswork out for anyone else looking to buy it down the road. I might add an AW4 transmission to improve MPGs someday, but for now the 727 works great.
Once I get the cash together I think Edelbrock heads, single-plane intake, Sniper EFI, and a decent cam will be all I want for the top end. I think that Pro-Flo 4 system may just be too overpriced for my needs.
Again...I get the stay AMC/stock thought process. However....
Edelbrock heads $3k
Engine rebuild $2k
Can easily buy a dropout LS changeover for less.
Understand spending more for exhaust/driveshafts/mounts/etc.
But honestly you need to consider the $ you're gonna spend just on stock rebuild+performance parts. for such little gain other than it "fits".
A swap isn't gonna be any more difficult to deal with for a future owner than stock. You're talking 30-40yr old crap(wiring/parts/etc.) already.
I don't know if it's the best thing to do, but it's what I did and I like it.
1) Machine to higher compression (9.5:1)
2) 260H cam
3) Performer manifold
4) Machine heads to take studs and use roller rockers
5) 4 barrel
This is a lot like what I'm thinking about lately. As Tony pointed out above, the cost of Edelbrock heads alone is close to a full rebuild of the stock long block, so I doubt I'll go that way at this point.
I may just have the stock dogleg heads rebuilt, mill a bit off the bottoms if possible, as apparently the heads flow decently if everything else around them is upgraded. If I can raise compression, put a better cam in it, and lower frictional losses with just a few more dollars spent that's sounding pretty good to me. I already have the Howell kit installed, so a 4bbl adapter plate for a new intake would be easy enough.
I just don't want to "reinvent the wheel" with an LS swap if I don't have to. It's all the detail work and extra time spent bastardizing things I wouldn't look forward to, though the HP/TQ upgrades are a nice-to-have.
All depends on how much coin and time I want to throw at it, and how to balance those out so I don't begin to hate the process.
I spent $1200 on my 401 heads being rebuilt. That was clean them, deck them, 5 angle seats, stainless exhaust valves, and assembly. I provided the valve springs, retainers, roller rockers, and rocker studs (the cost for the stuff I provided was not in the $1200 fee). I did a home port match on them, too. That was a lot of money, a lot of work that didn't net much.
I think even with rebuilt heads, an LS is still the better investment. You are going to drop $3000 on a mostly stock rebuild and end up with maybe 200hp and maybe 250lb/ft of torque. If you buy an adapter and put an LS in front of your TF727, you will end up with 300+hp and Torque, better MPG, will drop about 100 pounds off the front of your truck, and 10000 times better aftermarket support. My rebuild was almost the same as johnsonic's except I had a 268H cam, EFI, balanced, and forged pistons.
An LS gives you a lot more options in the future too. What I mean is, you can swap in a 4 speed auto much easier. You can add power adders, you can get repair parts at any McParts store, etc.
I'll add last pair of heads I had redone cost me over $1k. Simple valvejob + new springs/retainers/locks.
Spent $900+ on machine work for a SBC LT1 block ~same time.
A basic rebuild of an AMC is not gonna be cheap. Probably be in $3k range
Bought a 120k 5.3 LS with harness/pcm for $600...
Dropping a used LS into a FSJ will save a guy $ even WITH the added expense of the other bits.
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