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AMC 258
- Thread starter bigred88
- Start date
This thread is just going to follow me building an AMC 258 for my AMC Spirit. Most of the car is a 20 year old restoration that my dumb high school self attempted with varying degrees of success. I've never opened up the engine, and it's long over du
bigred88
1/2 ton status
If theres any interest, I figured I'd post a build thread for the engine in my Spirit. Definitely not a square body, but there's a few non-Chevy build threads on here.
I've had the car for 20 years, turned every nut and bolt and done a halfway decent for a highschooler resto job, but I never opened the engine, and its tired. Never been the quickest car, and it still won't be, but I'm gonna build a mean little 258 that should liven it up a bit.
Rough plan: 258 block bored 60 over, 4.0 head ported and polished, Lunati cam (262/268 duration, .507/.527 lift, 112 LSA), clifford intake, probably a Truck Avenger 470, factory 4.0 "header" with dual outlets and dual exhaust all the way back w/x pipe and cherry bombs. Might need a new torque converter, definitely going to need to regear. Lunati recommends 3.55:1, so I'll probably be going with that.
Hope to have it all done by summer. We'll see- 2 small kids equals not a ton of garage time.
First step- getting it ready to pull! Got help coming over on the 27th, so I'm going to try and have as much of the prep done as possible before then. Realistically I'm working on it 30 minutes here and an hour there, so it'll take a few days.
Radiator and fan out.
I've had the car for 20 years, turned every nut and bolt and done a halfway decent for a highschooler resto job, but I never opened the engine, and its tired. Never been the quickest car, and it still won't be, but I'm gonna build a mean little 258 that should liven it up a bit.
Rough plan: 258 block bored 60 over, 4.0 head ported and polished, Lunati cam (262/268 duration, .507/.527 lift, 112 LSA), clifford intake, probably a Truck Avenger 470, factory 4.0 "header" with dual outlets and dual exhaust all the way back w/x pipe and cherry bombs. Might need a new torque converter, definitely going to need to regear. Lunati recommends 3.55:1, so I'll probably be going with that.
Hope to have it all done by summer. We'll see- 2 small kids equals not a ton of garage time.
First step- getting it ready to pull! Got help coming over on the 27th, so I'm going to try and have as much of the prep done as possible before then. Realistically I'm working on it 30 minutes here and an hour there, so it'll take a few days.
Radiator and fan out.
Subscribed
bigred88
1/2 ton status
More progress:
4.0 head torn down, ready for the machine shop. These are a popular swap onto 258s- bolt right up, they say they flow better but I don't have numbers to prove it. The combustion chamber is about 10ccs smaller, so it does make a bit of a compression boost.
All wires disconnected and labelled. Thankfully there arent that many.
No going back now! Not gonna need this old single exhaust anymore! Also, any excuse to use a sawzall is a good one.
4.0 head torn down, ready for the machine shop. These are a popular swap onto 258s- bolt right up, they say they flow better but I don't have numbers to prove it. The combustion chamber is about 10ccs smaller, so it does make a bit of a compression boost.
All wires disconnected and labelled. Thankfully there arent that many.
No going back now! Not gonna need this old single exhaust anymore! Also, any excuse to use a sawzall is a good one.
bigred88
1/2 ton status
One more update for the day- this is why I should check my stuff more frequently. I didn't remove that bolt...
bigred88
1/2 ton status
Minor update- pretty much everything stripped other than trans linkage. Ready to pull on Friday! Bonus points if you find the CK5 swag.
Also, MAW is in full effect as I'm strongly considering a manual transmission swap while I'm at it. The trans needs rebuilt anyways and I hate slushboxes.
Also, MAW is in full effect as I'm strongly considering a manual transmission swap while I'm at it. The trans needs rebuilt anyways and I hate slushboxes.
bigred88
1/2 ton status
Merry Christmas from Brown Santa! Decided on a QFT 450 carb. Didn't need to buy it yet, but it was on sale for $306 so now seemed like a good time. Hard to beat that price for a brand new carb.
cool build . . . 
bigred88
1/2 ton status
Thanks!
And it's out! My garage is wrecked, probably have a day of just cleaning before I get to tearing down.
And it's out! My garage is wrecked, probably have a day of just cleaning before I get to tearing down.
bigred88
1/2 ton status
Stripped and ready for the machine shop. Still waiting for my intake manifold to get here, and I need to buy the exhaust manifold so I can drop them at the machine shop too and have the head ported/polished. Hoping to have the exhaust manifold soon, and have the whole thing to the shop in a couple weeks. I'd like to sooner but next week is stupid busy and I won't have a chance to get it there.
First time I've ever opened this engine up, and there were no unwelcome surprises. Everything was clean enough for a high mileage engine, but no abnormal wear patterns. A few rockers were a little loose, and there was a bit of slack in the timing chain. The piston pin on cylinder 1 was stiff- took more effort to move than the other 5. But thankfully everything looks great for something I'm fully rebuilding anyway. I think some top end work and a new timing chain and this would have been running much better.
Also- scored a bellhousing for a T5! They're a bit hard to come by, and that was going to be the only hitch in my possible manual swap plans, so now that I have one of those the manual swap is a go! Going with a WC T5 out of a 83-93 Mustang. Probably going with a new aftermarket one. More research to do there...
First time I've ever opened this engine up, and there were no unwelcome surprises. Everything was clean enough for a high mileage engine, but no abnormal wear patterns. A few rockers were a little loose, and there was a bit of slack in the timing chain. The piston pin on cylinder 1 was stiff- took more effort to move than the other 5. But thankfully everything looks great for something I'm fully rebuilding anyway. I think some top end work and a new timing chain and this would have been running much better.
Also- scored a bellhousing for a T5! They're a bit hard to come by, and that was going to be the only hitch in my possible manual swap plans, so now that I have one of those the manual swap is a go! Going with a WC T5 out of a 83-93 Mustang. Probably going with a new aftermarket one. More research to do there...
Neat build! Near and dear to my heart. My Dad's hot rod when I was a kid was a 82 Spirit with a 360/904 combo with a Maverick 9" in the rear.
there is nothing like a built straight 6 or 8 for RAW power .
do your reading and squeeze every bit you can from that sucker .
make it more bad a$$ with a gear drive over the timing chain for that nasty sound . . .
do your reading and squeeze every bit you can from that sucker .
make it more bad a$$ with a gear drive over the timing chain for that nasty sound . . .
Subscribed for a different build
bigred88
1/2 ton status
This car was a high school project between me and my dad. My dad at the time had a 81 Spirit with a 401 and a Ford 9" (and a 3 speed trans but I can't remember which one). That was a fun low 12 second car. Still the fastest car I've ever driven. There's a pic or two of both of ours together, I'll have to see if I can find one to post. I was raised in various fast AMCs, and the occasional Wagoneer.
there is nothing like a built straight 6 or 8 for RAW power .
do your reading and squeeze every bit you can from that sucker .
make it more bad a$$ with a gear drive over the timing chain for that nasty sound . . .
This is my plan exactly. Max compression, max bore, big cam. I want this thing to be pretty damn mean.
It'll never hang with the built V8s, but that's ok. V8s are boring. Everyone has a V8. I want something different. I have no idea if anyone make a gear drive for a 258, but it's not a bad idea... 
bigred88
1/2 ton status
First one I could find. My dad's on the left, mine very much in progress on the right.
bigred88
1/2 ton status
Oh man. Don't tempt, it won't take much...
Truthfully- this is my first engine build. I did think about going that route, but the amount of custom built stuff I would need to make, not to mention the additional theory I would need to wrap my head around over top of all the basic engine building theory... I felt like going that route was too likely to turn into the never finished kind of project. Next time though...
Truthfully- this is my first engine build. I did think about going that route, but the amount of custom built stuff I would need to make, not to mention the additional theory I would need to wrap my head around over top of all the basic engine building theory... I felt like going that route was too likely to turn into the never finished kind of project. Next time though...
This car was a high school project between me and my dad. My dad at the time had a 81 Spirit with a 401 and a Ford 9" (and a 3 speed trans but I can't remember which one). That was a fun low 12 second car. Still the fastest car I've ever driven. There's a pic or two of both of ours together, I'll have to see if I can find one to post. I was raised in various fast AMCs, and the occasional Wagoneer.
This is my plan exactly. Max compression, max bore, big cam. I want this thing to be pretty damn mean.
We had a 401 for Dad's with a set of reworked heads. It just never got put together.
We also had a 83 gold colored one with Chevy engine mounts that was originally a 2.5L chevy car with a 904 that was supposed to be mine with a 350 Chevy but Dad decided to go farming and sold off the cars when I was about 14.
Looking forward to seeing your progress!
Everyone here knows I like straight sixes...I'll be following this thread..
Over the years I've had a few 250 GM straight sixes,a 235 in a '56 Chevy pickup,and I liked them all..one truck I had,a '79 C-10 Bonanza with a 250 (integral head design,not GM's best effort) had a 2 bbl Rochester E2SE carb that sucked,I adapted a Edelborock 600 CFM carb to its original intake ,but had to disable the secondaries ,it didn't like that much air & fuel being dumped in..it ran very well on the primaries though..
That engine lost the #6 piston at 117,000 miles,the fact those "camel humper" integral head engines always spark knocked probably is what ate the top ring land--the cylinder got scored bad,and I drove it 20 miles home rapping--I hated to swap a V8 into the truck,but I did ,I had a 305 from a van I put in it...I felt it went better with the 250 six in it..
One thing that affects the inline engines is the fuel distribution ,the end cylinders tend to be lean while the center ones run richer...the "heat riser" is needed to heat up the underside of the intake to help promote better fuel atomization,some aftermarket intakes lack any heat source,others have coolant pasages cast into them to pre-heat the air fuel mixture..this improves cold driveability and wards off carb icing..
I rode in a Ford Econoline van a friend had ,with a 300 straight six and a C-6 transmission--he put the Clifford intake on it,a exhaust header,and found an aftermarket camshaft that was ground for more low end power...he used a Holley 4 bbl 390 CFM carb on it..
The thing was a torque monster..taking off from a dead stop required a very light foot on the throttle,or you'd squeal the tires just past idle..it accelerated much better than stock,and he even claimed it got slightly better gas mileage...
The Holley proved to be a pain though,he had multiple issues with it flooding,and popping power valves,the engine tended to spit back thru the carb when cold--he tried a Q-jet carb on it,which required some adapting,but in the end it ran even better with the Q-jet..when you floored it,the secondaries only opened up as far as they needed too,while the Holley just opened them up too much too soon and would result in a bog ,then it would take off..
It will be interesting to see how this build pans out..
Over the years I've had a few 250 GM straight sixes,a 235 in a '56 Chevy pickup,and I liked them all..one truck I had,a '79 C-10 Bonanza with a 250 (integral head design,not GM's best effort) had a 2 bbl Rochester E2SE carb that sucked,I adapted a Edelborock 600 CFM carb to its original intake ,but had to disable the secondaries ,it didn't like that much air & fuel being dumped in..it ran very well on the primaries though..
That engine lost the #6 piston at 117,000 miles,the fact those "camel humper" integral head engines always spark knocked probably is what ate the top ring land--the cylinder got scored bad,and I drove it 20 miles home rapping--I hated to swap a V8 into the truck,but I did ,I had a 305 from a van I put in it...I felt it went better with the 250 six in it..
One thing that affects the inline engines is the fuel distribution ,the end cylinders tend to be lean while the center ones run richer...the "heat riser" is needed to heat up the underside of the intake to help promote better fuel atomization,some aftermarket intakes lack any heat source,others have coolant pasages cast into them to pre-heat the air fuel mixture..this improves cold driveability and wards off carb icing..
I rode in a Ford Econoline van a friend had ,with a 300 straight six and a C-6 transmission--he put the Clifford intake on it,a exhaust header,and found an aftermarket camshaft that was ground for more low end power...he used a Holley 4 bbl 390 CFM carb on it..
The thing was a torque monster..taking off from a dead stop required a very light foot on the throttle,or you'd squeal the tires just past idle..it accelerated much better than stock,and he even claimed it got slightly better gas mileage...
The Holley proved to be a pain though,he had multiple issues with it flooding,and popping power valves,the engine tended to spit back thru the carb when cold--he tried a Q-jet carb on it,which required some adapting,but in the end it ran even better with the Q-jet..when you floored it,the secondaries only opened up as far as they needed too,while the Holley just opened them up too much too soon and would result in a bog ,then it would take off..
It will be interesting to see how this build pans out..
