AMX engine components

[Barron]

Hi all, another noob here. I am restoring my 69 AMX that I have had for about 20 years. I have been working on it on and off for the past few years and am ready to start on the engine. I want to use the later model dogleg port heads on the 69 390 block and would like to know what machine work is involved in doing this. I have a set of heads, but don't know the specs on them or what engine they came from. I dry fitted them this afternoon just to see how close everything lined up and they seem to look OK except that the front and rear seal gap btwn the intake manifold and block looks a little wide. The locating bushings are a different size too, apparently for the later model 1/2" head bolts but that is manageable. I was told once that the deck height was different on 70 and up engines but don't have any real data to go on. What needs to be done to the heads or block if anything?

Barron

[Big Bad AMX]

Hi Barron and welcome!

The 1969 and prior V-8 head bolts are 7/16", 1970 and later are 1/2".

What you'll need to install the dogleg heads on your '69 390 is four "step-dowels". You can buy these from American Performance Products in Florida (do a Google, I don't have their # handy or try your favorite AMC vendor). Then you'll want to buy a new set of head gaskets for the 1970-up AMC 401 V-8. Copper Coat one side and drop the heads onto your 1969 390 block and torque them to 105 lbs/feet. There is no machining needed to do this, it is a simple drop-on. The deck height differences between the earlier and later V-8 blocks are in the block, not the heads.

Be certain to use a 1970 and later intake manifold - whether it's an aftermarket or stock. There is a slightly different bolt pattern (center holes only) between the intake holes on a 1969 and prior head and intake and the 1970 and later. Don't hog out the holes on the 1969 and prior intakes.

Use Permatex/Aviation Form-A-Gasket #2 non-hardening to seal the ends of the intake manifold, especially around the water jacket areas. DON'T USE SILICONE, black or blue or any other color.

Use stainless steel valves in place of the earlier valves. Use for both the intake and exhaust valves. Because AMC used a high nickel content in the block and heads (which makes the heads and blocks hard enough to start with) hardened seats are redundant and are a waste of money on any AMC V-8.

If you're planning on using stock exhaust manifolds you'll want to get a pair of the 70 and later Free-Flow manifolds, preferably without the tubes.

One other thing; The 68/69 390s had a 10.2:1 compression ratio. The larger chambers on the later 58cc heads will drop your compression ratio to approximately 9.6:1. Not a bad thing on today's gas, though you'll still want to use octane boost.

[Barron]

Thanks for the info. This is a great resource.
How can I tell what kind of heads I have? Are there some that are not worth putting on the 390. These heads could have come from a 304 for all I know. I want to be sure they are better than the older head
I am also putting a 727 behind it so I will have to have the Crankshaft machined out as well. Do you know where I can find the right sleeve/bushing where the torque convereter fits?

Barron

[donsjave]

The heads from a 304 has smaller valves on them. I am not sure of the inch diameter, but I know the valves themselves are smaller. This info could be found in any pre 75 shop manual (ie. Chiltons, Peterson's etc.). The other place is in the AMC shop manual if you are lucky to have one. On the 390's I believe the intake valve size is like 2.02" and the exhaust is 1.75" although I am not real sure on that number since my shop manual is at work and not here, I try to remember to look it up and get back to you tomorrow on it. Otherwise have fun and will write later

Note: Do not attempt to install 304 heads on your 390 engine. I do not beleive they will fit anyway. Just an after thought. Besides with smaller valves, you would be much better off finding any set of heads 360 CI or bigger. The 360,390, and 401 heads are basically the same with the 304 and 290 being different in the aspect ofthe valves

[Barron]

I had a look a them last nght. The valves are, Intake approx 2.03 and Exhaust approx 1.67. The valves are still installed and that was as close as I could get. Not much room to expand. Sounds like they may be 390 heads. I have the AMC part of a very old Chiltons manual but the valve diameters are not given, just everything else.
The 2 center holes on the intake manifold aren't even close. I wouldn't consider opening them up. I'll look for a 70 model. Probably go with an aftermarket.
Looks like I'm ready for the machine shop.

Barron

[Big Bad AMX]

Just an FYI: Ye old AMC Service Spec books show the '70 360 and 390 valves to be:
Intake = 2.025"
Exhaust = 1.625"

The '70 304 valves are:
Intake = 1.787"
Exhaust = 1.406"

[Big Bad AMX]

The following was written by Tony Zamisch of California Classic AMC, Inc. (http://www.amx-perience.com/california_classic_amc.htm)
You may find it useful for choosing an intake.

Listed below are the aluminum intakes that were available from the
dealer, and aftermarket sources over the years for the AMC V/8. There were some obscure and experimental manifolds from Traco, Kaplan, Penske, and Enderlie/hillborn, none of which went into production. I also have some cool info and experience with blower intakes and fuel injection manifolds.

Manufacturer, manifold configuration, RPM range and application:

Edelbrock R4B:
Dual plane, single four barrel
1500 to 6500 RPM
68/69
70/up

Edelbrock Performer:
Dual plane, single four barrel
Off idle to 5500 RPM
70/up

Edelbrock Torker:
Single plane, single four barrel
3500 to 7500 RPM
66/69
70/up

Edelbrock S.P.2.P.
Dual Plane, single four barrel
off idle to 4000 RPM
70/up

Edelbrock "STR-11" Cross-ram
Single plane/open, cross-over, dual quad
3500 to 7500 RPM
68/69
70/up

Edelbrock "UR-18" Tunnel Ram
Single plane/open, dual quad
3500 to 9000
70/up

Offenhauser "360 degree Equa-flow"
Open plenum/divider, single and dual four barrel designs
3000 to 8000 RPM
66/69
70/up

Offenhauser "360 Degree Dual port"
Dual plane open/dual port
2000 to 6000 RPM
66/69
70/up

Holley "Z" Series
Single plane/divider
Off idle to 4800
70/up

For more information on these or any other V/8 and 6-cyl manifolds,
blower intakes, etc, call me. I've used them all at one point or another.
Lots of stories to tell. Remember, an intake manifold is only as good as the
cam that you use with it. Other factors also apply.

By the way, the casting number for the standard (not Machine) 70
360/390, 71 360 cast iron 4-bbl intake manifold is #3195532-C. Casting
numbers ARE NOT the same as part numbers. What's in the parts books are PART numbers.

[fenceman]

Great and very timely info.My car happens to have the Edelbrock R4B,combined with a Holley street avenger 670 c.f.m. and a Isky cam.I have the cam card and am wondering if you might comment on it if i post the lift,duration,etc? The car has stock factory exhaust manifolds and seems to like them,although i wonder if headers might make a big difference?The distributor is a bit different in that it dosent have external "towers",is this stock or aftermarket? It appears to have a "Mallory" signature on the cap surface.Thanks for any info. Mark.

[Big Bad AMX]

Please post the cam specs. Do you know the rear-end ratio? Also, what are you looking to use the car for?

Do you have the stock lincoln log style exhaust manifolds or the later Free-Flow manifolds? Free Flows breathe quite well, not quite as good as headers but much better than the log style. Personally I don't like headers. Yes, they're a bolt on performance improvement but every pair I ever had was an exhaust leak waiting to happen, a starter ready to cook, busted spark plugs and scraping every speed bump. Of course that was before the shorty headers became available (I've heard mixed reviews on those too).
One thing for sure; do not use the log style exhaust manifolds on the dog-leg heads.

For street use 670 cfm is plenty big for a 390. I'm not sure by you're description of the distributer but it sounds aftermarket. Is it a single point, dual point or electronic unit?

Don't let anybody talk you out of that R4B. :)

[fenceman]

Please post the cam specs. Do you know the rear-end ratio? Also, what are you looking to use the car for?

Do you have the stock lincoln log style exhaust manifolds or the later Free-Flow manifolds? Free Flows breathe quite well, not quite as good as headers but much better than the log style. Personally I don't like headers. Yes, they're a bolt on performance improvement but every pair I ever had was an exhaust leak waiting to happen, a starter ready to cook, busted spark plugs and scraping every speed bump. Of course that was before the shorty headers became available (I've heard mixed reviews on those too).
One thing for sure; do not use the log style exhaust manifolds on the dog-leg heads.

For street use 670 cfm is plenty big for a 390. I'm not sure by you're description of the distributer but it sounds aftermarket. Is it a single point, dual point or electronic unit?

Don't let anybody talk you out of that R4B. :)Cam index card tells the following:"Intake timing", open 42 before tdc,close 78 bdc,cam lift 291,valve lift 467. "Exhaust timing":open 78 before tdc,close 42 after tdc,cam lift 291,valve lift 467.The above timing is checked at 007 lifter rise.Different timing is taken at .050" and is "Intake" open 9 before tdc,close 45 after bdc. "Exhaust" open 45 bdc,close 9 after tdc.I am looking to use the car for straight line application,maybe a little mountain driving.I would have to say the exhaust manifolds are the "Log" style,very plain tubes.Actually my car came with a 390,but currently has a 343 under the hood now.It seems to handle the 670 very well? The car is a rocket ship thru the gears.I dont know the rear end ratio,i would guess its on the high side,car winds out on the quick side,seems like a 1/4 mile set-up if i had to guess.The distributor is electronic,"Mallory unilite". Dont worry bout the Edelbrock,ill keep it under lock and key.Thanks,Mark.

[Big Bad AMX]

I am looking to use the car for straight line application,maybe a little mountain driving. I would have to say the exhaust manifolds are the "Log" style,very plain tubes.Actually my car came with a 390,but currently has a 343 under the hood now.It seems to handle the 670 very well? For your 390 are you looking for mainly street use? Occasionally a weekend drag race up to 5500 rpm or so? Are you looking for reliability, improvement in horsepower (40-60 more) and mileage or is high performance your main goal? Sorry for the extra questions but it'll give me a better idea of what you looking for out of the 390.
Nothing wrong with the 343, I've had two and both ran strong. One stock, one with mild mods. I used the same carb on both, a 625 Carter (same on my 390s). For street use a 670 is plenty. It's real easy to over carb though.

[fenceman]

Im probably more interested in high performance,with a degree of reliability. ;)

[Big Bad AMX]

Im probably more interested in high performance,with a degree of reliability. ;) I can tell you what I did to mine. It's running 'about' 365-375 hp. 390 auto. Will go anywhere reliably and gets 22+ mpg on the highway, 18+ city. How's that sound?

[fenceman]

I can tell you what I did to mine. It's running 'about' 365-375 hp. 390 auto. Will go anywhere reliably and gets 22+ mpg on the highway, 18+ city. How's that sound?
That sounds like the best of both worlds.im all ears.......... ;)

[Big Bad AMX]

That sounds like the best of both worlds.im all ears.......... Okay, here we go.........
AMX Enterprises in Arvada, CO did the rebuild. I wanted an increase in performance, milage and reliability. 1969 390, stock auto trans, 3.15 rear ratio. I rarely run over 5200 rpm, 5500 is absolute max.

It was bored .030. I went with cast pistons, stock compression of 10.2:1. Balanced it. The heads are late model 58cc off a 1973 401. Rebuilt the heads, new valve guides, springs, stainless steel valves, both sides. Hardening the seats is a waste of money, they're hard enough already. The larger 58cc chamber (stock is 51cc) equates to an approximate .6 drop in compression so it's running a 9.6:1 ratio.

Put a new timing chain cover on it - this really is a must for good oil pressure and longevity of your rebuild. At the time I bought an NOS one from Chrysler for $650.00. There were quality issues with the aftermarket pieces then. Aftermarket units are still available and I beleive they have all the initial bugs worked out. They run about $280.00 (if I remember right.)

The cam is an Erson. .478 lift / 292 duration. Highly recommend for street and weekend performance. Very slight lope. Excellent power throughout the power range but really strong from 3000-5000rpm. Very good economy. Very sensitive to timing though.

Intake is an Edelbrock Performer. The similar (improved?) Air Gap intakes were not out at that time and I've never had one so I can't comment on those.

The carb is a Carter AFB 625 CFM (not original carb it's a later model) only 'mod' is it's jetted for this altitude (6,500 to 7,500 feet).

Distributor and coil - New but stock. Yep, good old single points.

Exhaust manifolds are stock AMC 1971 Free Flow w/o tubes. These run into 2 1/2" exhaust which go through chambered mufflers and exit via Reproduction Trendsetter sidepipes. What a sweet sound. And from 3000-5000 rpm they really open up and wow. I didn't think they were that loud until a Harley rider flipped me off. :eek:

It has the Borg Warner M12 automatic, it was rebuilt stock with a rebuilt convertor (stock stall) and an NOS flex plate.

The rear-end is original with the stock R&P. 3.15:1 Ratio.

I say "It's running 'about' 365-375 hp" because its never been dynoed. All I can do is figure the factory rated them at 315 hp and 425 ft lbs torque. Even though the compression dropped by .6 the later heads, carb, cam, intake and exhaust 'should' be worth about a 50-60 hp gain over the original 1969 factory parts. That's my opinion, I don't have solid numbers behind it though.

I run only premium fuel with Protek lead additive/octane boost in every tank. The last four tanks of fuel were one through the city and into the mountains up to 10,000 ft and it got 18.5 that tank. Next tank was 90% city driving and it managed 19.5 mpg. Next was city, highway, mountains and it was 18.6. The only all-highway run so far was a 225 mile run with the A/C running maxed out for about 60 miles and it managed 22.1 mpg. 60-65 mph. All runs had at least 'a few' romps. On the highway stay below 3,000 rpm or your milage will stink. With a 3.15 rear 3,000 rpm is 70mph.

Power wise (keep in mind 7,800 ft and a 3.15 rear) with no wimpy power braking, just off the brake and on the throttle from an idle to wide open it'll smoke the tires off the line through first gear. It gets a good 10-12 feet in second, no chirp in third. I have not had it on the track for 1/4 mile times.

It is exactly what I wanted when deciding to rebuild it. Much better milage, more power and it's as reliable as the sunrise, I'd drive it anywhere.

I could upgrade the ignition and get a couple more horses out of it but I grew up with points and have little desire to change it. If I was racing and wanted every .01 sec I would but I don't so I won't.

I think donsjave has a similar rebuild in his '70 AMX 390, 4-speed. Maybe he can advise if he did anything different and how satisfied he is with its performance.

Hope that helps.

[fenceman]

Thanks,ill start the decision process... ;)

[Barron]

Just an FYI: Ye old AMC Service Spec books show the '70 360 and 390 valves to be:
Intake = 2.025"
Exhaust = 1.625"

The '70 304 valves are:
Intake = 1.787"
Exhaust = 1.406"

What does the book say about piston specs? I'm trying to get pistons and need to know what the compression distance and pin dia are in order to make sure I get the 69 pistons and not 70 up.
Also, is there any way to get a copy of the book?

Thanks,
barron

[Big Bad AMX]

Here's what the spec books show-

Piston / Cylinder info for 1969 390:
Compression ratio: 10.2:1
Cylinder Compression Rating: (cranking speed at sea level): 145 PSI
Bore and Stroke: 4.166" x 3.574"
Piston to Bore Clearance: .0010"-.0018"
Piston Pin to Piston Clearance: All Pieces Room Temperature: .0003"-.0005"
Piston Ring Width: All Engines Top and Second Compression: 5/64"
Piston Ring Side Clearance: 290-343-390: 1 and 2 .002"-.004" 3 .000"-.005"
Piston Ring Gap Clearance:All Engines: 1 and 2 .010"-.020" 3 .015"-.055" (Rail Gaps)
Cylinder Bore Diameter: 390: 4.165"-4.167"
Cylinder Bore Out of Round: All Engines....Max .005"
Cylinder Bore Taper: All Engines....Max .003"


Piston / Cylinder info for 1970 390:
Compression ratio: 10.0:1
Cylinder Compression Rating (cranking speed at sea level): 145 PSI
Bore and Stroke: 4.165" x 3.574"
Piston to Bore Clearance: .0010"-.0018"
Piston Pin to Piston Clearance: All Pieces Room Temperature: .0003"-.0005"
Piston Ring Width: All Engines Top and Second Compression: 5/64"
Piston Ring Side Clearance: 290-343-390: 1 and 2 .002"-.004" 3 .000"-.005"
Piston Ring Gap Clearance:All Engines: 1 and 2 .010"-.020" 3 .015"-.055" (Rail Gaps)
Cylinder Bore Diameter: 390: 4.165"-4.167"
Cylinder Bore Out of Round: All Engines....Max .002"
Cylinder Bore Taper: All Engines....Max .005"

They don't have pin dia or skirt length to pin. There is a visual difference between the early/late years so it's not easy to mix them up.

The AMC Service Specifications books are small measuring approx. 4 1/2" x 6 3/4". So they can be carried in a pocket. Your best bet is to contact Tony Zamisch at California Classic AMC (http://www.amx-perience.com/california_classic_amc.htm) since he gets them in from time to time. Or try the AMC Classifieds (http://www.amx-perience.com/classifieds/index.php) or ebay.

Edit: You can now download the AMC Service Specifications books free from this website. See this thread for more information:
http://www.amx-perience.com/AmericanMotorsForum/showthread.php?t=911


.

[Barron]

Well, I am having trouble finding pistons for my 69. I did find some 060 over for a 70 model. The only difference I see is the recessed head. Does anyone see any reason I shouldn't use these? From what I can reason, they are the same except for the .135 recess in the top. From the compression ratio spec difference in the 60 vs 70, it looks like I will only be losing .2 compression. That with the 70 heads dropping it to 9.6 will give me 9.4 theoretically. Is this a problem? 9.4 still seems like a decent spec.The only other choice at this time appears to be custom pistons at 2-3 times the cost.

Barron

[donsjave]

Okay, here we go.........
AMX Enterprises in Arvada, CO did the rebuild. I wanted an increase in performance, milage and reliability. 1969 390, stock auto trans, 3.15 rear ratio. I rarely run over 5200 rpm, 5500 is absolute max.

It was bored .030. I went with cast pistons, stock compression of 10.2:1. Balanced it. The heads are late model 58cc off a 1973 401. Rebuilt the heads, new valve guides, springs, stainless steel valves, both sides. Hardening the seats is a waste of money, they're hard enough already. The larger 58cc chamber (stock is 51cc) equates to an approximate .6 drop in compression so it's running a 9.6:1 ratio.

Put a new timing chain cover on it - this really is a must for good oil pressure and longevity of your rebuild. At the time I bought an NOS one from Chrysler for $650.00. There were quality issues with the aftermarket pieces then. Aftermarket units are still available and I beleive they have all the initial bugs worked out. They run about $280.00 (if I remember right.)

The cam is an Erson. .478 lift / 292 duration. Highly recommend for street and weekend performance. Very slight lope. Excellent power throughout the power range but really strong from 3000-5000rpm. Very good economy. Very sensitive to timing though.

Intake is an Edelbrock Performer. The similar (improved?) Air Gap intakes were not out at that time and I've never had one so I can't comment on those.

The carb is a Carter AFB 625 CFM (not original carb it's a later model) only 'mod' is it's jetted for this altitude (6,500 to 7,500 feet).

Distributor and coil - New but stock. Yep, good old single points.

Exhaust manifolds are stock AMC 1971 Free Flow w/o tubes. These run into 2 1/2" exhaust which go through chambered mufflers and exit via Reproduction Trendsetter sidepipes. What a sweet sound. And from 3000-5000 rpm they really open up and wow. I didn't think they were that loud until a Harley rider flipped me off. :eek:

It has the Borg Warner M12 automatic, it was rebuilt stock with a rebuilt convertor (stock stall) and an NOS flex plate.

The rear-end is original with the stock R&P. 3.15:1 Ratio.

I say "It's running 'about' 365-375 hp" because its never been dynoed. All I can do is figure the factory rated them at 315 hp and 425 ft lbs torque. Even though the compression dropped by .6 the later heads, carb, cam, intake and exhaust 'should' be worth about a 50-60 hp gain over the original 1969 factory parts. That's my opinion, I don't have solid numbers behind it though.

I run only premium fuel with Protek lead additive/octane boost in every tank. The last four tanks of fuel were one through the city and into the mountains up to 10,000 ft and it got 18.5 that tank. Next tank was 90% city driving and it managed 19.5 mpg. Next was city, highway, mountains and it was 18.6. The only all-highway run so far was a 225 mile run with the A/C running maxed out for about 60 miles and it managed 22.1 mpg. 60-65 mph. All runs had at least 'a few' romps. On the highway stay below 3,000 rpm or your milage will stink. With a 3.15 rear 3,000 rpm is 70mph.

Power wise (keep in mind 7,800 ft and a 3.15 rear) with no wimpy power braking, just off the brake and on the throttle from an idle to wide open it'll smoke the tires off the line through first gear. It gets a good 10-12 feet in second, no chirp in third. I have not had it on the track for 1/4 mile times.

It is exactly what I wanted when deciding to rebuild it. Much better milage, more power and it's as reliable as the sunrise, I'd drive it anywhere.

I could upgrade the ignition and get a couple more horses out of it but I grew up with points and have little desire to change it. If I was racing and wanted every .01 sec I would but I don't so I won't.

I think donsjave has a similar rebuild in his '70 AMX 390, 4-speed. Maybe he can advise if he did anything different and how satisfied he is with its performance.

Hope that helps.
I did basically the same thing as Bad did to his car and can attest to the power gains and the such. I did install electronic ignition on the car since I was suffering somewhat from a high idle miss (lean miss ?) and it meaning the miss was detectable at high way speeds. AMX Enterprises did the basic engine rebuild and did a great job on it. Managed to find a stock 70 forged crank for it (guess they are a little different from year to year) and had it installed replacing the crank that was somewhat beaten up due to abused. Gas mileage depends again on the rpm's that engine is running, below 3000 rpm it runing at about 17-18 mpg and above 3000, it runs at about 15. Car has the 4 speed manual with 315 gearing. Runs like you what what. Guessing that engine is cranking out about 350 horses although I have never dynoed the car itself or the engine. Just taking basic numbers from AMC and adding in for the intake and the 51 cc heads on the car.

[Billjhenry]

Is there a difference in deck height and if so does it have an effect on the seal for the intake? I have heard the intake story both ways. Thanks, Bill

[Barron]

I can tell you that I used the 70 up dogleg port heads on a 69 block with an Edelbrock 69 intake and the front and rear gap for the seals was no different. I did use the gray silicone like newer vehicles instead of the original rubber ones. I did this after lots of research and talking to friends that race. I am pleased with the result although I have yet to start the engine. Just make sure you get the bead thick enough because the gap on newer engines, at least on my 97 GMC pickup, is not as wide.
I know I said earlier in this thread that I wouldn't open up the two center holes in the intake but I had already purchased the Pro flo system and could not return. I jigged up with a router and it turned out fine. I also understood that if you used a 70 up intake on a 69 block you would have to machine the head mating surfaces on the intake. Should be firing it in a couple of weeks.

Barron

[Billjhenry]

Thanks for the info. Please let me know how it works out.

[FASTESTAMX]

Hi all, another noob here. I am restoring my 69 AMX that I have had for about 20 years. I have been working on it on and off for the past few years and am ready to start on the engine. I want to use the later model dogleg port heads on the 69 390 block and would like to know what machine work is involved in doing this. I have a set of heads, but don't know the specs on them or what engine they came from. I dry fitted them this afternoon just to see how close everything lined up and they seem to look OK except that the front and rear seal gap btwn the intake manifold and block looks a little wide. The locating bushings are a different size too, apparently for the later model 1/2" head bolts but that is manageable. I was told once that the deck height was different on 70 and up engines but don't have any real data to go on. What needs to be done to the heads or block if anything?

Barron DONT BOTHER THE DOG LEG HEADS ARE NOT AS GOOD AS THE EARLY HEADS.IF YOU HAVE ANY QUESTIONS YOU CAN GET ME AT FASTESTAMX@AOL.COM
JOHN