beyer05
- Can you shave the heads to bump the compression up?
- How much compression and still safely run 91 octane?
- What is a good off-road (torque) cam for a TBI set-up motor?
Thanks.
SwampRat
The most effective way of gaining compression is decking the block and getting the "squench" or piston to head clearance close. I'm sure the AMC castings are too thin to take a substantial amount of flat milling and angle milling introduces a whole new set of problems. Angle Milling becomes expensive since it requires the exhaust manifold and intake manifold faces to be re-ground as well. It also requires using offset dowls or re-facing of the head bolt bosses for the new alignment. I've seen both sides of this, I've seen a engine with a .060 angle mill bolt onto a engine fine (especially with head studs) and I've seen .060 angle milled heads destroy a block by pulling out so many threads. Angle milling also effects the flow of the heads, positively or negatively, that depends.
The rule of thumb for iron heads on 91 octane is about 9.5:1 static compression ratio, with fuel injection the cam has to be small and with limited overlap so I wouldn't feel the need to push the compression, it gives small power gains in exchange for making the engine increasingly more apt to ping. But a good read on this subject is here...
http://www.popularhotrodding.com/tech/0311_phr_power_squeeze/index.html
Like I said a cam for a fuel injection engine needs limited duration and a wide LCA, something like 114 with 205-215* of duration @.050
Holeshot
Actually beyer05, getting the "QUENCH" tighter is as easy as bolting on early model heads (not sure what you have). The early heads (70~71) had 50cc combustion chambers, 2.025" intake and 1.68" exhaust valves, getting around 12.5~1 with flattop pistons. They went to 57.92cc chambers in late '71 early '72. The early heads are available almost weekly on Ebay. The later heads can be milled enough for most any purpose. There is an AMC head # post somewhere on this board.
In addition, the AMC heads are fairly tolerant of high compression and resistant to detonation, so long as you don't DROP the compression too low, and get the head of the piston too far away from the cylinder head. I have a set of TRW forged slugs here rite now that somebody turned around .125" off of the center of the head, thinking that 9~1 would be "safer", pinged like a bi#ch, less on race gas, but still no good. Still made well over 500 HP, though. To get good QUENCH, the head of the piston should be .040"~.045" from the head at TDC when using steel rods, more for aluminum. 11~1 is a good upper limit for the AMC design, so long as everything is set up properly and you get enough mix in and enough waste out. Those Chevy "rules of thumb" simply don't apply to the superior AMC design.
If you use aluminum heads, you can get by with 11.5~1 on PUMP gas with cast (KB) pistons (I like forged, tho), so long as attention is paid to the blueprint details.
Another issue to address is that the cylinder head design will flow enough to rev well past what the other brands stock heads will. It's my belief that you should build your engine to compliment your heads, since it's pretty hard to make those ports flow less than they already do. The goal should be to match the carb, intake, cam, & exhaust to the heads.
The byproduct of doing that would be more HP & torque than you may have expected. The (fresh) stocker HP peaks by 5500 at a little over 230 HP (early engines were a bit more), and torque peak is around 250 ft/lbs in the 4300 RPM range. By upping the CR to 10.5~1, adding a Torker (an R4B may be better for a milder app), 850 CFM of airflow, a Comp 292H & kit, and large-tube headers, the numbers go to a HP peak of around 450 at 6000 and a tq peak of around 440 at 4500 RPM. The numbers are approximate, but the trend is definate, and the curves are pretty flat and cover a wide range, maki9ng for a hard pulling engine. A point of interest is that where the stocker peaked at a little under 240 ft/lbs. of torque, the modified engine STARTS out at 2000 RPM with almost 315 ft/lbs. and goes rite on up past 400 ft/lbs. by 4000 RPM. Dropping to 650 CFM carb loses over 20 HP and over 10 ft/lbs. of torque all through the range. So much for the "smal carb is better" "small cam is better" "low compression is better", cookie-cutter GM guys.
Always CALL your cam maker with your engine & drivetrain specs to get sound advice. They build engines like yours with the cams they sell and know more than anyone here about camshaft applications.
SwampRat
Those Chevy "rules of thumb" simply don't apply to the superior AMC design.
Oh come on, I tolerate a opinion, but what makes you think this? Both have their pros and cons, do you not think so?
Holeshot
I stand by that statement, compared to the smallblock chevy (original design 283~400), the AM V8 (a smallblock) is FAR superior. The SBC is a throw away engine. Drive it till it blows then toss it and start over. I went through my share. See if you can find out how many guys on this board have blown a 390/401 rod, crank, or block. If you find any, find out how much NOS or boost they were running, how fresh the bottom end was, or if maybe it may have been assembled without doing something correctly. Speaking from my own experience, most times when you tear down an AMC V8, you wouldn't even have to bore it, except for that we want to make sure that any seasoning & settling of the bore dimensions are corrected and use an aftermarket piston. I may even go so far as to say that the generation of SBC LT-1s that went into all those late model Camaros and T/As is inferior as well, but I stopped paying attention to those long ago. From what I gather, they are not high rpm engines, but can be turned into stump-pullers with some boost and big bucks. I prefer to have something that doesn't take thousands of dollars worth of diagnostic equipment & can be worked on & see your improvements right off the bat.
What naturally aspirated smallblock are you gonna use standard (nothing extreme) bolt-ons, an over the counter cam & kit, blueprinted bottom end with no aftermarket parts except pistons & ring package, home ported heads and be able to make well over 500 HP (around 900 with NOS) and rev past 7000 to 8000 (390/401 rotating assy), if the cam & kit is capable? May as well compare apples to apples and specify a first design SBC before they released the Mercury Outboard designed ZR1 engine of the 90s.
What I am trying to get across is that, when building a performance engine, you shouldn't just ignore the port flow properties and choke it down. The engine should be modified to take full advantage of the heads since they are "cast in stone" and not usually changed out frequently.
Would a BBC guy building a trail machine take a pair of L88 heads (extreme example but same principal) and use a torque cam, dual plane small runner intake & 600 CFM carb with it? Whatever mixture velocity was gained thru the small runner intake would be lost as soon as it got to those big ports and valves.
Same story for a MOPAR Hemi guy, what sense would it make to choke that thing down to LOSE HP & torque? Of course, the "street" hemi would not rev like an AM V8, and weighs a couple hundred pounds or so more than an AM V8. I'm not sure if all did, but some 426 Hemis came with dual quads and 1000 or 1200 CFM, and redlined at what, 6000 or 6500? Would it make sense to choke that down with restrictive components?
What kind of sense would that make?
None, you'd build your engine to run in the range that the heads excel in.
I would, anyway. Oooops...gotta go chop up a bird.
SwampRat
I guess it's you against the rest of the world then. I prefer to give both engines credit when due. Not to say either is one is totally inferior. AMC and Chevys both had forged rods that both were very durable. Pro Stock in the 70's had chevy 327 engines using stock cranks and stock cylinder heads making 700-800 Hp @ 10,000+ RPM. And this is only one example of the most popular racing engine ever. I can't imagine why this would if they were only "throw-aways" compared to a AMC.
Holeshot
Yeah - "stock cranks and stock cylinder heads making 700-800 Hp @ 10,000+ RPM"
Dream on!!!
I'm sure there's a chevy board out there somewhere where you chevy guys could intoxicate each other with your chevy myths.
Like I said, you came to the wrong board to preach your chevy gospel.
SwampRat
Pick up a copy of the book, "How to Hot Rod: Small Block Chevy" By Bill Grumpy Jenkins, if you don't believe me, and that was fourty years ago, technology has come a long ways since then, and so has the small block chevy. LS1's are the power-makers of tomorrow.
Holeshot
Oh great news: "LS1's are the power-makers of tomorrow"
That would be what, $20,000+ for an engine you can't work on & that might make as much power as an engine designed almost 40 years ago. Oh, and you'll probably have to have an electronic-controlled trans to plug in to the computer that you will have to buy, to get the thing to start or move.
Whoopeee
And wo unto you if you get caught with a 2007 engine in a '32 Ford (for instance) - "where's the CARB sticker?" and "You can't use that without an emissions rating and MPG certification" and "where's your inspection certification". I'd much rather have an old AMX with an old carbureted AM V8 pushing around 600 HP. They will have a hard time outlawing that. Or even an Allison or Merlin 12 cylinder P-51 engine, or a helicopter engine. Those are all things a guy can work on without an electronics lab. Not too many of us are gonna be able to burn our own chips & get late model drivetrains adapted to early iron, let alone be able to afford multiple tens of thousands of dollars for something that will take an electronics technician to adapt or re-tune, and reward us with maybe a 10% increase in power. Maybe a Boyd Coddington or a Chip Foose.
Looks like the (new) "power-makers of tomorrow" may be non fossil fuel to me. So we better have fun with the muscle cars while we can.
Like I said, you came to the wrong board to preach your chevy gospel and knock the AMC products.
SwampRat
You have a serious insecurity problem with your AMC's, how can you say I'm "knocking" them? I haven't made one statement saying anything degrading about their design or performance. I have asked you about their oiling problems and you have even ignored that question, I swear you believe that the AMC should've been the only internal combustion engine ever produced. Why won't you talk about what's wrong with them instead of trying to do the inevitable and try to convince people that they are leaps and bounds better than a small or a big block chevy, Or I'd guess you'd say they were better than a SBF, BBF, SBM, BBM, ect, ect.
Of course some engines make more shear horsepower than a LS1 but not many can rival it's drive-ability and low end performance and economy. And you can go get a Ls1 from GM right now for under 7 grand, not twenty. Soon twenty will buy you a LS7, with titanium rods and valves, full CNC port heads, and 500+ drive-able everyday ponies. You better go get one for your AMX :shock: :roll: :t:
Holeshot
OK, there you go again with the personal attacks.
I guess that proves that you just can't let go of your partiality towards your favorite brand.
Again proving the point, YOU came to the wrong place to spread your dis-information.
I can only surmise that you are doing this to give yourself a rise, and I'm not going to give you any more of that sick type of gratification.
(but for this shot!!!)
Most of the rest of us here on this board have already been thru the off-brand machines and needed something more, something the cookie-cutter crowd didn't have. Turns out it was the AMC, a small granny-car builder, 40 or more years ahead of their time. In the late 60s, they awoke to see the rest of the world embroiled in a horsepower war, and granny-mobiles with creature comforts losing sales. So they bought up some of the competition's top powerplants and put them on the Dyno, built them every which way. Converted their dimensions into blueprints. And then took the best ideas from each of the other manufacturer's designs: Huge 1" wrist pins from the Hemi; valves, springs, retainers, large-diameter lifters, & bore-centers of the bigblock Mopar; smallblock Ford rockers, so we can bolt on 1.7 ratio rockers; 5.85" rods so we can easily turn down the 401 crank & use H-beam Carrillos made for SBC; 4.165" bore, we can use SBC 400 pistons (cheap); Delco distributor internals; SBC pushrods (+.100"); Ford "Duraspark III" CDI box; BOP (Buick Olds Pontiac) fan spacer, pushrod guideplates; an OUTSTANDING cyclinder head design of their own design, like nothing else; etc. The list goes on, but that's what I can think of off the top of my head.
So the American Motors product really did become all-American, and I defend it as such, Red White & Blue.
They also did something none of the other makers did. While the other makers would usually produce only the minimum number of assembly line units to conform to the sanctioning bodies (NASCAR, NHRA, etc) rules (500 units), AMC made their race-bred designs normal production items. So EVERY 401 station wagon (or whatever) could donate it's engine to someones racing program. In addition, AMC had a very long list of AMC numbered options that included Holley carbs, Edelbrock intakes, headers, Detroit Lockers, gears up to 4.44, cams & kits, 4-wheel disc brakes, traction bars, etc., etc.
They also hired a top-notch Italian (DeTomasso (?)) company to design a "sporty" car. The rest is now historic. If you don't already know the story, sorry,
I'm not going thru all that again, it is all over the web. My fingers are getting too short!!!
SwampRat
Please re-read my previous posts, I think that is my first "attack" toward you, and the reason was, that I was sick of you imagining and saying that I "knocked" the AMC engine. I surmise you are getting a sick "rise" in self-esteem by telling me that I hate AMC engines as well, when I haven't said anything of the sort.
That is a great piece of AMC history, but are you ever gonna disscuss with me their oiling problems. On the American Motors forum it is somewhat of a hot topic, why don't you want to talk about it? What do you do, what does a "prepped" AMC buttom end invovle for oiling system modifications that allow it to live at 8000 RPM?
pyagid
Guys, Chill out. How is any of this helping Beyer with his original question? Please stay on topic and if you wish, start this discussion in its own topic You have both already been asked to cool it off a few days ago, we dont want to be forced to make you do it.
-Paul
Holeshot
The oiling issue is addresed in GREAT detail in a thread DEVOTED to that specific issue.
It is only an issue at over 6500 RPM, so most people will never have any oiling issues unless their engine is not assembled correctly.
The moderators of this board actually manufacture GREAT products for the AMC oiling system.
I'm not going to duplicate points that have already been made in those threads addressing the issue.
These issues have been hashed & rehashed since the late sixties and it's about the first thing most any person building an AMC V8 learns.
So, again, in answer to beyer05's question, increasing compression on an AMC V8 is as easy as bolting on early model heads (not sure what he have). The early heads (70~71) had 50cc combustion chambers, 2.025" intake and 1.68" exhaust valves, getting around 12.5~1 with flattop pistons. They went to 57.92cc chambers in late '71 early '72. The early heads are available almost weekly on Ebay. The later heads can be milled enough for most any purpose. There is an AMC head # post somewhere on this board.
The head of the piston should be .040"~.045" from the head at TDC when using steel rods, more for aluminum. 11~1 is a good upper limit for the AMC design, so long as everything is set up properly and you get enough mix in and enough waste out. The Chevy "rules of thumb" simply don't apply to the superior AMC design.
CALL your cam maker with your engine & drivetrain specs to get sound advice. They build these engines with the cams they sell and know more than anyone here about camshaft applications.
Sorry, pyagid, I have a hard time watching uninformed people dish out incorrect advice without correcting it. I guess it comes from my years as service manager of a multi franchised motorcycle dealership. One mistake and a rider could go down.
Last post for me in this thread.
Goose
Whew, Danga!! is it safe yet? :shock:
Blown7
SwampRat wrote
That is a great piece of AMC history, but are you ever gonna disscuss with me their oiling problems. On the American Motors forum it is somewhat of a hot topic, why don't you want to talk about it? What do you do, what does a "prepped" AMC buttom end invovle for oiling system modifications that allow it to live at 8000 RPM?
Swamprat a good place for you to start would be all the oiling modification threads here in the forums and archives, if you asked a question like that on the IFSJ board without stating you did a search the members would chew your butt. If after you have read all the threads and then asked for clarification of a particular issue I'm sure alot of folks would chime in to help. "Daddy aways taught me if your gonna ask a question of a man, do it nice and always have your hat in your hand". Jeff
SwampRat
I apologize, I just wanted his opinion on what he thought needed to be done. I see some on the American Motors forum don't believe that the AMC oiling system is all that bad, and since he states that AMC drag engines can easily rev to 8000 RPM's I just wanted to hear his opinion on it.
Henry Lavrenz
swaprat, what kind, type ,or year AMC do you have?. I believe most of the members here actually own a American Motor Corp. vehicle. Hankrod
SwampRat
I don't own a AMC, are you gonna boot me off the site now?
jeepsr4ever
No you dont have to go but I want to make it clear to you guys that you need to treat each other with more respect. After reading through the threads I am telling you guys (and you know who you are)
Dont be dumb
