Originally Posted By: 440Magnum
Originally Posted By: sasilverbullet
I'm going to rebuild the engine in my 70 Lincoln Mk III. It's a 460 rated at 365 hp and 500 ft lbs torque. It's rated stock at 10.5:1 and it's a totally original engine w/97k miles on it.
To keep it from pinging I've been having to run premium along with a bottle of Amsoil Octane boost (one bottle for 15 gals) and having the timing retarded to 0 degrees. I have a Pertronix II replacing the points and the carb is a fairly new Edelbrock 1604.
My goal for this rebuild is to end up with at least the stock rated hp and torque and that it run on premium with no pinging. (with the timing set correctly of course)
I'll also be towing at 4,000 lb trailer with it.
Recommendations please on how to achieve my goals.
Details like: what cam to use? pistons? valves and valve seats? Valve springs? Should I go to roller cam?
Of course I'll be replacing the cam, lifters, oil pump, all bearings, valves, valve seats, valve springs, valve guides, timing chain/gears, and having the crank turned.
I want to do this right - I'd like to drive this car a LOT for the next 10 years and not have it apart every other week for engine maintenance!
The best recipe for reducing pinging is to convert to aluminum heads. The faster heat dissipation really pays off. Also pay attention to getting the right quench area, which is related to combustion chamber shape and piston-to-head clearance. This lets you run higher compression "closed"-chamber heads and still avoid detonation- there's almost certainly a recipe for doing this with a Ford Lima. I'm generally familiar with the technique and recipe for BB Mopars, but there's a similar method for Limas I'm sure.
Cam overlap and duration also play into it, but if you get the chamber and quench right it lets you tailor the cam more for the power curve you want with less worry about detonation. Don't get greedy with static compression even with aluminum heads- 9:1 (real) static CR is about as high as I'd go for pump gas. You don't need tons of compression for a towing engine anyway- you need mid-range power.
And by the way- if you use short-skirt hypereutectic pistons, get coated skirts. I used a set of older non-coated KB hypereutectics in the 440 build for my 66, and it sounds like a 7.2 Powerstroke when its cold from all the piston slap... and we even tore it down and RE-CHECKED the clearances to make sure they were tight enough per KB recommendations. The coating is the key to making them quiet. I've put over 20k miles on it (and thrashed it really hard at times) with no issues other than the noise, so its not a reliability worry.
Quench: Quench is more likely to be the cause of detonation as a result of having improper quench
thickness more so than topographical (plan view) quench area shape and size. (thicknesses of 0.040"-0.050" are a good range)
Aluminum Heads: Rule of thumb, Al heads possess a
much higher coefficient of thermal conductivity as compared to Fe heads and cast Aluminum alloy heads often tolerate approximately one additional compression point more than the more durable cast iron heads before the onset of detonation.
Piston Slap: Many things contribute to this audible phenomenon. Forged vs cast, alloy choice, pin height, rod length, etc. Ive never considered coatings as an issue for slap constraint, but more for skirt/bore scuffing wear control and friction reduction.
Piston material, rib design and machinist's skirt to bore room temperature clearance (as per the manufacturer's piston skirt operating temperature "fit-strategy") all contribute to this noise. I believe there are better pistons for towing than Keith Black Hypereutectics.
Skirts are designed to keep the ring pack square and the piston crown from rocking into the cyl. head, but skirt rib stiffness does not necessarily predict just "how" a particular piston "grows" as it reaches it's full operating temperature.
The best piston makers study these issues and test a multitude of evolutionary prototypes to destruction in search of the best design as is required by each specialized engine usage.
Another huge factor is piston pin "offset". Centered, thrust-side biased or not, where each varying pin placement will affect power (ring seal and rod-angle), longevity, NVH, bore wear differently.
Cam Selection: Cam design is very important toward giving you good torque and drivability in the required RPM range, while maintaining reasonable fuel consumption rates and long term engine component reliability.
A hydraulic "retro" roller lifter cam will pay dividends if chosen carefully, I prefer to run them when excellent parts are available and the budget permits.
If you "re-use" your 1970 heads, make sure you check them for having OEM hardened inserts or at least flame hardened seats.
Around this time fuel lost it's "lead" additive (and octane), so heads not having durable seats, compatible valves and/or hard inserts resulted in accelerated valve recession, ruining these heads and a steady loss of performance after any prolonged running of unleaded fuel.
Modern aftermarket heads will all tolerate unleaded fuel, and buying new heads will save you from the expensive machine work required to install up to 16 new seat inserts.
Speaking of "modern", these older cars never had what we take for granted today, vehicle onboard computer monitored data gathering to maintain very close to ideal stoichiometric mixtures and near perfect ignition timing under all conditions.
Also knock sensors in today's vehicles "listen" for the onset of the specific frequencies indicative of destructive ping/knock/detonation onset.
Your old car will not have these tools in it's arsenal to save it from self-destruction, unless you install "modern" fuel delivery and ignition management systems. Worth exploring, but not mandatory.
Last advice: Be careful not to gather too much good information that somehow re-combines itself into a build of a lot of great parts and strategies, but are in conflict.
I've seen many, many customers (who've been swayed by well intentioned friend's advice, popular magazine articles, manufacturer's wild claims) wind up building expensive, and sometimes gorgeous "boat anchors".
My point, please keep in mind that the best result will be achieved from assembling a properly balanced combo of adequate (or better) components, competently machined and assembled into the package that most accurately and realistically targeted your specific goals.