Marvel tells you on the can how many ounces of mystery oil per gallon (s) of gas. The oil will soften the carbon buildup in the heads and on the stem side of the valves. reserved. It happened quite a bit back in those days. I would also change to synthetic motor oil although, I would like to hear some experienced opinions on this. Burns Hotter of course, so what Plum says is true for both Marvel, or crankcase oil getting burned in a wore-out cylinder. Others say a bit of Marvel Mystery oil in each tank is a good idea. an answer for you. Using the product is the best solution for extending the service life of rubber components. Powered by Invision Community, Lead additive in low-mile, original SBC engine from 1966, TEL is a fuel additive, first being mixed with gasoline, in the 1920s ( NOT 1950's) as a patented octane rating. However, I wonder what adding oils to the fuel may do if the engine is prone to detonation or ping, as if your engine "uses oil", that oil introduced into the combustion process usually actually increases detonation and/or ping. 2/ Will Marvel Mystery Oil Reduce Oil Consumption? The amount of TEL in the higher grade fuels has increased the I sometimes add twice that proportion to help with starting to cleanup any gunk in the fuel system and rings while running a car that has sat for a long time and there's no trace of smoky exhaust. The biggest problem with E-10 crap fuel is the hydroscopic action of the alcohol. Anyone want to suggest that's a bad idea? Timothy. Mystery Oil is a top cylinder was going to eliminate lead completely. (Pack of 2) 1,388 $1776 $19.40 FREE delivery on $25 shipped by Amazon. This was a hot topic in the late 80s and early 90s. After a few such experiences, the airport put It is not their machine and they are not going to be paying for your repairs. 100LL. Aluminized valve faces on the 283 engine with applications in the 50 series trucks slow the formation of deposits, keep valves cleaner and longer-lived. because the gasoline comes from a region where ethanol is not used. The exhaust valve must have been stuck before I sprayed the MMO. The leading theory is to use Marvel Mystery Oil. a prop? The extra few bucks may not really be necessary, but is not hurting anything and to my mind is worth theprecaution. Anyone who has never tried them will decry them and put forward all sorts of 'proof' that they cannot work. How much MMO do you use? But aviation fuel continued to contain lead, so the An average passenger car tank is 15 gallons so you would add 6 ounces at every fill-up. 5 Reasons Why You Should Use Marvel Mystery Oil, Whats Customers Say About Marvel Mystery Oil. In a few months all those untouched seats had no problems but the one which had been cut saw the valve bury itself well into the seat, about 3mm down. Mystery Oil also improved gas mileage and minimized engine wear. Anyone who has used them knows they work and has had a good experience with them. I believe mine is the 225 hp version from what I'm seeing in the literature. Some say its a miracle oil, while others suppose that its not worth the money. Never saw that before but was RPO ZL1. Then I can tell you it definitely improves the fuel economy. Just drive it on whatever gas comes out of the pump at your local gas station. know, so I called the 800 number on the side of the can. The trick on a 65 hp Continental is to take the primer blended with TEL. If you're only driving it a few hundred miles a year, it'll outlast your great-great-grandchildren. This oil keeps rubber parts such as hoses, seals, gaskets, and wire well lubricated and prevents them from drying out. Marvel Mystery Lubricating Oil is safe for catalytic converters and oxygen sensors. It's more cleaner than oil. Reply to this topic . So, whats the truth? Marvels popularity soared as word spread of its effectiveness in treating all types of . And guess what? Genesis 1:1-5, 26-31 I Corinthians 8:1-6 John 1; 8; 14 Colossians 1; 2 It is the "interesting" engines that may need more protection but few of these are driven often and mostly use race/AV gas. Its formula contains an oil-thinning ability that solves this problem. The 'lead replacement petrol' wasn't doing any good at all. I installed new pistons (and liners) and had that one seat cut and lapped in the valve. to do the cleaning job. 3. Marvel Mystery Oil. been a lot of talk about what to do so that lead fouling can be But, it will reduce friction making your engine easier to start and run smoother and may even pick up a little extra gas mileage. The pickup is driven sparingly, just a few hundred miles per year, if that. If residual fuel is left in them, the methanol draws moisture from the atmosphere, causing corrosion. Colder than that, and we couldn't fly, engine. Lead was added to gasoline to deposit a metallic cushion and lubricating film on exhaust valves way back in the early days of auto and aviation engines. It works, and has for a long time. erosion incidents, reported on some lower compression engines. Can MMO be used as a lead substitute? Besides, water may condense inside the cylinders and crankcase in cold temperatures, gradually eroding the protective oil film. my great uncle was a ww 2 army air corp airplane mechanic .. he swore by the stuff .. he put marvel in everything that ran on fuel.. he instilled his great wisdom to me an so do i.. weedwackers , mowers, scooters, outboards , an vehicles they all get marvel in the fuel ,, an in the oil crankcase for 4 cycle engines.. 2 cycle / 4 cycle ,, they all get treated every fill up .. just the other day ,, pulled the 3 plugs from my 40 hp 2 cycle outboard an the porcelain was brand new white.. an i ran them all summer since spring .. anyway,, this stuff works .. and what else is on the shelf in the auto department thats been around for a 100 years..!! Well, Kano Kroil Penetrating Oil is a fine substitute to use instead of PB Blaster. This diesel fuel additive does not comply with the federal ultra low sulfur content requirements for use . line off the carburetor, hook up a tube, and run Mystery Oil It was going to be extraordinarily expensive to do it all at once, changing tanks, pumps, and refineries, so they convinced the government that there were all these poor schlubs out there whose cars were going to self-destruct without the "cushioning effect" of the precious lead. N201MKTurbo. Thanks, PFitz. Each exhaust valve required adjusting after that time, about 0.015" on every single one of them. The old timers would use it Product description. the Warbird's Forum Let's end this nonsense before the cloudy waters become opaque, eh? AMC switched to induction hardened valve seats a little later then the other manufacturers. high manifold pressures the wartime engines were operating at, Tetra Ethyl Hard seats are added to earlier heads by machining out the old seats and installing an insert. The size of the valves was only increased from 1.625 to 1.628 to give a little more margin and help them run cooler in the leaner mixtures. There is not really any difference in the seat area. OR THE CROWING OF THE NOBLE COCK BENEVENTANO. and with the wind whistling through the gaps between the windows and the If not removed, these carbons might cause engine damage. The only drawback I know of to using synthetic in older engines, is that it can make oil leaks worse. Then there is ALCOR TCP. sodly gasoline ignites, it is vaporized and soaks into the carbon buildup I wouldn't call Marvel Mystery oil a "lead additive." I don't see any pickle. Sorry for beating a dead horse, guys. MMO is a good product and will help keep your carb clean though. When you buy through our links, we may get a commission. The Dick Van Dyke Show is an American television sitcom starring Dick Van Dyke as Rob Petrie, Mary Tyler Moore as Laura Petrie, Morey Amsterdam as Buddy Sorrell, Rose Marie as Sally Rogers, and Richard Deacon as Mel Cooley.. This improves your gas mileage by increasing the . Mixing the Marvel Mystery into the motor oil aids in the prevention of water condensation in your engine. Quote; Link to comment Share on other sites. To mix with fuel, you put six ounces of additive for every 15 gallons of fuel. I found at the time there is a simple fact relating to these devices. If you have a question and call, Petersen has AMC engines never really have issues with valve recession as they used good materials in their heads. Carburetor1; Feb 14, 2022; OTC and Third Party Oil . However, it turned out later on that the fears were overblown. I am bringing this discussion out of the archives. And then I fitted the canister and drove another 50,000kms without having to touch a thing. A nice fellow WHEN I DID THIS I ALSO CLEANED OUT THE PUSH RODS AND POURED MMO IN THEM. and hardened valve seats became common after 72. At the instant of Some people swear by it, some people swear at it, See for yourself. Best Seller K&N Performance+ Octane Booster: Boosts Octane and Improves Engine Performance, 16 Ounce Bottle Treats up to 18 Gallons, 99-2020 29,253 $999 Save more with Subscribe & Save A quart of MMO in the oil will help clean up a sludged up engine and free up piston rings that are stuck in the piston grooves due to gum and varnish. And it was back to working again, just like that. I use marvel mystery oil in my 2003 f150 Ford pickup and am extremely pleased with it , I have used Lucas fuel injector cleaner before and its a real good cleaner and additive but seems like marvel mystery oil may give me better fuel economy and it seems like my truck runs better on it MMO than Lucas, I have read that these later model engines dont need this put in the gasoline due to nature of fuel injection systems and some mechanics ie Scotty Kilmer for one, does not recommend it. But they're better at protecting their manufacturers from bankruptcy than they are at doing anything significant for your engine's long-term health. This chemical is a petroleum-based fuel that provides long-lasting protection and can be used in a wide range of engines and machinery. Also does Marvel mystery oil work? You don't spill this stuff on your MY 86 CJ-7 NEEDED THE HEAD GASKET REPLACED. He spends his weekdays working for his garage and writing stories for oilsadvisor.com. Started it up and of course it smoked for a little while, but I couldn't believe how much better the thing ran. Unlikely that you'll see any notable damage to your pickup's engine using straight unleaded gas. Many users also stated that they would order this product again as it helps improve the fuel economy. If you want your engine to last as long as possible add a little Marvel Mystery Oil, Bardahl, Redex or your favorite upper cylinder lubricant to the gas. In the 60's Amoco gasolines were unleaded and generally cost a few cents more. for every 10 gallons of gasoline. Para Dichlorobenzene, a precursor used in the production of chemically and thermally resistant polymers, <0.1%[2]. AMC engines never really have issues with valve recession as they used good materials in their heads. This is generally regarded as good stuff, and a lot of people are using it. Back in the late 1940s and early 1950s, at military air bases However we are addressing two totally different problems. When I bought my AMC Javelin/AMX 302(8:1 compression "smog motor") in the spring of 72, it came with hardened seats. As for using a lead substitute, I don't know how anything that wasn't actually lead could be expected to have the same properties. Are unneeded now but have not seen any more efficient valve shapes, rather 4 valve cyls are now common (except for hemis which cannot without very expensive valvetrains). 4/ Marvel Mystery Oil Vs Seafoam: Which Is Better? Moving on ten or fifteen years, we were using 'lead replacement petrol', which had varying degrees of usefulness I'm told. I have a 2010 2500 with a 5.7 Hemi with 200k and no oil leaks and does not burn oil, (knock on wood). TEL had been identified chemically in the mid-19th century, but its antiknock effectiveness was discovered in 1921 by the General Motors research laboratory, which had spent several years attempting to find an additive that was both highly effective and inexpensive. So, whats the verdict? So when the pump in the tank of the wife's Voyager started to hum its death tune, I poured a pint of Marvel in the tank for dungz and giggles, figured I'd be dropping the tank soon enough anyway. Marvel MM13R Mystery Oil. Thank you. 1 1993_VG30E_GXE Joined Apr 4, 2009 Messages 355 Location Ontario, Canada Dec 12, 2009 #1 Does anyone know of a substitute or name a few, as MMO is discontinued now in Canada. So, by doing it before the seats fail, you are just doing something ahead of time that might never need to be done, and might cause a failure in the meantime. Then, in the new oil, Reply #2 on: September 30, 2020, 09:06:35 am . experience with mogas and, finally, by an email from Terry Lutz, expanding answered, I do, how often do you have to change your brake pads?). The "Turbo-Fire" 327, by comparison, had a 10.5:1 compression ratio. Most gas has about 10 to 15% these days.E-85 has as much as 85 % ethanol, but out west here it's more like e-40 or 50 . I also put a qt. If you have not had your valve seats replaced with hard seats, a lead substitute is a must. Regularly adding this additive to your fuel tank can increase your cars fuel mileage, eliminate carbon deposits, clean your engine and fuel system, etc. Where did you get your information. Low HP cars are doing these grades in low gears barely making 40MPH. It's mostly mineralspirits with some light oil, red die and fragrance added. MMO is basicly automotive ATF. They serve comparable purposes but with subtle distinctions. To prevent oil from thickening in cold weather, add the product to 20% of the crankcase capacity. I forget the MIL spec number. We had charts that told us how many gallons of MMO to put in per Ninety-five percent of customers gave it a four-star rating or above.This MMO received a lot of good comments from users. (2501) Check price. The leading theory is Finally I took off the spark plug and sprayed MMO into the hole at what appeared to be the exhaust valve. While dibromoethane was added to leaded gas to do the same, some lead oxide did stay in the engine. There is a very good article on RVP and specific gravities as well as othe things relative to custom blending of racing fuels available from Torco and I beleive Sunoco has some litteriture also. LRDaum. ADDED TO ENGINE OIL:Use Marvel Mystery Oil or Marvel Ultimate Oil in the crankcase to enhance oil lubrication and sludge control. Marvel mystery oil,the idea behind it was and still is,it is basically a cleaner,it removes sludge from lifters and helps to soften the carbon built up between the rings.We used to use a quart of. Right. It is possible that the people who have the most problems with gas are the ones who are also great price shoppers, the ones who will stick any nozzle in their filler to save 3 cents. So it seems that the residual lead on the seats from beforehand had continued to provide protection, but once cleaned off by cutting the seats valve seat recession commenced. Added to gas it cleans and lubricates fuel injectors and carburetors, improves gasoline mileage, extends spark plug life, reduces and prevents varnish and gum build-up. Unleaded was just coming in on the Australian market then and I was told it did the same. Use the directions on the back for amount to put in the fuel per So, when it is about Marvel Mystery oil vs. Seafoam, the Marvel Mystery for around $4, Seafoam charges you double of it for the same quantity. "High alloy steel inlet valves. More sharing options. I had to study more of it than I wanted to in chemistry (which was never my favorite subject - but who knew it would have some practical use???) I think this gas additive hypeis more a necessity for sales thanbased on any actual need for protecting the engine. I think perhaps time to add some to this computer.. Matt is worried about ruining the Wag's engine - I told him to just run gas in it. The original oil enhancer AND fuel treatment cleans the engine from the inside out, increases fuel economy, and protects against temperature extremes. Websites 1997-2019 Daniel Ford; all rights We are putting 89 octane in, and adding a can of lead substitute every tank right now. EXCLUSIVE: Why this pro-gun Colorado Democrat thinks he can beat Lauren Boebert in a rematch: Businessman Adam Frisch criticizes his own party for abandoning him and rural Americans - and says . It had 69,000 when I got it, about 88,000 now. Marvel Mystery Oil is top end lubricant , not an octane booster. sebastian seymour, lord seymour Chevvy was most notorious for this rating the "racers only" Z-28 302 at 290hp and the "public" SS-350 at 295 hp. hours. It can be used as a fuel additive by mixing it with the gasoline in your tank. It's all BS but it worked, and the unleaded was phased in over a period of years. Carbon deposits will cause motor oil to burn more than usual. There wasn't widespread valve seat recession and engineers at the oil companies wondering how to keep it from happening. As it turns out, the valve seat recession occurred in engines that were run hard (such as towing and drag racing), and in ordinary street engines not so much. whether because of transportation problems (alcohol absorbs water) or What's Customers Say About Marvel Mystery Oil. Many believe that when used correctly, it can do good things in your cars. It can free up stuck lifters and help loosen up dirt to flush it out. venerable taildraggers. Or any? A mechanic I know says to put a little of this in. Using Marvel mystery oil in your fuel extends the life of these vital components by providing them with lubrication that fuel alone does not provide. Sorry if this has been discussed before (I know it has been). I do the same for the '65 Corvair, '37 Buick Roadmaster, and '88 Corvette. Marvel Mystery Oil, an additives found in Marvel Mystery Oil, can extend the life of your vehicle's engine. Sounds like MMO might be a cheap, simple compromise if I decide to go that route. When valves are beginning to stick, it will The advantages of this additive are described in full below: This is an absolute must-have product if you wish to keep the internal components of your engine clean. If you drove 100 k miles a year at full throttle then I would say you need hard valve seats, and you do not! Share Followers 0. So does Amazon if you click through to that store. in the bottom of the oil kidney. It's amazing how tertra ethyl lead was used to reduce emmissions way back at the turn of the century? In all parts of the world many high-spirited revolts from rascally despotisms had of late been knocked on the head; many dreadful casualties, by locomotive and steamer, had likewise knocked hundreds of high-spirited travelers on the head (I lost a dear friend in one of them); my own private affairs were also full of despotisms . TEL had been identified chemically in the mid-19th century, but its antiknock. I found that the airplane motor crowd uses it for top cyl lubrication, but i don't know if there's necessarily much correlation between airplane and car engines in this area. Thank you. Before that is was all the hype about new cars being unleaded only. cut-off time, for first use. Could you share with us your experience of using this MMO in the comment box below? All your true octane booster that do any thing are toxic , highly toxic , which why they took them out of gasoline and will not sell you any that does much good. the formula for TCP and used it for years in car gas, which was also | Facebook I can't say if MMO enhances the fuel upon firing, but MMO may well aid sealing of valves, and rings at that critical moment when added rationale to fuel. Even when using more MMO breaking in a fresh rebuild and adding a quart of motor oil to a 20 gallon tank, it's tough to see much smoke in the exhaust. An 11-year-old girl in Detroit had to get staples in her head after . Tetra-Ethel Lead is not an octane booster either. This in turn caused increased vehicle performance and fuel economy. 1100 to 1200 RPM. This oil helps to prevent bad gas millage by removing fuel residues from fuel injectors and carburetors, lubricating and cleaning pistons, intake valves, and cylinders, and eliminating fuel residues in fuel injectors and carburetors. Yeah, anything can fail, but there is no way I would take that engine apart because of the valve seats. . It is a rather critical machining process, and if you get it wrong, a seat can fall out and hold a valve open. The best use I found for it still applies to today's engines and that is to add a quart to 20 gallons of fuel before a road trip. The good of E-85 is it's 105 octane, the bad is the ethanol you have the lower your gas mileage gets. Therefore, important engine components will not be adequately lubricated. The says there were two 327 versions for trucks, one (185 hp) at 8.0:1 compression and another (225 hp) at 8.5:1 compression. At the temperatures found in the combustion chamber of a cylinder, MM oil will be vaporized. creates great clouds of smoke, and extends engine a life for a few more Regularly use Marvel in your oil and fuel for a smoother, quieter engine. Air cooled VW's loved MMO for long road trips! It was thought that since the automakers were induction hardening valve seats in the unleaded era that it must be necessary. Back in 2016 I started having poor idle symptoms and stalling at stops. He explained why in a post on the Cub Builders mailing list, Interesting discussion, back in the 30's salesmen would dip there ties in tetraethyl and wave over a knocking engine which would clear up. much of northern New England's gasoline comes arrives. It was Marvel mystery oil,the idea behind it was and still is,it is basically a cleaner,it removes sludge from lifters and helps to soften the carbon built up between the rings.We used to use a quart of ATF to do the same thing.Marvel mystery oil makes a good penetrating oil and is great for an air tool oil.As for lead lubricating the heads,NO,it did not.The lead in leaded gasoline lubricated the valves,it kept them from eating themselves up,which is why when they switched to the unleaded fuels,the hot rodders were constantly looking for unleaded heads to swap into their cars. AMC generally did not have head problems other then those 73/74 heads, which most people learn to stay away from. There is no reason to use it in a "clean" engine. Along with being better fuel, I make sure it flows through the carb as fast as possible. ", "Hydraulic valve lifters, both inlet and exhaust.". Ha ha! To go into more detail, the mechanic who advised me to use it said it would dissolve varnish and gunk, free up rings, etc. Many of the older, better-known oil treatments on the market do not make claims nearly so lavish as the new upstarts. Wether you use it right before a change, to replace a quart of oil, or just use it in the fuel tank is a matter of preference and I'm sure wont' hurt a thing used any of these ways. load up with straight mogas before it was adulterated for highway use. They recommended to run a tank of leaded every seventh fillup. Your email address will not be published. This oil helps your car start more quickly in cold temperatures and keeps it running smoothly. Charles Kettering discovered that lead would boost octane in the 1930s, and it was cheap, plentiful, and easy to add to fuel so there it was. Marvel Mystery Oil helps unleash maximum power and performance while extending engine life. As I understand the While some oils are suitable for use with metal parts, they do not work well with rubber components. Looks like the 185 hp version was used in larger straight trucks. It contains additives that help lubricate and protect the engine. Marvel Mystery Oil is a blend of mineral oils, which are a byproduct of the fractional distillation process used to make gasoline. Marvel Mystery Lubricating Oil is safe for catalytic converters and oxygen sensors. Slippery stuff! Followers 4 . Think about the whole scenerio . Please provide proof so we can switch to the perfected heads. Add To Fuel To Clean Engines And Increase Gas Mileages. Then some guy tells him that 2-stroke oil like he uses in his chainsaws would be just as good or better -- and maybe cheaper too. Not to be confused with the Benzites, eh, Ms. Edmonds? I know this has been talked about before but I didn't see any information specifically about original, un-modified engines-- ones that haven't had hardened valve seats put in like mine. Contact Us - DO NOT EMAIL CAR QUESTIONS. Dan Ford, Other websites: paint job, and is difficult to carry it with you in the airplane. I fitted another head which had good seats and valves, freshly out of the machine shop. can put mo-gas in the tank 75% (TEL 0.002 ml) and 25% av-gas It looks like you're new here. LOL. mogas. Used Marvel mystery oil on an oil change because lifters were sticking in my 94 trooper. So if you run a multi viscosity oil such and 15w-50 you are changing the properties of the oil, and potentially reducing the oils effectiveness. As Matt said it may not be necessary but doesn't hurt. During your next oil change, substitute 20 percent of your engine oil with Marvel Mystery oil. Worse, I once had the engine quit as I was coming in for a landing, tank of fuel. By Tundra1, January 17, 2015 in General Discussion - Any topic is welcome here!!! In addition, Marvel Mystery oil helps you to avoid unnecessary rubber parts repairs or replacements. Drive it as it is, put regular gas in it and stop worrying. Inquiring minds want to I presume this was about the most de-tuned version of the 327 (just my guess). Remember too, cold weather (and New Hampshire can get really cold), they often stalled. The metal parts of your engine rust over time and eventually fail. the engine passages and crevices and hydraulic lifters, and stores it There's plenty of anecdotal evidence for additives and mystery ingredients, but anecdotal evidence isn't evidence. Aluminized head retards build up of deposits and chrome plated stem reduces scuffing and wear. ", "Long life exhaust valves. I would also change to synthetic motor oil although, I would like to hear some experienced opinions on this. Old standbys like Bardahl. So it must be scrubbing a bit of carbon off. email. In the late 60's and early 70's we were assured that leaded fuel would be available of our older cars. Just like the topic of using non-detergent oil. Page 1 of 3 1 2 3 Next > lucky6600, Dec 1, 2010 #1. lucky6600 Long timer. or intake manifold. The product will help release any corrosion that is causing the spark plug to seize. This oil was very useful in older aircraft engines to scavenge lead deposits. Informacin detallada del sitio web y la empresa: labonneoccase.com, +49803921568627 LA BONNE OCCASE - Vente d'lectromnager d'occasion et neuf avec dfaut d'aspect Some people say its great because it helps clean your engine and keep everything running smoothly. Marvel oil is used in the gasoline of inboard and I/O engines as an upper cylinder lubricant, and to lubricate fuel system components,( especially the fuel injectors). The verdict on Marvel Mystery Oil is that its a great product with many benefits. From the stories I had heard I figured my carburetor must look like a glue factory inside. I know valve jobs were a common job for mechanics back in the 60's and early 70's, but for cleanup the valves and dealing withvalve guide wear. Others argue that its actually bad for your car and can damage the parts over time. My understanding is that valve rotators were developed to prevent lead deposits. RVP has nothing to do with octane and is almost always lower in modern gasoline than it was in the old days. Post in the forum instead. Your donations help keep this valuable resource free and growing. Use additives if you want, it won't hurt the engine. It's easy! A mechanic saw me doing that, picked up his jaw, and told me to use MMO in the oil. I don't remember hearinganything about valve seat recession from the mechanics I hung around with,. including the guys who did marine engine rebuilding, fire departmentcompetition trucks,and race engines. created during WWII because the cooler cylinders on the multi-row radial story, there's no alcohol in the fuel when it comes ashore at Portland, It was very popular back before detergent motor oil was invented. Okay, thats not a trick subject line. Robert Parker used Marvel Mystery Oil to reduce the buildup of lead Probably not an issue with racing, however. The popular theory is that the MM oil acts as a vapor blast and keeps carbon and lead deposits soft and passing through the exhaust valve rather than adhering to the valve, seat, or guide. Born in Chicago in 1923, Marvel Mystery Oil was developed to combat deposits on carburetors caused by poorly refined gasoline of the age. I contacted the maker and he asked what fuel I was using. Marvel Mystery Oil can be used to keep the fuel system clean. You are actually in error on many of your assumptions. recommend the procedure. Problem with regular Marvel Mystery Oil is that it will combine with castor oil residue and, over a period of time, form a hard red crud. Or did you purchase a vehicle in January and feel lucky you locked it in before prices rose higher through February? There were re-portly 7 different cylinder head redesigns in 1973 and 1974 until all the problem were solved in the 1975 and up V-8 heads in particular, these are generally the 502 heads, a little bigger port, a little bigger valves, and supposedly induction hardened valve seats.