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By Ted - 10 Years Ago
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While it’s pretty much a given that using the gaskets on exhaust manifolds where they mate up to the iron heads increases the propensity for the exhaust manifolds to crack, what’s the general consensus for what happens with the same exhaust manifolds when used on the aluminum heads? I ask this due to the rarity of the Thunderbird exhaust manifold and the number of those Thunderbirds now getting a set of aluminum heads. At this point, there doesn’t seem to be a ‘best practice’ for either gasket or no gasket when using factory exhaust manifolds on the aluminum heads. Thoughts regarding this subject or personal experiences welcome.
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By Bob Gardner - 10 Years Ago
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Gasket. The surface irregularities in the iron manifold will need a gasket to conform to the aluminum head...IMHO.
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By RB - 10 Years Ago
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I have had great luck with no gasket. Machine the exhaust manifold flat and smooth. Use Hi Temp RTV to seal the joint.. They never leak
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By pintoplumber - 10 Years Ago
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No experience with this, just asking. Wouldn't you want to use a gasket, not so much for leaking, but the two different rates of expansion.
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By aussiebill - 10 Years Ago
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Hi ted, i dont have a definite answer but my thoughts over the years of cracked exhaust and intake lugs has been because some people just over tighten the front bolts because they are easy to swing on and as you suggest the gasket can give and cause cracking of those lugs. If we think back they came without gaskets when new if i,m right. If not wanting to use gskts then a smear of hi temp silicone sealer like on race car headers etc would eliminate the problem.
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By FORD DEARBORN - 10 Years Ago
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Greetings to all: In regards to Ted's exhaust manifold gasket question brings to mind, heat transfer. Aluminum being a better thermal conductor may tend to absorb some heat from the cast iron manifolds? The manifolds are being hit as from a blow torch and I would think this would be the hottest area? Perhaps this may make an interesting experiment on the dyno mule employing the use of a laser pointer type pyrometer. This may also have some effect on exhaust valve temperature. Just my $.02 thought.
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By Joe-JDC - 10 Years Ago
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All the newer 4.6 engines with aluminum heads and headers come from the factory with a thin steel shim between the heads and headers. I agree with Royce that if the header flange is perfectly flat, I would use a smear of RTV on the flange, and bolt them up very snug, and retighten after a heat cycle. On my SBFs I use a multi-layer header gasket between the aluminum heads and headers, even on the race engines. The blue Fel-Pro exhaust header gaskets work great for the FE and SBFs with aluminum heads. Joe-JDC.
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By 2721955meteor - 10 Years Ago
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I use the gaskets from the oh kit,but i use cat(from cat dealer) hardened washers with cat grad 8 bolts.from my 1st block in 1957 a 272 in a 1955 meteor til to day and many ys inbetween have used this approach, with the crude holes in thes manifolds and temps they reach soft flats just give up. with ind. grade 8 (cat) the head is thicker and the elasticity is good,just use the correct length and torque.I cant coment on alum heads as thay are not within my budget. my 1957 ranchero has no ex manifold isuesand it runs prity warm with 180 stat and a heavey foot
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By Larry D - 10 Years Ago
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Would a soft copper gasket work to smooth out any surface irregularities and offer a good seal? I know someone was selling them on ebay a while back.
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By 56_Fairlane - 10 Years Ago
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Every engine I've rebuilt that had aluminum heads and cast iron exhaust manifolds used metallic thermal gaskets. They were a sandwich type with metal surfaces and an asbestos looking inner material.
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By Ted - 10 Years Ago
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Thanks to all for the comments. My initial concern was some chaffing or erosion on the exhaust side of the aluminum heads taking place when the manifolds are bolted to the heads without gaskets. I have since looked at some of the factory aluminum headed core engines I have here and find that some of those use a cast iron manifold bolted directly to the head while others use a steel shim gasket. I’ve used copper gaskets for engines on the dyno and they do not appear to be a long term solution. While I have copper exhaust gaskets here for the Y engines, they are on the hard side and do not conform well to irregularities even when the gaskets have been annealed.
AussieBill makes a good point about the exhaust manifolds being over-tightened with the gaskets in place thus forcing those manifold end tabs to break off. On the race engines, simply bolting the headers to the aluminum heads with a thin film of high temperature RTV without a gasket has worked well for a good number of years now. With all that in mind, I’ll be recommending that the exhaust manifolds on this latest aluminum headed Thunderbird engine build be attached to the aluminum heads without gaskets and with only a thin film of red RTV. Checking the manifolds for straightness and machining where necessary is an understood necessity on any head.
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By DryLakesRacer - 10 Years Ago
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We have had extremely good luck with Mr. Gasket layered aluminum on our race car. I've checked and there are none for the Y. I've seen some scrubrolet headers mated to Y heads so maybe their gaskets can be done too. Good luck
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By 5d6fairlane - 10 Years Ago
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Anybody tried remflex gaskets. That is what I bought tho I have not finished building the headers to try them out.
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By pegleg - 10 Years Ago
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Ted, with the copper if you anneal the gaskets with a torch (tuned rich, soft flame) and air dry, they'll become soft again.
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By Pete 55Tbird - 10 Years Ago
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What do car makers who make engines with aluminum heads and cast iron exhaust manifolds use? I am sure that their R&D budgets are large enough to have looked at this. If they could save a dime by not using a gasket I am sure that they would.
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By Y block Billy - 10 Years Ago
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If you note the original manifolds, the center hole is near a shouldered hole and the others towards the ends have a larger hole, this is to allow for some thermal expansion, with aluminum and steel having a different rate of expansion, depending on the type header used, many of the cast ones could have cracked due to people tightening them too much and not allowing them to expand. The factory washers used were flat hard ones which may have allowed for some sliding action during expansion and contraction. some header flanges have slits at the bolts to allow for this similar to why the intake has hold down clamps near the exhaust crossover, because it is hot there but at the ends is cool from the intake ports, different rates of expansion, if they were directly bolted with the crossover would probably all crack.
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By ian57tbird - 10 Years Ago
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I would be reluctant to use copper gaskets for aluminium heads on a more permanent installation with the risk of damage from electrolysis.
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By HT32BSX115 - 10 Years Ago
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Howdy Y'all!
Has anyone had the Rams that John [Mummert] sells ever crack with or without gaskets?
tnx/Rick
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