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.

Lorena, Texas (South of Waco)

Gasket.  The surface irregularities in the iron manifold will need a gasket to conform to the aluminum head...IMHO.

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

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.

  Dennis in Lititz PA

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.


  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

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.


64F100 57FAIRLANE500

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.

JDC

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

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.

Larry D

Winnipeg, MB Canada Eh!


'57 Fairlane 500 Club Victoria

'58 Custom 300 Tudor

'56 Crown Victoria

'61 Starliner Z Code

'51 Ford Victoria

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.


~DJ~ AKA "Bleach"
1956 Ford Fairlane Town Sedan 30K original miles