Fiat twin cam - starting head gasket failure?

[Nut124]

I received head, block and crank from shop. They said head checked out OK and did not need to get surfaced, which I had hoped for.

Got second thoughts after examining the head gasket that came out of the engine. It seems to show tiny flame paths past the fire ring. The head has matching defects in it.

Is this what It seems - fire ring failure?

What is the slimmest cut that can be taken from an aluminum head like this? The head has cast iron seats that may be in the cut path? Is that going to mess up the surfacing cut?

[AC sports]

Resurface it. It's ok if the cutter takes out the top of the cast iron seat inserts. It's very common on those heads. Just not to the point you got to sink the 45* contact face too much otherwise you will need to top your valves.

[BCjohnny]

x 2

Machined a few of these in the past, mostly to get the comp up a tad

It's ok to kiss the seats, as long as you don't go mad

[allencr267]

Is this what It seems - fire ring failure?

More a failure to prep the surface right, looks horrible, and not re-torquing it, maybe no lube or rough bolt head surface caused under torque.
I'm not afraid to smooth a lousy machine shop rough cut with wetordry or emery & a block. I've got a piece of marble, bur even a rubber body work type block can smooth it out if done lightly & evenly.

[Truckedup]

Looks like a hemi with quench ,lucky you!

[Nut124]

Thanks for the replies, again.

I took the head to another shop. The owner said his mill will produce a flawless finish. Was not worried about seats affecting his cut. Good for MLS. May have to recut the intake seats if seat width gets too narrow.

I received a new cam today. Italian. Duration is a bout the same as my hot street cam, 300deg at 0.016 lash. This one has much wider lobe tips. Twice as much lift at TDC - about 3.5mm or 0.140". Kind of looks like the Guy Croft Stg2 lobe profile. Lot of lift integral.



The previous 300deg street cam on the right. I plan on using it for the exhaust.

[MadBill]

Verify the block surface first. Some aluminum blocks (e.g. Alfa Romeo) are specced for a thous or more of sleeve protrusion. The machine work on a friend's Alfa block left the sleeves at zero and he suffered head gasket failures until it was corrected.

[BCjohnny]

Block's iron ... integral cylinders

[MadBill]

Fiat-Alfa; tomato-tomata

[allencr267]

Looks like a hemi with quench ,lucky you!

Do you weld them in?
Thanks.

[4vpc]

That's detonation.

[Kevin Johnson]

Fiat-Alfa; tomato-tomata

Renaults had protruding liners and both iron and alloy blocks: tomate.

[Kevin Johnson]

That's detonation.

TTT

[AC sports]

For someone that pretty much builds just Fiat and Alfa classic engines....I assure you they are chalk and cheese!
I can assemble a Fiat twincam in half the time.
The Alfa is an older design but all alloy with iron sleeves.
And alloy head. Fiat has a cast iron block and alloy head with a better more modern chamber as you can see. Alfas chamber is hemi without squish and ports are virtually horizontal. Fiats have a slight down draft from horizontal. I currently have one of each on the stands. Much prefer the Fiat, although the Alfa does have the best wet sump system af all !

[Momus]

For someone that pretty much builds just Fiat and Alfa classic engines....I assure you they are chalk and cheese!
I can assemble a Fiat twincam in half the time.
The Alfa is an older design but all alloy with iron sleeves.
And alloy head. Fiat has a cast iron block and alloy head with a better more modern chamber as you can see. Alfas chamber is hemi without squish and ports are virtually horizontal. Fiats have a slight down draft from horizontal. I currently have one of each on the stands. Much prefer the Fiat, although the Alfa does have the best wet sump system af all !

Alfa wet sleeve fours would be one of the most recalcitrant engines ever designed.

I had one, a 2 litre 40 odd years ago that would pull the main bearing bores out of round when the head nuts were tightened on the through-the-case studs sufficiently to seal slightly increased compression. After an inordinate amount of work- with very limited resources- we were able to get about 90hp per litre from it.