Fiat TC Head Gaskets

[robert kenney]

Hello All,
I am currently building a Fiat TC for a family member. The car is a 1978 124 Spider 1800. I am running a 90 mm crank (stock 2Ltr) in the 1800 block, custom(to my CAD drawing) CNC'd Chro-Moly rods 5.492 CtoC with a hardness of 43 RCS, custom (to my CAD drawing) 85mm forged pistons 1.177 CH with offset valve reliefs on 1 and 4 plus light tool steel pins, a reworked and ported head , waffle manifold toped with a pair of 40mm IDF's, and a 4 into 1 headerwith 2 1/4 collector.

I will be running the piston .005-.008 proud of the deck so I need to make sure I have enough fire ring clearance. Who do you recommend for a head gasket. This is a street motor so long term durability if a major factor in my choice. Also I would like to end up with a .042-.045" compressed thickness.

Any other suggestions would be appreciated for a Fiat newbie.

Robert

[Guy Croft]

Robert, hi

since you kindly asked - it's my Q&A and my website too so I will recommend what I sell. I recommend the NV gaskets that I stock, there is no other suitable type for that performance motor and I speak as one whose livelihood depends on getting the strongest ones available.

Yes, it is thicker than you call for and that is unsurmountable. About 1.5mm compressed. There is no thin MLS type for that engine. Moreover the NV fire-ring bore is 85mm so you will have to chamfer the crown of your pistons in a lathe to make sure they don't hit it. They need race bolts -which I sell, my own spec. and late OE head washers, dowels too.


GC

[robert kenney]

Guy,
Thanks for the suggestion, I guess I could deck the block .5 mm. I had not planed to but I will do a mock up when I recieve my pistons and see where exactly I end up.
Sorry for the vendor referances, I removed them after reading the fine print.


Robert

[Guy Croft]

Robert, hi

Thanks for your courtesy - actually I don't object to vendor references (in most cases!) provided the remarks are within the scope of the site rules for 'referring to vendors'.

I think we have crossed lines - you say 'proud of the block' a term I use to describe the pistons being above the block deck, whereas reading your last post about decking (machining) the block I think you mean yours will be below it?

If as you said 0.008" below block deck at 85mm bore then that is OK provided pistons are radiused or chamfered say 1.5mm around edge of crown to clear fire ring under compressed-hot-running conditions.

Yes, best check the crown height when they arrive and we can talk again.

G

[robert kenney]

Robert, hi



I think we have crossed lines - you say 'proud of the block' a term I use to describe the pistons being above the block deck, whereas reading your last post about decking (machining) the block I think you mean yours will be below it?

G

Guy,
No, you were correct to take proud as meaning "Above" the deck in my post.
In all of my engines I am able to get head gaskets in the .040 - .045 compressed thickness and designed my pistons with that assumption. Well this is out side of my normal engine realm. I will most likely use the NV tried and true head gasket. With 1.5mm compressed thickness, I will need to adjust the deck about .4-.5 mm. to acheive proper quench and compression numbers.

I am also interested in the bolt/washer set. I will contact you later regarding the parts off line.

Thanks Again :!:
Robert

[Guy Croft]

Thanks for clarifying Robert!

GC