434 Kit / Head Gaskets - Serious Details

Greetings all,


well we all know that there is just a TON of info on this subject and I have trawled through much of it over the years. Some things are very very clear (both rights and wrongs) but I would like to get very very specific .....


If I were buying a new 434 kit I would go with 1 of the 2 reputable good ones e.g. CW. I have heard that the cheaper ones blow head gaskets, though I am not sure how bad this is ?

I inherrited a cheaper 434 kit when I bought some other parts so considering using it. So, here are some questions .......


Do the cheaper kits use a stock cylinder that has been bored or are they just made with a slightly thin sealing area ?


Are there still head gasket issues (or at least more than with stock) when a Comtec gasket is used and the head is Torqued to 43 Ft / Lbs ? and should the copper goo be applied ? Does that help ?


When the cheaper 434 kit head gaskets fail, where exactly on the head do they fail ? E.g. Is it right by the exhaust valve ?


Can mods be made to detur the failures ?


I suspect that compression ratio at Cams may also be a player.


As always I truely appreciate any and all responses :)



Edited by Our Man Flint

Name the kit you have that you are concerned with.


What is this "cheaper" kit you are referring to?


 I know of no currently available BB kit that reuses a stock cylinder bored and plated from 90mm to 94mm. 

 Some of the older kits used a paper base gasket... if you have that throw it away and use a metal one OEM or COMETIC.


Some of the older kits supplied copper washers for the head bolts.. if you have those throw them away and re use the OEM steel ones.. make sure you install them correctly flat surfaced side down toward the head.


 Some of the kits use an OEM pattern cylinder and bore it over 94mm.. those have a high head gasket failure rate

Use a Copper Coat Spray on the head gasket .

Hi guys, thanks for the replies.

I presume that the copper coat spray helps to keep a good seal, correct ?

I have no idea what my kit is as there was no box with it - I got it used with some other parts. It is a Namura piston with very very little wear. it has 93.96 stamped on it which undoubtedly is the diameter, so the bore will be 94 mm. There are no markings that I can find on the cylinder. I believe the guy paid about $400 or $450 Canadian dollars for it new so around $400 USD (almost at par).

When I refer to cheaper kits I mean not the Athena or CW. There are a bunch of kits around the $400 mark.

I have a really really good engine builder / tuner called Bondi Engineering who will inspect and measure for me. What would you say is the minimum completely realisable measurement between the cylinder wall and water jacket i.e. not prone to blowing gaskets.

I truly appreciate your input. I know that the knowledge is out there so I don't want to leave anything to assumption or chance. I want to know my subject inside out and be completely informed before proceeding.

Perhaps I should buy a Forged piston to go with this cylinder ?

Thanks again,


Edited by Our Man Flint

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