340 Magnum Piston/Head Clearance

[GermzD74]

Hello guys, need a little advice before I continue my build any further.

Building a 340 with EQ magnum heads, KB 243 30 over pistons. The pistons come out just a tiny bit...I believe that small rise (that comes out of the deck) on the pistons are almost .030...not sure if I measured right.

For those that have used magnum heads, what is generally the best way to do this? Thicker head gasket or milling of .030 from the top of pistons?

This will be a mostly street driven car but want to leave power on the table. If I mill the pistons compression will go down...therefore, what is the best route here?

Thanks,

-Germz

 

[dodge freak]

Mine came up at spec which was .018, not .030. But i used open chamber heads so no worries here.

 

[GermzD74]

Bump

I don't think I measured right, I was in a rush, from the pictures, can anyone tell? I think that might be .018 or less no? If so, is leaving it like that and using a thicker head gasket better for horse power? Need to know whether to mill them or not before sending it to get balanced. Thanks

 

[dodge freak]

fel pro makes a .053 thick gasket, lets see, .018 from .053 gives a clearance of .035

.030 is about the limit I believe, those are not short skirt stroker pistons, so less piston rock--the more the piston rocks the less clearance there is.

It should be OK, I believe others have said on here they did it and it was OK..would I be comfy hitting 7,000 rpm everyday with it, nope but I don't like pushing stuff to the limit

 

[IQ52]

Well, if you use the thicker head gasket you will lose more compression than if you mill the pistons. That seemed to be a concern of yours. Perhaps you should get an accurate measurement before you make the decision? I think there should be some measuring and calculating rather than quessing from photographs. Howsabout doing a .500" down fill volume and cc'ing the heads before doin' anything?

 

[GermzD74]

Re measured with the gauge and they come out close to .040 out the deck which was surprising; thought they would only be .018 like factory. Will definitely have to be cut down if I want to use EQ magnum heads. I will go shopping for metal now to have a friend make me a piston vise so we can fly cut them on his mill. Then I should be cleared to use the .039 fel pro head gaskets.

 

[dodge freak]

that doesn't look like .040 from what i can see

take some feeler gauges and lay them next to the pistons and use a flat edge or even your hand and check again. Guess if the deck been milled it could be .040