cals400ex

iTrader: (27)

i recently purchased some afr 215 heads for my stock bore ls1. afr's site recommends a gasket with a bore diameter of 4.135" or larger. i have read some do this and some don't. i am just looking for opinions.

Sales2@Texas-speed

iTrader: (5)

Might check with them directly, but I do know the 225's require a 4.135" bore gasket or larger. Their 245's say 4.200" or larger, which is one of the most absurd things I've read in quite a while.

cals400ex

iTrader: (27)

yeah, their website does say this, regardless of engine bore size...

Sales2@Texas-speed

iTrader: (5)

Like I said, I do know the 225's require the big bore gasket (first hand experience with a 402ci short-block and 225's pushing water immediately after first start-up...terrible way to learn this lesson), but I do not know 100% on the 215's...sorry I'm not of more help on this one.

vettenuts

iTrader: (4)

Measure the chamber, you will find your answer. I am running 4.160" with my mamofied chambers.

XtraCajunSS

iTrader: (2)

This ^^...

The reason you MUST run a large bore gasket is because the head gasket itself CANNOT protrude into the chamber at all. If it does, you risk burning the gasket and causing a failure not to mention the increased potential for detonation.

Basically it comes down to this, you must run a head gasket that is AT LEAST the same as the bore size (+ chamfer) AND the chamber at its widest point. I always place the new gasket over the surface of the head to make sure it doesn't protrude into the chamber at all.

The gasket can be much larger than the bore size.

Thanks,
Shane

Tony Mamo @ AFR

iTrader: (13)

This pretty much sums it up....

And yes....you need a minimum 4.135 bore to clear the chambers of the 215 head.

Nothing absurd about it....you need a big chamber to effectively use a large valve (an AFR 245 has a 2.165 diameter intake valve)....otherwise the larger valve may hurt more than help you (a large valve shrouded against a chamber wall is very inefficient and low/mid-lift flow suffers quite a bit in a situation like that).

In the case of the 245's it's the chamber that dictates the bore diameter of the gasket required. And lets face it....the 245's were primarily designed for large engines, most of which will feature a 4.125 bore or larger any how. By the time you cover the chamfer on top of the cylinder your needing a 4.155 - 4.160 gasket already simply based on the bore of the block....a 4.200 gasket is only .020 per side larger (and once again mandatory on any 245 install for the fire ring of the gasket to adequately clear the chamber for proper gasket clamping).

There is a method to all our madness when it comes to cylinder head design I assure you....

-Tony

cals400ex

iTrader: (27)

now that we have this covered, is cometic the way to go? the gm ls9 gaskets are only 4.100" i believe.

Tony Mamo @ AFR

iTrader: (13)

Yes....You can order them in practically any thickness you need to help set your quench height and ultimately your CR.

BTW, any gasket from 4.135 to 4.160 would work fine in this application....dont sweat the bore of the gasket a whole bunch. Unless your alot bigger than either the chamber or the cylinder bore require its no big deal (but smaller is bad!)

Hope this helps....

-Tony