Mercruiser 420 - Blower Prep - Head Gasket P/N
 

Good Evening OSO,

Removing my heads on the factory Mercruiser 420’s in my Formula 357SR1 to have them inspected. I plan on adding 250 TBS blower setups this year so I wanted to install the appropriate head gasket while the heads are off. Does anyone have the Part Number of the appropriate (or recommended) head gaskets when adding boost to the HP420 engine? Also the ARP part number for the head bolts? This would allow me to order the parts this week before pulling her back out of storage this weekend. These are low hour factory engines, standard bore. Thanks in advance!

distantthunder
Be careful if you stay with stock OEM gaskets as it seems as if there's a difference depending on what your engine serial number is as there's a note suggesting 2 different part numbers if your serial number is above or below 0D725500...Item number 24's, https://www.mercruiserparts.com/bam/.../31303/949/200

Might be the same with after market as well.

https://www.mercruiserparts.com/420-...-0a398941-thru

MK-IV gasket for your 454s. FelPro 1037 or 17046 (same gasket).

.039 compressed with 4.37 gasket bore, stainless steel core.