Engine Bed Plate Sealant


The Mopar engine I’m working on specifies Mopar bed plate sealant between the bed plate & the block . I’m having trouble finding it anywhere . A couple sites advertise it but what they’re really selling is gasket maker which is different & yes I’ve tried the local dealerships .
I’m sure Mopar isn’t the only company that makes engines with bed plates . This is a special 0 clearance sealant because the bed plate holds the bottom half of the main bearings .
I’d like to know what the pros or anyone knowledgeable uses besides the Mopar sealant .


I think you want Hylomar M, “The original and genuine non-setting gasket and jointing compound” It will seal metal-to-metal joints without curing and adding thickness. Hylomar Blue is a good choice, too and seems to be easier to get in the USA. Grainger carries it.

Or Permatex Copper Spray-a-gasket hi-temp sealant. Normally I’d spray both sides of a steel shim head gasket with this. It dries but is easily removable. You spray it and assemble while still tacky. It is a good metal-to-metal seal as well and more easily available in auto parts stores.


Thanks , I’ll check it out .


Anyone know why the bed plate would require a special sealant, compared to other sealants that work fine in an engine?


Instructions for bed plate sealant specify an Anaerobic sealant that is zero clearance . Anaerobic means that it cures in the absence of air & the sealant must be zero clearance to prevent excessive clearance in the main bearings .


I would think that some of the other 100’s of engine sealants qualify. Permatex may have specs that let you find one that anaerobic and zero clearance, or you could call their customer service number.


Permatex has three different anaerobic sealers. Download their catalog here, look on page 15:
You can also call them. The ‘zero clearance’ requirement is odd - any clamped parts will squeeze out the sealant as necessary.


Permatex & Loctite & maybe other brands have anaerobic sealant & I tend to agree that any excess should squeeze out . Those sealants list suggested applications & none specify engine bed plate although they do specify other engine applications .
In Mopar’s sealant chart they list at least two anaerobic sealants but only one of those is recommended for bed plates . Maybe I’m overthinking this but main bearing clearance is critical & if the bed plate happens to leak the whole engine has to come back out & be torn down to repair . I definitely want to avoid either of those problems . I will call Permatex & see what they say . Thanks


I understand your concern, it’s a big deal. I would classify ‘bed plate’ and ‘split crankcases’ (the “Anaerobic Gasket Maker”) as the same thing, but that’s an assumption on my part. See what Permatex has to say.


Permatex says their part # 51813 anaerobic sealant will work .


I’ve used the Permatex product you linked for several different applications (GM, Asian, Euro) that require an anaerobic no-clearance sealant. The smooth and even application of the product is as important as the product itself. For example, in the factory service literature, Volvo shows (and gives part numbers) using a mini paint roller and tray to apply the product evenly only when needed.

And as you already know, torque values are critical.