Firewall sealer/undercoat

429scott_old · February 5, 2008 at 9:17 PM

My 67 Fastback NJ restoration

Please correct me if I am wrong but it is my understanding that after all components were assembled on or threw the firewall that a sealer/undercoat was sprayed on the area of the parts that stuck threw the firewall into the engine compartment, i.e. blower motor, master cylinder, wiring harness. This was presumably to seal against water intrusion from above. This sealer looks like black undercoat. Was this really sprayed on all cars or just cars from specific assembly plants and did it matter if the car had or did not have the undercarriage undercoated at the factory? And finally, is black undercoating and acceptable replacement for this sealer or is there something else. I believe this is what is referred to in the MCA rulebook as line Z. Thanks Scott

CharlesTurner · February 5, 2008 at 10:14 PM

The amount varied from car to car and from assembly plant to assembly plant. Have not observed an original unrestored car that did not have at least some traces of sound deadener/sealer used on the firewall.

Keep in mind that the sealer was applied before the engine/trans were decked.

429scott_old · February 5, 2008 at 10:35 PM

Thanks Charles, do you think that a heavy spray-on black undercoat would be a suitable replacement.

CharlesTurner · February 6, 2008 at 5:31 AM

There are many products available. I've used spray-can type and also spray-gun type. The original stuff seemed to be somewhat stringy, which is hard to replicate.

toolbox · February 6, 2008 at 4:04 PM

Does anyone have any thoughts or opinions on using a spray on bedliner product (like for pick-up trucks...Rhino liner comes to mind) as a sound deadener on the inner fenders? It seems to dry very hard and be very durable.

J_Speegle_old · February 6, 2008 at 9:58 PM

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Does anyone have any thoughts or opinions on using a spray on bedliner product (like for pick-up trucks...Rhino liner comes to mind) as a sound deadener on the inner fenders? It seems to dry very hard and be very durable.

Not if your attempting to make the final product look factory IMHO. I do know at least one restorer who has stated that they are using the product but then overcoating it with traditional sound deadener/undercoat products.

One issue is always getting the correct amount of buildup, texture, sag and make it look like it was done in a single pass (though it will likely take many coats)

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