[b-man]

The #143 heads came on 1967 290 HP 400 engines, factory compression rated at 10.5:1. In actuality it will be about 9.75:1 or 10:1. That much compression might be pushing it for pump gas operation.

The press-in rocker studs on your heads may not be too happy with the fast-acting cam and the valve springs you have chosen.

Another problem is the '72 pistons have valve reliefs that don't match the valve location and angle on the #143 heads. In mid-'67 the head design changed, your heads were made before that change occured.

My take: Find some different heads.

Yours have too much compression, press-in studs and the wrong valve angle to match your pistons.

The press-in studs will pull out in time. The valves may hit the pistons. The engine may suffer damge running pump gas on 10:1 compression.