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Our chromoly Manton pushrods feature extended lifter tips and hardened rocker tips.
Our order consisted of three different lengths. All exhaust pushrods are 1/2” diameter x 11.124”, while intakes were 7/16” tapered in lengths of 10.953” and 10.805”.
Here you can clearly see the length differences. From left to right: 11.124” exhaust pushrod, 10.953” intake and 10.805” intake pushrods.
The 1/2”-diameter exhaust pushrods felt like ball bats. Wall thickness is 0.188”. If these guys bend, we’re in deep doo-doo.
All intake lifter bores required a notch relief for pushrod clearance, due to the 0.180” offset intake lifters.
Naturally, I discovered the need for lifter bore notching a bit late, so I cheated. With the block upside-down, I relieved the bores with the aid of a shop vac and lots of masking.
Clearancing the heads for pushrod clearance required long hours on the bench with an electric die grinder.
Grinding through a few intake port walls wasn’t a boo-boo. It’s just the nature of the beast. After all, the pushrods need what they need.
Here’s a port-side view of a typical hole (see finger behind hole).
Using 0.032” dead-soft aluminum, I cut patch panels and epoxied them over the holes on the port side. After allowing a 24-hour cure, I then gently dressed and blended the patches.
Epoxy was then applied on the pushrod side as a backfill, and later dressed down for a smooth blend.
In all, I wouldn’t be surprised to find that I removed about one pound of aluminum from each head as a result of the clearancing.
Note how the intake pushrod guide area was opened and bell-mouthed at the bottom.
After grinding, washing and reassembly, our final pushrod clearance is fine. At the tightest spots, we have at least 0.020” clearance (0.010” is considered minimum).
Lighter checking springs allowed us to more easily actuate the valves while making our clearance checks.
All pistons were clayed and checked for valve to piston clearance. Using a razor, I then gently cut each piece of clay to reveal a measurable thickness section.
Our intake clearance measured at 0.140”, and exhaust at 0.155”, more than enough from a safety standpoint.
Tags: ASSEMBLY, DART, INTAKE LIFTER BORE NOTCHING, JESEL, MANTON, PISTON TO VALVE CLEARANCE, PUSHROD CLEARANCE, PUSHRODS
