Biscuit vs. Spool Motor Mounts

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69GT

69GT

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Does anyone know if there is a difference in how high a small block engine sits when using pre-73 biscuit motor mounts vs. 73-up spool mounts?
 
I wouldn’t be surprised. I know that the header fit to the torsion bars and steering box with a set of Doug’s D453’s is a little different between the two styles of engine mounts.

But I didn’t specifically measure the height, and of course there’s also differences from one car to the next with production tolerances.
 
I was just curious as I may be changing my plans for my 69 Dart. I have a newly built 400/470 stroker motor that I had built for the car and a DC big block spool k-frame to install it in the car. When I started building it, I wanted something a little more radical with plans on going to the track. However, things have changed and now I don't see that happening so the car will only be driven on the street. That being the case, I would rather opt for a more stockish 340 for the car and sell the 470. In the event I do that, I have both types of k-frames available for a small block and would prefer to go with whichever one allows the motor to sit lower in the car.
 
I've never built a spool mount small block car, but within the manufacturing tolerances they should be the same. One thing that makes a difference is the early vs. late steering linkage. I have more oil pan clearance using late linkage on my Barracuda than my son has on his Dart.
 
One member here put on a pretty good rant claiming that the old style mounts were better than spool mounts for torque. But I have no idea where you ACTUALLY get QUALITY pillow mounts, anymore.

When I had my car together, I converted to a spook K, and it was my impression that the mounts reduced header clearance, and I remember a fight trying to get to the drain plugs in the block.
 
67Dart273 said:
One member here put on a pretty good rant claiming that the old style mounts were better than spool mounts for torque. But I have no idea where you ACTUALLY get QUALITY pillow mounts, anymore.

When I had my car together, I converted to a spook K, and it was my impression that the mounts reduced header clearance, and I remember a fight trying to get to the drain plugs in the block.
Click to expand...

So a mount that can literally pull apart under torque leaving the whole drivetrain free to lift is better than one that can’t? Because ultimately the spool mount retains the bolt, if the bolt isn’t completely loose. I’ve literally watched an old 318 try to climb out of the engine bay of a power wagon when the drivers mount failed. It was shocking how much that engine moved.

The block drain plug access definitely sucks with the spool mounts, it’s not impossible to get at them but if you’re trying to break a plug loose forget it, you won’t get that kind of torque on the plug.

I think the biggest indicator is just all the header threads. The Doug’s D453’s are probably the best example, it seems like they fit the spool mount cars pretty well, with some folks reporting they did nothing to get them to clear. But with the biscuit style mounts a lot of people shim the mounts to raise the engine slightly for clearance.

Now, I’m not saying the factory changed the crank centerline, but maybe all the reproduction biscuit mounts are shorter than the factory ones were. Or maybe they’re more likely to sag a bit when tired, lowering the engine.
 
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