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I have what appears to be a relatively stock 351C in my newly adopted '72 Cat. The engine was supposedly balanced and blueprinted sometime in the mid '90's by a former owner which may well be the case. The engine still has the original factory appearance, intake, carb, valve covers, etc.

My question is this - will a carb spacer give any performance gains with the stock carb & intake in this situation? I have toyed with replacing the intake & carb; however, I really like the appearance of the stock engine. The car is currently in the shop undergoing some upgrades and now would be a great time to bump the performance if possible.

Any insight would be greatly appreciated.
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You might want to PM racerdave here on the forum.
His engine looks totally stock with the correct stickers,paint and plating etc.
He has done some mods to it that make it run much better but not change the outward appearance.
He also retains the factory carb.
His looks like a well sorted car, you should contact him.
The '72 motor has a spread bore Autolite carb without egr, its a pretty good intake system as it stands. The carb flows about 700 to 750 cfm.

Because of the 4 hole/spread bore design of the intake manifold there are no matching 4 hole spacers available, and an open spacer just wouldn't be a good match. In all the years I've been around Clevos I've never seen anyone use a spacer on the factory spread bore intake manifolds.

The best way to wake that motor up while keeping the stock looks shall be to replace the heads with the 1970 or 1971 closed chamber heads, the 1971 head shall bump the compression ratio up from 8.8:1 to 9.7:1, the 1970 head shall bump it further to 10.0:1. Replace the factory exhaust system with the later model GTS exhaust system. Finally install a hotter camshaft. With the right camshaft you can hit 400 bhp with just those mods (and some porting/valve seat work). Of course, you'll want to install a good breakerless distributor too if the motor still has its breaker point ignition.

Be warned, if your motor has the oem Ford valves in the heads, or a 37 year old balancer snugged on the end of the crankshaft, it is a ticking time bomb.
Ditto on everything George said. Did all that and more, plus I took it a step farther and stroked the motor to 377ci. But don't tell anyone, I keep telling the Porsche and Vette drivers (track day) my engine is bone stock!
You could do everything George suggested without even removing the engine from the car. A lot more HP for not a whole lot of money.

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A thing of beauty she is. I like the looks of a good modified engine like the next guy or gal; however, there is just something about the look of a late '60's / early '70's stock performance engine that gets me every time - especially one that performs.

Thanks to everyone for the advice. At this stage, I definitely want to keep the motor in the car. I would have thought the motor would have had to have been pulled to get the heads off and to change the cam - very good to know this can be done without pulling the motor out. The car is currently at Precision Pro-formance undergoing a few updates so I'll talk to Don to see what the damage would be.

One thing that I forgot to mention in my original post is that she already has a big bore exhaust on her as well so it sounds like that will only help. What prompted my original question was that I had seen a 4-hole phenolic spacer on PI's website that claimed around 40 horses and I didn't know if would apply or not.
quote:

One thing that I forgot to mention in my original post is that she already has a big bore exhaust on her as well so it sounds like that will only help. What prompted my original question was that I had seen a 4-hole phenolic spacer on PI's website that claimed around 40 horses and I didn't know if would apply or not.


Like all ads, you have to take that one with a grain of salt I think. There may be applications where a spacer could give a 40 hp boost. There will be others where it will give zero boost, or other where it could even hurt your power development.

Every dyno test result I've seen implies that the benefit of a spacer depends on the specific configuration of a specific engine and the only real way to tell if it is helping you or not is to dyno test it. There are engine combinations that perceive no benefit from a spacer, and others that do. 40hp sounds a little generous regardless based on what I think I've seen based on dyno tests...
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