[Skidmark]

Originally Posted by pontiacstogo

Pretty sure this is the case. On my 74 the block off plate was 'epoxied' on to the shaker. It was easy enough to remove the block off plate and replace it with a functional flapper.

https://www.ebay.com/itm/256181333556

Not sure about the performance increase, but definitely improved the intake noise (plus I kept the block off plate so it's reversable if needed).

This is the way I will probably modify mine.

[Skidmark]

Originally Posted by HWYSTR455

Restore a Musclecar has grates that can go in place of the block off plate or door, just to say:

https://store.restoreamusclecar.com/custom-parts.aspx

You can put a piece of foam in from the outside and it won't get sucked in.
.

Thanks for the link.

[GOAT8U2]

You can use the low compression to your advantage later when you get the car solid, add a Torque Storm SC.
You can make back all the lost hp and tq from that era real fast and the cheapest way possible vs new engine etc.

[Baron Von Zeppelin]

The 72 intake eliminated the EGR presence from the car.
The exhaust sounds ideal with RA manifolds and true duals going to a transverse muffler.
At least ideal for clearance and better performance over stock 75 stuff.
That's exactly what I would want on it.

I'd check the axle ratio.
An economy axle downgrade might not show up on invoice.
Or an owner might have swapped for better highway use.

The shaker screen would be a quick get by until you do the functional flapper.
But opening it up one way or another should prove noticeable with the exhaust and rocker arm upgrades.

My 79 4spd had similar upgrades with cam and exhaust , all emission controls removed or disabled.
Except it still had stock log exhaust manifolds and was 3.23 gears

[Baron Von Zeppelin]

Here are a couple pics from a 73 currently on BaT.
This is how my 73 shaker looked with the provision for 3 bolts/screws for the removable block-off plate.

I never owned a 74 75 76 so I don't know if those shakers had this built in provision or not.
So far it sounds like , not.

[70KGOLD]

Get a set of 5c heads from a 350 CI engine assuming you have a 400. These are great heads and will up your compression and should be cheap to purchase. They were available in 1975. Call butlerperformance.com for a cam and lifter set. Go with a 355 rear gear. You should feel a difference in the driving seat and still have gas money left.

[steve25]

A 6X head casting with the -4 stamped on one of the exh side vertical bosses has the same size chamber as the low production ( California) 5C head.