1970 318, Rockers installed on wrong side

[LSS&B]

I purchased 1966 Coronet 318/727 2025-01-16, original 318 poly replaced with later 1970 318 LA 29K miles since built. Aftermarket cam, specs unknown, no lope.
Vacuum at 1000 rpm is 12 inches, not steady. Increases to 17 inches steady at 1800 rpm.
Replaced all hoses and rubber plugs. No change in vacuum. Sprayed carb and intake gaskets with soapy water, no change in vacuum.
Engine sprays oil out from under left side valve cover onto intake and carb, also leaks oil onto header.
When I removed valve covers, right side rockers are installed correct, but left side are installed with the tips of the rockers offset inside instead of outside.
Talked with previous owner: he never touched rockers. This problem could have been ongoing for 29000 miles (total mileage on engine since build) although the engine has only been in the Coronet for 2000 miles.
I expect the left head's valve seats are damaged.
*Do you think damage to valve seats could cause low idle vacuum?
*Could prolonged use of rockers misaligned on valves crack the left side head?
*Has anyone had this head problem long term? What repairs did you make?
Cylinder 1, rockers marked LT should be installed to left but are installed on right.

Cylinder 3, exhaust rocker looks fairly new and is correct. Intake should be left offset.

Cylinder 5, both rockers installed wrong

Cylinder 7, both rockers installed wrong


Oil leak on header from valve cover contains coolant, but cold engine withstands coolant pressure test at 15 psi without leak down.

 

[R413]

I has a single plane aftermarket intake and headers. It could have a bigger cam with low vacuum. Can you measure the total valve lift at the retainer?

How hard was the guy running this engine? How much RPM is the question. What rear gears?

 

[GTX JOHN]

I would remove rockers and check valve stems for wear/damage.

With a single plan intake you are running, 12 inches at idle should still
run OK even if not optimal

 

[PurpleBeeper]

I don’t think it would crack a head. Yes, a leaking valve seat would lower engine vacuum

 

[LSS&B]

I would remove rockers and check valve stems for wear/damage.

With a single plan intake you are running, 12 inches at idle should still
run OK even if not optimal

Hi John
Are you talking about wear on top of the valve, like worn canted toward the misplaced rocker tip? Thanks!

 

[LSS&B]

I has a single plane aftermarket intake and headers. It could have a bigger cam with low vacuum. Can you measure the total valve lift at the retainer?

How hard was the guy running this engine? How much RPM is the question. What rear gears?

318 does have a big cam. It has terrible gas mileage. I don't have a miles per gallon, because gas gauge and speedometer are inoperative. I guess under 10 mpg, maybe significantly under. It also will burn a single wheel when accelerated hard from stop.
How do I measure valve lift at retainer? I have not heard of doing that.

History of engine:
*318 engine was rebuilt probably 10-12 years ago by a friend of the owner previous to the previous owner. No receipts to say what rebuild was conducted, so cylinder walls could be smooth or have giant ring ridges. Valves are not oiling the spark plugs, so expect the heads were redone along with adding the big cam. Mechanical oil pressure gauge shows 60+ psi at cold idle, so high volume oil pump is part of the build.
*318 engine is supposedly out of a Duster and the builder put 27000 miles on it, so with the big cam and single plane intake, it was probably used street/strip in an A-body. RPM unknown.
*Sometime around 9 years ago, this friend sold the 318 to the owner previous to the owner I bought the car from. That owner installed the 318 in the 1966 Coronet. He installed headers and 2.5" dual exhaust, 3/8 fuel lines, and 26" radiator and drove the car a few hundred miles at most before selling it. His phone number is disconnected. This owner also installed 1973-1976 A-body front disc brakes, power brake booster, and dual master cylinder.
*Previous owner bought the car 8 years ago and put a total of 1500 miles on it over 8 years, all street driving.
*1966 Coronet has 8 3/4 rear with 3.23 gears and an open differential
*Brakes are stiffer than I'd like, but I started with 9 inches of vacuum before I deleted an old vacuum canister and replaced hoses and rubber plugs. Brakes work significantly better with 12 inches of vacuum. Also checked intake and carb bolts for looseness. Brake check valve is new and works properly.
*Cylinder pressure is leaking past the valves on left side and blowing oil out from under and over the valve cover gasket. New steel core valve cover gasket does not help.
*My plan is to pull the heads and check the cylinders. I posted this thread for advice before I start disassembly. Wanted to see if there was something I didn't think of.

 

[R413]

The camshaft profile is where your missing vacuum went.
Probably didn't hurt the heads.
Could have worn the guides or valve stems.
Since it's not oil fouling the plugs put the rockers on correctly and run it.

The power brakes being stiff is not good, and could be dangerous.
Crashing is not good.
Either swap out that big cam, or remove the power brake booster and have manual brakes.