Good Afternoon: New to the Forum and new to a Firebird. Just purchased a 67 400. Green w/ Black Vinyl top. I'm wondering if anyone has or has seen this type of engine build before.
Engine is a 400 (code on the block is WT (not original block to the car) ) Heads are 18 Code (believe from a 350HO (68cc)) Intake is a Edelbrock (says Torquer Pontiac on it) Carb is a 650 Holley Spread Bore Cam is a Crane (Blazer 288-2H Grind) Intake Open 30 Closes 78 Exhaust open 84, Closes 36 Lift Intake @ Cam 300 Lift Exhaust @ Cam 310.
I do not know what pistons are in the car (haven't borescoped yet) though I'm thinking they are pretty deep dished with 68CC heads as previous owner ran it on Pump gas for over 10years. Yes I know. I was like "What! No. That wasn't a good idea". It's now drinking premium. Engine sounds good. Runs a little rich. And it likes to drink gas.
Runs to me a little warm (it was a warm day yesterday about 82F and cruising on the highway sitting around 200F sneaking towards 210 when stopped). (Recently ordered Firebird Radiator Upper Baffle Support Top Cover Filler Panels so that should help put a little more air through the Rad)) and will in due course take the water pump off and confirm the gap between the vanes and housing. Under load on those conditions could hear what I think is some intial light knocking but not sure. Overall it feels alright but I'm thinking it isn't putting out the Torque I thought a 400 pontiac would put out. I'll have a chance next week to drive a friends 69 Grand Prix with a factory 400 in it for comparison.
Do a compression test and report back on what the cranking compression is.
Without knowing exact combustion chamber cc the heads are and what piston dish if any your just throwing darts at a wall guessing the compression ratio. Maybe those radiator baffles help maybe they don't. I drive my car here in AZ when its 100+ out and it never goes over 180 degrees coolant temp. what are you looking for in your bird? performance, cruise to anywhere car?
More cruise than performance say 60/40. Don't need big numbers. If it's in or around 300hp and pushing 400lb/ft I am good all day long. A solid push from a stop and strong pull from say 40 mph to 65-70mph for passing I'd be happy all day long.
I still have some intial carb tuning to do. Accelerator Pump is now spot on. Need to tweek the idle just a little then get the idle mixture dialed in.
Engine pulling well is that last major piece on the car. Previous owner did the Suspension (Full Hotchkis) & Front Disc Conversion w/ a Artcar 200-4R 4 speed auto plus a few other upgrades (Steering box & Starter)
I had the same sort of heat issue on mine, back when it wasn't in pieces. Going through it, it was due to how the heater was bypassed. Does your car still have a heater in it? Are the hoses going to the correct places on the intake? When the engine rebuild was done, ran the by pass correctly. I had one of those Torker intakes, and couldn't get rid of it fast enough. If you are looking for drivability, you'll prob want a dual plane intake.
1957 Thunderbird 289 1967 Firebird Base 461 1968 C-20 327
Compression is 180 PSI on 7 of 8 Cylinders(cold engine). #1Cylinder is showing 92Psi. Believe we've tracked it down to the intake valve on #1 Cylinder. Now to figure out if I have press in studs or adjustable ones and confirm / reset the lash on all the valves and see if that helps Cylinder #1.
Heater hoses appear to be correct. One coming off the back of the head into the cabin / heater box, other coming out going to the proper spot on the front. . Heater core is still there. Was an AC car and only seems that the AC components in the engine bay were removed. Baffles seem to have helped running steady 195 degrees. I have a new water pump gasket so will pull the water pump when I get a chance in the next couple weeks and see that the gap between the impellers and the backing plate is correct.
Big Chief: Compression test has 180PSI on 7 of 8 Cylinders. #1Cylinder is at 92PSI. Squirted oil in chamber and PSI remained around 92PSI. Pressurized Cylinder when at TDC and air coming out of Carb.
Hi Flingwing, I'm new to this forum so forgive me if someone has already answered. What you describe is most probably either a burnt valve or a valve kept open just enough to not allow full compression. If it was rings the oil you put in would have sealed them and brought your compression up higher, the fact that it didn't and you can hear air out of the carby suggests an inlet valve. If it's a new build you could try tapping the valve stem gently or backing off the valve adjustment 1/2 to 1 turn and see if that helps. Cheers
These engines are over 50 years old and wear out. By now the cylinder heads would have at least 2 re builds and it's time for another. Piston rings don't hold tension forever and pistons wear out. So do cylinder walls.
Con: Thanks. bought the car about a month ago. It's an old build from the paperwork I have on the car. Probably been in the car for at least 20 years maybe even more. Not a lot of miles on it since it was built from what I can tell. Going to pull the valve covers and adjust the valves and see if that helps on no 1 cylinder specifically. Have no idea when the last valve adjustment was. Though there is no real valve train noise. So we will see.
Bigchief: Looking to get it through the summer and plan will be to pull the heads this winter. Get a good look inside. Heads will be changed out regardless and new ones installs. Combustion chamber size of heads will be set by how low the pistons sit in the bore for a total volume that will let me run Premium (91 Octane) all day long. Would like to do full engine rebuild but too many other projects and money commitments to go that route. With 180 PSI across the board less no1 cylinder at the moment I'm comfortable as well going a while longer before having to pull the motor and freshen the bores and rings.
