[ajorda14]

I have a 400 pontiac with 670 heads and a turbo 400 tranny.

What is the durability on these pontiac 400's?? Could I take it to the track on street tires without worrying?? I don't want to break it lol. I have no idea of the engines history.

Edelbrock 650 carb
Performer manifold
670 heads

What about the Turbo 400 tranny? I heard they can take anything??

any body have any info ? thanks

[Half-Inch Stud]

Weak links:

Heads: the 2-pieces valves and flimsy springs.
TH400: the GM Torque Converter's sprag mount.

[chiphead]

I'd be more worried about blowing a head gasket or throwing a cast rod. I hope you run 93 octane or better gas with those 670s. I run those heads on a '67 400 in a '67 GTO/LeMans. The 670s are great heads, just high compression with most pistons. Don't revv your engine over 5200, use good gas and you should be OK. Just watch oil pressure and engine temps. Listen for detonation, which sounds like valves rattling.

The 8.2 rear ends that came stock in '67-69 Firebirds or GTOs can only take so much abuse too. Typical failure is twisted axles or broken gears. Taking any car to a dragstrip is an assumed risk. No lifeguard on duty, swim at your own risk. Did I mention to check your U-joints and brakes before flogging at a dragstrip? Ending up in the kitty litter doen't impress the chicks. Ask me how I know. LOL

good luck

robertg

[ajorda14]

The engine shouldn't rev over 5200 if I'm just using a reg automoatic shifter right?? It's not like I'll be throwing it into gear manually or anything.

Also a friend told me that if I'm just driving it around town that I can use regular 87 octane, will that hurt anything??

[mrrat1]

I use 10 gal super with 5 gal cam 2. You should never use reg gas street or strip with that engine. If you break the trans the engine will rev tooooo??? Til it breaks or you shut it down! Dave K.

[ajorda14]

if i just baby it around daily driving, I still could not use 87 regular gas???

[chiphead]

NO, Nyet, Nada, Ne Pas, Nein, Non, O-NA. No in any language is still no. LOL.

670 heads have 70 CC chambers, on a typical 400 that will yield 9.5 to 10.25 compression. This requires good gas. 93 octane gas is an absolute must whenever the engine is under load. (read- anything but idling).

A buddy of mine had a car just like yours, a '67 Firebird 400. He ran regular gas, and his ignition system was just slightly out of tune. He was replacing head gaskets once a month until he started using good gas. Even then, the motor had hammed the rod bearings too much. He was going down the highway at 70, when the engine barfed a rod thru the pan. Teardown showed detonation damage from running cheap gas.

I got the heads and rebuilt them for my 400. I used dished pistons to get compression down to 9.3:1. Even then I use 93 octane gas. The rule of thumb is this: Multiply your compression ratio by 10 to get the required octane. 9.3:1 compression needs 93 octane. And I'm pretty sure your engine has more than 9.3:1 compression with 670 heads on a 400.

See, most of our hot-rodder buddies know Chevy engines. Chevy can run 9.5 or 10:1 compression in a 350 and get away with it. So they think their Pontiac cousins can do it too.

Often its not so in a Pontiac. Cheap gas and high compression IS self-destructo land because of the chamber design of a Pontiac cylinder head.

[pontiac_fanatic]

I ran my 31 year old Formula 400 at the track this year. It was the first time it has ever been to the track--it survived just fine.

Took my old 74 Firebird to the track as well--no problems. Chances are good that you'll be okay BUT if it breaks---it was going to anyway!

[Half-Inch Stud]

Reduced-Ping Pump-Gas RamIII Pontiacs:

Run Q-Jet Primary rich
Run a big cam
Run leaky Intake Lifters
Fill Cross-overs
Unshroud Intake & Exhaust chamber
Whack the Plugs Ground-lugs to side-gap
Run HEI Teens initial, Total in at 2400RPM

Toss water crossover, Make a Y-combine at Upper hose. Mech Flex fan. Remote oil filter for cooler oil. Headers for cooler heads.
Remote Trans cooler set aside of radiator.
AC off!

Run pump gas to the 12.0ET catagory. 10years Street/Strip life to Head-gasket breech first failure. Only minor ping-pocks in the old Slugs.
---------------------------------------------
That is why I now will attempt 8.3:1 with pump gas. Runs but not yet driven. I might lack the off-idle response of Hi-Comp.