CID Years Bore Stroke VIN Color
260 '75 - '82 3.500 3.385 F metallic Blue
'79 - '80 3.500 3.385 metallic Blue Diesel
307 '80 - '84 3.800 3.385 Y Black No roller lifters, and w/5A heads: 150hp
'85 - '90 3.800 3.385 Y Black Roller lifters, and w/7A heads: 140hp
'83 - '90 3.800 3.385 9 Black 442, H/O engine; Roller
lifters w/7A heads '85 and up.
330 '64 - '67 3.938 3.385 T Gold
350 '68 - '72 4.057 3.385 M Gold
'73 - '74 " " " metallic Blue
'76 - '80 4.057 3.385 R metallic Blue
'78 - '79 4.057 3.385 B metallic Blue
'78 - '81 4.057 3.385 Z metallic Blue Diesel; Roller lifters '?? and up
'78 - '85 4.057 3.385 N metallic Blue Diesel; Roller lifters '?? and up
'80 4.057 3.385 8 metallic Blue
403 '77 - '79 4.351 3.385 K metallic Blue
and "Head" sections for more information.
The 307 stayed carbureted until the bitter end. Every 307 used a 4bbl carb -
there were no 2bbl models. The last of the GM 4-bbl
engines. In fact, it came on the Caprice wagon, Olds Custom Cruiser wagon,
Buick Estate wagon, and Cadillac Brougham (5.7L Chevy V-8 was optional on
ESC (Electronic Spark Control) was
added to 1988-90 307's. On these engines, the knock sensor is screwed
into the driver's side coolant drain hole.
Some say the 307 H.O. engine has a propensity for detonation, because
Oldsmobile always ran high timing (20 degrees advanced). Cracked or rusted
A.I.R. tubes create a similar sound.
While a knocking noise probably means a spun bearing, check
for loose bellhousing bolts and a cracked flexplate. Both times that
this happened to me, the crack in the flexplate would snap back and
forth, making a noise that I was convinced was
a spun bearing. You may need to pull the converter back to
properly see the flexplate.
Sometimes, the main intake-to-heads gasket goes bad,
and coolant leaks out at the front of the engine, on the driver's side.
The coolant dribbles down by the water pump, and the water pump appears
to be bad. This seems to be a problem with the steel heads and intake
mating to the aluminum intake.
To make a 307 VIN Y into a VIN 9 (high performance), just use the following:
|Part ||Part Number |
|Long Duration cam shaft ||22519934 |
|High Rate Valve springs ||22510372 |
|Harmonic Balancer ||417142 |
|Rochester 4MV carb ||17083553 |
|Dual Snorkel Air Cleaner Assy. ||25042690 |
|Intermediate Exhaust Pipe ||22516113 |
|Muffler and Tailpipe Right ||22526204 |
|Muffler and Tailpipe Left ||22526205 |
|2400 RPM locking stall converter || ?? |
If you are thinking of replacing a 307 with a 330, 350 or 403, consider the
Everything except the pistons should swap across. Unless
it's an 1985 and up 307 w/7A heads (has the roller lifters),
then you won't want to use the heads, intake, and exhaust manifolds because
they have puny ports.
You're better off using as many 350 parts as you can. The only
parts I could see using off of the 307 would be the intake (if the 350
is only a 2bbl) and maybe the heads for higher compression. You probably
need to use the 307 intake if emissions are strict in your area (at least keep
it, just in case). Although
the stock heads from a 307 may not flow as well as stock 1972 heads.
You don't have to dump the 307's computer controlled carb at all.
Doug Roe's Rochester Carb
book has a good chapter on modifying an electronic Q-jet (which, of course,
is computer controlled); highly recommended as a reference for anyone doing
work on a Q-jet. Only part-throttle and idle is controlled by the computer,
which formerly was controlled by vacuum on a non-electronic Q-jet;
everything else (accelerator pump, secondary barrels) is open loop, so the
same mods for an older Q-jet apply there as well. In fact, as long as your
350's cam isn't too wild, the computer should be able to compensate for the
extra 43 cubic inches. You could use a stock 307 intake, or probably even a
Performer, as long as you have the hookups for the lines and sensors.
Whatever the case, even a mild 350 will be a big improvement. You
should also swap in some better rear gears to complement your engine's
newfound power. If you start looking right now, you might just find a
10-bolt 8.5 3.73 posi rear from a H/O/442/T-type by the time your motor is
ready to go in.
[ Thanks to Ed Atlee, Tom Lentz, Bruce D. Brumm, Jason Adcock,
Paul Hartlieb, Daren, Bob Barry
for this information ]