72and86

Without documentation how do I tell a 1969 300hp from a 350hp motor as it sits in the car?
I understand the VIN isn't an indicator in the year, correct?

tyrant

The suffix at the end of front deck stamp<br ><br >

Brcmpbl

Engine code as above. The stamp will be on the passenger side front of the block.

If it is an L-46 car originally, it also must have had a manual transmission from the factory, a 6,000 RPM redline tach, and finned aluminum valve covers. All of that stuff can be changed of course.

Dynra Rockets

In addition to what Brcmpbl said, the L46 should have screw in rocker studs and not press in. If it is a CE block and the valve covers have been changed (both common) then the studs are a good indication also (but not conclusive)

MelWff

I've owned my 69 L46 since 73. The L46 has press in studs.

ballen06

Also a 4 bolt main block.

Dynra Rockets

all 1969 small blocks had 4 bolt mains, even the 300 hp. (plus checking for a 4 bolt can't really be done in the field).

Dynra Rockets

you're right. Never mind on the screw in studs.

Grahamred70

Mine was a 350/350 4 speed originally but now has a truck block so numbers no clue but I suspect the original hi po bits have been rebuilt into another block for whatever reason. So far I've checked the pistons and they're high compression with quite a hump on them, used an endoscope through the plug hole, rocker covers finned alloy, 3 fins I think, right heads, Edelbrock Performer inlet. Next I intend checking the cam lift to see if that gives any clues. Goes well though that's for sure!


Regards
Graham

ballen06

oops.. I stand corrected..

gbvette62

Sometimes the head casting number can help you identify a 350/350, but not always. Heads with the casting number 3947041 were only used on 350/300's, while the 3927187 was used exclusively for the 350/350. Unfortunately, casting 3927186 was used for both 300 and 350 horse engines. An engine with "187" heads, is likely a L-46, and one with "041" heads is a base motor, but if it has "186" heads, it could be either.

Both engines used the same intake, 3927184, but the 350/300 came with Q-Jet #7029203 (manual trans) and the 350/350 used Q-Jet #7029307.

The same exhaust manifolds and block casting numbers, were used for both engines, so they're of no help.

The 300 used distributor 1111490, while the L-46 used 1111493 with points and 1111491 with TI.

The L-46 required either the wide ratio (M20) or close ratio (M21) 4 speed transmissions, and was not available with the 3 speed or automatic. The 300 was not available with the M21 close ratio 4 speed.

The radiator in the car might help identify it also, as the L-46's came with a copper radiator and attached tanks. The manual trans, base motor, without air conditioning, came with an aluminum radiator and a separate expansion tank. 300 horse cars with air conditioning and/or automatic, did use the same copper radiator as the L-46 though.

Bremquest

as far as the radiator goes, does this account for early first month production 69’s? My 350hp and a couple other early production members on here have the same setup (aluminum radiator, steel shroud, expansion tank). I confirmed the 350 hp with the rear axle, tach, and TI.

Factoid

I have an early '69 (first 1000 made) L46 and it has an aluminum radiator and expansion tank. Generally speaking the points above (as corrected) are consistent, but there are carry overs from previous years and up dates that happened along the way.

Bremquest

Thats great info! Mine is number 2764. While replacing radiator components lately I have had so many "experts" tell me my car must not be an L46, or that it has the incorrect cooling system.

PJO

Here are Quick Reference Charts I with the help form other members made to judge at Bloomington and the NCRS. John Woods made the other Mechanical sheets could also help. Make yourself copies.

ballen06

Valve covers.

L-46man

Measure the harmonic balancer diameter...8" = L-46 6"= Base.
Then of course is the stamping pad code.

ps all the 69 350's were 4 bolt mains.

Bremquest

My car had a different engine in it when I bought it so it was a little bit harder to diagnose. The final determining factor for me was the remnants of a TI system.

terrys6t8roadster

The sticker on the air cleaner. The 300 hp says 300 hp and the 350 hp says 350. T

Bremquest

mind blown 🤯