Jvette73

Suppose you were looking at an old Impala that has 400 emblems on the fender. You pop the hood to look at the engine. At quick glance most Chevy SB's look similar. What are the ways to verify that it is still a 400SB in there? I got my eye on a 72 impala that has 400 emblems on the fender. Its still a running and tagged vehicle. Sooner or later im thinking of offering to purchase when the owner is ready to part with it. It belongs to an elderly man living on my mailroute.

PatsLs1vette

some not all have 3 freeze out plugs on the side of the block,also the balancer has a weight on it on the inside of it,towards the timing cover.

Racer16k

:iagree: It would probably also have a staggered bolt pattern on the starter. The balancer would have some relieved 180 degrees from the extra weight. The relief is easy to see from the outside. It will also be the large diameter balancer.

Racer16k

Cool! I just noticed this is an all 73 post so far. Cool.

Larry B.

A small block 400 is what is known as an externally balanced engine. This means that it has a unique unbalanced balance and fly wheel Those parts are NOT interchagable with other small blocks althought they will bolt up. Also the 400 has siamesed cylinders and steam holes in some places. 400's tend to run warmer than the 350's. Also there were NO four barrel carb'd 400's. They all had 2BB carbs.


[Modified by silvervetteman, 6:55 PM 3/14/2003]

BB73Chris

As I understand it 3 freeze plugs on the side means it's an early 400, which could have 4 bolt mains and the later 400's have the number "509" stamped under the timing cover (which wouldn't help you in this case). Not all of the early 400's have 4 bolt mains though, as I have an example in my garage right now with 3 freeze plugs and 2 bolt mains. If you can read the block casting number at the back on the driver's side, you can go to http://www.mortec.com and it will tell you what it is for sure.

Jvette73

Thanks for all the info on 400 id. Sooner or later im gonna ask him about it. Hopefully there was never an engine swap and it is still the 400. Im just lookin down the road for a possible 406 build up. The car is in decent shape. He even had it painted a couple of years ago. Somethin tells me hes gonna hold it till he dies. He's probably gonna chase me outta there swingin a stick.
:eek: :eek: :eek:

Marv

My factory ordered 1971 SS Chevelle 400 c.i. was rated at 300 hp and had a four barrel carb/duals exhaust. I traded my 68 L-68 in because I wanted a "family" car and it was the highest non-BB horsepower option in Chevelles that year. It was a very snappy and trouble free performer.

Marv-

Racer16k

The 78 400 I got from a truck had a 4 barrel on it. My father-in-law had a 73 Caprice or Impala with a 400 4 barrel. I have heard that most were 2 barrels though. If you can find a "509" block, build up that one. The "509" is much harder casting. I think the newer 400's only had 2 freeze plugs, while the older had 3.

biggjimm

Looking at the harmonic balancer or the flywheel is the only way to know with just a quick glance. It will have the big balancer and a weighted flywheel. I have a 400 block in the garage right now that is waiting for $ to do my 406 buildup and it is stamped 509 with 2 freeze plugs and two bolt mains. When I looked it up on mortec it showed it was used from 74 until 80. I looked up the date/engine suffix code located on the right side deck surface in front of the head above the water pump mount, It showed that particular block came in a 1974 chevelle with a 4 barrel carb and 200 HP. It showed a lot of other 400's with four barrels too. good luck Biggjimm

Larry B.

OK OK.... I spoke too soon. I just assumed that 400's didn't come with 4BBl's All of the ones I have seen were 2BBL's. I was wrong.. open mouth... Insert foot. :withstupid:

427V8

The only way to know for sure is to check the casting numbers.
I doubt you will be able to see either the flexplate or the balancer :rolleyes:

AS far as freeze plugs go it's an old wives tale.

BTW, the two bolt blocks are actually stronger, and if you really need the beef go to a splayed cap 4 bolt anyway :smash

Go here for the casting numbers

http://www.mortec.com/castnum.htm

PRNDL

My next door neighbor has a very original 73 Caprice. Kid drives it to high school. It looked like any other smallblock to me, and I was very surprised to learn it was a 400. He still has some original stickers under the hood that say engine is 400 ci. No emblems on the outside proclaim it is a 400. :) MJ