I found an engine with the letters YH what year is this engine?

Depends on the size of the engine. They manufactured several engines for the large vehicles. The V8 350, V8 400 and the V8 428. These had many possible horsepower outputs depending on the cubic inch size, intake, exhaust and weather they were a "Super Duty" or High Output" engine. It could have had a 2-barrel or 4-barrel carburetor, or even a special order Tri-Power in 1967. The Tri-Power is 3 2-barrel carburetors.
The horsepower ratings ran from 265hp to 390hp. I would say if your 1967 Bonneville has the original engine it may well have been a first year V8-428 running either 375hp or 390hp. Check on the (*facing the engine) "Head" , front face, behind the A/C, you should see 2-letters stamped, such as: WG, YH, WJ, or YK.
These letters designate which block-type the V8-428 is. Which will tell what horsepower it was rated at. If it happens to be a V8-428 with the very rare special-order only Tri-Power intake it is said they were rated at 425 horsepower!

If you can locate a "Motor Auto Repair Manual" from the 1960's (1961 through 1967) it will list the engine identifications, block marking, as an example a V-8 428 "YH" engine was rated at 370hp with an automatic transmission. The manual will list a multitude of information about the full mechanical workings of those Pontiacs. I have several, they are great. These manuals list many automobile makes and models made during those years.
Good luck, and I hope this helps!

Hi
The engine code on VW's are usually on a white sticker on the side of your timing belt cover (left side of the engine) you might have to slightly lift the main plastic engine cover the code consists of 3 letters and then numbers its the 3 letters that are the engine code I own a UK 2015 VW Golf GTD and that's where I found mine
I hope this helps Nick

If we are talking about the engine size in cubic inches, look at the serial number. Check the fifth digit. The letter Q or U indicates a 305 cid the letters L or T indicates a 350 cid engine.

Need to know,year,make,model and engine size to answer Phil.lIST IT AND i WILL TELL YOU WHAT THOSE LETTER'S MEAN...

old post in Samurai forum. ????
no engine stated, suz made many 1.3s some diesel.
the engine has a Letter , number and letters.
DOHC 1.3 engine, SOHC?
no year stated. id bet the 95 sammy year is bogus, right?
6 engines
http://en.wikipedia.org/wiki/Suzuki_Cultus

The engine CODE for any vehicle
is the Letter in the 8th Digit of the VIN#
found on the drivers side dash,registration,
tittle,or B pillar post inside front door

If you go to a site like Wix Filters, you will
see your engine size by that code letter

The engine code is located on the engine block (different locations depending on the engine). It is a 3 letter code followed by six digits. You may also find the code in the service manual of the car.
AWD, AWW and AWP are 1.8L gas
ALH is a 1.9L turbo diesel
BEW is a 1.9L turbo diesel (PD)
AEG, AVH, AZG, BBW, BEV are 2.0L gas
AFP, BDF are 2.8L gas

Engine designation is also found in the VIN. It is the 5th digit in the VIN. Go to BentleyPublishers.com for more details on what it means for your car as it varies by year and model.

the vacuum line in broken, check for same, start fromthe engine compartment, check to make sure the a/c doors are not jammed. check all fuse and relays