Carl, uk

recently done some detailing work, service and renewed alot of parts in the engine bay... everywhere is listing my engine valve rocker covers as a 8 stud pattern,, the stud pattern on mine is 5,, 3 lower 2 higher off set pattern ??
intake has pro performer 350 olds embossed on it which has always led me to believe im running a 350 5.7 olds motor...
not to mention the manifold has stamped on it GMY 411961,,, engine block to near sparkplug holes has stamped 4A (this is large) also has 654 717 stamped very central to top edge of block.. any help is greatfull..

oldsmobiledave

403

MDchanic

... And the valve covers for an earlier engine would have ten bolt holes, not eight.

- Eric

Carl, uk

403 ?? for defo that then ?? block has evidence of blue paint, figured the 411961 stamped on the manifold was the year of production for the manifolds.. what year approx will my engine be then.. ?? ta

MDchanic

A 403 should have a large cast-in number on the shelf at the front of the block, behind the timing cover of 553990, 554990, or, probably, 557265.

The 4A heads are definitely 403, as are the fact that the valve covers are five-hole and the blue color.

411961 is a code "1" later-years left hand side exhaust manifold, which also goes with a 403. 411961 is the last six digits of the part number.

Is the 654717 on your intake manifold?

To find out the year, look here:



The last digit of the year is the second digit, right after the 3 and before the letter.

- Eric

oldsmobiledave

the 403 was produced from 1977-1979

Carl, uk

eric.. yeah code is 557265 and the 654 717 is just above where the manifold attaches to the engine block,, having trouble finding numbers relating to year of engine though

Carl, uk

its the same engine as i had in my 77 trans am then 6.6.... truley gutted its not the original engine and just goes to show my insticts were correct when asking myself (that engine doesnt look original) not to mention the previous owner also didnt know, just as well i love my car and want to know everything about her and her history.... thanks chaps..
one more thing, is my 403 engine less desirable than the 350 ?? heard a few horror storeys whilst i had my trans am...

MDchanic

So, 557265 is a 403 block, without any question.

The engine number is stamped into a pad, covered with grease and rust, and located beneath the alternator bracket (on an A/C car).

Here are some pictures from John's excellent Engine ID thread:

P1010400-1.jpg

P1010401-1.jpg

P1010412.jpg

- Eric

Kennybill

How was the 403 that you had in your Trans Am? I'm guessing it was fine. I heard all the horror stories about them also. Then I bought a project car and one came in the deal. I resold the car, finished the 403 using odds & ends I had already. I beat it pretty good and never a problem. I find most the people who bad mouth them never had one. I still have that 403 plus I picked up 4 more cores. Ken

joe_padavano

That's not the block, it's one of the cylinder heads. The same number is on the other head on the other side (or at least, it SHOULD be the same). Read it again, that number is really 554717, which is the correct cylinder head casting number for a 403. Look next to the #1 and #8 spark plugs and you 'll also see a large raised "4A" cast there.

Fun71

Depends upon who you ask and the intended application. I think the 403 is better for a street engine due to the much larger (HUGE!) bore diameter.

Carl, uk

I never had any problems with my trans am absolutely loved it...

Carl, uk

[QUOTE=MDchanic;665703]So, 557265 is a 403 block, without any question.

The engine number is stamped into a pad, covered with grease and rust, and located beneath the alternator bracket (on an A/C car).

Here are some pictures from John's excellent Engine ID thread:

P1010400-1.jpg

P1010401-1.jpg

P1010412.jpg

Found it...
281 1271 18
Means nothing to me ???

hurst68olds

2 = Pontiac
8 = 1978
1 = ?? if it's a "L" = Van Nuys, CA assembly plant
127118 = VIN sequence

GM built T/A "F"-bodies at Van Nuys for '78 (not sure if other bodies were built there also?)

Carl, uk

Thanks for that, greatfull.. So now it's official my engine isn't original,
On my registration document the engine number is 395558 do these numbers means anything because I can't find any of these numbers on my engine, I personally think the engine change hasn't been reported.....
I'm in the process at the moment waiting for my cars full history details coming back from the dvla, my cars been in the uk now 10years, really hoping some good history comes back to me...

Carl, uk

yep, educated myself.. the 395558 would have been the original engine number..

Kennybill

The 403 has "403" stamped in large numbers on the sides of the block near soft plug areas.

MDchanic

395558 is not the original engine number.

395558 is the original block casting number. Essentially every 350 before the late seventies had the same number.

You engine number would be stamped on the pad on the side of the block, where you looked, and would be something like 33Mxxxxxx, where "3" represents "Oldsmobile," "3" represents "1973," "M" represents the Lansing plant (or a different letter for a different plant), and "xxxxxx" represnets the last six digits of your VIN.

- Eric

Carl, uk

ok.. we got that sorted.. now im trying to learn to read the vin number displayed in the front screen and the embossed stamped tag plate attached in the engine bay...

MDchanic

The VIN is not on the Fisher Body tag on the firewall.

That has a Fisher Body number, which is internal, and has no known outside significance, and codes for some options and the week of manufacture.

- Eric

joe_padavano

As Eric notes, the VIN visible through the windshield is the ONLY full VIN on the car. There are VIN derivatives (which are only partial VINs) on the original engine block, trans case, and frame rail. We already know that you don't have the original engine.

The cowl tag is used by Fisher Body and the numbers on it will not match the VIN (unless there is an incredible coincidence).

73aussie455

Carl this is how I decoded my '73 Delta88 coupe royale VIN. Can't remember where I found this info, but it worked for my car. It's only the first 7 digits you need. I left the irrelevant (to you) info out. Not too confusing really.
I have a virtual library of info for this year/model I've been collecting for the last year or so. Let me know what you need, I've probably got it.
BTW, love the stripes mate..

1973
First symbol indicates the division of General Motors.
Second symbol indicates the series:
Third and fourth symbols indicate body style.
Fifth symbol indicates type of engine.
Sixth symbol indicates model year.
Seventh symbol indicated the assembly plant.

VIN sequence
...1...2...3/4...5...6...7

(1)3 = Oldsmobile

(2)....L = Delta 88
(3,4)......57 = 2dr coupe
...........39 = 4dr hardtop
...........69 = 4dr sedan

.......N = Delta 88 Royale
...........57 = 2dr coupe
...........39 = 4dr hardtop
...........69 = 4dr sedan
...........67 = 2dr convertible

(5).............H,K,M = 350ci V8
................T,U,V,W = 455ci V8
..........................[U*= 225nhp 2v]
..........................[T = 250nhp 4v]
..........................[W = 270nhp 4v]

(6)..................3 = 1973

(7)......................E = Linden, NJ
.........................G = Framington, Boston
.........................L = Van Nuys
.........................M = Michigan (Lansing)
.........................R = Texas (Arlington)
.........................X = Kansas City
.........................W = Willow Run

Remaining symbols vehicle production number
The starting number was 100001 at each plant.

Engines (there is no relationship to an assembly plant)

1973
250ci 6cyl CC* 100nhp

350ci V8
QN/QO/QP/QQ/QS/QT = 160nhp
QA/QB/QJ/QK/QU/QV/QC/QD/QE/QL = 180nhp

.