Hello all, I'm in the process of reassembling a 1972 455 that I picked up a few years ago and I would like some info from the Olds experts on cam selection. This is my first Oldsmobile so go easy one me The back story on this engine is that it was purchased new back in the 70's for someone's boat and they never ended up installing it so It sat in a semi covered yard site for nearly 50 years until someone decided to do a cleanup and I bought this rusty lump for scrap price. When i opened it up it turned out to be a brand new never fired crate motor straight from 1972. Apart from having to sleeve one cylinder due to deep pitting the rest of the engine is pristine internally and after cleaning everything up (inside and out) I am now at the point of reassembling it. I've determined that it has a 409691 cam and after measuring The compression should be right at 10.5:1 so my question is, how is this thing gonna run with that cam and compression on modern pump gas? It's going into a 1969 cutlass convertible. Would this be a decent street cam to use or would I be much further ahead choosing a more modern grind?

 

No 1972 Olds motor would have come from the factory with 10.5:1 CR. It WAS possible in 1972 to purchase an earlier model engine assembly with higher compression. How do you know this is a 1972 motor?

 

A few things point me to the conclusion it's a 1972, One being it has "Ga" heads on it. I'll add a few pictures from when i first tore it down for context here. The L2E on the vin pad and isn't the "278" on the bottom of the head a date code?

 

Did the marine engines hew to that as well? I ask because in 1972, the 409691 cam is listed for "Marine High Compression" engines.

 

That's actually a good question. I'm looking at the parts book, but it doesn't list marine engines.

 

Post a pic of the tops of the original pistons…and the part number on the distributor
.
just because someone bought it to put in a boat..doesn’t mean it ever was a marine engine. By the looks of the brackets and water pump..it was from a car originally….or going into a car

 

The cam specs are within a degree or so of those of the W-30 automatic cam of 1970. I have experience with that combination, and it runs well on pump premium fuel. If you have any problem, it will be sufficient to back off the total timing by a degree or two.

If you want to go with a modern grind, send a Private Message to cutlassefi on this site for cam recommendations.

When you complete the engine, have it run on an engine dyno using pump premium. The dyno operator will tell you the correct total timing to avoid detonation. You will be able to check for leaks and have the rings broken in at the same time.

 

Pistons are I believe the smaller dish high compression pistons, I measured them at I think about 14cc.

 

"just because someone bought it to put in a boat..doesn’t mean it ever was a marine engine. By the looks of the brackets and water pump..it was from a car originally….or going into a car"
It was absolutely a marine engine, i have no doubt of that much from the research I've done. The L2E and the lack of a vin on that side pad indicates marine engine. Ive been cross checking part #'s and paint marks with info I found in the engine assembly manual and everything points to it being a `marine spec motor, The bigger intake valves, high comp pistons, the 409691 cam and the fact it came with a flywheel pretty much clinch it. And if that's not enough evidence I found a number stamped on the starter pad that corresponds to a Engine Assembly part number that proves it.

 

Theyre advertised at about 13cc or so. HOWEVER they’re .030 shorter than most others so that’ll lower compression. Gotta figure that in too.

 

Post a pic of the number that clinched it for you.

are you saying this is exactly like it came? And it’s a GM piece?

 

looks like a factory piston

 

L on the pad only means it was a service replacement block from GM. The heads were probably put on by whoever bought it. All service blocks I’ve had here are stamped starting with an L

I have one here right now.

It has a pretty big space between the valves for being a big valve head. It’s looks like a 2” intake ?

 

"Theyre advertised at about 13cc or so. HOWEVER they’re .030 shorter than most others so that’ll lower compression. Gotta figure that in too." These ones measure 0.019 below the deck. and I measured the valves, They are 2.072" intake and 1.624" exhaust.

 

how big is that gap between the valves?

 

👍

 

I hope you’re not gonna run away because you don’t like the answers you’re getting here.

the lack of a vin as you say, does not automatically indicate a marine engine. What yours has is a number stamped as a service replacement engine, which has no significance unless you have some kind of paper work to go with it. there is no rhyme or reason to those numbers that anyone can prove. It’s like a work order number , that’s all.

I’ve come across a few service blocks and still have some. The numbers are hand stamped by a person as they get built..they start with an L , some have the numbers upside down, some are 3 numbers, 4 numbers or 5 numbers long.with a letter or without.

original marine engines supplied by GM do have serial numbers, just like a car. that’s how GM kept records of where engines went, the date and engine specs. Those went to Berkeley, Hardin or one of the other marine builders where they added the marine stuff like , water pump or block off , marine fuel pump and marine carb, alternator etc

I know that because I bought a jet boat in the 90’s off the original owner that still had the original engine. I still have the boat and the marine survey/appraisal from back then which lists all the serial numbers, including the one on the engine. . It was the 330 HP H.C. engine. It’s a 1974 SeaRay SRV 190 that had K heads.

it’s and old wives tale that marine engines had that L stamp on the pad

 

Did not Marine engines come with Ka heads?

 

Well first of all The only "Answers" I was looking for was advice on whether the cam I have will work well in my application, So no I am not as you say "running away" As for the discussion on whether or not this is actually a marine engine I think I have clearly established that it is, and I have stated my reasons for that belief but let me repeat them, The lack of a vin is significant because it proves then engine was not originally installed in a car at the factory, As has been stated on this thread by others, No automobile engines in 1972 would have come in @ 10.5:1, I measured the piston dishes and they are 14cc I also measured combustion chambers and they are 79cc's the pistons are 0.019 below the deck, go plug those #'s into any of the many online compression calculators and you will get what I got. Also from the assembly manual small dish pistons with a V notch only came in Marine and Irrigation engines in 71-72, you can clearly see the V notch in one of the pictures I posted. Then there is even further evidence, The starter is stamped 08389 That p/n was only supposed to go on B or C bodies with a 4bbl or marine and irrigation motors. This engine has a flywheel not a flexplate, How many B or C body Oldsmobile's came with a manual in 1972!? Then we come to the water pump, It has a rubber cap installed on the heater outlet, Why would the factory do that if this was to go in a car with a heater core? Then if all that isn't enough, the final nail in the coffin is the spark plugs, The Assembly manual shows R44S plugs as only coming on "Marine" engines. And what plugs does this engine have in it? If you guessed R44S you would be correct.

 

For 1972 Oldsmobile offer 7 marine engines according to my information. 6 were 455 base, 1 was 350 based. Of the 6 455 based engines there were actually only 3 engines. This is based on on the following. 3 of them were equipped with (water pump, fan pulley, fan belt, water outlet and thermostat.) The other 3 didn't have the fore mentioned items. 2 of the 455 used the stock 10.25 compression pistons. Only 1 used the 409691 camshaft. The other used the 400117 camshaft.

The 455 not covered above was equipped with 8.5 compression pistons and used the 400117 camshaft. While the marine part numbers are no longer useful I can put them up if needed. The big cam engine was rated at 325 net hp. The smaller cam engine was rated at 285 net hp. The low compression 455 was rated at 270 net hp with the same smaller camshaft. The 350 was rated at 240 net hp with 8.5 compression and a 402486 camshaft. Hopefully this helps.

 

Looking into this alittle more, the big cam in the above posting is very similar to the 1969 455 365 hp engine. I would try the timing specs for the 69 455 engine and see how that works for you as a baseline. I wouldn't hesitate about running it. At the most you can look into a more modern camshaft if you desire to go that route. There are plenty of people that can recommend a more modern camshaft.

 

That is very interesting, yes please do post up any information you have. The plan at this point is to just use the 961 cam as it is brand new and considering all the problems people are having with flat tappet cams these days, I don't think I will find better quality stuff than original
OEM cam and lifters.

 

That "961 cam" should be just fine for your purpose.

 

I replied to your PM. The 691 cam was a split duration and split lift cam featuring 1* more duration on the exhaust. 286 on the intake and 287 on the exhaust. The lift however favor the intake and was as follows .474 intake lift and .472 on the exhaust lift. For the people who wanted to keep that engine stock but upgraded with factory parts it was recommended to change the camshaft to the 409759 which had a split duration of 294 for the intake and 296 on the exhaust. Lift was .472 on both valves.

If the cam was change, they recommended setting timing at 15* at 800 rpm on vacuum or 35* at 4000rpm. If you haven't already installed your intake it is suggested that you block off the exhaust crossovers if you do not need the choke working. For the carburetor they recommended installing .071 - .072 main metering jets and AX secondary metering rods part #7033549.

 

"I replied to your PM" That's strange I didn't PM you and didn't get a PM from you? "If you haven't already installed your intake it is suggested that you block off the exhaust crossovers if you do not need the choke working" Yes I have already filled the exhaust crossovers in the heads and done a slight bit of port cleanup. Thanks for the advise, Do you have any experience with this cam personally? How is the idle?

 

Here is my personal experience behind the assurance I gave in post 7...

• 409691 has one degree more exhaust duration and three degrees more overlap than 393859, which was the OEM cam in 1970 350 4-bbl manual transmission engines. I had that manual engine in a 1970 Vista Cruiser. Even though cams act more radically in smaller engines, the 393859 had just a hint of idle attitude. The heavy VC was faster than any of the "hot" malaise era cars. Although the side-firing VC exhausts blew smoke rings from exhaust pulses when idling in cold weather, there was very little drama from inside the car at idle. Judged from this experience, the idle would be smooth in a 455 with 409691.
• 406768 has 8° more intake duration, 9° more exhaust duration, and 7° more overlap than 409691. The 406768 was OEM in 1970 442 (455) manual transmission cars, one of which I drove for 15 years. The 406768 in the 455 was smoother than the 393859 in the 350. Using this example, the 409691 in your 455 will have a very smooth idle.

Full disclosure...

• I don't know the lobe centers on the 409691. The OEM cams I had experience with in my cars had ~114° lobe centers, which creates a smoother idle. I assumed the 409691 had similar lobe centers because all the GM moderate performance cams of the era have lobe centers in the 113° to 114.5° range. Only the radical 402569 didn't fit that mold. It had 110° lobe centers, which created a dramatic idle and gave power in the upper rpm range.

 

Good insight Thank you, i believe the 9691 is on 113 degrees from what i have read. I imagine it will make for a very street able mild performance engine Not too far removed from a Pontiac RAIV cam which I am quite familiar with..

 

I thought 1972 455 came with Ga heads not C heads? My 1972 455 cutlass supreme had Ga heads when I bought it.

 

Yes, you are correct . The OP clearly stated his engine has Ga heads.