Mak

Can anyone enlighten me on what the differences between the Rocket and Super-Rocket engines where... and whether my engine is either one and/or a high-compression engine? I've got a 67 Delta 88 w/ 425 BB... just curious.
Seems I remember reading the Rocket had a 4bbl and the Super-Rocket was high-compression w/ a 2bbl? Seems kinda backwards.

jaunty75

I'm not sure I can answer all your questions, but I have a '67 Delta, too, and it has a high-compression engine. At least I assume it does because the gas cap is original and says "premium fuel only." It has a 2-bbl carburetor.

If your car has its original air cleaner, the color of it will tell you. High-compression engines came with red air cleaners, and the plate that says "Super Rocket" on it will say "use premium fuel."

Low-compression engines came with a black air cleaner.

At least, this is all the way I understand it, at least for the '67 Delta 88. If I'm all wrong, I'm sure someone will come along and correct things.

Mak

Yeah, that's the problem, mine has an Edelbrock carb/intake and non-original air cleaner... so I'm not sure how it was originally equipped. I've always run reg fuel since I've owned it, but wonder if I should be running premium. I'm also kinda curious what HP rating the engine has.

jaunty75

According to Setting the Pace, three versions of the 425 were available. They're not broken down by compression or carburetor type, but I'm going to guess that they are low-compression 2-bbl, high compression 2-bbl, and high-compression 4-bbl.

Anyway, the base engine had 310 hp, and 365 and 375 hp versions were available as options.

Just out of curiosity, is your gas cap original? If so, what does it say?

wmachine

First go to Wild About Cars and look up your Chassis Service Manual. In the front section it shows where your engine unit number is (stamped on a machined pad on the front of the passenger side head). There will also be a chart there to tell you what engine you have based on that number.

Wild About Cars. http://wildaboutcars.com. An information supersource, especially Oldsmobile. More Olds content than anywhere else on the internet and continuing to grow.
You'll find Chassis Service Manuals, Product Information Manuals (AKA Assembly Manuals), Inspector's Manuals, and other documents that will contain this and much much more.
Dealer Brochures, magazine ads and articles, and a home page for you online. You can even have your very own club there and a personal forum.
Free to join, free to learn.

MDchanic

As Kurt says, this is a question easily answered by consulting your Chassis Service Manual.





Note that your engine will be listed with the full sized cars, and not the F-85s, because no 425s were put into midsize cars.

- Eric

jaunty75

Unfortunately, that scanned photo of where the engine stamp is is a little hard to see. The stamping is way in the upper left of the photo oriented at a 45 degree angle going upward from left to right. The other problem is that that photo is so close in that it's actually a bit hard to pinpoint the landmarks and determine exactly what you're looking at.

That is the fuel pump in the lower left, but the orientation of the pipe coming out of it that goes to the carb is actually different from the way it's mounted in my car, and for the longest time, that photo led me to look in the wrong direction.

I actually have this manual, and even WITH the manual if front of me, it took me a while to figure out what I was looking at. Once I realized that my fuel pump was oriented differently, everything fell into place.

Finding the engine number is actually very easy if you know where to look (obviously)! Don't bother with the orientation of the fuel pump. The stamping is on a flat spot directly under the front edge of the passenger side valve cover. It's just behind and slightly to the right of (when looking from the front of the car) the alternator, assuming the car doesn't have A/C and so the alternator is on the passenger side.


Here's a MUCH better photo of where the engine number is located. I took this just now on my car, and the location is circled in yellow. (And, yes, before anybody says anything, I know the engine is not supposed to be gold, but the previous owner was a 78 year old man, and his wife wanted it to be gold, so he painted it that color. One of these days, I'll paint it the right color. I DID do the valve covers.)




Strangely, on my car's engine, I cannot make out the numbers on this little pad. I don't know if they've been sanded off, although I don't know why anyone would do that, or if they're actually there and just very faint. The pad, like the rest of the engine, was covered in gold paint, and I tried scraping it off as best I could. I may try to get a paper and pencil in there and do a rubbing. I do know the engine is a 425 based on the number cast into it behind the water pump. That number, at least, is easily readable.

Mak

Okay, so I'm clearly mentally challenged. The # on the head is P076060... the # on the block is 389244D. So it appears the P indicates a 2bbl and the D indicates a big block (if I'm not mistaken)... but I still can't figure out if it's a high or low compression engine... or how that effects whether it was referred to as Rocket or Super-Rocket... or neither. Little help here. :-)

jaunty75

I think we can figure it out. You have the prefix "P" but no suffix code letter. That would put you in the first row of the last section on the Engine Identification Chart that Eric posted.

The first three entries in that chart have the prefix P, but only the first one has no suffix. So your engine is the one in the first row. Looking across that row, you have the high-compression engine (10.25:1) with a 2-bbl carburetor. That's what I have in my car.

You should be using premium fuel. It's the Super Rocket engine.

bigoldscruiser

The way I read it -- The prefix "P" says its a 2bbl, no suffix says its 10.25:1 high compression and that would make it a Super Rocket. All the 4bbl's use the prefix "R" and use the appropriate suffix to show the compression ratio. Only the Delta Custom (formerly Starfire) and the Toro have 10.50:1 compression and are still Super Rockets. They both have 4bbl's and the appropriate suffixes (S or T). All are red except the Toro, which is blue.

wmachine

Check the pad on the back end of the driver's side head.

MDchanic

Also, the oil filler (provided it hasn't been changed, which is unlikely) labels it a 425 - they changed to the twist-on type in 1968, so all twist-ons are 455s.
Works for the 330 / 350, too .

And, yes, P076060 means a 10.25:1 2bbl motor.
The possible suffixes that year were E, L, S, T, or none at all.
Nothing indicated the standard engine (10.25:1)
E indicated low-compression Export (think banana republics) (8.3:1)
L indicated US Low compression (9:1)
S indicated Super (10.5:1)
T indicated Toronado (10.5:1)

So you've got a motor that is amenable to increasing to 4 barrels (cam is the same in the 2 and 4bbl motors, other than 442, etc., as far as I can tell), and to a bigger cam, if desired.
You've also got a motor that MUST run on at least 93 octane all the time.

Congratulations!

- Eric

ps: here's another pic of the number location, for posterity (you can see it just inboard of the alternator):

Oldsmaniac

I always thought...(yeah I few times I farted and ended up shizing myself as well) that the new generation 330 Rocket in 1964 was just that and in 65 when the big block came out it was referred to as the Super Rocket not meaning HC or LC but just the bigger rocket.

MDchanic

I agree, Joe - I don't have an encyclopedic knowledge, but I seem to recall the external differentiation being the "Ultra High Compression" label, and not Super vs non-Super.

In the big picture, it doesn't really matter anyway - they're all just big greasy rusty things that turn expensive gasoline into unwanted air pollution (and smiles ).

- Eric

Mak

Interesting. I've been running reg (87) fuel since I've had it... and I'm pretty sure the previous owner did also for the short time he had the car after he had the engine rebuilt and installed carb & intake. I've never noticed any pinging/detonation. Sounds like I better start spending even more money on fuel... bummer.
Thanks to everyone for all the help.

Mak

Thank you! And thanks for the help. I've already got an Edelbrock 4bbl and performer intake manifold... not sure about the cam, but I suspect it's not stock.
I'd sure like to find the brackets to move my alternator to the passenger side (like the pic you posted). My car originally had A/C, but it been removed and I have no plans to replace it... it would be nice to get the alt moved over.

MDchanic

I've got a couple of sets, but I'm not near where they are.

If you can't find any near you I can send you a set the next time I'm in the NY area (could be over a month). Just PM me.

- Eric

jaunty75

You are the MAN! It was right there, clear as day. But it's 180 degrees opposite of where the service manual says it should be. It wouldn't have occurred to me in ten times ten thousand years to look somewhere other than where the book says to look.

I saw your response on my smartphone this morning while I was eating breakfast, and I had to get my wife's hand mirror (she's used to these sorts of things) and a flashlight and go down and take a look before heading off to work. I simply couldn't wait until the evening on this!

I did need the mirror to see it. The number is just like Mak's, PXXXXXX (P226949). A "P" prefix with no suffix. So it's the high compression (10.25 to 1) engine. I always thought it was that, and it's nice to have confirmation.

It's interesting the difference in the numbers themselves between Mak's engine and mine. The book says that the starting sequence number for these is 001001. So his, being number 076060, would be the 75,059th engine of this type built.

Mine, with number 226949, is the 225,948th one built. That's makes it much later in the sequence. I know from the cowl tag that my car was made in May 1967, which is fairly late in the model year.

Mak, did we ever establish when your car was built? There is a number-letter code on the cowl tag. On my car, it's 05D, which means means fourth week (D) of May (05). Not that it's any big deal, but I'd be curious to know when your car was made to see if there is any parallel between the build date and the engine sequence number. The low number on your engine suggests your car was assembled much earlier in the model year.

jaunty75

Just out of curiosity, what's wrong with where the alternator is now?

wmachine

Almost certainly the heads were removed at some point and put back on "backwards". The heads are interchangeable from side to side, so it is not unusual for them to be put (back) on without considering where the stamp ends up.

jaunty75

Thanks. That's even more interesting. Tells me a (tiny) bit more about the history of the car. Now I don't have to condemn the service manual any more!

MDchanic

Use a rag or some such to firmly wipe away the grease and dirt at the front of one head, where the head and the block meet, in an accessible place.
Look at the space between the block and head.
If it has a factory steel shim head gasket, you should be able to see a shiny silve line after a good rub
If it has a (thicker) aftermarket gasket, it will be dull and fibrous and won't shine up.

- Eric

Mak

Nothing wrong with it where it is... just might look a little cleaner under the hood since it's now a non-A/C car. If I could pick-up the brackets for cheap it would give me something else to tinker with... if not, no big deal.

Mak

Enlighten me on this if you would. High-compression requires higher octane fuel to prevent pre-detonation (pinging), correct? I've never noticed any since I've been running regular fuel. What's the danger in continuing? I certainly don't want to damage my engine... and don't have a real problem changing to premium fuel... just trying to understand better.

jaunty75

I understand. Was just curious. Of course, with the alternator where it is now, and with the A/C gone, you have unfettered access to the right side of the engine. In fact, there is so much room under the hoods of these cars, you could probably build a little storage compartment in that space!

jaunty75

In my totally uninformed way, I was kind of wondering about this myself. The gasolines of 2011 are far different from what they were in 1967, and I wonder sometimes if a regular fuel of today can't work just fine in a premium-requiring engine of 40 or 50 years ago.

I could see the problem the other way. Higher octane fuels need the higher compression to properly detonate and combust, and if you use them in a low-compression engine, you might not be getting complete combustion, which leads to loss of power and build up of carbon and other by-products of that incomplete combustion. They also burn at a higher temperature, and that can lead to an engine running hot, dieseling, or overheating. But I don't know any of this for sure. I'm just speculating.

I know a guy who puts the various grades of gasoline in a car based on how many cylinders it has. If it's 8 cylinders, it gets premium, if it's 6, it gets mid-grade, and if it's 4, it gets regular.

After I got up off the floor from laughing, I asked him what he puts in his lawn mower.

Blaster

In my limited knowledge, I seem to remember when fuels switched to unleaded & octanes got lowered, I was told some mechanics were "retarding" engine timing, & other tricks, so that older/premium cars could run on regular 87 unleaded, which of course also killed some of the car's power....
If I'm not mistaken, "Regular" leaded was 89 octane, hence the current unleaded '89' "plus", which originally came out for boat & car engines that were spec'd for 89, & it replaced the '89 leaded that was sold side-by-side for a while in the 1970's, with 87 unleaded , & 91-94 premium......
It might be possible that your 425 has had "work done" that allows it to run on reg unleaded, & you might have to get that restored before you gain any benefit from premium fuel.
Also it's my understanding that higher octane 93 burns/combusts fine in an engine that only needs 87, most owners manuals just specify a "minimum" acceptable octane rating, you would be just paying extra money needlessly...

Mak

I've never experienced any issues running regular... engine runs & sounds great.

Mak

Interesting... I'll check that out and let you know (I'm curious, too). I'm back at work today, so I won't be uncovering the beast until Sunday.

jaunty75

%#%$ work! It gets in my way, too.

Mak

Okay, mines 11B... I'm thinking maybe November of '66?

jaunty75

Yup. 11B would be the second week of November, and that would be November 1966. So there is some consistency between the car's build date and the engine sequence number, at least for our two data points!

Mak

Jeez... that was a fast reply! I hope you haven't been sitting at your computer waiting for that date code since Friday! lol

jaunty75

No, just happened to be near it before heading off to a meeting!

Mak

I filled up yesterday with premium (I was on empty, so it took a full tank)... drove the whole tank out (we were gone all day). I'd say the car definitely seems to run better on the premium... although I changed out the hammered auto-lite plugs with a set of new NGK's on thursday, too. Whatever the case, it ran excellent all day!

MDchanic

To get back to the compression / octane question -

Octane has ABSOLUTELY NOTHING to do with combustion - only with ignition.

ANY gasoline will ignite when combined with air and exposed to a spark.

Increasing "octane" rating indicates an increased resistance to ignition caused by heat and pressure (rather than by a spark). The higher the octane, the higher the compression can be before a pocket of high pressure and / or temperature somewhere in the cylinder starts the mixture burning before it should, which would have the effect of hammering the piston backwards down the bore, against the direction or rotation, robbing power, and damaging piston, rings, and bearings.

You can run high octane gas in a low compression engine, and it will not have any effect.

If you run low octane gas in a high compression engine, though, you will get preignition and ultimately engine destruction because of it.

Octane ratings are independent of fuel composition - whether knock resistance is conferred by tetraethyl lead, by modern additives, or by octane itself (yes, it is a chemical and does reduce knock) does not matter - the test doesn't care what is in the gas, only what it does.

In your case, Mak, three possibilities are:
• Your timing is retarded to allow the use of lower octane fuel, which will reduce power and fuel efficiency.
• The person who removed the heads installed taller aftermarket gaskets or spacer shims, thus lowering the compression, making an efficient high-compression into an inefficient low-compression engine.
• You aren't hearing the predetonation, possibly because of loud exhaust, loud music, hearing damage (from the previous two ), or just not knowing what it sounds like.

Regardless, you cannot safely run an iron-head 10.25:1 engine on 89 octane gas with an anywhere-near normal cam unless the timing is very retarded. If you could do this, half of the technical discussions on this board would never have taken place.

- Eric

Mak

Thanks Eric. I'm thinking the timing is probably retarded some... I'm gonna check it Wed morning & go from there. Like I said, it's running great right now... but like you said, the timing would have explained it not pinging on regular fuel. I want to convert to electronic ignition anyway. I don't want to go the HEI route, so I'm gonna just do a Pertronics conversion. I have a couple buddies who've used them and have no complaints... plus I can still use the stock cap/rotor.

Mak

The service manual timing specs show: 425 2bbl HC @ 5* and 425 4bbl HC @ 7.5*. I'm assuming since mine was originally a 2bbl... but is now a 4bbl, I should start at 7.5*?
Also I started a new thread about Pertronix installation, which I plan to do tomorrow. Any expertise you can pass along would be greatly appreciated!

https://classicoldsmobile.com/forums...-question.html

MDchanic

Well... I honestly can't say from experience which timing setting is the best.
Personally, I tend to advance until I get some pinging (or until it just doesn't "feel right," usually in low compression engines), then retard a couple of degrees, but there is always a risk with that technique that it will be too advanced and there will be some inaudible detonation that could damage the engine.

I am uncertain whether the 2bbl and 4bbl engines in your year had the same cam.
It would be reasonable to check the Parts Manual to see whether they did, and base your tuning on that information - if the cams are different, then your engine should be able to run at 5°, but not at 7½°, but if the cams are the same (as they were a few years later), then you MAY be able to advance to 7½°, but only if there's no detonation.

Ultimately, the standard advice is to adjust your timing for about 36° total advance at about 3,000 RPM, then see where that leaves you at idle, since your timing at operating speeds is far more important than your timing at idle. You can then tidy up your idle and low-RPM timing by varying advance springs and vacuum diaphragm adjustments or parts.

- Eric

67442nut

The second pic is the complete list of engine specs for all the '67 Olds engines except the W-30.
It is off the back cover of the '67 dealer brochure pictured in the first photo.
It lists displacement, torque, horsepower, compression ratios, carb type and availability.
I think it answers all your questions.
Hopefully, it is legible enough.