Andy

Probably a silly question but maybe I can learn something. I read where the 400 G engines were only good up to about 5000-5400 before you could potential have some problems. So, I’m curious why Oldsmobile put the red line at 6000 on those two years on the rally pac tach?
appreciate facts or educated opines..

Koda

The short and sweet is because there was also a 350 that year that some have wound to 6000. The G 400 runs out of power about 5200, originally maybe 5400. There's no point in pushing it further. Factory gauges are somewhat less accurate than aftermarket ones on the high end of the price range. It's worth noting that the 66 Sidewinder and the 66-67 Ralley Pack have no red line delineated. I also think it was bragging to put it at 6k.

The only factory tachs that moved the red line per engine config were Corvettes. My old man's 71, being a base model, has the red line about 5000 which is 3 oclock, Better, high revving engines went up to 6500, I think, and were about 4:30. Plus they are cable driven and 8 inch diameter, so damn big all the other gauges are on the console.

Andy

Thanks…makes sense..

acavagnaro

As a long time owner of a '69 with its original 400G, I would say you're pretty much a masochist if you're taking a stock version of this engine to 6k. Even very aggressive street driving yields little gain after ~4500 in my opinion.

BangScreech4-4-2

My G has a bit of a cam in it (218/224, 0.462/0.469, 110 LSA) and there's still not much point in taking it over 5200. I had assumed the redline was just decoration as the Tic-Toc Tach itself was pretty much for display purposes only.

CANADIANOLDS

I don’t know where these old wives tales come form about the late 400 not being able to make power past a certain rpm?

there don’t seem to be the same thing said about the 455 , when in actuality , being 55 cubes bigger should have the problem , not the 400.

Same heads, same rod ratio, same compression and cam, carb and intake, the 400 will make its peak power several hundred rpm higher than the 455. I know a guy who raced a 68 W30 from the day he bought the car new…did extremely well with it. Raced it for many many years.

he took down a lot of other cars with it. He ran a lot of gear , wasn’t afraid of turning a lot of RPM

BangScreech4-4-2

My understanding is that it wasn't necessarily the long-stroke reciprocating assembly that limited RPM potential, it was more (or just as much, anyway) due to breathing restrictions because of the small bore.

CANADIANOLDS

no. I’ve flowed heads on small bores like that and it’s insignificant. Olds heads don’t have a high flow area on the outboard side of the int valve in the first place.

BangScreech4-4-2

Well, okay. I guess the G just gets a bad rap because it's so much more practical to build a 455.

CANADIANOLDS

It gets a bad rap because of internet engine builders who don’t know what they’re talking about.

sure, it’s an under square design, but so is the 455, yet you don’t hear complaints about the 455 not making power in the upper rpm’s.

the 68/69 W30’s had a reputation for blowing up before the warranty was up. That’s because the cam duration was huge and in the 400 you actually had to rpm the crap out of it , which was easy to do and blow it up.

that same cam in the 455 was much better. Power came in at a much lower rpm . Bad combo, big cam, smaller cubes, long stroke …ka boom

BangScreech4-4-2

What actually failed at high revs in those engines?

acavagnaro

I'll never bad-mouth the 400G so don't misinterpret my point. A stock 442 400G isn't making much power above 4500rpm. Period. Sure, you can build one to make power higher but I'm talking stock. And my experience on the subject is not one of an engine builder but of an owner of an original car for going on 30 years. I've driven it hard and can tell you from first hand knowledge that, 1) it's a helluva lot of fun down low, and 2) it stops making useable power around 4500.

CANADIANOLDS

the vast majority were spun rod bearings. My 68 W30 came with the original numbers match engine with, spun rod bearings.

Bryan Burch

That was the source of failure (twice) on my first 1969 442 with the 400G. First failure was so bad I could feel it in the gas pedal. Second one I knew what I was hearing so I just shut it off. Eh...I was 17, didn't know much (still don't!).

CANADIANOLDS

yep, same here. The original owner of my car blew it up twice. Both times a rod bearing…..car was parked after that for many years.

3clicks

I had a 69 with a 400 back in the middle 90's that I drove pretty damn hard but always tried to keep rpm's below 5k due to some wise words from my Pops. I passed the same advice off to the new owner when I sold the car. I told him to pay attention to the gauges, watch his rpm's and oil pressure. He was only 17, it was his first car and damn happy to be buying a 442. About a week and a half after he bought the car he called me and asked what was wrong with the motor because he thinks that it blew up while driving on the freeway. I already had a good idea of what happened. He took it to a local shop that was familiar with the Olds and did work on mine and a bunch of my friends cars as well, and as said above, he spun a rod bearing, bent a connecting rod and did some other damage. Some good $$$ later getting the engine rebuilt and the lesson was learned, right? Apparently wrong...I happened to be in the shop about 7, 8 months later where the engine was initially rebuilt to get some suspension work done on my 72 Cutlass and much to my surprise my old burgundy mist 69 is sitting in the corner of the garage, hood off, engine out.. I asked the owner what the heck happened and he told me that "the kid" blew the motor up...again. That, and it had a nice watermelon sized smash on the pass side quarter near the marker light. I guess we were all 17 at one point, but damned if I did not feel a little bad for that poor car. I always wondered what happened to it, and did it survive that teens ownership.

allyolds68

Years ago there was a thread on ROP (yes, we actually used to talk about Oldsmobile stuff on ROP and not just bicker) that said there were two Rallye Pac Tachs, one for BBO and one for SBO and they had different red lines.

I tried to confirm it with the parts book I have but there are so many listings for different Rallye Pac parts I can't be sure it's true. It does appear that there was a 442 specific tach from 70-72

CANADIANOLDS

I’ve heard that same story many times.