Why The 455 & 403 Motors Are Great For The GMC Motorhome - Jim Bounds

[@arthurgarcia5961]

Hi Jim. Great video and I agree with your perspective. When I rebuilt my 1976 455 back in 2015, the heads were changed to aluminum and were ported, the cam was custom ground and with roller lifters, and the pistons were designed for 10:1 compression. Before going back into the coach it pulled 420 HP and 570 ft. lbs. These motors are beasts!

[@clarkinthedark1]

That’s awesome! How’d the transmission hold up with that power?

[@jverrelli1]

Love the olds 455, No LS swaps here!!

[@Jeffbob442]

Spot on Jim! I have raced big block Ford, Chevy and Olds motors in jet boats ...I built many motors for me and other guys around our area back in the 70's and 80's I also Raced ...gee...about everything with a bunch of cubic inches, and today still helping a friend with his 455 86 cutlass race car. We got exposed to [make that, had our doors blown off ] by a school buddy who got a 1970 Olds W30 442! He waxed about everybody he raced on the street. So, a couple of us guys got into Oldsmobiles too. We formed a 442 Club here in Champaign.We even took a trip out to van nuys to see Joe and Benard Mondello [1974ish] What a great guy joe was, helping us greenhorn kids with knowledge and parts over the coming years. It was Joe who told us about Olds motors being so well suited for Jet boats....what's a jet boat Joe?...Well ,once back in Illinois I got hooked on jet boats too! I built my first Marine 455 with allot of help from Joe and Benard and Mondello parts. That Olds motor would go for miles at 6300RPM and STAY Together!!! I sold it after 4 yrs on the lake..the next guy ran it another 3 years or so, and never an issue! I thought i would try that on my next project boat with a chevy 454LS 5 motor.....I thought it would be much faster than the Olds because of those huge ports and valves,pushrods, etc..but over the next 3 years it seems it was always ...something...valve springs...bent push rods....burnt piston... Here is what I learned..you can not beat an Olds for any Heavy duty application were TORQUE is needed more than anything else. Also, there valve train will stay together for long distance flat out running better than many! Oh, and Jim , pound for pound, I LOVE that 403 too!!

[@davelowets]

Then your tach was way off... Running a factory block Olds big block at 6300 RPMs would come apart in 10 minutes. 5500 RPMs MAX, and not for miles either.

[@Jeffbob442]

@@davelowets When you use the best crank , rods, pistons, arp's, etc..and have Everything balanced AND spend the LONG dollars, they will do it in a jet boat as you are at a constant speed with a constant even load [good water& rev limiter] .But yes a stock big block 455 would not make 6300 for 3 min let alone 10!

[@davelowets]

@@Jeffbob442 You dont have to tell me about that.. My 505" Olds big block doesn't have 1 factory piece in it. It's 100% aftermarket from the 4-Bolt block, to the billet crank, to the symmetrical port CNC aluminum heads, and so on.. I've built MANY different versions of Olds big blocks over the last 30 years, until I finally arrived at the bullet-proof one I have now.

[@yesmendo11]

Great info! I wondered why GM chose that motor

[@josermalavejr466]

I have a 403 in my 72 cutlass. And I'm looking to build my 455 . Its So awesome to hear how great these motors are. So when I see them I'm going to buy them.

[@jasonhumphry5836]

As a oldsmobile man this was very informative peace and much respect to you 👍

[@davelowets]

I wouldnt listen to a whole lot if you want to have a successful big power olds

[@bikertrash9318]

Thanks again Jim!!! Keep the knowledge coming!

[@6.8SuperDutyDriver]

@3:26 All Small Oldsmobile Engines have a 3.385" stroke, including the 350 and 403.

[@jime9305]

What would be considered high mileage on the 455, original, in the 76 Palm Beach well maintained but idle for a few years, thanks! And thanks for your videos and wealth of knowledge and experience, it's priceless

[@ShowemRight]

I miss my 77 Buick Riviera that had that 6.6 L 403 cubic inch Badass engine in it. I heard it was GMS largest small block.

[@gordonborsboom7460]

Thanks for this tidbit of Olds history. I have been wondering why the Oldsmobile V8 engines were produced as long as they were and why they ended up in the marine industry. I’m sure there is more to these stories but the people who were directly involved are largely gone now. Would you recommend any resources that would shed information of the Olds V8 development?

[@hugieflhr03]

These engines were also used in agricultural industries for water pumps for irrigation .

[@reishiramzi]

I'm excited to restore my 455 and enjoy it for a while before electrification is feasible. I agree these make excellent candidates for that purpose, and with products like the ford eluminator crate motor we're getting there!

[@jeromehebert3184]

so a 45 year old engine if you going to upgrade to the fi-tech, alternator, new fuel system, would it also be a good idea to have the engine rebuilt at the same time as you do all the other upgrades assuming you can afford it at the same time?

[@arthurgarcia5961]

So far so good

[@Drifty325i]

Thanks Jim great info

[@capricetony]

Olds 307 was a lil workhorse engine too! 👍

[@AcmeFigures]

Thats why Vector chose the Olds block for its engine, twin turbo intercooled. The guy who founded that Vector super car, before the malaysians bought it apparently had taken the notes righto out of the jet boat play book.

[@jasoncarpp7742]

Hey Jim. Awesome video! Awesome perspective! Call me naïve, but I would think that the larger 455 V8 engine would've been the better engine for the GMC Motorhome than the 403 V8 engine, probably because of the size of the vehicle.

[@davelowets]

The 403 has a much bigger bore than the 455. The bigger bore makes for a better breathing engine.

[@jasoncarpp7742]

@@davelowets Probably. But for hill climbing, and possibly towing, I'd think the much larger (455 cu. in.) engine would be the better choice.

[@michaelkoceja5552]

Great video. What’s the way you would build one?

[@davelowets]

Aftermarket block, and Billet crankshaft to start with.....

[@alekjuskevice]

What does over in patroon mean? I don’t know what a patron is

[@sabre6986]

I have a core with a Trans and final drive that need a home

[@johndillinger8482]

this guy is crazy

[@davelowets]

Sure is... 😕 I've never heard so many untrue facts about Olds engines all in one place before. 🤦🏻

[@rik6T6]

The increase in mass is not why they engines held together. The weight on the feather is a bad analogy. It is simply because of strength that results from the added mass. Dynamically, more reciprocating mass is bad for speed. In modern days, when you now have aluminum components, you can get the same or greater strength, with significantly less mass, and you can go even faster, without stretching the timing chain as much.. The extra weight of the thicker parts is not what make the engines run faster. It is the strength that you get from the thicker parts that raises the maximum speed limit.

[@HappyHarryHardon]

UUUUUGHHHGGGH! UUUUUUUGGHHGGGH! The olds motors were and are still so good that there is no aftermarket for them. If hp and torque is important then the LS is they way to go. It’s easy to make 800hp and 850 ftlbs on a stock bottom end with a single turbo. And cheap. Parts are available at every single part store in the country. Good luck finding a water pump for the olds motors.

[@davelowets]

"Oldsmobile engines are race motors".... Huh? 😕 Where in the HELL are you getting THAT information from? They are NOT high rpm race engines, the bottom ends of these engine are WEAK, and you'll drive over your crank trying to get a bunch of horsepower and RPMs out of it. "Drag racers love the 403.." Umm, NO. The windowed main webs of a 403 is the worst bottom end setup G.M. ever came up with. The main bulkheads are VERY thin to begin with, and then G.M. cut huge windows into them, making the issue even worse. You try to get 500+ h.p. out of a 403, and you WILL rip the main saddles right out of the block, and you'll end up driving over your crank. I've been there, and done that, with a 455 block TWICE already. The ONLY way to get big power out of an Olds big block, and have it live, is to use an aftermarket block. I've broken SO many Olds engines until I finally wised up and built one with an aftermarket block. NOW I have a killer, bullet proof, 500+c.i., Olds big block that stays together, which won't happen with a factory block unless you use a diesel block and convert it to gasoline. Those are a tough block, but then you are stuck with a small block. By the way, the Olds 403 is NOT a "bored and stroked 350". The 403 has the SAME stroke as a 350, but has a much larger bore, and the 403 block HAD to go to Siamese cylinders to fit the big bore. The 350 is NOT a Siamese bore block. The 350 and 403 are 2 completely different designed blocks. Yes, some of the parts will interchange, but they are different inside the block. I have to laugh at some of the stuff you come up with in this video. I don't know if you are just making it up as you go, or if you read those untrue facts somewhere else and just don't know any better. 🤷🏻

[@mtut]

Yeah, many errors. And for all that, there's still a really good case for using the Oldsmobile engine in the GMC motorhome, as GMC did. He misses the point he's trying to make, even when his information is correct (which... oof). From stock, they are very torquey and reliable in normal use in a wide range of driving conditions. These are big, heavy vehicles with a Toronado-derived FWD transaxle that's solid enough but basically limited to a 3-speed automatic (THM-400). Now, there are engines that produce more horsepower, now, and even in the 1970s the Chevy V8s would tolerate more RPMs in racing. But the stock Olds was a stump puller. What torque it had, it was all in at fairly low RPM. With a three-speed auto transmission, to use an engine that likes higher RPM, like most LS'es, you could use a looser converter (BAD idea hauling this much weight around for hours at a time), or modify the chain and/or final drive ratios. But, gearing it down is going to cost fuel economy, and most people want to be able to take their motor home down the highway. The Olds V8 and this transaxle just happened to have enough extra capacity to make an acceptable FWD motorhome. There's a version of this transaxle (from the 1982-85 Toronado) that has overdrive. However, the transmission part of it is designed around the 200-4R - it can be built to handle a lot of power in a street/strip car but for hauling 10,000+ pounds around regularly in a vehicle that's 9 feet tall, I wouldn't be asking anyone to hold my beer. I think the 4th gear clutch pack has like 2 clutches and 2 steels. Maybe someone has tried it, but GMC probably looked at the lack of extra load redundancy in the new Toronado transaxle and if they hadn't already given up on the motorhome, the reality would have set in. There's a lot of bad information on the 403. As you've said, the windowed mains are an issue in a high-RPM application. These were (except in some Pontiac Trans Ams) not ever represented as high-RPM engines. Some morons looked at the bore-to-stroke ratio and surmised that these would love to rev. B/S is BS. And then there's this crap about siamesed cylinders. The 400 SBC had siamesed cylinders and in the Chevy world, there were problems that got blamed on them. (Often the problem was people swapping in heads or head gaskets that didn't have the steam holes and then blaming Chevy). Siamesed cylinders aren't the enemy, either. Nowadays they are very common. Seems the closed deck was the idea for stiffening the block that didn't work, once the material was aluminum. The Olds water jacket is adequate and for crying out loud, the factory compression ratio on a 403 was about 8:1. Olds brought a 1-legged man. They didn't sign him up for an ass-kicking contest. I'd rather have a 455, especially in a big bitch of a motorhome, or even a diesel (GMC was making big trucks with Detroit Diesels, but the Toronado drivetrain would have stuck them with the Olds 350 diesel without a bunch of extra engineering and they dodged a bullet not using the Olds diesel). But these vehicles were really unique and ahead of their time - I first saw one in the movie "Stripes" when an early 70s GMC moho was portrayed as some kind of futuristic tank - and I have a suspicion that if someone is in business restoring them, he's got a lot of people wondering why their 1970s powertrain isn't pumping out 500 horsepower and why they didn't get a 10-speed transmission, and a pony for their 10th birthday and why they can't lure kids into their motorhome, even after they traded off the Econoline cargo van for something more posh. He's probably got people wondering why Scotty can't beam them up. The Olds engines did their job. Today's consumer is confused - knows too much, understands too little. So, I just wish the information he'd assembled was more to the relevant point, which is that the real-world gains from screwing up a historic motorhome with a fashionable engine swap seem to be pretty moot. Anyone who is drag racing in a GMC motorhome is in another league of crazy, and what the hell. A 12-second motorhome is cool and all. Much respect. But not when it's 95 at night, the mosquitos are biting and I need to take a crap. "It's 95 at night, the mosquitos are biting and you need to take an air-conditioned crap. Thank your lucky fucking stars that this is damn sure your father's Oldsmobile, butter biscuit., because it's the only thing getting you laid tonight."

[@arthurgarcia5961]

If someone had an extra $100k laying around, a FWD dual motor electric drive system is close to turnkey today. The problem is the batteries. My math says you want a minimum 150kwh of battery capacity. With today's batteries that's a LOT of weight (and a lot of money). But IMO there's a new generation of batteries on the horizon that will make the idea of an electric motorhome not only good, but potentially a game changer. Imagine however having a (say) 30 kw hydrogen generator on board, to act as both a range extender for the battery pack and as backup power when boondocking. Hydrogen generators produce water as their exhaust. If the mythical hydrogen generator were feasible you could reduce the size of the battery by up to 50%. But all of that magic is at least 5 years in the future. For today, give me a big Olds 8 cylinder sucking dinosaur farts through a glorified coffee can with holes and a butterfly valve

[@bigblue66]

Well said!

[@TheRnorman33]

Gonna rock my 403 till they pry it from my cold, dead hands!

[@rik6T6]

Electric is dying. Hydrogen will replace electric. Gas engines will be able to be retrofitted for Hydrogen.

[@jamesclaygarrison7192]

Why do they all need rebuilding at 50k miles?