What was the last year for the slant?

-
Can the early forged crank be used in the 1975 blocks?
 
I completely concur!

Thanks, Scott. I appreciate the support.

One additional benefit derived at by laying the engine over 30-degrees on its side, was that it allowed them to move the water pump back beside the engine, which made it even "shorter" from fan-to-firewall.

Made me wonder why, if the bigwigs were so intent on moving heaven and earth to achieve a "short" (lengthwise) engine, why they didn't just bite the bullet and build a V-6 version of the poly 318.

It was a wide engine, though, with big cylinder heads, and might not have fit the 1st genration A-Body engine compartment very well.

And, its 90-degree construction would have given them fits on the NVH issues; look at all the hoops GM had to jump through to make that 3.8-liter V6 workable... offset crankpins, "even firing order," and finally, balance shafts.... whew!:banghead:

Maybe MA had the right idea all along... LOL!:blob:
 
I want to build a cast crank turbo someday for the Duster. It is much lighter, anf can be cut down to be even lighter. Get-er-spinnin quick! I have plenty of forged stuff.

If you want to spin find a 170 and add boost. I am curious how a 170 would rev with a set of light modern rods and pistons.
 
mcnoople you are correct, the blocks are different. If you search Mopar Muscle Magazine they have a story from about 10 years ago about slant blocks.
 
Thanks, Scott. I appreciate the support.

One additional benefit derived at by laying the engine over 30-degrees on its side, was that it allowed them to move the water pump back beside the engine, which made it even "shorter" from fan-to-firewall.

Made me wonder why, if the bigwigs were so intent on moving heaven and earth to achieve a "short" (lengthwise) engine, why they didn't just bite the bullet and build a V-6 version of the poly 318.

It was a wide engine, though, with big cylinder heads, and might not have fit the 1st genration A-Body engine compartment very well.

And, its 90-degree construction would have given them fits on the NVH issues; look at all the hoops GM had to jump through to make that 3.8-liter V6 workable... offset crankpins, "even firing order," and finally, balance shafts.... whew!:banghead:

Maybe MA had the right idea all along... LOL!:blob:

Is the GM 3.8 a shortened Northstar?
 
Is the GM 3.8 a shortened Northstar?

No the 3.8 is 70's era tech with pushrods. The northstar is a 32 valve overhead cam v8. The northstar is normally 4.6L, but in the oldsmobile intrigue and aurora they had a baby northstar. These engine were a 4.0L v8 and a 3.5L v6. The most important thing to know about the northstar is they are a pain to work on and you don't ever want to try to fix them when they leak oil.
 
No the 3.8 is 70's era tech with pushrods. The northstar is a 32 valve overhead cam v8. The northstar is normally 4.6L, but in the oldsmobile intrigue and aurora they had a baby northstar. These engine were a 4.0L v8 and a 3.5L v6. The most important thing to know about the northstar is they are a pain to work on and you don't ever want to try to fix them when they leak oil.

The Northstar engine's claim to fame was that it was a DOHC design with 4 valves per cylinder, the first such V8 for Generic Motors.

The 3.8 (or, more recently, "3800") V6 motor dates back to its origins as an all-aluminum 2-valve-per-cylinder V8 that was 215 cubic inches and went into the Olds F-85, the Buick Special and the Pontiac Tempest, compacts for G.M. in 1960 or '61 (can't remember which; I've slept since then.)

As with the slant 6, the aluminum construction didn't prove to be somethg they wanted to deal with, long-term, so the engine construction material was changed to cast iron after while,

Aftwer that, a V6 version was created by hacking off two cylinders, yielding a vibration monster.

The V6's that are in good balance, inherently, employ a 60-degree V angle. This engine was a 90-degree V8, and there was no reasonably economical way to change that design parameter, so they lived with the vibration... for a while.

They designed a crank with rod journals that were built so that connecting rods on a common crankpin, had different orientations (locations) that took away some of the geometrical imbalance, and made for an engine that had a more "even-firing" reciprocating assembly. They designed and built special motor mounts with excessive complicty, giving the engine a soft cushion to sit on for its still, not smooth, gyrations.

Finally, a big redesign resulted in the addition of balance shafts to further quell the engine's tendency to want to jump out of the engine compartment....


Eventually, and after many years, this "once a V8, now a V6" motor was smooth enough to power most anything G.M. had to offer, so it lived a productive life in a variety of vehicles, but not without having hosting a boatload of technical advancements, over its long life.

It has no ties (engineering-wise) that I know of, to the Northstar.
 
It is possible to make a 90 degree v6 that is smooth as silk and has a high redline. Gm just never has had the best powertrain engineers. The engine family in this link powered luxury cars and 8000+rpm supercars and all were 90 degree v6's. I have driven the 3.2 and 3.5 variants and they are smooooth. http://en.wikipedia.org/wiki/Honda_C_engine
 
Thanks for all the input, I will put this information in the file for future reference. A super charger made me think of serpentine belt systems. Do they make serpentine belt systems for the slant?
 
There was some misinformation earlier about net vs. gross horsepower. Hope this helps (from Wikipedia).

SAE gross power

Prior to the 1972 model year, American automakers rated and advertised their engines in brake horsepower (bhp), frequently referred to as SAE gross horsepower, because it was measured in accord with the protocols defined in SAE standards J245 and J1995. As with other brake horsepower test protocols, SAE gross hp was measured using a stock test engine, generally running with few belt-driven accessories and sometimes fitted with long tube (test headers) in lieu of the OEM exhaust manifolds. The atmospheric correction standards for barometric pressure, humidity and temperature for testing were relatively idealistic.

SAE net power

In the United States, the term bhp fell into disuse in 1971-72, as automakers began to quote power in terms of SAE net horsepower in accord with SAE standard J1349. Like SAE gross and other brake horsepower protocols, SAE Net hp is measured at the engine's crankshaft, and so does not account for transmission losses. However, the SAE net power testing protocol calls for standard production-type belt-driven accessories, air cleaner, emission controls, exhaust system, and other power-consuming accessories. This produces ratings in closer alignment with the power produced by the engine as it is actually configured and sold.
 
After having put together one of these little jewels, I can assure you that building the header was far and away, the most difficult part of the exercise.

Somebody needs to build these things (turbo-headers) for sale. My racing partner built ours and he had never built a header before in his life. It can't be that hard, once you have one to work off of...

So, Bill, when are ya going into the business of making those things? Ya know you left yourself WIDE open for that!

ATB

BC
 
I'm probably gonna take a lot of flack for this, but I'm gonna say it anyway, because after reading all the analytical performace information I could get ahold of on this site and others, I really believe it to be true.

That slant six can be made into a real powerhouse IF you don't try to do it using the tried-and-true, conventional methods of hot rodding.

These engines have several factors that make them very poor candidates for horsepower upgrades by increasing the breathing using say, a 4bbl manifold, headers, a longer duration, high-lift cam and higher compression.

Those are all methods that work well on MOST normally-aspirated engines.

They don't work very well on slant sixes BECAUSE, the basic engine design of the slant six was arrived at through the dictates of upper management at Chrysler REQUIRING a short engine (fan-to firewall) in order to produce an engine that would fit a "short" engine compartment (fan-to-firewall) for the new Valiant and Dart. They also wanted to have a low hood line, but that's another story.

The engineers were required to design an inline six that was smaller in a front-to-rear dimension than was really practical for an inline, but they did it anyway, the only way they could: They designed it with small-diameter pistons (and bores) and the 170 was born.
The 170 had a lot going for it; it had a good rod-length-to stroke ratio, a short stroke (low piston speed) great rpm potential and a cylinder head that fit the displacement very well; it breathed so well that even at 7,000 rpm, it made good power. The Hyper Pak was born and proved to be just about unbeatable in racing for engines of that class (displacement.)

The following year, Ma Mopar needed a station wagon/grocery-getter engine for the B Bodies. What to do?? The 170 was just too small.

Some genuis got the idea to stroke the 170 a full INCH, which did several things:

Made gobs more torque than the 170.

Changed a great breathing 170 into an asthmatic, strangulated also-ran, because in their haste to get that engine (170) to market, the guys who designed it didn't leave much room for improvements in breathing for the new 225, which was THIRTY-FIVE PERCENT bigger than a 170.

They never changed the valve or port size of that original 170 head.

So, you can port that head and add bigger (1.75" X 1.5") valves to it, but it's never going to breathe like what is needed, to make good horsepower/cu. in. numbers.

A 300 HP 225 slant six is a real accomplishment, and that's only 1.3 HP/CI.

You can build a 3,000-pound A body street car that will run low 14's, but it will have to be a radical-cammed engine with lots of compression and a good exhaust system. Deep gears will be needed to make it really perform...

If low 14's is fast enough for you, that's probably what you should do, but swapping a 360 Magnum in there with a mild cam and headers will give you better performance, cheaper.

The alternative, if you want to run quicker than that, and keep your slant 6, is to put a turbo or supercharger on it. The slant six basic engine has a very strong infrastructure and can stand quite a bit of boost before bad things start to happen... like over 20 pounds...

A 300 HP boosted slant six would probably last forever (nominally) and is pretty easy to put together.

Food for thought...
Thank you, as soon as I read the word bolt ons I decided I wasn't touchin this thread
 
Thank you, as soon as I read the word bolt ons I decided I wasn't touchin this thread
CORRECTION: I decided I wasn't touchin this thread unless somebody else had already explained it. :D

As much as I love to share my knowledge, I've typed the very same explanation that you Bill have provided, too many times to too many people on too many forums and I really didn't feel like doing it again. Especially considering I type all day for a living while answering phones :banghead:

I think I'm gonna write one really good article on this subject, as well as a few other slant subjects and save them so I can just copy and paste in the future. :glasses7:

Do you mind if I use some of you're explanation Bill? Cause there were a few things in there I didn't know and I really liked, paticularly the part about why they stroked the 170.

I do gotta ask though Bill, you made it sound like they made a different head for the RG block but retained the G block's port and valve dimensions. I held the understanding that both blocks shared the same head. So is there an RG and a G head? Or are they interchangable?
 
It is possible to make a 90 degree v6 that is smooth as silk and has a high redline. Gm just never has had the best powertrain engineers. The engine family in this link powered luxury cars and 8000+rpm supercars and all were 90 degree v6's. I have driven the 3.2 and 3.5 variants and they are smooooth. http://en.wikipedia.org/wiki/Honda_C_engine

From the Wikipedia srticle:
"The engine utilized a 90 degree V-angle to the crankshaft in preference to the taller but more common 60 degree design, with a compression ratio of 9.0:1. The crankshaft had crankpins offset 30 degrees..."

That is really interesting. I never knew that.

The crankpin offset on some of the "almost even-fire" 90 degree V6's is 18-degrees, which was a compromise aimed at (probably) maximizing crankpin overlap in the interest of component strength at the expense of smoothness. I think (but don't know) that the 4.3-liter Chevy motor had this feature.

The bean counters often had their way (particularly, with lower-priced cars) when it came to balancing (no pun intended) cost vs. NVH issues, so we have a variety of designs out there.

I guess the inherent design features of inline sixes made balance shafts and any sort of compromise on crank design, unnecessary. I think some of the early Chevy sixes (215 or maybe 230) didn't even have counterweighted cranks... so good was the original balance...
 
No the 3.8 is 70's era tech with pushrods. The northstar is a 32 valve overhead cam v8. The northstar is normally 4.6L, but in the oldsmobile intrigue and aurora they had a baby northstar. These engine were a 4.0L v8 and a 3.5L v6. The most important thing to know about the northstar is they are a pain to work on and you don't ever want to try to fix them when they leak oil.

I had a 99 Intrigue with the baby Northstar. At about 25K miles, it started burning a quart of oil every 2500 miles.
 
-
Back
Top