Differences between earlier /6 engines and newer ones

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Schyrjajew

Schyrjajew

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Hey guys.
Today I was reading something about the Valiant.
I saw, that for exampe the 225 engine till 1971 has 145 hp an 215 lb-ft
And from 1972 it has "only" 110 hp and about 170 lb-ft.

Now I am asking you:
Was this just for the insurances or is it really like that?
Did someone feel the difference?

I want to swap from 170 to 225, but there are only newer engines to buy here in Europe

Slant Six.png
 
I heard the new ones are good for just under a million miles, while the old ones are good for just over a million miles.
 
early slants had solid cams, later had hydros
early slants had spark plug tubes, new ones didnt
early slants had no intake EGR, later ones did
real early ones didnt have a alternator bracket boss on the head
came in 3 sizes, all with the same head
early ones had non emission cams, later ones did and lost power as they 'progressed'...
early ones were measured on a test stand with nothing attached, later ones were chassis dyno'd with the freakin lights on....
 
Well I have a 67 Dart that had its original slant in it. I had to switch it to a slant from 73, I only bought the stuff between the oil pan and valve cover meaning i transfered carburetors, intakes etc. from the old engine.
There is no noteable difference in performance of the two engines.
It is like the article says, the measuring methods changed and that is why hp readings differ.
 
other than the fact they changed how they measured the horsepower, nothing else that changed would prevent you from putting it in your car. The last 225 slant 6 made by chrysler was in 2005, last one was installed in a forklift. If it were me, I'd find a newer/later model one. Manufacturing procedures and equipment improved a ton over that time.
 
No, sir. The '67-'74 Slant-6s are the "cream of the crop": they have the forged crank (instead of weaker cast starting mid '76), they have the bigger bearings and stouter connecting rods (smaller bearings and narrower rods to go with cast crank starting mid '76), they have the improved combustion chamber (started '67) with gasket-seat spark plugs (more options in those than in the taper-seat plugs that started in '75, plus the '74-down heads weigh less and you can R&R the lifters without removing the head). These blocks are also sturdier than the later ones which were cost-reduced by taking metal out. Hydraulic cam started in '81 (after a large production-engine test run of them in '78)…nice that you don't have to adjust valves, but the stock hydro cam is small/weak/wheezy.

Easy to understand how and why they got away with cheapening and weakening the Slant-6: at the same time they were letting it die a slow death by not updating and upgrading it, just de-tuning it further and further to squeak past tighter and tighter emissions regs. By the sad end, it was wheezing out 85 horsepower...not enough to break even much weaker parts.

If you're going to the trouble to do a performance build, might as well start with the best, strongest parts. If all you need is a motor and you don't care beyond that, then it doesn't much matter. But be aware that in addition to needing to use the oil pan and pickup that goes with the vehicle, the crankshaft counterbore and torque converter nose diameter changed after '67. You can use a '68-up large-counterbore crank/engine in front of a '67-down small-nose torque converter but you must install a ring to take up the space between the TC nose and the crank counterbore or you will eat trans front pump bearings and seals. You cannot put a '67-down small-counterbore crank/engine in front of a '68-up automatic trans unless you have a special torque converter custom-built, or you build up a "FrankenTrans".
 
Insure the block has 5 "freeze plugs" in a row. The earliest engines (until ~1966) have 3 staggered freeze plugs. They will still work, but people say the later blocks are slightly stronger. But, also avoid even later blocks w/ cast-iron crankshaft (SSD says 1976+). Heads interchange. Look for the earlier style w/ spark-plug tubes, termed "drool tube" (new tube gaskets are cheap to avoid that). The later "peanut heads" without the tubes require removing the head to get at the lifters (rats, Chrysler did that in my 2002 3.8L also).

For max performance, read-up on tuner tricks at www.slantsix.org. One trick is to swap rods (198 cu in?) into a different block, I recall w/ pistons from a later Mopar engine (2.5L 4 cyl?) to make a "stroker" engine. But, sounds like you just want to get a decent setup from parts you can source in Europe, so good luck. In its last days, after U.S. sales stopped due to emissions, I recall slants were shipped to Brazil and Europe (Turkey), but those were probably the later engines to avoid.
 
slantsixdan said:
"You can use a '68-up large-counterbore crank/engine in front of a '67-down small-nose torque converter but you must install a ring to take up the space between the TC nose and the crank counterbore or you will eat trans front pump bearings and seals. You cannot put a '67-down small-counterbore crank/engine in front of a '68-up automatic trans unless you have a special torque converter custom-built, or you build up a "FrankenTrans".
Click to expand...

Part number for that spacer ring?
Thanks!
 
The crank spacer ring is not a standard part, but custom-fabb'ed by some nice people with lathes. I got one from member Charllie_S here for ~$20, or if he is dry try TorqueFlitePatty (or such) who I recall is also on ebay. BTW, I understand it is the same size as the spacer ring needed for small-block engines too, at around the same time, so if you run across that it "should work". I never heard that Chrysler dealers sold one.
 
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