Hmmmmm, 198 issues

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dddDuster

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Ok- today I decided to do a compression check on my 1970 198 in my 1970 Duster. 1-6, 90-90-90-90-90-85. Definitely low, but pretty even and remember I live at 5000’ above sea level. At any rate, I’m a thinking the old girl is kinda tired and needs a freshening. As I see it I’ve got a few way to go- a few years ago I was going to put a 340 in it to make it like my high school car, alaskanTA talked me straight out of that since the entire car except the radiator is original and plus I kind enjoy the slant.
So now, should I freshen it up, or maybe hop it up a bit- reground cam, offy 4 bbl intake, increase the compression ratio by milling the head and/or block, get the head cleaned up a bit, maybe with bigger valves, maybe use the offy and Gill Welding to go MPFI? I don’t think I want to do forced induction, because I’m old enough I really like my A/C.
The other option is to return to the small block idea, will need new trans, drive line, rear end etc.

Car is 1970 Duster, 198, 3 speed A903, 7 1/4 rear end.

Thoughts?
 
I would stay with the slant, unless you are planning to upgrade the trans, and rear, also. If you were happy with it, before I would not go crazy with it. Maybe bore over size (if necessary) definitely increase the CR by milling the deck and/or head. More cam to help it breathe.
 
Charrlie_S said:
I would stay with the slant, unless you are planning to upgrade the trans, and rear, also. If you were happy with it, before I would not go crazy with it. Maybe bore over size (if necessary) definitely increase the CR by milling the deck and/or head. More cam to help it breathe.
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Thanks Charlie, that’s where I’ll probably go. I can’t really find any info or discussion on the 198. Seems like maybe it would be a decent compromise between the zippy 170 and the long stroke 225. Hopefully be a fun little ride.
 
Sounds like you want a nice driver. But what else do you want? Burn outs, limited traction in first gear? If you have power aspirations beyond that of a modern commuter car, I would go V8(big block IMO).

If you want something to tinker with that will run decently enough to keep up with modern traffic keep the slant. I’d go with the Aussie speed mid length 2 bbl manifold, Holley 500 2bbl,dutra duals and at least 3.55’s out back. With a solid 10:1 compression and a cam over .480 lift. You have a reliable 200 HP and 250+ ft lbs of torque.

This is just my opinion, I grew up building slants and have a fondness for it. But the reality is it’s easier to go faster with a v8. If your Steve McQueen days are over, and you just want to cruise out he slant is a sweet little motor.
 
How many miles snd is it using any oil yet? At 5000 feet of altitude, I would consider around 4 to 6 or so pounds of boost after refreshing it.
 
Garrett Ellison said:
How many miles snd is it using any oil yet? At 5000 feet of altitude, I would consider around 4 to 6 or so pounds of boost after refreshing it.
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85000 miles according to the odometer ( I think it’s correct). Oil usage is what started me checking, seems to use about a quart every 500 miles.
 
I like the Boost suggestion. Really, though, the 198 is a sweet engine, eager to rev and very smooth. You can take advantage of the revs with the 3 sp manual. I have a '74 Duster with 198/auto combo at 22K original miles and like it alot. I can't justify a V8 swap. The only thing I am considering is a 2 barrel/ 2 barrel intake and slightly larger exhaust to add a few ponies.
I would check on the valve seals. Has it has been sitting? maybe drive it to see if the rings are stuck and to loosen them up. What ever you do, Have Fun!
 
If you love a six they are fun.
If you want easy go with a v8.

That being said if it was mine....
Super Six 2 Barrel intake.
Mill the head to get around 9.5 CR.
Larger single exhaust system, 2 inch.
And enjoy being different!
 
OK- thanks Valley and Hyper, I’m pretty much decided to stay with the slant, I have added over the years a super six manifold and BBD carb. I’ve also put the TTI 2.5” exhaust system in. What is y’all opinion of the group buy pistons Charlie mentions over at dot org? I dunno, but I’m fairly sure the old girl is just like it was when it left the factory. The pistons seem not cheap, but not terrible for forged pistons? I’ve just ordered a JP Rollmaster timing chain. I do have a offy 4 bbl manifold, was thinking sending to Gill Welding to add FI bungs and converting to MPFI, what do you guys think of that idea, MFPI with mini squirt to control?
 
There's a really good chance of cutting or even eliminating the oil burning.... I've had v8s that were dang near that bad and solved them with new valve guide seals. The good news is that if you have Access to a good compressor (well, compressors---- air and valve spring) it can be done with the head still in place. Other things to check out are the pcb system (they love to "coke up" and plug the vacuum nipple on the base of the carb meaning pressure can build up in the crankcase, just the thing the PCV system is meant to alleviate.
 
Those early engines IIRC were already 8.5 Scr., and the pressure at sealevel mighta bin in the range of 125 (+/- 15)
But at 5000 ft the Sealevel pressure may be down in the range of 90>120psi
In other words, there may be nothing wrong with your current pressure at 5000 ft elevation. You need to do a LeakDown test to see how bad things are leaking..... if at all.
To get the pressure back up to say 140psi, the static would need to be ~9.5, but 140 is still pretty feeble.
To get to snappy, would be 155psi, and with the 50*Ica , that would take ~10.2/1
Good luck making that happen on a modest budget.
And even if you get the pressure up, finding air to burn at 5000 ft is still gonna be a chore.
And then you may have to deal with detonation.

Do yourself a favor, install some performance rear gears like maybe 3.91s and be happy.
Or supercharge it, as already mentioned.
or just bite the bullet and install a V8, and because yur at 5000, my vote is a 360. any 360. Even a tired stock 8/1 360 will be a minimum 50>60% more powerful below 3000rpm, with NO mods at all.
Will it break the 903?
Well that will depend on how you drive it. But probably yes, lol.
But so will a supercharged 198.
If you like,
I can ship you a couple of pallets with any size SBM core on it, a 4-speed, and an 8.75 with 3.23s, and a reconditioned sureGrip, and almost everything you need to make the swap except no exhaust, unless you want to run standard A-body logs, possibly including 340 logs.
Or you can jump in a pick-up, and come and get it, and we'll sit around and bs for a day, or two.
I got two empty bedrooms.
I don't to beer, but I got plenty of Pop.
Bring the Duster and a trailer, and I'll rig up an LD tester.
 
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AJ/FormS said:
Those early engines IIRC were already 8.5 Scr., and the pressure at sealevel mighta bin in the range of 125 (+/- 15)
But at 5000 ft the Sealevel pressure may be down in the range of 90>120psi
In other words, there may be nothing wrong with your current pressure at 5000 ft elevation. You need to do a LeakDown test to see how bad things are leaking..... if at all.
To get the pressure back up to say 140psi, the static would need to be ~9.5, but 140 is still pretty feeble.
To get to snappy, would be 155psi, and with the 50*Ica , that would take ~10.2/1
Good luck making that happen on a modest budget.
And even if you get the pressure up, finding air to burn at 5000 ft is still gonna be a chore.
And then you may have to deal with detonation.

Do yourself a favor, install some performance rear gears like maybe 3.91s and be happy.
Or supercharge it, as already mentioned.
or just bite the bullet and install a V8, and because yur at 5000, my vote is a 360. any 360. Even a tired stock 8/1 360 will be a minimum 50>60% more powerful below 3000rpm, with NO mods at all.
Will it break the 903?
Well that will depend on how you drive it. But probably yes, lol.
But so will a supercharged 198.
If you like,
I can ship you a couple of pallets with any size SBM core on it, a 4-speed, and an 8.75 with 3.23s, and a reconditioned sureGrip, and almost everything you need to make the swap except no exhaust, unless you want to run standard A-body logs, possibly including 340 logs.
Or you can jump in a pick-up, and come and get it, and we'll sit around and bs for a day, or two.
I got two empty bedrooms.
I don't to beer, but I got plenty of Pop.
Bring the Duster and a trailer, and I'll rig up an LD tester.
Click to expand...
Thanks AJ, I’ll do the leak down tomorrow, dunno why I didn’t do it yesterday, I’ve got a tester around here somewhere. I think I am gonna stay with the 198, I do read your stuff on the N&P, would be quite fun to sit and have a soda with you one fine day…. Cheers!
 
I have a high elevation Dart with a 225. I'm the third owner and it lives at a similar elevation to you, 4800 feet. The guy I bought it from stored it in an airplane hanger, and maintained it like it was his second airplane. He tested compression every year and I have the log. At 53000 miles he tested it and got low 120's in psi all around. He lives slightly lower than me at about 4600 but the car swapped between here and Montana which may have been slightly higher. I think most of the tests were done here though. His tests a few years later were about ten points higher (an outlier), so I assume at least that test was done in a different place. Lowest and highest cylinders matched in both tests.

It was mentioned that your engine has a static c/r of 8.5 from the factory but I'm pretty sure all slants measure much lower from the factory. Mine burns about as much oil as yours, and while it is possible to be valve seals mine burns oil on very new seals (head was rebuilt with hardened valve seats not too long ago). Unless the car was equipped with a high altitude carburetor it is likely rich (I know mine is). Unsure what years or where those changes were made, but I know they did that with some cars in Colorado. Mine probably just washed the cylinders with a nice stream of rich gasoline its whole life.

The lowest psi my records show is 115, and he replaced the head with a burnt valve at 60. 90 sounds pretty awful.

Hope that helps,
Brandon
 
Leanin'Dart270 said:
It was mentioned that your engine has a static c/r of 8.5 from the factory but I'm pretty sure all slants measure much lower from the factory.

Hope that helps,
Brandon
Click to expand...
Depending on which book/manual, you read the CR for a slant was 8.2-8.4 to 1. I never did a 198 engine, but any 170 or 225 I took apart and measured while disassembling, was never more than 8-1 CR. All except for one engine was in the range of 7.8-1 CR. That was with the factory shim head gasket. If doing nothing but a repair, and replacing the head gasket with a aftermarket gasket, the CR got even less.
 
Leanin'Dart270 said:
I have a high elevation Dart with a 225. I'm the third owner and it lives at a similar elevation to you, 4800 feet. The guy I bought it from stored it in an airplane hanger, and maintained it like it was his second airplane. He tested compression every year and I have the log. At 53000 miles he tested it and got low 120's in psi all around. He lives slightly lower than me at about 4600 but the car swapped between here and Montana which may have been slightly higher. I think most of the tests were done here though. His tests a few years later were about ten points higher (an outlier), so I assume at least that test was done in a different place. Lowest and highest cylinders matched in both tests.

It was mentioned that your engine has a static c/r of 8.5 from the factory but I'm pretty sure all slants measure much lower from the factory. Mine burns about as much oil as yours, and while it is possible to be valve seals mine burns oil on very new seals (head was rebuilt with hardened valve seats not too long ago). Unless the car was equipped with a high altitude carburetor it is likely rich (I know mine is). Unsure what years or where those changes were made, but I know they did that with some cars in Colorado. Mine probably just washed the cylinders with a nice stream of rich gasoline its whole life.

The lowest psi my records show is 115, and he replaced the head with a burnt valve at 60. 90 sounds pretty awful.

Hope that helps,
Brandon
Click to expand...
Thanks man, great info! It never had a high altitude carb, and now it has a BBD, it runs pretty rich for sure.
 
Ok, I finally got around to doing a leak down test and rechecked the compression yesterday, here’s what I got-
1. 90 psi, LD 18%
2. 90 psi, LD 18%
3. 90 psi, LD 16%
4. 90 psi, LD 16%
5. 90 psi, LD 18%
6. 90 psi, LD 18%

I then fogged all the cylinders with oil and re ran the LD, that made no noticeable in the LD%. Please give me your thoughts, I’m thinking it’s a little tired, but not dead just yet. I’m going to replace the valve seals next, see if that helps a bit with the oil consumption, then try and see if I can lean it up some, it runs pretty rich for sure. Might add an A/F gauge to confirm. Thoughts?
 
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