Actually, I had a vehicle that was mis-timed and ran... It occasionally started hard, only made power to about 2500 RPM, and WOULD. NOT. rev past 4500 at all, whatsoever(in neutral with throttle resting against the firewall)... I also think vacuum was down, because the brakes got weaker... But it ran, and that was how the mechanic fought his obligation to fix the issue... I kept telling him to check the cam timing, but he wouldn't, assuming that any mistiming at all would have ruined the engine...

 

had a '80 Grenada--jumped time, still ran. Had to idle at 2K to keep from stalling. Not enough vac to keep tranny in gear. Drove it like a three on the tree

 

I have not pulled a twin cam engine down and tried to get it back together but I did have to change the timing belt (not chain) on my Mitsubishi three or four times in the 300,000 miles I put on it before it was sold.
And on one of those times I got the cog on wrong and when I went to start it the thing ran like Crxp. Doggy in performance etc. and had to take it back apart. The cog belt cam drive had bigger steps in the resolution of the belt vs the size between chain cogs so it would be a bigger change in cam timing and despite the fact it was a 16 valve engine it only had a single cam.
Interference engines as you know will lunch them selves it if looses a belt or chain but that pretty much means if and the operative word is IF, a valve hangs open it will whack a piston. Not partially open, all the way and because the cam quit moving. Some engine will tolerate that, others won't. But with the cams hooked up and running you have wiggle room if things are not too far off.
As to running them that way? As I am my own mechanic the thing comes back apart to get put together correctly.
I have always been partial to my Saturn and am familiar with a lot of stories about them in terms of having long lives and with chain drives and good oil they are almost indestructible.
The light weight oils that are now so trendy are death to them. I am still adverse to using a 5W20 oil unless it Is below freezing on my thermometer. Todays adjustable cam shaft function depends on knowing oil pressure at a given engine rpm and I think depends on a light weight oil and I have yet to read what mileage and wear which will change oil pressure will do to the engine with adjustable cams. So I guess if I am going to error it is going to be on the heavy oil side based on viscosity vs temperature charts which I have not seen change. My Saturn run on a diet of 10W30 or 40 and 20E50 for the last 40,000 miles and my 07 Chrysler on 15W50 Mobil one oil since new do not show any indication of oil consumption at 100,000 miles. But take into consideration it will be over 100 degrees here again.
If I lived in a weather belt that included snow I would use a 10W30 oil year around with out looking back.
But that is me.
And if I bought a car with an adjustable cam it too will run on 20W40 and will bank on the mileage lasting until the thing turns to dust before I worry about what the engine is doing.
Dang the plastic on my Saturn is actually in worse condition the 40 + year old AMC cars I am putting back together.
Back to work. Later
John

 

Had the oil changed in the SC2 last weekend. I wiped the dust off the dashboard and crud off the steering wheel yesterday. Now it looks better. Next will be to clean the inside of the windows. Now that I ride my bike to school, the car isn't moving much. That will change next month. Plus I'll have to figure out how to wedge 4 people into it without them cursing too much. Hope they are short.

I'll start commuting an hour to Effingham to start student teaching every day until Thankgiving. Can't wait for the 5AM wakeups and 5PM falldowns when I get back home. I'll probably break 200k miles sometime in the next few months.

 

If you have anyone over 5 feet tall, then the back seat thing is going to be a challenge, Dave. Good luck with that.

 

I started tearing into my '98 SC2 for an engine swap. After I got the timing cover off, I could tell it's been apart before, so I'm not going to chance it.
When I got the battery tray out I found a junkyard heat sink warranty plug on the tranny's bell housing. Which I hope is a good thing. I've got a call out to the guy I got it from to see if he knows anything about it. He had told me he was selling it for his buddy who got deployed before he had time to get it running.


uncljohn, on another note, in my previous life, I broke a valve spring on my 390 AMX motor, during an episode when I could have used Rube's lead foot prayer. I made an air fitting that screwed into the plug hole, and a notched pry bar that attached to the rocker bolt. Pressured up the jug at TDC to hold the valve up, compressed the spring, removed the keeper, replaced the spring...viola GTG. PAX

 

Using air pressure is a not uncommon way to keep a valve closed long enough to change a spring or a keeper on a valve.
A rebuild of an engine is not really a crap shoot, but there are different levels one gets into when doing a rebuild.
A valve job is not a necessity depending on how it is defined. Such as replacing all valves is not automatic. If there is nothing particularly wrong with the seats, a valve is re-lapped back in. If a seat is badly damaged, it might be re-done along with a new valve or if is a deep pocket rebuild, all valves and seats get replaced. But the bottom line in most cases, is valves will only be replaced or machined as needed. Not a problem except when done, the valve stems are probably going to be a slightly different heights. If so, then the top of the valve stems will be machine off so they are the same height above the heads, this is done so each valve operates the same as the others when the cam makes the rockers work. The alternative is all new valves and extra machining to the valve seats. Sort of 6 of one or a half a dozen of the others and the engine unless built to run on the ragged edge of it's performance window, is not going to fail and it will run well.
The advantage is cost.
The down side is if the machining gets real close to the keeper, than that valve stem is weak. That is when it get important to be able to use tricks like air pressure to change things. I have never had a bad rebuild done. And block or head damage is interesting to be seen as to how it can be repaired to salvage a component. I have had good luck with rebuilt engines and rebuilding them. AMC engines are high nickel content and are hard to damage. I have seen AMC blocks where the Piston was damaged or destroyed by detonation leaving the connecting rod rattling around inside the bore and not damaging things bad enough that a good hone would make the block serviceable. Something that would have put it through the side of the engine from other manufacturers. AMC designed and built a very good motor that worked well as a hot rod motor. Apparently though when used as a NASCAR motor at the 425 cu in level the heads which breathed very well in their own right, could not breath well enough over 400 cu in to develop competitive HP with.
AMC only had one block for their "V8 engines then. The competition at that level had a whole separate "BIG" block for displacements over 400 cu inches. Thus an advantage.
By the time NASCAR limited engine size to 350 cu in, AMC was no longer building cars.

 

I've only rebuilt a few V8s, 390 AMC, 260/289 Fords, and those I sent the heads out. But I've done a ton of air cooled VWs, along with B20 Volvos and flat 6 & 8 Dodges. I had a Sioux seat grinder, and with a little work I could make duel port HP out of single port VW heads, which were the only ones around used at the time.
I've heard from more than one person that the main weakness on high revving AMC iron, was oil return with the stock system. They benefited from dry sump system to extend the power range reliably. One fella was the guy I got my '70 AMX from. He campaigned that car bought new off the show room floor, but had a displacement restriction of 360ci. because of weight. I forget what class series, but it was against the big Mustangs and Vettes.
Oh, and I reset my oil change light on my SL2 today. Yesterday I went to the junk yard to scout for a '98 DOHC engine. Found several, 125K, 100K and the best candidate had 94K miles, but some hammer mechanic busted off an AC mount flange/boss on the head, ruining an otherwise good looking motor. PAX

 

The oil return issue is an often mentioned and minimally understood problem but it existed from day zero. I think the TransAM engines which were de-stroked and sleeved 360 blocks were not reliable until dry sump oil systems were allowed. I have seen ads for external belt driven oil pumps, but not lately. Anyway they were competitive in there time. My 390 has been street fast and tunable since I built it in about 1983 or so when leaded premium gas disappeared. And I have a 258 that has been fuel injected since 1992 or so and I figure that one for about 180HP and I just finished a 4bbl carbed 232 with rockers on a shaft rather than stud mounted rockers. It should be good for about 140 hp. And if I get it tuned right I kinda expect my Mercury Marine engine out to be around 425.

 

Glad to see this is taking off... I had new rubber put on and replaced a leaky brakeline on the sc2 today. Noticed that the engine cradle is in some need of attention.