What does the inside of a 200K mile 400+rwhp SC motor look like?

XR7 Dave

Registered User
Finally got around to pulling the motor from our XR7, the one that has 200,000 miles on it and has seen 6500rpm, lots of detonation over the years, more than a few lean passes at the track and in the end 440rwhp. Some people thought it would have broken rings, bent connecting rods etc.

Well, no bent connecting rods, no damaged pistons, no broken rings, no scuffed skirts, no spun bearings, nothing. It was almost boring pulling it apart. I've said on here before that I think Mobil 1 is good stuff, and particularly 15w50, and this motor really looks decent for the mileage and use. The main bearings barely show any wear at all except for the front one which shows the typical wear spot due, I assume, to extreme loads on the crank from the supercharger. The rod bearings are worn smoothly down to the copper pretty much like every other SC motor I've ever seen but the journals all seem very smooth to the touch. I'll be checking clearances after a little cleanup. :) There are no desposits in this engine at all. It will clean up with just a little solvent. Most of the ugly stuff is on the outside due to a cracked oil pan and timing cover (haha, those were my fault).

The cylinders have a ridge and we'll be checking that too for wear just to see what it looks like. Cross hatch is still visible and the motor had about 135psi compression on all cylinders +/- 5psi.

Just thought that might be interesting.
 
midgetchaser said:
u said u were running 5w 50 in the summer, and somehitng else in the cold right.

No, I run 15w50 in it and I don't drive in the winter. What weight oil you run in your SC depends on the condition of your bearings and the oil pressure that the motor makes. Mine made 35-40psi hot idle and 65-70 hot cruise. If 10w30 will get you those numbers then use it. Mine would drop down significantly with 10w30 so I didn't use it.

I'm not a petro engineer so I'm not going to make specific recommendations on what you should do. I'm telling you what I did and how it worked for me. Your results may vary.

It was recommended to me that a heavier oil may provide more cushion to the bearings in high boost and borderline detonation situations. The logic sounded good to me so I followed the advice. I dont' know if it helped me but my bearings show nothing other than normal wear.

I did get some main bearing cap walk on the two center caps. Not much, but it's there and I've seen this on many SC motors. I've been told it's not serious and particularly since my bearings like almost like new, I don't think it's a big concern.

I know there are stud girdles available but for most people that seems like a lot of extra cost. Hopefully the ARP's are enough...
 
I use 10W-30 in my motor and it gets 60psi at a hot cruise and 25psi at hot idle. I have cut all of my filters open and there has been very very little specs. I probably should change though
 
I get preety crap pressure at idle. But it does pass the 10psi per 1000rpm rule. Im thinking of maybe throwin some 10w40 in there. i currently use 10w30 mobil1
 
CMac89 said:
I use 10W-30 in my motor and it gets 60psi at a hot cruise and 25psi at hot idle. I have cut all of my filters open and there has been very very little specs. I probably should change though

I had to read this 3 times before I realised it was FILTERS and not FINGERS.

Doh. :rolleyes: :D
 
It would be interesting to find out how "round" the cylinders truly are since there is a lip. I have on more then one occasion opened a motor and found it looking "great" only to measure it and find the cylinders are oval shaped. Also, it would be neat to see what the measurements between ringlands are from piston to piston.
 
Well, of course they are going to be out of round. That's 16 years of heating up , cooling down, AR pounding it, 13.5:1 afr's, etc... Takes a filled block to control most of it, but it still doesn't cure.

The only way to get the cylinder as round as possible is by a Sunnen CK-21 machine. There's one guy I know (Mike Blackstone) who has one, but then again I haven't searched for people with one. Other than that, just clean the cylinder up .030" or more then put the damn thing back together.

What's the plan Dave? I'm glad you found some time to work on your own stuff.
 
cylinder walls

I have been told that from the factory these blocks were not a very "true" around bore, same thing when comparing the deck height on either side.
 
mywhite89 said:
I have been told that from the factory these blocks were not a very "true" around bore, same thing when comparing the deck height on either side.
I highly doubt they were. Considering they had to do thousands of blocks by slapping it on their bore/hone machine from 1945 and doing the job in 3 minutes.
 
I'd have to say that one major reason nothin is bent in there is because the car is so well tuned there sparky..:D ;)

Rick
 
wo

amazing :eek: when i first started looking in to these cars i didnt think the motors were able to see 100k lol i guess i just had bad luck
now what are your plans for the car dave??
 
Sweet90SC said:
I'd have to say that one major reason nothin is bent in there is because the car is so well tuned there sparky..:D ;)

Rick

The car was not tuned until late 2003 when I first got the SCT software. I fought pinging and detonation continually from when I first modded it until I finally learned how to tune it on my own. Knowing what to listen for though probably made a big difference. ;) I also had an EGT gauge for a few years before I started tuning and used that as an indicator of when to "let off" many times.

I plan to measure everything before rebuilding anything basically out of curiosity more than anything. The motor will go back together with some bushed 94 rods, forged pistons, a windage tray and ARP hardware. That's about it because this motor/car will not be anything exotic. The car does belong to my wife so I plan to make it what the SC was originally intended to be - a nice handling, smooth riding, quiet and semi-luxurious car with working A/C. Initially at least it will have even have an early style M90 on it. I wouldn't mind being the first to break 300rwhp with an early style blower and just pump gas. :D

Most likely the motor won't get built until next year anyway, so far all I've done is pull it apart....
 
Speaking personally: At the end of my semi long MOD list is "Custom Tune By Dave Dalke"....I have seen first hand the end result of a heavily modded engine without a tune....I think the hole where the rod shot through the oil pan was measured at about 3 inches in diameter...not pretty

Rick
 
2003 Mercedes CLK 380 (guess how much I get to drive this one)
Let me guess, wife's car? :D

I'm not sure how to take the above post. Are you saying I tuned your car and it tossed rod or that your want me to tune it in hopes of preventing a tossed rod? Must be the latter because I haven't tuned your car yet that I know of....:cool:
 
XR7 Dave said:
Let me guess, wife's car? :D

I'm not sure how to take the above post. Are you saying I tuned your car and it tossed rod or that your want me to tune it in hopes of preventing a tossed rod? Must be the latter because I haven't tuned your car yet that I know of....:cool:

Yes`wifes car....see at least you get to drive your wifes.:D ..NO thats my point..we all came over for the Dyno tune you did and he didn't come...he never had it tuned and ....I wish I could find the pics to show you...it was ugly...Fortunately it wasnt my SC...you didnt tune mine that day because I hadn't done anything to it yet..
 
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