New member help! in Compression test results purchase decision needed

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DennisLJacob

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Hi guys I was hoping to not have a "help" post as my first topic. I'm looking at a '74 e9 with the M30B32 motor with twin weber carbs. I don't know the mileage on the motor since it was a transplant before I came along. Supposedly about 70k miles from the owner's recollection. I need to make a decision on a purchase of this car (still haven't seen yet) and I'm concerned about poor compression test result. I'm looking for possible reasons besides a tired motor as a reason. So the readings are as follows checked against two gages.

102, 90, 95, 94, 92, 98.

Now based on those numbers (taken at 1,000 foot elevation) seem really, really low. I'm told the car starts right away. That it idles fine for a carbureted engine. I'm told It runs perfectly fine with the usual power. I'm told it doesn't seem to have any blow by or smoking.

I haven't checked for a cold start video or view - yet. I'm looking to make a long drive tomorrow to see the car in person and make a purchase decision tomorrow or Friday morning. I'm very nervous about this. Other wise the car is in immaculate condition with the right updates, 5 speed, LSD, no rust, no accidents, new leather interior. Basically a great car but those compression numbers bother me. I have no idea what a complete rebuild might cost.

What are your ideas? What are your thoughts? Is there a simple explanation that doesn't include a tired motor? The shop that did the test, said all spark plugs were removed and the throttle was held wide open. The car was warm.
 
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Those numbers do look low. A healthy US M30 should closer to 150-155 with no more than 10% difference from lowest to highest. When driving the car get it safely up to highway speed 55-65mph put it in 3rd gear let the engine slow the car down while watching the rearview mirror for puffs of smoke. this usually indicates worn rings.

The most important thing about your post is mention of no rust, no accidents, new leather interior. Those are all such strong points that keep me inclined to buy this car if it just came down to a tired engine. You should anticipate spending roughly $1,200.00 per cylinder to rebuild the engine. Take that in to consideration and possibly make it a negotiating point. A repaint could cost you north of $20,000.00, leather up to $10,000.00, and rust repair $$$$$$$.
 
A great test for blow by is to go down a long steep hill and at about 1/4 from the top let off the accelerator , let the engine act as a brake. With a heavy load and high vacuum at that time will let you know if she smokes at all Yes bottom end If nothing and when you get to the bottom, hit the accelerator and then see if it smokes, guides if so
 
Well you've all suggested my own thoughts. Cold start for white smoke. After warmed up, stomp on it for rings and blow by. Then high rev engine braking for valve seals. I think I've got it. Does that all sound right?

Craterface, this car is a Coupe King restoration from about 5 to 8 years ago. Body shop PPI did paint meter readings all over with 90% 7.5 mils with only two spots higher in areas that are not rust prone that sounded like a ding on the hood near the grills and on the roof near the front left side. Non-sunroof car. No visible rust and paint as new condition. No signs of ever being in an accident.

I'll be able to see the car in person tomorrow. So I'll see the cold start, and both driving modes to see if we can generate exhaust smoke. Any other suggestions?

And thanks for the rapid and quick comments. Like I said I hate to have my first post being a HELP post. But I wasn't expecting these low compression numbers. Neither was the consignor/dealer.
 
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Really poor numbers...
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If CoupeKing did a resto on it years ago, you could call or email them and ask what they did and what their opinion of the body was. Unless it spent the subsequent years outdoors in the northeast, it probably has not gotten too rusty after that. As everyone said, the motor is the least of your worries. Well, as long as the price is reasonable that is of course. Speaking of which, how much are they asking for it?
 
They are asking a ton - IRA fund ton. The car looks like you could eat off of the undercarriage clean. Same for the suspension and subframes. I agree, if everything else is great, then the motor could be rebuilt or changed. But I'd have a lot of money tied up in it. The chassis/body has about 70k miles on it. When CK did their work, they rebuilt most of the suspension with the restoration. They did the 633 engine and 5 Spd swap. But they don't recall the mileage, just that it was a solid engine and transmission. They put the LSD in it too. They didn't do the paint or leather though. They picked this up as a stalled restoration project. But sold it feeling that it was CK quality. It bounced around two high end collector clients. So I don't think they would let a "lemon" go out of their shop knowing their clients expect a certain level of workmanship. I've been told they sold it for mid $60k's. But who knows how it has been driven since then. I'll find out tomorrow.

Thanks everyone. I appreciate the advice and thoughts.
 
I asked the PPI shop the same question and their reply was yes warm, all plugs out and wide open throttle when cranking. Unless there is something weird with the weber carbs, I'm not sure why the low readings, but consistent across the board. You'd think with numbers that low, the car wouldn't even start, little alone run well.
 
Agree, that just doesn't sound right

DennisLJacob said:
I asked the PPI shop the same question and their reply was yes warm, all plugs out and wide open throttle when cranking. Unless there is something weird with the weber carbs, I'm not sure why the low readings, but consistent across the board. You'd think with numbers that low, the car wouldn't even start, little alone run well.
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DennisLJacob said:
I'm not sure why the low readings, but consistent across the board. You'd think with numbers that low, the car wouldn't even start, little alone run well.
Click to expand...

That is strange, with such even and consistent low numbers and with the owner stating everything is OK, I'd suspect the compression meter or the mechanic did something wrong while using it.
Make sure the engine is cold when you start it and then take it for a long test drive, that should tell you what you need to know.
 
The car is in Oregon. In talking/chatting with Chris, we are wondering if the gages were suspect. I'll find out tomorrow with in person cold start-up viewing and then driving observations. It just doesn't make a whole lot of sense that the engine would be so consistently low, but have the car run fine. Everything else with the car is checking out fine. I have a body shop owner do a PPI and then an independent shop do the rest of the PPI. Compression levels are the only concern excepting a few minor items. Ugh.........

Hi SFDon. I grew up in San Jose. I've been a member of CCA since 1975.
 
@DennisLJacob, I have seen your bids and comments on the E9s on BaT. Please when you see this coupe, which sounds very promising, put your phone in that inner fender cavity so you can visualize it. And see if the seller will remove the rocker covers. Alternatively, if they can provide photos of the car under resto with the front fenders rwmoved, then that will be enough evidence to know that the hidden rust has been addressed. Would love to see pictures of the car as it sits. Best of luck with the purchase.
 
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