Cam question...

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nodemon

nodemon

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I bought an engine on a handshake. The seller seemed genuine and trustworthy..."seemed". Doesn't always work out, but you can get a feel for a person...instinct, etc...
Now, this was not a high dollar purchase, so going on instinct is a lot easier and less risky, of course.
But then again, money is money.
I was told it ran, but pulled due to seller finding the engine they were looking for. It's a 1971 318. It has been worked over. "J" heads, double roller chain and through a borescope, I could see the .040 stamped pistons. My real question is, if someone does this kind of build, is it possible a stock, or close to stock cam was used..? Are most going to go with something pretty beefy..?
Just looking for opinions on what you've done or would do and the probability on what the cam may be.
I guess there's no easy way to know what's in there without removing the water pump and timing cover, right..?
 
Ask the "honest" seller what cam he used.
Could be stock, could be way overcammed, could be a "thumper" that's all noise and no balls. Could have 3 wiped lobes for all you know, having never heard it run...
You can get an idea of the specs by putting a dial indicator on the rocker, but that'll only get you into the ballpark.
If I could tell you exactly what was inside an engine without cracking it open, I'd be a rich man. I'm afraid if you want to know for sure, open it up.
 
If you have a flywheel and bellhousing (or even a worn out automatic), it's easy enough to set one up to do a compression test and measure the oil pressure before proceeding farther. Well, if you just have to know what cam it has, you can always pull the rear cam plug by installing a screw and using a slide hammer (of course they'll be some shavings to remove with a magnet) to see if it has any part numbers on the rear and install a new cam plug when you're done.
 
J heads and a double roller would indicate that somebody maybe mighta screwed something together with half a brain.

i doubt it'd be some custom grind, so more than likely you cold grab lift off rocker and pull thru the books and find something that matches up.

but yeah, somebody totally could've just knocked back in a stock or close to stock cam because it would've been cheap.
 
junkyardhero said:
J heads and a double roller would indicate that somebody maybe mighta screwed something together with half a brain.

i doubt it'd be some custom grind, so more than likely you cold grab lift off rocker and pull thru the books and find something that matches up.

but yeah, somebody totally could've just knocked back in a stock or close to stock cam because it would've been cheap.
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Half a brain...lol. What's meant by that..? They didn't know what they were doing..or J heads a dbl roller is basic and no big deal. Really, I'm confused.
 
nodemon said:
Half a brain...lol. What's meant by that..? They didn't know what they were doing..or J heads a dbl roller is basic and no big deal. Really, I'm confused.
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they might've half had a clue about what they were doing. or it's entirely possible that they were just using up what they had laying around.

"J heads" and "double roller" is keywords toward performance. though J heads could have either the big valves or regular size valves.
 
Professor Fate said:
Ask the "honest" seller what cam he used.
Could be stock, could be way overcammed, could be a "thumper" that's all noise and no balls. Could have 3 wiped lobes for all you know, having never heard it run...
You can get an idea of the specs by putting a dial indicator on the rocker, but that'll only get you into the ballpark.
If I could tell you exactly what was inside an engine without cracking it open, I'd be a rich man. I'm afraid if you want to know for sure, open it up.
Click to expand...
Honestly, I don't really care what it is, to a point, as long as there's no issues running and driving. Just was curious what someone may do if it's punched out .040.. if that even matters.
I don't know enough about engines, or building them for performance or otherwise to have an idea.
Just an engine to get me by until I have the original one rebuilt.
 
junkyardhero said:
they might've half had a clue about what they were doing. or it's entirely possible that they were just using up what they had laying around.

"J heads" and "double roller" is keywords toward performance. though J heads could have either the big valves or regular size valves.
Click to expand...
Right on.. and you're completely right about the half a clue thing.. because I know little to nothing about building an engine and automatically thought of "performance" because of the heads and dbl roller.
 
nodemon said:
Honestly, I don't really care what it is, to a point, as long as there's no issues running and driving. Just was curious what someone may do if it's punched out .040.. if that even matters.
I don't know enough about engines, or building them for performance or otherwise to have an idea.
Just an engine to get me by until I have the original one rebuilt.
Click to expand...
is it all together and somebody said ran when pulled and it doesn't look like it's wore slap out and been sitting on the shop floor since jesus was private?

install it and run it.

you're 40 over on a 318, there's nothing for you to do that doesn't result in diminishing returns. maybe a different cam or gaskets or something but as far as the short block goes? there's money better spent elsewhere.

it's a stop gap, snap it in and ship it.
 
If those are flat pistons and you can see thick head gaskets and they look like they don't come to the top of the deck when you've got the bore scope in it, you don't want much more than a stock cam with J heads. You'll have a whopping 8:1 compression if you're lucky...
 
Yeah, since it's a temporary engine just plop it in and go.
If it's too hairy for your liking, you don't have to live with it forever.
If it's too mild, well, you'll appreciate your new engine even more.
Back in the days of yore, I had a 'teener that I threw together out of orphaned parts, and I used that while I was going through my 340. Turns out it was pretty darn good- I kept that thing around for years as a spare that found it's way into a number of cars while piecing together "better" engines for them. All these years later I still kinda miss that old mule- it was a hoot, took a lickin' and never missed a beat.
 
Garrett Ellison said:
If those are flat pistons and you can see thick head gaskets and they look like they don't come to the top of the deck when you've got the bore scope in it, you don't want much more than a stock cam with J heads. You'll have a whopping 8:1 compression if you're lucky...
Click to expand...
Can you tell much just by looking at a limited view of the cylinders...mileage, wear, etc..?
Screenshot_20241127_183548_Photos~2.jpg
 
Professor Fate said:
Yeah, since it's a temporary engine just plop it in and go.
If it's too hairy for your liking, you don't have to live with it forever.
If it's too mild, well, you'll appreciate your new engine even more.
Back in the days of yore, I had a 'teener that I threw together out of orphaned parts, and I used that while I was going through my 340. Turns out it was pretty darn good- I kept that thing around for years as a spare that found it's way into a number of cars while piecing together "better" engines for them. All these years later I still kinda miss that old mule- it was a hoot, took a lickin' and never missed a
Click to expand...
Screenshot_20241127_183548_Photos~2.jpg

Professor Fate said:
Can you tell much just by looking at a limited view of the cylinders...mileage, wear, etc..?
Click to expand...
 
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junkyardhero said:
is it all together and somebody said ran when pulled and it doesn't look like it's wore slap out and been sitting on the shop floor since jesus was private?

install it and run it.

you're 40 over on a 318, there's nothing for you to do that doesn't result in diminishing returns. maybe a different cam or gaskets or something but as far as the short block goes? there's money better spent elsewhere.

it's a stop gap, snap it in and
Click to expand...
Screenshot_20241127_183548_Photos~2.jpg

junkyardhero said:
Can you tell much just by looking at a limited view of the cylinders...mileage, wear, etc..?
Click to expand...
 
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nodemon said:
Can you tell much just by looking at a limited view of the cylinders..?
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i mean, sorta? if there's a dome, you'd know. sometimes you can tell what it is by the type or lack of valve reliefs. so if you could ID them you could potentially say oh it has these pistons so it probably has around this much compression.

but that's dependent on the CC of the combustion chamber and thickness of the headgasket. so you can formulate an educated guess based on those.
 
"Limited view"? You can tell they're stamped .040, should be able to see if they're dished, flat or have a dome... Doing a compression test will tell you more.
 
You bought it as a temporary motor, so install it and see how good it runs. You’ll really only know what it’s got in it by tearing it apart and what’s the point in doing that? Let us know how it runs after you get it installed and running.
 
I like the train of thought stated above. But do a full compression test and log the data early on in case you have trouble in the future. Looking at the cross hatch in the bottom of the bores and the overall condition, I'd run it! The bottom of the bores look pretty fresh (aside from the scuff marks), anyway. It looks decently clean, too.
 
I'm with Garret/post 21
A compression test is gonna give you a darn good idea of how it's gonna run below 3500ish, irrespective of the actual cam specs, which relate more to power over the nose..
And, you can get a feel for the cam by the amount of over lap it has.
And You don't have to be very accurate in measuring it, you can measure this off the balancer, by distance between the points, then converting that to degrees by using the balancer's circumference. But if the lifters bleed down during the test, then the test is bogus. So if the result is repeatable, yur golden, otherwise it's likely a waste of time.
The following are rated at a measured .008 tappet rise.
The factory 318 cam has 20*
The factory 360 cam has 30*
the factory 340 cam has 44*
A modest aftermarket might have 50*
A weekend warrior around 60*
a street/strip maybe 70*
I'm also with Rusty, so long as the lifters don't bleed down.
 
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AJ/FormS said:
I'm with Garret/post 21
A compression test is gonna give you a darn good idea of how it's gonna run below 3500ish, irrespective of the actual cam specs, which relate more to power over the nose..
And, you can get a feel for the cam by the amount of over lap it has.
And You don't have to be very accurate in measuring it, you can measure this off the balancer, by distance between the points, then converting that to degrees by using the balancer's circumference. But if the lifters bleed down during the test, then the test is bogus. So if the result is repeatable, yur golden, otherwise it's likely a waste of time.
The following are rated at a measured .008 tappet rise.
The factory 318 cam has 20*
The factory 360 cam has 30*
the factory 340 cam has 44*
A modest aftermarket might have 50*
A weekend warrior around 60*
a street/strip maybe 70*
I'm also with Rusty, so long as the lifters don't bleed down.
Click to expand...
If he really wanted to get fancy, he could reach in through the head and flip a lifter upside down for something solid to measure against. If it was mine, I'd get the intake off. That'd make it easier, plus give a chance to have a look inside. I mean, intake gaskets are cheap and if it's out of the vehicle, that's a ten minute job.
 
Looks fresh. Get a dial indicator on the rocker above the push rod , Find the lift and multiply it by 1.5. This will give you the actual valve lift. Should be easy to figure out especially if the cam is purple..
 
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