340 cam in a 318

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I had the aforementioned LA 318 in my Dart with 3 91 gears, and a 4 speed. Everything stock LA except the intake, cam, 4 barrel, headers and 2.5 inch exhaust. I ran it on the street and it was fun but it ran about as fast as my bone stock 86 Mustang GT convertible which is a 15 second car. Now I hear tell stock 340 darts can do 13s so...my 340 Dart is going back together and maybe one day I will see, this year Ill be running my Mustang again at test and tune night...my Mopar is more of a resto than a race car...still has 14 inch E 70s on ralleys for example. I mean yeah you can scratch your head and dick around with 318 LAs swapping pistons grinding ports but why? get a LA 360 or any magnum (for the heads) and build it and save yourself some time.
 
krazykuda said:
I was in college and had 2 bad cylinders in the 318 in my Barracuda... My brother gave me a 72 318 short block with 10.5 TRW pistons... Then he offered me the stock cam from his Lil Red Express that he upgraded his cam on... I assembled the short block and installed the top end of the other 318 on it and installed it in my daily driver Barracuda for under $400 including Rhodes lifters, gaskets, oil, and antifreeze....

Broke college student, you throw together what you have...

Until I had the overheating problem... I spoke to my engine class professor and he told me my compression was too high and the mixture was self igniting before my spark and I had two flame fronts colliding due to the high compression and I needed to lower my compression... The 360 heads brought me down to 9.2... It ran great after that, I drove that engine to 500,000 miles....
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You just said basically what i was saying in my last post. Who has time to dick around finding out the hard way. i dont want an engine that pings and carries on on a warm summer day, I just want to cruise. I get it you were in college but you did alot of wrenching / swapping untill you threw those 360 heads on am I correct? I don't mean to come off as cranky Im just old and don't have time to build engines that will eventually get yanked and put in a corner it isn't cheap these days either...:)
 
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Bakerlite said:
Here's an example..
If you called Bullet cams, gave them some basic engine specs and also how much valve drop you have at TDC, then they can pretty much tell you the limits of what you can install.
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What’s the drop at 10-15 degrees before and after TDC because that’s where they are close.

Plus, whatever the drop is won’t be the same when the valve train is installed. They only way to know for sure what you have is to measure it. Anything else is a guess.
 
Rat Bastid said:
What’s the drop at 10-15 degrees before and after TDC because that’s where they are close.

Plus, whatever the drop is won’t be the same when the valve train is installed. They only way to know for sure what you have is to measure it. Anything else is a guess.
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Really? I'm not explaining it..
I will say this, If you know the cam lobe specs and it's timing relationship to where the piston is in the bore, then you can get pretty close. Once you get the cam, then you can do a final measurement .
 
Bakerlite said:
Really? I'm not explaining it..
I will say this, If you know the cam lobe specs and it's timing relationship to where the piston is in the bore, then you can get pretty close. Once you get the cam, then you can do a final measurement .
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I don’t need you to explain anything. Your answer that if you know the valve drop at TDC you know your P/V is wrong.

The valves are not at their tightest point at TDC. So there’s that. And second, when you add in valve train flex (because using checking springs won’t tell you how much P/V you have either) you still won’t know what your P/V is.

With valve drop (or more correctly VOTDC or valve opening at TDC) all you know is exactly that. How far the valve is open at TDC. It has no real bearing on P/V.

And on top of that, unless you specify the ICL where the cam will be installed you have added another error into the math of it.

The ONLY real way to know what your P/V clearance is is to degree the cam, install the valve train and measure it.

Anything else is a guess.
 
Farrrk.. Sometimes I don't know why I even bother to post here.
The drop at TDC is a reference point. From that reference, knowing the cam lift points at EVERY degree of crank rotation tells me how far the valve will be off it's seat ( obviously multiplied by rocker ratio) at it's closest position to the piston, which as you pointed out is not usually TDC .
Can I change the lift? Can I change the duration? Can I change how aggressive the lobe is? Can I change the LSA, what if I change the installed centerline or the rocker ratio when I'm looking to upgrade a cam without changing the base engine configuration?
Knowing the valve lift at every position of crank rotation ( piston location in bore) makes this possible.
Is this making your head hurt?
Spring pressure, valve train flex etc, usually increase piston to valve, compared to no load on the valve train..
 
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Bakerlite said:
Farrrk.. Sometimes I don't know why I even bother to post here.
The drop at TDC is a reference point. From that reference, knowing the cam lift points at EVERY degree of crank rotation tells me how far the valve will be off it's seat ( obviously multiplied by rocker ratio) at it's closest position to the piston, which as you pointed out is not usually TDC .
Can I change the lift? Can I change the duration? Can I change how aggressive the lobe is? Can I change the LSA, what if I change the installed centerline or the rocker ratio when I'm looking to upgrade a cam without changing the base engine configuration?
Knowing the valve lift at every position of crank rotation ( piston location in bore) makes this possible.
Is this making your head hurt?
Spring pressure, valve train flex etc, usually increase piston to valve, compared to no load on the valve train..
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No ****? Valve train flex INCREASES P/V??? No duh and that’s my point.

Your whole premise of knowing valve drop at TDC is just a number that means little without other numbers.

Most guys run WAY TOO MUCH P/V and kill compression with big, power losing notches because they used a method of measuring the clearance without the valve gear on.

Here is what you need. With a gear drive you can run piston to head clearance for intake valve clearance. That means if you have .040 deck clearance that’s all you need for intake P/V. If you have a belt drive add .020 and add another .020 for a chain.


Double that for the exhaust valve and send it. Now, if you have 450 on the seat and 1300 over the nose and 7mm stem valves with a 2.400 head, you’ll have to add some clearance because the valves will wiggle and hit things.

Does your head hurt yet? It should.
 
318willrun said:
Shoooooooot !!!!!!!! That's what I forgot !!!! I forgot to check the piston to valve clearance when I put the cam in the Bombcycle (5.9 mag)
:eek:
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Ralphie SOB.jpg
 
Dartswinger70 said:
I get it you were in college but you did alot of wrenching / swapping untill you threw those 360 heads on am I correct? .:)
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Nope, I put it together the first time, then when the overheating started I knew to seek proper guidance with my engines professor... Threw the 360 heads on and was done, no more wrenching needed...

Recognizing you are over your head and seeking guidance from more knowledgeable people is the right thing to do.... You have to recognize your limits...

Einstein.jpg
 
Rat....
Obviously what I'm trying to explain to you is over your head. Guess I'm trying to explain rocket science to a guy who only knows how to light the wick on a bottle rocket.
I'll keep doing the calcs when I need to, like I've done for many years, because somehow they seem to be on the money when a manual check is done with the cam installed, and you can do whatever it is that you do, or is that can't do?
Maybe you could call someone like Bullet Cams and they might take the time to spoon feed you through it, because they too use these calculations..
Now...go away..
 
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Bakerlite said:
Rat....
Obviously what I'm trying to explain to you is over your head. Guess I'm trying to explain rocket science to a guy who only knows how to light the wick on a bottle rocket.
I'll keep doing the calcs when I need to, like I've done for many years, because somehow they seem to be on the money when a manual check is done with the cam installed, and you can do whatever it is that you do, or is that can't do?
Maybe you could call someone like Bullet Cams and they might take the time to spoon feed you through it, because they too use these calculations..
Now...go away..
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Lol. I’ll keep exposing your nonsense. Now go learn something.
 
The only thing your exposing is your ignorance and inability to learn something.
No skin off my nose. This thread is here for anyone to read. Maybe someone who is a little better educated than you will come along and understand it.
 
Bakerlite said:
The only thing your exposing is your ignorance and inability to learn something.
No skin off my nose. This thread is here for anyone to read. Maybe someone who is a little better educated than you will come along and understand it.
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No sir, I understand exactly what you are saying. I’ll say it again. Valve opening at TDC nothing when it comes to determining valve to piston clearance.

Isky has published those numbers for decades in their catalogue. So has Comp. Most don’t bother because it’s one small number among many that are far more important.
 
No, you don't understand at all.
Knowing the Valve drop at TDC allows you to calculate what the valve drop would be at say 15 deg BTDC. Then if you know what the valve lift is at 15deg BTDC, then you have your answer.
You can then calculate for every degree of crank angle as long as you know the lift of the cam for that degree.
Pretty simple.
 
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Rat Bastid said:
No sir, I understand exactly what you are saying. I’ll say it again. Valve opening at TDC nothing when it comes to determining valve to piston clearance.

Isky has published those numbers for decades in their catalogue. So has Comp. Most don’t bother because it’s one small number among many that are far more important.
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Bakerlite said:
No, you don't understand at all.
Knowing the Valve drop at TDC allows you to calculate what the valve drop would be at say 15 deg BTDC. Then if you know what the valve lift is at 15deg BTDC, then you have your answer.
You can then calculate for every degree of crank angle as long as you know the lift of the cam for that degree.
Pretty simple.
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Is there a different way to calculate a rotary engine ??? I don't want to damage anything ......
 
All engines should not have a cam and only a glow plug, running on Nitro. We'd never have a flat cam lobe or a VtP collision again. We'd have more power too...
 
318willrun said:
All engines should not have a cam and only a glow plug, running on Nitro. We'd never have a flat cam lobe or a VtP collision again. We'd have more power too...
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We already have them. Diesels! :rofl:
 
Or headers installed backwards and upside down with cutouts in the hood...basically the collectors would be out in front coming out of the hood :)
 
Maybe just a couple of Pulse Jet engines hanging out the back..
 
Bakerlite said:
No, you don't understand at all.
Knowing the Valve drop at TDC allows you to calculate what the valve drop would be at say 15 deg BTDC. Then if you know what the valve lift is at 15deg BTDC, then you have your answer.
You can then calculate for every degree of crank angle as long as you know the lift of the cam for that degreePretty simple.
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And then you install the valve train and all the bullshit math you did is just that. You don’t have a clue what the P/V is.

Evidently they put stupid in the water down there because there is no other excuse for you and your personal issues.
 
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