340 cam in a 318

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Dan the man

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I've read a lot on the use of the 340 cam in the 318. With the 340 being a performance engine, wouldn't the duration at 0.050" be 228* on the intake and 235* on the exhaust? My question is, isn't that a lot of duration at 0.050" for a 318?
 
Remember, that is all "gross" numbers, not net.
Factory camshafts were quite tame compared to what can be bought aftermarket.
 
No it's not:

20200416_091649.jpg


"With the 340 being a performance engine".
Now the 318 is the performance engine.

The unique thing about it, it's all mopar parts top to bottom.
 
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Not too big. 114 lsa smooths the idle.

If you use one in a 318... install 4 degrees advance for best results.. unless the 318 is setup just like a 340, big heads, intake, 340 manifolds or headers, 10.5 pistons etc.
 
^ Yup, about 4* advanced. A good friend had a built 318 back in the day with the old TRW 340 repo cam. Ran like a scalded dog in a Dart Sport with 3:55's.
 
Question for the guys, Will it work with a stock convertor or is it on the edge?
 

Those are not stock 340 @ 50 numbers not even close 208 on the intake and 215 on the exhaust are factory numbers.but to answer your question that camshaft will run very well in that combination you can also use a stock converter and it will all come together with the 355 gear ratio.
 
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aaronk785 said:
Lots of companies make that cam. Summit racing has their own. Sum-6920
Click to expand...
I'm sure that this has been asked about a million times, but this time I'll write it down. I'd like a cam that has a decent noticeable idle, something more than a comp 268. Would a cam with 220* @ 0.050 and a 110* lsa work
 
Dan the man said:
I've read a lot on the use of the 340 cam in the 318. With the 340 being a performance engine, wouldn't the duration at 0.050" be 228* on the intake and 235* on the exhaust? My question is, isn't that a lot of duration at 0.050" for a 318?
Click to expand...
Dan the man said:
I'm sure that this has been asked about a million times, but this time I'll write it down. I'd like a cam that has a decent noticeable idle, something more than a comp 268. Would a cam with 220* @ 0.050 and a 110* lsa work
Click to expand...

in a low-compression 318,
installing a 340 cam; 268/276/114+4, ( perhaps 208/215@.050)
with NO OTHER changes,
your cylinder pressure will drop about 15%, from about 134 to 115; due to the late-closing intake valve.
This will drop your low-rpm performance about 25% from a P/V of 110 to 84.
read about P/V here V/P Index Calculation
You will certainly be disappointed if you keep the current stall and gears.
The factory 340 cam has only about 44* of overlap, so the rpm has to be set very slow, and timing very retarded, to hear any rumpiddy-rump. IMO, it is NOT the best choice unless you already own it.
The comp Xe268 is 268/280/110+4 and is 224/230@.050 almost three sizes bigger and the overlap is 54* ; But the intake closes 4* sooner so not quite as doggy down low. I had a cam of about this size; 270/276/110/53* overlap and 223/230@.050; but in my 367 the lope was just barely noticeable at 700rpm with 14* idle timing. My Scr was 11/1 with alloy heads, and I had a 4-speed so stall was not an issue.

With either of these cams, your Scr should be brought up for best results. 115psi is not very much pressure.
 
AJ/FormS said:
in a low-compression 318,
installing a 340 cam; 268/276/114+4, ( perhaps 208/215@.050)
with NO OTHER changes,
your cylinder pressure will drop about 15%, from about 134 to 115; due to the late-closing intake valve.
This will drop your low-rpm performance about 25% from a P/V of 110 to 84.
read about P/V here V/P Index Calculation
You will certainly be disappointed if you keep the current stall and gears.
The factory 340 cam has only about 44* of overlap, so the rpm has to be set very slow, and timing very retarded, to hear any rumpiddy-rump. IMO, it is NOT the best choice unless you already own it.
The comp Xe268 is 268/280/110+4 and is 224/230@.050 almost three sizes bigger and the overlap is 54* ; But the intake closes 4* sooner so not quite as doggy down low. I had a cam of about this size; 270/276/110/53* overlap and 223/230@.050; but in my 367 the lope was just barely noticeable at 700rpm with 14* idle timing. My Scr was 11/1 with alloy heads, and I had a 4-speed so stall was not an issue.

With either of these cams, your Scr should be brought up for best results. 115psi is not very much pressure.
Click to expand...
But that's in a 360 and not a 318
 
AJ/FormS said:
in a low-compression 318,
installing a 340 cam; 268/276/114+4, ( perhaps 208/215@.050)
with NO OTHER changes,
your cylinder pressure will drop about 15%, from about 134 to 115; due to the late-closing intake valve.
This will drop your low-rpm performance about 25% from a P/V of 110 to 84.
read about P/V here V/P Index Calculation
You will certainly be disappointed if you keep the current stall and gears.
The factory 340 cam has only about 44* of overlap, so the rpm has to be set very slow, and timing very retarded, to hear any rumpiddy-rump. IMO, it is NOT the best choice unless you already own it.
The comp Xe268 is 268/280/110+4 and is 224/230@.050 almost three sizes bigger and the overlap is 54* ; But the intake closes 4* sooner so not quite as doggy down low. I had a cam of about this size; 270/276/110/53* overlap and 223/230@.050; but in my 367 the lope was just barely noticeable at 700rpm with 14* idle timing. My Scr was 11/1 with alloy heads, and I had a 4-speed so stall was not an issue.

With either of these cams, your Scr should be brought up for best results. 115psi is not very much pressure.
Click to expand...
Hence the advice of moving the stock cam installed 4*’s…..
 
AJ/FormS said:
in a low-compression 318,
installing a 340 cam; 268/276/114+4, ( perhaps 208/215@.050)
with NO OTHER changes,
your cylinder pressure will drop about 15%, from about 134 to 115; due to the late-closing intake valve.
This will drop your low-rpm performance about 25% from a P/V of 110 to 84.
read about P/V here V/P Index Calculation
You will certainly be disappointed if you keep the current stall and gears.
The factory 340 cam has only about 44* of overlap, so the rpm has to be set very slow, and timing very retarded, to hear any rumpiddy-rump. IMO, it is NOT the best choice unless you already own it.
The comp Xe268 is 268/280/110+4 and is 224/230@.050 almost three sizes bigger and the overlap is 54* ; But the intake closes 4* sooner so not quite as doggy down low. I had a cam of about this size; 270/276/110/53* overlap and 223/230@.050; but in my 367 the lope was just barely noticeable at 700rpm with 14* idle timing. My Scr was 11/1 with alloy heads, and I had a 4-speed so stall was not an issue.

With either of these cams, your Scr should be brought up for best results. 115psi is not very much pressure.
Click to expand...

9.2:1 factory compression is not a low compression engine. Add in the thin .028 ths head gaskets and you are creeping up on 9.5:1

It's all good . . .

And a .010 ths clean up of the original Head. Yes Sir . . .

☆☆☆☆☆
 
George Jets said:
9.2:1 factory compression is not a low compression engine. Add in the thin .028 ths head gaskets and you are creeping up on 9.5:1

It's all good . . .

And a .010 ths clean up of the original Head. Yes Sir . . .

☆☆☆☆☆
Click to expand...
It does depend on what year. 70 318's compression dropped to 8.8 from what I have read. Different compression height pistons is what I saw. Were they still using the embossed steel shim head gasket back then?
 
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