Summit cam for a 318 LA

[AJ/FormS]

Before I would do anything, I would do a compression test with a top-quality screw-in tester.If you have about 162 psi, then you already have the most torque from idle to 2500 that any teener will ever make. And so almost any cam you put into it will rob low-rpm cylinder pressure and trade it it for midrange, mostly.Trying to get that little B off the line will then be slower than it is now........unless you also put in more TC and or upgrade the rear.
This is about what you should have now, if you really have a 9.2 engine;
Static compression ratio of 9.2:1.
Effective stroke is 2.86 inches.
Your dynamic compression ratio is 8.07:1 .
Your dynamic cranking pressure is 161.70 PSI.
V/P (Volume to Pressure Index) is 133.............................................133
For pumpgas, this is close to the maximum you can run.
So, if you have 160ish, then you have a great base from which to build, so don't spoil it all with a slow-ramps Summit cam, especially with that big ol' A/C compressor in there..

Here's what the 6901- 276/288/114 will do for you, in at the 109 recommended install. This makes an ICA of 67*
Static compression ratio of 9.2:1.
Effective stroke is 2.50 inches.
Your dynamic compression ratio is 7.18:1 .
Your dynamic cranking pressure is 138.80 PSI.
V/P (Volume to Pressure Index) is 100..............................................100
That's giving up 33 points of VP, and 23psi of cylinder pressure!
that's a lot of torque to give up in a B with 2.94s and a factory convertor.
This is a very slow-ramp cam. The .050s are 218/228. So on the intake 276 less 218 =58 degrees of ramps, about the slowest out there. sure, the overlap is 54* so you'll get a little lope, but it will be a huge disappointment when you put it into low.
For low-speed torque, your teener is already at the top of it it's game (with a true 9.2 Scr and 160ish psi.). So if you are looking for a bit more off the line, a far better idea IMO, is more off-the-line rpm. Like a 2800TC, I love those. This will about double your available take-off torque. Maybe more as I have no idea just how low your torque number currently is with the 1750factory TC.
But that 2800 is about at peak torque on a teener, so it can't get any better,lol! If you still want more, the next thing would be more gear.
And then a custom cam, with a similar ICA to what you currently have.
But this is all based on the compression test. If your pressure is more typical, at 140psi, then just forget about a cam period. Unless you are also prepared to get a bigger TC. And so you might as well get the TC first and see how you like that.
Psssssst 2800. I love that thing. I guarantee you will too. In my 3650 Barracuda (me in it) It's like a slingshot. From an idle, I hit it. The rpm spools up, the TQ-secondaries open,and then........then chit happens.

 

[RustyRatRod]

I give up.

 

[rumblefish360]

I'm with ya Rusty! To much goobledy goop bullshit droning on & on splitting hairs as if it ment the whole world is at stake.

 

[rigger3006]

i ran that 6901 in a 360, tad bit of performance idle so it should sound nice in a 318, perfect choice!

 

[toolmanmike]

i ran that 6901 in a 360, tad bit of performance idle so it should sound nice in a 318, perfect choice!

Wish you had a video. Off to you tube I go. A "tad bit" in a 360 might sound like "top fueler" in a 318. LOL

 

[toolmanmike]

i ran that 6901 in a 360, tad bit of performance idle so it should sound nice in a 318, perfect choice!

Here's a 360 video:

 

[toolmanmike]

Here's the cam in a 318 pick up: Nice lope.

 

[nm9stheham]

I LOOOOOVE those 66-67 2 door HT B-Bodies. Glad you came onto FABO!

With this 318's CR actually being in the low 8's, and not the 9.2 Mopar advertised CR, and with the heavier car, and low gear number, I would certainly expect this car to be boggier off the line with the 6901 cam. At least the wide LSA and slow ramps will help the overlap to not be too much, so the mid-range will come back on quicker than one might expect. How much vacuum it will give is something I do not know.

FWIW, I personally would go with something more like this: https://www.summitracing.com/parts/sum-k6900/overview/make/dodge

Or, better yet, like this: https://www.summitracing.com/parts/crn-693902/overview/make/dodge

Either of these will be better at lower RPM's, work better with a stock TC, and give higher vacuum for the power brakes. I would prefer to shift the torque band down in RPM range for this car, gearing, TC, etc.

If you do use the 6901 cam, then yes, for sure, degree it in but I personally would advance the cam timing another 4 degrees to help lessen the bog. (I am assuming that the 6901 has 4 degrees of cam advance already ground in so total advance would end up at 8 degrees; ICL would end up at 106 degrees.)

And you may already know this: Whatever cam you select OP, since this is your first cam swap, be sure to read up on ZDDP levels and oil selection, and on proper break-in procedures for a new cam. Both topics are vital to understand, and will save you from a lot of grief.... like a ruined new cam, and perhaps tearing down the motor to clean out the particles of cam/lifter metal that would result.

 

[nm9stheham]

Most guys @ FBBO are good fellas with good intentions. And they are stuck in having a big block only mind set. They have every answer why you should spend all of your money and take a second mortgage out to rid yourself of the 318 and use a big block.

God forbid you do a 383 or a 400 without stroking it!

So it's not just me noticing this? LOL

 

[nm9stheham]

OBTW, OP, where do you think you will end up in rear gear? I have assumed this is more of a cruiser car, but that may be wrong.

 

[TrailerParkGinger]

OBTW, OP, where do you think you will end up in rear gear? I have assumed this is more of a cruiser car, but that may be wrong.

Well I really dig the superstock look of Landy and Ronnie Sox, so I plan on putting 29" tall tires on the rear with a bit of rake. So probably 3.91s or 3.73s. I probably won't get the Landy look, he's got really tall tires and probably custom springs. I'll end up more like this:

 

[TrailerParkGinger]

Well so much for my hopes of a camshaft. Might as well just buy a crosswind intake and a cam for the magnum. Or is there a decent TC for relatively cheap, because I see most people recommend Dynamic Converter and thats more than the whole cam swap

 

[Aaron65]

I'm not sure that slow ramps are as big a cylinder pressure deal breaker as one might think. This is not a 318, but I've had two cams in my 289 Mustang recently, a Comp 252 with 206/206 at .050 and 33* overlap, and an old "Performer" cam with 204/214 at .050, 280/289 (!) rated duration, and 61* rated overlap. Idle vacuum is roughly the same, less than 1 in. difference at best (17-18 in. in neutral at 800-900 rpm). I did a quick cranking compression check on cylinder #1 with both cams (without even pulling all the plugs), and they were both at something like 145-150, with roughly 9:1 compression.

They both idle in gear with a stock convertor at 600-650, and they're both about equally smooth. One has about the slowest ramps ever, the other has much faster ramps.

Of course, this is just one anecdote and one engine.

 

[AJ/FormS]

My 1969 FSM lists 318s at 9.2Scr. As I remember it, the compression height was quite a bit higher for 69 pistons, making the deck clearance quite a bit less than the mid seventies. I seem to remember 69 was the last year for those tall-crown pistons. I could not find specs on deck clearance.
Cranking cylinder pressure is listed at 125 to 155.
So those are the numbers I worked with. Well that, and the OPs statement about it being a pretty good runner. That's not usually a comment to go with a heavy car and 2.94s.

On another note
Since when has it become popular to select a cam based on how it idles? IMHO, that is a really um, um,insert you own adjective here, reason to select a big 276/286/114 slow as molasses ramps, for a teener wanting some more oomph. And how many times this past summer have we not heard guys singing the blues about their ridiculously soggy bottom ends with the 268*,not-even-big-yet cam?
One thing I can tell you for sure, from personal experience; If you put a 340 cam and X-heads onto an otherwise stock,low-C 318, you will find out right away, that this was a mistake. Even with a 340 TC it is doggy. Even with 3.23s and that 340TC it will still be doggy. And if you put it into a heavy car, you will be sick about it. You might say, I just had a doggy engine to start with. And you would be wrong. I still have that engine today and it is now back as a 1973 stock teener, and still with the same rings even. And with 3.55s in my 3650 Barracuda, and with a 2.74 wide-ratio 904 now, and a 2800TC, it's a pretty good ripper with just a TQ and TTIs.
So I gotta preach 2800 and TM, and leave the cam in the box.
Here is the OPs question

So I was wondering how much cam could I get away with and not have a dog of a 318,

The correct answer is any cam with a 50* ICA

Now it's my turn to give up.

 

[toolmanmike]

https://www.summitracing.com/parts/sum-k6900/overview/make/dodge[/URL]

Or, better yet, like this: https://www.summitracing.com/parts/crn-693902/overview/make/dodge

Both of these cams have super slow ramps. Any cam that starts out with duration @.050 and has 280+ advertised is slow slow slow! Correct me if I'm wrong but the lower the @.050 spec and the higher the advertised spec, the slower the lobe.
Those old grinds probably came from Crane, designed way before valve train technology could make them modern.

So it's not just me noticing this? LOL

Your point is???

Well so much for my hopes of a camshaft. Might as well just buy a crosswind intake and a cam for the magnum. Or is there a decent TC for relatively cheap, because I see most people recommend Dynamic Converter and that's more than the whole cam swap

Don't be disappointed. Cam selection is very complicated and as you can see there's lots of choices and opinions. I'll send you a PM. Need a reasonably priced converter? Contact Precision and talk to their tech people. You should almost have your basic engine figured out first so they can get you what you need. Precision of New Hampton | Torque Converters, Transmission

 

[RustyRatRod]

I'm not sure that slow ramps are as big a cylinder pressure deal breaker as one might think.

I've tried preachin it before, but no one listens. Slow lazy ramps are good for an everyday driver. Who wants to beat their valve train to death? Ok. I told myself I wouldn't comment anymore. I am out.

 

[Johnny Dart]

You have already done some upgrades to the motor. I would add some gear, and focus on the 360 magnum.

 

[nm9stheham]

I'm not sure that slow ramps are as big a cylinder pressure deal breaker as one might think. This is not a 318, but I've had two cams in my 289 Mustang recently, a Comp 252 with 206/206 at .050 and 33* overlap, and an old "Performer" cam with 204/214 at .050, 280/289 (!) rated duration, and 61* rated overlap. Idle vacuum is roughly the same, less than 1 in. difference at best (17-18 in. in neutral at 800-900 rpm). I did a quick cranking compression check on cylinder #1 with both cams (without even pulling all the plugs), and they were both at something like 145-150, with roughly 9:1 compression.

They both idle in gear with a stock convertor at 600-650, and they're both about equally smooth. One has about the slowest ramps ever, the other has much faster ramps.

I think your thinking is on the mark; in working up DCR numbers, if the cam ramp is slow like these, I have started subtracting 6 to 10* from the advertised durations to try to compensate for this. BTW, your Performer cam advertised durations are 270/280, and so are not as long as you thought.

Some differences FWIW: you have 9:1 SCR versus the OP's actual 8-ish level; that explains the better cranking compression numbers you are seeing. He is starting closer to 'poor-DCR-land' (for lack of a better word) than that 289.

 

[nm9stheham]

Well so much for my hopes of a camshaft. Might as well just buy a crosswind intake and a cam for the magnum. Or is there a decent TC for relatively cheap, because I see most people recommend Dynamic Converter and thats more than the whole cam swap

Sorry to hear that you have gotten discouraged, OP. I am curious why you don't go with a smaller duration cam like I listed to work with the stock TC, forego the TC change, and still get the benefits of higher valve lift to compliment the increased breathing parts you already have. I had a 351C powered Ranchero with a 192 @.050" duration cam that would beat every stock 440 GTX that I ever came up against....for real..... and with a 3.08 rear gear! The headers and intake a 600 cfm 4 bbl carb like you already have worked with the mild cam; I did have 33 more cubes and 10:1 SCR, but my point is that it is not accurate to equate short duration to low performance.....

 

[forphorty]

Sorry to hear that you have gotten discouraged, OP. I am curious why you don't go with a smaller duration cam like I listed to work with the stock TC, forego the TC change, and still get the benefits of higher valve lift to compliment the increased breathing parts you already have. I had a 351C powered Ranchero with a 192 @.050" duration cam that would beat every stock 440 GTX that I ever came up against....for real..... and with a 3.08 rear gear! The headers and intake a 600 cfm 4 bbl carb like you already have worked with the mild cam; I did have 33 more cubes and 10:1 SCR, but my point is that it is not accurate to equate short duration to low performance.....

That kinda apples and oranges there. Clevelands have awesome heads, 318s have awful heads. Cleveland heads will provide a lot of air even if the valves aren't open long. Plus the Cleveland 1.7 rocker ratio makes big lift with short duration easier.

 

[toolmanmike]

That kinda apples and oranges there. Clevelands have awesome heads, 318s have awful heads. Cleveland heads will provide a lot of air even if the valves aren't open long. Plus the Cleveland 1.7 rocker ratio makes big lift with short duration easier.

Not even a close comparison. Compare a w2 small block to a 307 Chevy!

 

[rumblefish360]

So it's not just me noticing this? LOL

LOL, funny! Yes! I don't blame anybody or bash the idea. But the sneering tude towards small blocks and heaven forbid a 318 or 273 is a bit rude and distasteful. There not all like that, but, most see RB as the only deal unless you do a stroked B.

 

[TrailerParkGinger]

Well I guess I'll buy one of the smaller Duration cams as nm9stgeham suggested and keep an eye out for a good used TC. With the money I save I'll call around to shops and see how much a third member build up would be. On another note, the ESPO springs are awesome! No more saggy droopy springs

 

[TrailerParkGinger]

Sorry to hear that you have gotten discouraged, OP. I am curious why you don't go with a smaller duration cam like I listed to work with the stock TC, forego the TC change, and still get the benefits of higher valve lift to compliment the increased breathing parts you already have. I had a 351C powered Ranchero with a 192 @.050" duration cam that would beat every stock 440 GTX that I ever came up against....for real..... and with a 3.08 rear gear! The headers and intake a 600 cfm 4 bbl carb like you already have worked with the mild cam; I did have 33 more cubes and 10:1 SCR, but my point is that it is not accurate to equate short duration to low performance.....

I didn't mean to disregard your post, I forgot to reply. I'll probably go with a milder cam like you linked, its a fun car now anyway. Even a bit more cam to bring out more potential with the carb and headers would probably put a huge grin on my face. I'll look into a moderately priced converter and start pinching penniee to save for a dr.diff true-trac third member. Then save for my 360 magnum build, really liked the recent build up mopar muscle did and got 455hp and 460lbft

 

[Aaron65]

I think your thinking is on the mark; in working up DCR numbers, if the cam ramp is slow like these, I have started subtracting 6 to 10* from the advertised durations to try to compensate for this. BTW, your Performer cam advertised durations are 270/280, and so are not as long as you thought.

Some differences FWIW: you have 9:1 SCR versus the OP's actual 8-ish level; that explains the better cranking compression numbers you are seeing. He is starting closer to 'poor-DCR-land' (for lack of a better word) than that 289.

I think mine is the "Engine Pro" version, which is basically the Melling MTF-1...anyway, the cam card said 280/289, but they're probably all the same anyway. I think the cheap Summit 204/214 cam and lifters would probably be a good choice for a 318 as well. My 289 is really set up similar to the OP's 318...2.79 gears, stock converter. He's got quite a bit more weight to contend with, so the cam should be just right considering his extra 30 cubes. The Mustang has plenty of power for what it is, up until about 5000 rpm or so. By then, the heads are done anyway. It's certainly got a lot more top end than it did stock, and it's given up nothing down low. I've driven this car 80,000 miles over the last 23 years, so I know it pretty well.