340 cam in a 318

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OldmanRick said:
I was really serious Dan! Keep asking any questions you want. They make us all think, and that's a good thing...:thumbsup:
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K. Thanks. I will. I've heard a lot about those thermoquad carburetors, does edelbrock or Holley have a version of their own
 
Dan the man said:
K. Thanks. I will. I've heard a lot about those thermoquad carburetors, does edelbrock or Holley have a version of their own
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Demon. Actually called the Street Demon. Doesn't have two separate large secondary throttle plates. Has one almost as large one called a "goggle valve". Has the same step up piston/metering rod design as an AFB/Edelbrock. Give me a real TQ any day.
 
I have used a 340 auto cam in at least 6 or 7 318s from 1968-1974. 1 with a 2 bbl and rest with a 4 bbl. I with a 650 Holley double pumper. 1 with an AFB. Rest with a Thermoquad. I ran by 2.76, 3.33, 3.55, 3.91 and 4.10s. Kim
 
oldkimmer said:
I have used a 340 auto cam in at least 6 or 7 318s from 1968-1974. 1 with a 2 bbl and rest with a 4 bbl. I with a 650 Holley double pumper. 1 with an AFB. Rest with a Thermoquad. I ran by 2.76, 3.33, 3.55, 3.91 and 4.10s. Kim
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Which one of those was your favorite one?
 
oldkimmer said:
I have used a 340 auto cam in at least 6 or 7 318s from 1968-1974. 1 with a 2 bbl and rest with a 4 bbl. I with a 650 Holley double pumper. 1 with an AFB. Rest with a Thermoquad. I ran by 2.76, 3.33, 3.55, 3.91 and 4.10s. Kim
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Wow Kim, that's getting it going on!
 
Dan the man said:
I have a question about putting a 340 cam in a 318. From what I've found out, the 340 cam has a ivc point of 69* and this brings down the dcr to like 6.63:1 ( 18 psi lower cylinder pressure than a stock 318 cam ). Wouldn't this hurt performance rather than help? I based this on a 1973 318 with a 8.6:1 cr. Did I figure something wrong or have the wrong information?
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Dan, as soon as you come here and talk about a 340 cam in a 318, every man and his dog is going to comment how legendary it is. LOL
Now, as I can see, your interested in the way DCR changes with cam timing, and it's effect on performance, not just asking about how a 340 cam goes in a 318.
If you want to know how all this effects engine performance, then I suggest you download Engine Analyzer from Performance Trends. From memory you can use it for 10 days before you need to register it. If you have a spare computer, put it on that and when the trial period ends, just re-format your hard drive, load up your Windows operating system (XP would be fastest) and reload Engine Analyzer.
Get some generic head flow numbers, a bunch of cam specs and spend a weekend playing with it.
You will learn more from that then a 1000 questions here.
 
These were in the late 70s and into the mid 80s. Then I graduated to the 340s. I could buy the Street Hemi grind cam for $37.50 back then. Kim
 
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oldkimmer said:
These were in the late 70s and into the mid 80s. Then I graduated to the 340s. I could buy the Street Hemi grind cam for $37.50 back then. Kim
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Man, that's Cool as Can be! First Street Hemi grind was for my 383, in 90. Think it was 129then, the MP Electronic IGN conversion kit was, maybe 150? Flowmaster were 40 bucks, MP rod bolts 20$.....
 
Dan the man said:
I have a question about putting a 340 cam in a 318. From what I've found out, the 340 cam has a ivc point of 69* and this brings down the dcr to like 6.63:1 ( 18 psi lower cylinder pressure than a stock 318 cam ). Wouldn't this hurt performance rather than help? I based this on a 1973 318 with a 8.6:1 cr. Did I figure something wrong or have the wrong information?
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Did I figure something wrong or have the wrong information
Yes and no.
The 318 won't make 8.6Scr with the stock heads, and
You are 100% correct that the Later Ica of 69* compared to 48* of the stocker, is gonna drop a ton of cranking pressure.
As compared to the stock cam;
this is gonna KILL low rpm power.
Then the power will increase due to the " better breathing" with the later Valve events, but still be down because of the reduced pressure.
Eventually the reduced pressure will be offset by the greater cylinder filling.
and at high rpm the power will be considerably stronger as the engine comes up on the cam.
Except;
With 318 heads still on it, it will never really wake up.
This leaves you with a wheezing , gasping POS engine, that suddenly comes alive and just as suddenly hits the wall.
If you've been paying attention to the guys; they are, for the most part, telling you to install a higher stall convertor and something like 3.91/4.10s. The higher stall will overcome the low pressure, and the gears will overcome the laziness. But you are still stuck at the top when the heads choke.
So what you started with was; a reasonably peppy combo that is well able to rev and pull from the factory stall near 2000 up to at least 5000, with ANY gear over 2.76s
But with the 340 cam, firstly you have the added expenses of the TC and gears, and then your powerband is from 3000 to say..... still 5000, cuz of the heads.
But consider that ;
With the 318cam and say 3.23s, your shift points for 5000 are 52/88/127, and
65=2614 at zeroslip say 2700 at 3%
With the 340 cam and 3.91s, your 5000 rpm shift points are 42/71/103, and
65=3165 at zeroslip, say 3260 at 3%
But also consider what happens at the various speeds at which you will be cruising at. I'm gonna give all speeds at zeroslip.For instance,
take 32 mph.
With 3.23s, I get; 3150/1870/1290 And you wonder why the 318car is a dog?
With 3.91s, I get; 3820/2260/1558 Ok now show me why you would chose a low-dcr 340 cam at these rpms. It's pure madness.
Lets move to 50mph, another common roadspeed.
With 3.23s I get 4930/2920/2010
With 3.91s I get 5964/3530/2430
So you will have to be in second at 50 with either of these gears. Obviously now, the 3.91s have the edge in second gear. But with the 340 cam, the engine is just waking up, whereas the 318 cam is right in it's sweetspot.
The point that I am trying to make is don't neglect the importance of gearing and stall.
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As for me; I have at least 4 maybe five low mileage 340 cams on the shelf here, And I'd have to be pretty desperate to install one in any low-compression engine.
About swapping stock parts around;
My favorite odd-ball combo was a hi-compression 340 short with a complete 69 318 top end on it including the 2bbl cam. With nothing more than fenderwell headers and 2" duals. In a 65 V100 wagon, that was a pretty good ripper.
If I only had a low-compression 318LA;
and mechanically it was A-OK, then;
I would do NOTHING to the Long block except;
install some good valve springs to allow at least 5200 rpm, and
the 273 valve gear. , and
any old 4bbl set-up,
plus headers and I would hang
the biggest dual exhaust I could find in front of the mufflers.
And that is all.
I would run whatever gear gets me into the powerband at the roadspeed I spend most of my time at. If I would run an automatic, I would install at least a 2800TC, and this car would be a citycar. But more likely is that I would run a manual trans with a minimum 4 gears, because this makes it way easier to select a rear gear.

What I mean is this; I spend a lot of time at 30/35 mph. So that is where I want to motor from. With a 4bbl 318 and a 904 I'm gonna need the rpm to be about 3500rpm on the 2-1 downshift. So that will take 3.23s for 32=3470 at 10% And 65=2700
but with a Commando 4 spd (3.09low), I would need 2.94s for 32=3620 and 65=2380
Both combos will hit about 45@5200.
Obviously the manual trans combo is more suited to hiway use.
The Low-compression318 does pretty good with the Very-wide ratio A833od. With this trans you can run up to 3.91s but after that the starter gear gets to be a wee-bit low.
I have first-hand experience with ALL of these combos.
I have had two low-compression 318s pumping 135psi with 2bbl cams, that after the 340 cam went in, and with a stock stall TC, they were bar none the doggiest POS engines I ever drove.......... until the rpm got up. They had pretty good passing gears tho,lol. It took 4.10s and 2800s to wake them up. One of them got 340 heads.

Knowing what I know now after all these year; if I had to be content with a 318LA,
the first thing I would do is strip it down and throw those 8/1 pistons away and
the second thing would be to toss the heads and
the third thing would be to install a custom solid lifter cam/kit.
Oh wait, is it still a 318 lol.
 
I have seen 2 different 318 NHRA stock class cars go 11.70’s with a stock 2 barrel carb.
 
Dan,
[1] Forget about DCR with a hyd cam. It changes as the lifters bleed down. See how many have used DCR to ' design' a cam that will not ping...& got pinking anyway.
[2] Sure, a 340 cam will give more top end power. But it could reduce low end power. The 318...being only 318 cubes.......is not over endowed with low end tq......unless you use nitrous, blower, etc. So the answer is choose wisely & decide beforehand what if anything you are willing to forego, such as idle quality etc.
[3] I would NOT use a factory a factory cam. They are usually dual pattern to work with a restrictive factory exh system. They also have wide LSA [ no good ] to comply with emission requirements, noise etc.
[4] The cam I would use that you should give the butt meter a real kick in the butt, & retain all of it's street manners, is the Isky 262 Supercam.
 
[QUOTE="Bewy, post: 1973868920, member: The cam I would use that you should give the butt meter a real kick in the butt, & retain all of it's street manners, is the Isky 262 Supercam.[/QUOTE]
Is Isky still around?
 
LOL... Isky, yesterdays cams at today's prices.
That 262 is pretty expensive for a brown box RV cam.
 
I feel like you have asked this question before (possibly multiple times - hard to keep track), there are better cams for what you want to do.
 
Dan the man said:
I have a question about putting a 340 cam in a 318. From what I've found out, the 340 cam has a ivc point of 69* and this brings down the dcr to like 6.63:1 ( 18 psi lower cylinder pressure than a stock 318 cam ). Wouldn't this hurt performance rather than help? I based this on a 1973 318 with a 8.6:1 cr. Did I figure something wrong or have the wrong information?
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I used to do it all the time. But, I also added milled 360 heads, TQ, intake, dual exhaust, changed the curve in the distributor, added a windage tray, high pressure oil pump spring, and upped the pressure in the trans. For some reason they'd run like a 72-73 340... There are better cams today, I usually run a custom Racer Brown solid cam. Nothing wrong with Isky cams. Never had a problem with one. Call a cam company, be honest with yourself, and give them "all" the info on your car and engine. It is what they do. We didn't play with programs, we just put different combinations together and ran them. Building a 318 using all the good 340 stuff was a no brainer, the outcome was known.
 
Bewy said:
Maybe they are expensive because they don't fail....
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Maybe they are made of gold?
Maybe this , Maybe that.. I try to deal in absolutes, not maybe's..
When it comes to small duration, low lift RV cams. Isky is getting it's cores from the same suppliers as everyone else.
 
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Formula's, mathematics, can't because of..... shouldn't because of.... you'll be sorry on top of.....

wouldn't trade any calculations for first hand experience. some of us that have DONE it have testified. jury is in favor :)
 
318willrun said:
Formula's, mathematics, can't because of..... shouldn't because of.... you'll be sorry on top of.....

wouldn't trade any calculations for first hand experience. some of us that have DONE it have testified. jury is in favor :)
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You know how many times I've got into it with a Truss Engineer or Architect, even a GC or Foreman. Real World experience is the Real Deal. Theory is great, but does it always work?
 
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