Selecting Cam, getting that low rpm off-idle response?

Jonas Nordstrom

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I do want to build my new 440 engine with lots of torque down low and that instant response from low rpm idle.
I also want good vacuum (At least 15hg) and a smooth idle.

Cam selection is still a mystery to me so my question is:
- How far from a stock 440 cam can i go and still have the things I wrote above?

Engine specs:
440 block bored .030
Stock stroke crank
Eddy performer intake or CH4B
Single carb (Possibly a Thermoquad.)
~10:1 comp (depends on head)
3:23 gear on Auto car
Stock converter
28" rear tires.

Got no cylinder heads yet. (And the planned Trickflow purchase seems to be overkill for my combo.)
 
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451Mopar

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Performer or Performer RPM intake?
Headers? Exhaust?
Much of the response will be how well it is tuned, ignition timing and transition circuit AFR. I would go EFI, but that is another discussion.
A cam in the mid 220's to mid 230's @ 0.050" duration would be ok for the stock converter, but be a bit small for the compression ratio with low octane fuel, and way too small to take full advantage of the cylinder heads.
If a true 10.5:1 compression ratio, For pump gas, I like cam intake duration @ 0.050" at least 230 duration (around 8:1 or less dynamic compression ratio) to reduce the cranking cylinder pressure.
Don't limit yourself the the $100 stock torque converter. A modern high stall converter can be built to have little slippage at part throttle (but they can get expensive too.)
On trick flows web suite, the 440 with the 240 heads, their 240'ish @ 0.050" roller cam, and intake makes 620 HP.
It might not have 15" vacuum? but might be Ok depending on idle speed, ignition timing, and altitude. Idle speed likely around 850-900 RPM?
 

Jonas Nordstrom

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Performer or Performer RPM intake?
Headers? Exhaust?
Much of the response will be how well it is tuned, ignition timing and transition circuit AFR. I would go EFI, but that is another discussion.
A cam in the mid 220's to mid 230's @ 0.050" duration would be ok for the stock converter, but be a bit small for the compression ratio with low octane fuel, and way too small to take full advantage of the cylinder heads.
If a true 10.5:1 compression ratio, For pump gas, I like cam intake duration @ 0.050" at least 230 duration (around 8:1 or less dynamic compression ratio) to reduce the cranking cylinder pressure.
Don't limit yourself the the $100 stock torque converter. A modern high stall converter can be built to have little slippage at part throttle (but they can get expensive too.)
On trick flows web suite, the 440 with the 240 heads, their 240'ish @ 0.050" roller cam, and intake makes 620 HP.
It might not have 15" vacuum? but might be Ok depending on idle speed, ignition timing, and altitude. Idle speed likely around 850-900 RPM?
Performer intake
Headers and 2.5 exhaust system
It will be a flat tappet cam

Getting a new converter would be no problem but if higher stall Im worried that it would answer too late? (Though I have no experience with a high stall built with smaller slippage at part throttle.)
 

Geoff 2

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A cam in the mid 230s isn't going to idle smooth, will not make 15" of vac & will NOT like working with a stock c'ter. I had a custom ground Crower HFT cam in my 440. 232/232* @ 050; 108 LSA. Stock 727 & c'ter. It was an absolute pig, idled rough, was slower over the 1/4 in my 3800 lb Dart, 3.23 diff than the mild Crane cam I had in before. It came out after two weeks.....


For tq, the Performer with it's smaller runners would be best, especially with 3.23 gears.
I assume you want to use a hyd flat tappet cam, not roller.
If it was my car, I would get a custom ground cam from Bullet or Comp Cams. Not that expensive.
Using the the 128 rule, you would have it ground on 106 LSA. Duration at 050 would be 205-210*, intake & exhaust. Duration might seem low, but the LSA is tight which increases overlap. Very easy to over-cam it...& end up with a dog.


A word of caution from David Vizard from his BB Chev book, & hence my recommendation: 'If maximizing HP & Tq are the goal, spreading the LSA to improve the idle & low speed drivability is a veeeeeeeeeeery counter productive move. The correct answer here is not to spread the LSA but to go for less duration'.
 

Jonas Nordstrom

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A cam in the mid 230s isn't going to idle smooth, will not make 15" of vac & will NOT like working with a stock c'ter. I had a custom ground Crower HFT cam in my 440. 232/232* @ 050; 108 LSA. Stock 727 & c'ter. It was an absolute pig, idled rough, was slower over the 1/4 in my 3800 lb Dart, 3.23 diff than the mild Crane cam I had in before. It came out after two weeks.....


For tq, the Performer with it's smaller runners would be best, especially with 3.23 gears.
I assume you want to use a hyd flat tappet cam, not roller.
If it was my car, I would get a custom ground cam from Bullet or Comp Cams. Not that expensive.
Using the the 128 rule, you would have it ground on 106 LSA. Duration at 050 would be 205-210*, intake & exhaust. Duration might seem low, but the LSA is tight which increases overlap. Very easy to over-cam it...& end up with a dog.


A word of caution from David Vizard from his BB Chev book, & hence my recommendation: 'If maximizing HP & Tq are the goal, spreading the LSA to improve the idle & low speed drivability is a veeeeeeeeeeery counter productive move. The correct answer here is not to spread the LSA but to go for less duration'.
Yes, hyd flat tappet.

Interesting, yeah I dont want a dog and its not so important if the top end is 500 horses or 600.
The important thing is that it launches hard from 650rpm on 3.23 gears.
 

451Mopar

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The '71 Charger (around 700 HP?) has a custom built 9" converter from Ultimate converter, and in normal driving on the street and highway it seems as tight as a stock converter, but at WOT from a stop it will flash stall to 5,000 RPM. The not so great part was it cost a bit over $1,000.
I think most of the good converters with anti-balloon plates are going to cost at least $600+?
 

451Mopar

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A cam in the mid 230s isn't going to idle smooth, will not make 15" of vac & will NOT like working with a stock c'ter. I had a custom ground Crower HFT cam in my 440. 232/232* @ 050; 108 LSA. Stock 727 & c'ter. It was an absolute pig, idled rough, was slower over the 1/4 in my 3800 lb Dart, 3.23 diff than the mild Crane cam I had in before. It came out after two weeks.....


For tq, the Performer with it's smaller runners would be best, especially with 3.23 gears.
I assume you want to use a hyd flat tappet cam, not roller.
If it was my car, I would get a custom ground cam from Bullet or Comp Cams. Not that expensive.
Using the the 128 rule, you would have it ground on 106 LSA. Duration at 050 would be 205-210*, intake & exhaust. Duration might seem low, but the LSA is tight which increases overlap. Very easy to over-cam it...& end up with a dog.


A word of caution from David Vizard from his BB Chev book, & hence my recommendation: 'If maximizing HP & Tq are the goal, spreading the LSA to improve the idle & low speed drivability is a veeeeeeeeeeery counter productive move. The correct answer here is not to spread the LSA but to go for less duration'.

I think a cam like that would build too much cylinder pressure for pump gas when he has 10.5:1 static compression ratio, but it would be fun to try it.
 

Jonas Nordstrom

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I think a cam like that would build too much cylinder pressure for pump gas when he has 10.5:1 static compression ratio, but it would be fun to try it.
Engine is not assembled yet so lowering the compression a bit is possible.
Gas is 98 with oct booster added. (Dunno though how long that will stay around in these times.)
 

Geoff 2

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There are two golden rules of cam selection:

Rule 1: it is very easy to select a cam that is too big
Rule 2: Read rule 1 until the message sinks in...
 

Jonas Nordstrom

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There are two golden rules of cam selection:

Rule 1: it is very easy to select a cam that is too big
Rule 2: Read rule 1 until the message sinks in...
Def dont want a too big of a cam.

Though can I go "Too big" on the heads too?
Like 451 mopar said: too small to take full advantage of the heads.

So would I loose signal with a too small cam for heads combo?
 

451Mopar

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You have really good cylinder head for such a mild engine :)
I mentioned EFI because it has gotten alot more affordable, and pump gas around here has gotten way worse.
Very easy to get vapor lock on todays pump gas when used in the old factory low pressure fuel system (and 6,000+ ft altitude here in Colorado), and the fuel formulations change by season and regulation so a tune that was good in the spring might not be so good in the fall, and different stations/locations may have different amount of alcohol add to the fuel mixture.
Having full control of ignition timing makes getting a good idle speed and higher vacuum because you can add a bunch of advance at idle/high vacuum (after a lower cranking ignition timing), and then pull it out when manifold pressure drops under low rpm load, then have it ramp back in with RPM.

Some say that they can run pump gas with 200 psi cranking cylinder pressure? I never tried to, I think the margin for error would be pretty slim?
Pump gas, I usually look for 160 PSI or less. Hopefully others who do this more than me will comment with their examples?
I would look for a "D"-dish (about 19cc with the 78cc heads) piston to get about 9.5:1 compression, but retain a close quench chamber of 0.035"-0.040".
Problem is finding the correct piston. A quick check on Summit Racing shows the JE Piston 232456 could work, 18.1 cc dish, but it uses the 0.990" GM pin size, so the rods would need to be modified or replaced, The piston set is also $1,124 ! I would think you could custom order something like this with the larger stock size pin bore?
DODGE JE Pistons / Race Winning Brands 232456 JE Pistons 440 Inverted Dome Top Pistons | Summit Racing
 

451Mopar

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Def dont want a too big of a cam.

Though can I go "Too big" on the heads too?
Like 451 mopar said: too small to take full advantage of the heads.

So would I loose signal with a too small cam for heads combo?

With the stock intake port window (gasket) the heads won't be too big for a 440" engine.
I like smaller cams in engine with good heads for a street car.
The reason I mentioned 230 duration was to bleed off some pressure because the static compression of 10.5:1 and pump gas.
 

Jonas Nordstrom

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With the stock intake port window (gasket) the heads won't be too big for a 440" engine.
I like smaller cams in engine with good heads for a street car.
The reason I mentioned 230 duration was to bleed off some pressure because the static compression of 10.5:1 and pump gas.
Thanks, Glad I asked here first. I was just to tell my buddy to get me a pair of trickflow heads, though maybe I have to consider different heads?

I already have the block and full rotating assembly: crank, flat top pistons, rods etc.

But yeah, I want this engine to live for a long time, no overheating problems etc, so I am all for lowering the compression if it would fit the combo better.
 

66Satellite47

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No matter what cam you select, the torque convertor is the key. A top quality convertor makes the car. Get one from one of the top brands.
 

Jonas Nordstrom

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Have you called the comp cam tech line and discussed with them yet? What did they recommend?
Thats an idea. Though will look for recommendations here first and in my country before starting with overseas calls.
 

69a100

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There are two golden rules of cam selection:

Rule 1: it is very easy to select a cam that is too big
Rule 2: Read rule 1 until the message sinks in...
Rule 3: If you're on the fence between 2 different cams, choose the smaller of the 2. You'll be much happier!


Have you called the comp cam tech line and discussed with them yet? What did they recommend?
This is the worst advice anybody can give on the I-net!!! All you have to is read about all the problems people have had with Comp.!
Stay far, FAR away from this company, they know Squat about Mopar cams, even less about the quality of their products!
 

1967coronet

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One important part of your off idle response is your distributor .
Many times it is over looked but has as much effect as cam / carb selection.
myself I would point you to a thermoquad carb , a good fast curve in the distributor.
You want everything to hit at once , carb off idle response, a good tourqe style RV cam,
Going by your post of 650 rpm mash the gas.
Heck a good curve and thermoquad or any carb. tuned right is as important as the cam.
Tons of good advice on here, these guys will steer you right.
 

SRT_Blubyu

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Stop the fun suckers
Rule 3: If you're on the fence between 2 different cams, choose the smaller of the 2. You'll be much happier!



This is the worst advice anybody can give on the I-net!!! All you have to is read about all the problems people have had with Comp.!
Stay far, FAR away from this company, they know Squat about Mopar cams, even less about the quality of their products!
Interesting.. didnt know. hve had good luck with them in the times do change.. whos the go-to these days then?
 
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