Camshaft Selection Information

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1badfish67

1badfish67

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I am working on gathering parts to rebuild a SB 340 (Bored 0.030"). I am not rolling in the dough but am trying to purchase the best parts that I think I can afford. This is for what I hope to be a pretty good (I realize that what I call pretty good is all relative) but in the 400-425 hp range, if possible. RPM Max, probably up around 6000-6200. Not sure on SCR but maybe around 10.5-10.75:1. Car is 4spd with 3.23:1 SureGrip. May change to 3.55:1.

I have purchased a new set of ProMaxx 171 aluminum heads from Jason Collins (Have their published flow chart), PRW stainless roller rocker set from (SwingingDart; Thanks), new RPM AirGap intake (Supposed to be shipped by Edelbrock this month???) and new Holly dual line 770 Street Avenger carb.

Engine not torn down yet to determine piston characteristic(s)/manufacturer, deck height but appear to be aftermarket as seen using a bore scope through plug hole. It has original iron J heads and intake manifold at this time.

Having said all of this, I am trying to gather all required information that is required in order to try to spec a good street-able camshaft. Originally looking at Comp Cams XE274H but not sure. I have been watching some of David Vizards videos mentioning his 128 rule. I know he has some kind of software program or spreadsheet of some kind that may take into account more factors that just valve dia and CID but I can't afford that kind of program for a one time build for a street ride. I noticed he also had different starting number for Ford vs Chevy and SB vs BB in the formulas. He doesn't sound too impressed with just calling into the cam manufacturer or using their cam card specs, but I may have mis-interpreted the dialogue.


What information would you gather prior to calling a cam manufacturer or selecting the camshaft on your own if you didn't know an engine builder with sophisticated software like Vizards'?

Thanks
 
I agree with a solid lifter cam. You already have adjustable rockers. Skip the squishy lifters.

The gears will kill you. 3.73 minimum. 3.90’s would be better. You can’t cripple a 340 with tall gears.

You NEED a minimum of 3500 RPM converter. 4K would be better. Again, you don’t have much stroke. Use RPM to your advantage.

Using Vizard’s 128 formula I get a 109 LSA. That’s too wide IMO. 106 would be as wide as I’d go.

I‘d use a single plane intake if you can find a good one. That’s a Strip Dominator. Or a Victor. They both could use some work but they both work stock.

Skip that Avenger and find a 650 sized Holley clone. That’s all you need with a single plane intake. Any bigger and it will kill all your bottom end. EGT it right and the single plane will beat the dual plane everywhere.

Spend money on GOOD headers. Assuming an A body and power steering you are pretty much stuck with a Doug’s 1.625 header. If you have manual steering and IF a you can find them, Hooker 5204’s are the best middle of the road header.

I would have Howard’s grind a cam with the FM2383719A lobes. That’s 266/266 @.020, 238/238 @ .050, .558 lift on a 106/106.

To make an honest 400 with a 340 takes some RPM. 6500 with decent parts is Stu-paid easy IF you gear and converter it correctly.
 
1MeanA said:
People survived for decades without using software to select cams. Typically they want intended use, engine/displacement, compression, do you want hydraulic/solid/roller,etc, gearing and transmission. You could also look at using one of those DCR calculators if you want to get fancy.
Wallace Racing: Dynamic Compression Ratio Calculator
Click to expand...

And there was a ton of poor running junk out there. Sadly, there still is today because not many bothered to learn anything in 1970’s, 80’s, 90’s, 00’s, teens and now the 20’s.
 
Rat Bastid said:
And there was a ton of poor running junk out there. Sadly, there still is today because not many bothered to learn anything in 1970’s, 80’s, 90’s, 00’s, teens and now the 20’s.
Click to expand...
Yeah from not listening to recommendations and over camming :) Been there, done that.
 
I suggest telling your combo to Oregon Cam Grinders. Get one cut for your engine and the use of your vehicle. A car that is 98% driven on the street and see's the highway on occasion will run a different cam, gear, and converter than an all-out bracket car.
 
I'm not planning on any bracket racing just driving it on the street and when i say street I will drive it out on open road as well but not a daily driver. I have other vehicles for that. The car is a 4spd, so no stall converter.
Rat Bastid said:
I agree with a solid lifter cam. You already have adjustable rockers. Skip the squishy lifters.

The gears will kill you. 3.73 minimum. 3.90’s would be better. You can’t cripple a 340 with tall gears.

You NEED a minimum of 3500 RPM converter. 4K would be better. Again, you don’t have much stroke. Use RPM to your advantage.

Using Vizard’s 128 formula I get a 109 LSA. That’s too wide IMO. 106 would be as wide as I’d go.

I‘d use a single plane intake if you can find a good one. That’s a Strip Dominator. Or a Victor. They both could use some work but they both work stock.

Skip that Avenger and find a 650 sized Holley clone. That’s all you need with a single plane intake. Any bigger and it will kill all your bottom end. EGT it right and the single plane will beat the dual plane everywhere.

Spend money on GOOD headers. Assuming an A body and power steering you are pretty much stuck with a Doug’s 1.625 header. If you have manual steering and IF a you can find them, Hooker 5204’s are the best middle of the road header.

I would have Howard’s grind a cam with the FM2383719A lobes. That’s 266/266 @.020, 238/238 @ .050, .558 lift on a 106/106.

To make an honest 400 with a 340 takes some RPM. 6500 with decent parts is Stu-paid easy IF you gear and converter it correctly.
Click to expand...
Car has 833 4spd no converter worries.
 
Rat Bastid said:
I agree with a solid lifter cam. You already have adjustable rockers. Skip the squishy lifters.

The gears will kill you. 3.73 minimum. 3.90’s would be better. You can’t cripple a 340 with tall gears.

You NEED a minimum of 3500 RPM converter. 4K would be better. Again, you don’t have much stroke. Use RPM to your advantage.

Using Vizard’s 128 formula I get a 109 LSA. That’s too wide IMO. 106 would be as wide as I’d go.

I‘d use a single plane intake if you can find a good one. That’s a Strip Dominator. Or a Victor. They both could use some work but they both work stock.

Skip that Avenger and find a 650 sized Holley clone. That’s all you need with a single plane intake. Any bigger and it will kill all your bottom end. EGT it right and the single plane will beat the dual plane everywhere.

Spend money on GOOD headers. Assuming an A body and power steering you are pretty much stuck with a Doug’s 1.625 header. If you have manual steering and IF a you can find them, Hooker 5204’s are the best middle of the road header.

I would have Howard’s grind a cam with the FM2383719A lobes. That’s 266/266 @.020, 238/238 @ .050, .558 lift on a 106/106.

To make an honest 400 with a 340 takes some RPM. 6500 with decent parts is Stu-paid easy IF you gear and converter it correctly.
Click to expand...
I must have done something wrong on my calc using Vizards 128 eqn. I got 104.6 LSA. Bored 0.30" over I got 344.7 cid total and heads have 2.02" intake valves.
 
1badfish67 said:
I'm not planning on any bracket racing just driving it on the street and when i say street I will drive it out on open road as well but not a daily driver. I have other vehicles for that. The car is a 4spd, so no stall converter.

Car has 833 4spd no converter worries.
Click to expand...

Wait a minute? You want a driver AND 400 HP?? You need to figure out what you want.

400 HP with a isn’t that hard but you ain’t going to do it and make it drivable with a 2500 converter and 3.55 gears.
 
318willrun said:
I suggest telling your combo to Oregon Cam Grinders. Get one cut for your engine and the use of your vehicle. A car that is 98% driven on the street and see's the highway on occasion will run a different cam, gear, and converter than an all-out bracket car.
Click to expand...

How will that make 400 HP?
 
Rat Bastid said:
128-(344.7/8/2.02*.91) is 108.5893

I’ve run it 3 times. And that’s too wide IMO.
Click to expand...
I see it now. The eqn format is in non-standard form as far as algebraic order of operations. The eqn indicates that the 2.02" is multiplied by the 0.91 constant as a denominator itself (2.02*.91), not as 0.91 being multiplied by the resultant of (344.7/8)/2.02.

LSA=128-(((344.7/8)/2.02)*0.91) gives the correct order and the 108.5893 as you point out. I thought 104.... seemed tight when I first saw the formula on one of his you-tube videos earlier today and ran it on this combo. Looks like David is taking the individual cylinder block volume, dividing it by the intake valve size and then multiplying that result by the constant 0.91.

Appreciate you helping me get that straightened out. I haven't seen a video yet where David worked an example using the eqn or could have spotted it earlier. One of his straight line graphs shown in one video indicated the LSA or LCA as I think David used, showed would be around that 108deg mark. Also noticed David offered different starting angle depending on if it was a Ford or Chevy and SB or BB. Didn't see one for Mopar. He indicated the 128 formula was for a SBC with 10.5 SCR.

I'm not sure the combo would make the 400hp. That is just my goal. I had read a Motor Trend article rebuild of a stock 1970 340 (w/X Heads) and upgrading carb, intake, camshaft, valve springs and headers. Didn't these 340's have an advertised SCR of about 10.5:1? They used the Comp XE268H cam(110LSA), RPM AirGap intake, upgraded the valve springs, Edelbrock 800 AFB, 151/48 collector size headers. They didn't mention the tube dia but probably 1-5/8".

They said the combo cranked out 391.6 Hp@5700 rpm and 412 lb*ft of torque @3800 rpm on their dyno. I'm no expert by any means as this if my first Mopar build but I am willing to keep an open mind and learn.

Thanks again
 
1badfish67 said:
I see it now. The eqn format is in non-standard form as far as algebraic order of operations. The eqn indicates that the 2.02" is multiplied by the 0.91 constant as a denominator itself (2.02*.91), not as 0.91 being multiplied by the resultant of (344.7/8)/2.02.

LSA=128-(((344.7/8)/2.02)*0.91) gives the correct order and the 108.5893 as you point out. I thought 104.... seemed tight when I first saw the formula on one of his you-tube videos earlier today and ran it on this combo. Looks like David is taking the individual cylinder block volume, dividing it by the intake valve size and then multiplying that result by the constant 0.91.

Appreciate you helping me get that straightened out. I haven't seen a video yet where David worked an example using the eqn or could have spotted it earlier. One of his straight line graphs shown in one video indicated the LSA or LCA as I think David used, showed would be around that 108deg mark. Also noticed David offered different starting angle depending on if it was a Ford or Chevy and SB or BB. Didn't see one for Mopar. He indicated the 128 formula was for a SBC with 10.5 SCR.

I'm not sure the combo would make the 400hp. That is just my goal. I had read a Motor Trend article rebuild of a stock 1970 340 (w/X Heads) and upgrading carb, intake, camshaft, valve springs and headers. Didn't these 340's have an advertised SCR of about 10.5:1? They used the Comp XE268H cam(110LSA), RPM AirGap intake, upgraded the valve springs, Edelbrock 800 AFB, 151/48 collector size headers. They didn't mention the tube dia but probably 1-5/8".

They said the combo cranked out 391.6 Hp@5700 rpm and 412 lb*ft of torque @3800 rpm on their dyno. I'm no expert by any means as this if my first Mopar build but I am willing to keep an open mind and learn.

Thanks again
Click to expand...

Do you have a link to that build?? I wish they would shoe ore numbers other than the peaks. I’d like to see BSAC, BSFC, total fuel flow and the correction factor for the day, and what correction standard they used.
 
400 is easy out of a 340. Mine is .030 over with 10.2-1, 2.02 J heads with an air gap, Holley 750DP, TTI headers in a 72 duster, with 3 peddles (as a car should have aka 4 speed) to 3.91 gears. My current cam is a Comp XE285HL, which is 241/247 on 110. On the engine dyno, it made 391 at 5800. I will say that this cam is OK above 3000k but with a canyon carver 4 speed is kinda sucks. I have a cam that is every similar to the one he spec out above for ya. My bottom end is staying the same, but heads are changing to Fully ported RPM heads and airgap. Will know so, as the motor is coming out soon
 
Rat Bastid said:
Wait a minute? You want a driver AND 400 HP?? You need to figure out what you want.

400 HP with a isn’t that hard but you ain’t going to do it and make it drivable with a 2500 converter and 3.55 gears.
Click to expand...
To whom it may concern, the OP has a 4spd.
How did you miss that Mr. 4spd. lol :D
 
You're already at the point that you should be calling good camshaft companies and discussing grinds. Scheinder, Jones, Oregon just to name three.
 
1badfish67 said:
Sorry it took a while but I found that Motor Trend article I had read several months ago. Here is the link.

1970 340 High Performance Mill Dyno - Mopar Muscle Magazine
Click to expand...
+36 hp from a carb change sounds questionable. Since it is believed the factory rating of 275 hp was correct does how did they get 275 hp with a crap carb? Does this mean the dyno was 'optimistic'? I would be surprised if cam recommendations aren't in the XE268-XE274 range.
 
1MeanA said:
+36 hp from a carb change sounds questionable. Since it is believed the factory rating of 275 hp was correct does how did they get 275 hp with a crap carb? Does this mean the dyno was 'optimistic'? I would be surprised if cam recommendations aren't in the XE268-XE274 range.
Click to expand...

I’ve never tested it, but I have been told that a well tuned 340 would make 295-300 HP.

That would mean to get to 400 HP you’d need a 33% increase. That’s damned hard to do with bolt on‘s for sure.
 
another stock 340 that only picked up 10 to 13 hp with headers
nobody knows how to tune yada yada
thats a good write up read it moons ago
 
1badfish67 said:
Here is a site I found earlier. It looks to be head flow data from someone named Stan Weiss. Validity of data? They do have a disclaimer on it.

Stan Weiss' - Cylinder Head Flow Data at 28 Inches of Water -- DFW / FLW Flow Files for use with Engine Simulation Software
Click to expand...
That site is compiled data from so many different sources, different benches, & some are corrected/converted from lower delta's which if low enough isn't very accurate at the upper lift values.
The more popular/common heads have enough tests to get a decent "avg." expected input for sim use.
 
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