HTL4248AS For my 318?

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frosty_the_punk

frosty_the_punk

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Hey guys, I'm looking for a good solid cam to replace my hydraulic Comp Thumpr.



Specs are as follows
3200lb 67 Valiant. (estimated w/driver)

318+ .030
Forged pistons.
915 j heads 2.02" 1.6" slight bowl blend
10.25:1 comp
3000 stall 904, Transgo TFII
3.7 gears. 25" street tires.


The cam I'm replacing is a hyd cam.



227/241 @ .050". .486"/.473" 102 ICL. 107 LSA. (20 degrees overlap)


new SOLID cam is


242/248 @ .050" .543"/563" 103 ICL. 106 LSA. (33 degrees overlap)

I will be using reco factory 273 adjustable shaft rockers

I've been told that a solid cam will behave like a hyd cam with a .050" spec of approx 10 deg less duration. Is this correct?

If so then these two cams are probably quite comparable in terms of streetability. with the solid cam offering better performance.

Is there any other cams you have experience with and would recommend for my combo?

Thanks, Frosty.
​
 
Lot of cam,for a 318.The 10 @ .050 loosely fits.Hopefully,you have a adjustable valvetrain.Highly recommend the matching springs,possibly the epdm drilled lifters.I would break the cam in,pulling the inner valve springs.Run a high zinc based oil/additive.Looked at the Hughes site for combo,kinda shocked it fit your combo.I like solids,be prepared,to do some tuning to make it driveable.
 
Whats your reason for changing the thumper ? More torque ? More top end ? better idle ?
I'd be looking at something with around 20* @.050" smaller then the hughes piece or about the same specs as the comp.
 
I have almost the same gear and tire size, what is that bad body turning in rpm at 60 mph cruise?
 
That's a lotta cam and a big step up from what you have now. Your going to have a hard time with that small tire. From the performance view, it'll be nice.
Sorry I can not help with the comparo between the cam styles.
 
I know it's a big cam guys. and that's why I want it.

The Comp Thumpr had about 11-12" vacuum at idle and I loved it.

I know these "sound" cams have a reputation for being mild but they're not.

But now I'm chasing more horsepower at the top end and I believe I can get some without sacrificing any more idle vacuum or street manners by going for a comparable *quality* solid grind with lots of lift.

It's no every day driver but it's no drag car either.

I haven't had a tacho in the car but I did the maths and I believe the engine will sing along at 3200RPM at 60mph

So anyone running an aggressive solid in a 318?
 
I had a [email protected] with .520 lift solid in my 318 with 4.30's and 26" tires. My 67 Barracuda weighed 3250 including me. I was OK on the street, but bogged at the strip. It may work for you, but not with those gears. Be sure to change to lock nuts on the adjusters or you will be sorry. Ask me how I know?
 
Cheers Ted. I already have new adjusters with locking nuts. just have to install them.

I might look at the HTL3742AS. It's the smallest solid cam Hughes offer.

237/242 @ .050. 107 LSA, 104 ICL.

Though I feel this may be a step down in effective duration than the Thumpr cam. given that it's sweet spot rpm is listed as 1800-5600RPM

I have concerns about detonation with 10.25:1 and an open chamber head.
 
frosty_the_punk said:
I know it's a big cam guys. and that's why I want it.

The Comp Thumpr had about 11-12" vacuum at idle and I loved it.

I know these "sound" cams have a reputation for being mild but they're not.

But now I'm chasing more horsepower at the top end and I believe I can get some without sacrificing any more idle vacuum or street manners by going for a comparable *quality* solid grind with lots of lift.

It's no every day driver but it's no drag car either.

I haven't had a tacho in the car but I did the maths and I believe the engine will sing along at 3200RPM at 60mph

So anyone running an aggressive solid in a 318?
Click to expand...

No possible way that cam will pull anywhere close to 11" of idle vacuum. I'd bet the HTL3742 won't even pull that much. The 3742 is the biggest I'd even consider with your 318. The 3742 will sound pretty nasty in a 318 and you really need more stall for it but it should give you the top end hp your looking for. JMHO
 
I'm actually expecting the 3742 to be milder than the comp thumpr at idle. We'll see.
 
http://www.moparmusclemagazine.com/..._0312_solid_vs_hydraulic_lifters/viewall.html

This article shows a basic example of how much extra duration and overlap is needed to create the same quality engine switching from hydraulic cam to solid cam.

The hydraulic cam used in this example as a before spec is the 231/237 XE275HL, used in several 400hp 318 buildup articles. and it's generally agreed that it's an appropriate cam for a street/strip 318.

They replaced it with a 239/247 solid cam and got identical idle vacuum and cranking pressure.

I would consider running that exact grind if it wasn't custom. I don't think I could afford to wait the turn around time in a custom cam.

However this test was done with a 440.
 
frosty_the_punk said:
http://www.moparmusclemagazine.com/..._0312_solid_vs_hydraulic_lifters/viewall.html

This article shows a basic example of how much extra duration and overlap is needed to create the same quality engine switching from hydraulic cam to solid cam.

The hydraulic cam used in this example as a before spec is the 231/237 XE275HL, used in several 400hp 318 buildup articles. and it's generally agreed that it's an appropriate cam for a street/strip 318.

They replaced it with a 239/247 solid cam and got identical idle vacuum and cranking pressure.

I would consider running that exact grind if it wasn't custom. I don't think I could afford to wait the turn around time in a custom cam.

However this test was done with a 440.
Click to expand...

Doesn't translate the same way with 120+ cube difference. Trust me a cam that big will be terrible in a 318--terrible. If you do it and don't enjoy the lack of any kind of power until 4500 rpm-I'll say I told ya so. J.Rob
 
Both these cams would run differently in a 318 to a 440. but I don't see why they'd run differently to each other.

care to elaborate on your theory behind this?

Both these cams are rated at 1800-5600 and 2000-6000 respectively, I don't see why either would be still under the cam at 2500 let alone 4500.
 
Don't get sucked in by the cam company RPM range

You really think a cam will have the same RPM range in a 273" as it does in a 416" engine. For a SB consider the range appropriate for a 350" engine.
 
Dont be deterred I say.
My own personal experience is a have a 318, around 11:1 ported j's victor 340 manifold and it has a solid flat tappet with a 304/314 adv 260/[email protected]. Yes it is driven on the street and no its not a dog. The convert flashes to 3400 with 4:11 gears and 27" tyre. Its run a best of of 12.65@111. At the strip its doughy down low and launches slow due to being a charger and they dont like to launch also the combo of cam, convertor and gears.
If i was to recam it something around 240-250 @.050 would suit it.
As it is on the street it pulls hard everywhere even at 3500 all the way to 7500.
Hope this helps
 
crackedback said:
You really think a cam will have the same RPM range in a 273" as it does in a 416"
Click to expand...

I don't remember saying anything about a 273 engine or a 416.

Those rpm ranges are listed for a small block 273-360. the way I see it my motor is slightly above the middle of that range coming in at 323ci

If Hughes made cams for chevy and ford small blocks I would agree that they are all rated assuming 350ci.

Hughes lists all their camshafts for big block, small block and their stroker counterparts. Giving a different description respectively.
 
L4staero said:
Dont be deterred I say.
My own personal experience is a have a 318, around 11:1 ported j's victor 340 manifold and it has a solid flat tappet with a 304/314 adv 260/[email protected]. Yes it is driven on the street and no its not a dog. The convert flashes to 3400 with 4:11 gears and 27" tyre. Its run a best of of 12.65@111. At the strip its doughy down low and launches slow due to being a charger and they dont like to launch also the combo of cam, convertor and gears.
If i was to recam it something around 240-250 @.050 would suit it.
As it is on the street it pulls hard everywhere even at 3500 all the way to 7500.
Hope this helps
Click to expand...

Thanks mate, I sometimes think it takes an Aussie to give the 318 the respect it deserves!

I have a lot less cylinder head than you and run a dual plane manifold. but my gearing and stall would work out to be similar.

My car is also a VC which is a bit lighter than a full body charger with all the bells and whistles.


I'm now looking at Lunati's factory performance replacement cam.


  • Advertised Duration (Int/Exh): 270/270
  • Duration @ .050 (Int/Exh): 243/243
  • Gross Valve Lift (Int/Exh): .548/.548
  • LSA/ICL: 110/104
  • Valve Lash (Int/Exh): .018/.018
  • RPM Range: 2500-6500
Part Number: 30201011
Previous Part Number: 404A1LUN
 
frosty_the_punk said:
Specs are as follows
3200lb 67 Valiant. (estimated w/driver)

318+ .030
Forged pistons.
915 j heads 2.02" 1.6" slight bowl blend
10.25:1 comp
3000 stall 904, Transgo TFII
3.7 gears. 25" street tires.
227/241 @ .050". .486"/.473" 102 ICL. 107 LSA. (20 degrees overlap)
new SOLID cam is
242/248 @ .050" .543"/563" 103 ICL. 106 LSA. (33 degrees overlap)

I've been told that a solid cam will behave like a hyd cam with a .050" spec of approx 10 deg less duration. Is this correct?​

If so then these two cams are probably quite comparable in terms of streetability. with the solid cam offering better performance.​

Is there any other cams you have experience with and would recommend for my combo?​
Click to expand...
​

Your 318 is closer to a 273 - it's the stroke that really affects the "feel" and power curves of a given camshaft. The 3.31 stroke is the same. the 360s is longer and the additional stroke "milds out" the cam's performance a certain amount. That's also why RAMM says a 440 is different. It's a 3.75 stroke, and while yes, so long as the stroke remains the same for both tests the results "should" be a similar result as 3.31 to 3.31 - they won't be. The cam you want is a big cam. The engine you have is not. so as they say - you can do it and expect to "give" in terms of bottom end power and "get" in terms of high rpm power - or you can rethink it. IMO - you cannot compare solid to hydraulic. It's not as easy or cut and dry as the cam company programs make it seem.

Have you had the heads flowed? What are the car's incrementals at the track?
 
moper said:
[/LEFT]

Your 318 is closer to a 273 - it's the stroke that really affects the "feel" and power curves of a given camshaft. The 3.31 stroke is the same. the 360s is longer and the additional stroke "milds out" the cam's performance a certain amount. That's also why RAMM says a 440 is different. It's a 3.75 stroke, and while yes, so long as the stroke remains the same for both tests the results "should" be a similar result as 3.31 to 3.31 - they won't be. The cam you want is a big cam. The engine you have is not. so as they say - you can do it and expect to "give" in terms of bottom end power and "get" in terms of high rpm power - or you can rethink it. IMO - you cannot compare solid to hydraulic. It's not as easy or cut and dry as the cam company programs make it seem.

Have you had the heads flowed? What are the car's incrementals at the track?
Click to expand...

By this logic a 273 and a 340 will feel similar. But a 340 and 360 will not. are you sure about this?

The program I use to simulate cam comparisons may not be perfect but it has a price tag of $469 and a comes with a 287 page manual. so it's probably better than nothing.

I have not had my heads flowed but I' have the numbers in for a set of standard 360 heads that have been flowed with the same valves.

I have no incrementals, I haven't taken my car to the drag strip or put it on a dyno.
 
The cubes it's feeding, along with the stroke, alters the range.

Simulators are only as good as the code and inputs. Some sims have been almost spot on, some off by almost 100hp. Garbage in, garbage out.

Good luck with your build.
 
I have a old version of Desk top Dyno and Drag Dyno.

It a lot of fun to us, and i have learned a lot.

The best knowledge i have learned is that it is a GRATE comparison tool, as lone as you don't take the actual numbers at face value!

I can load a cam in and see the HP and torq curves between a 318 and a 360 and they should be fairly accurate Between the two eng. Just don't be leave that that stock cam you inputted will have 380 foot pound of torque and 400 HP. This will make for a vary disappointing build.
 
Yes I agree the sim programs are indicative only and don't always translate into real world numbers

But they are a good tool for comparing one thing to another. much the same as a dyno, flow bench, vacuum gauge, compression tester etc

My predicted vacuum at idle was way off because it somehow thinks 1500rpm is idle.

But still I can use this to get a good indication of what my baseline idle vacuum is and how aggressive a cam I can go without sacrificing any more.

It seems apparent that I am spoiled for choice in trying to find a cam that will produce better idle and more power output. There's quite a few to choose from.
 
frosty_the_punk said:
By this logic a 273 and a 340 will feel similar. But a 340 and 360 will not. are you sure about this?
Assuming the 340 is hobbled by small ports and no compression, yes. I'm sure of this.


The program I use to simulate cam comparisons may not be perfect but it has a price tag of $469 and a comes with a 287 page manual. so it's probably better than nothing.
So you spent $500 on a sim product (robbery IMO) but never have gotten a race result or had the heads flowed?
I have not had my heads flowed but I' have the numbers in for a set of standard 360 heads that have been flowed with the same valves.
Your numbers are guesses at best, and you said your heads were worked. So the inputs you're using are bogus too.
I have no incrementals, I haven't taken my car to the drag strip or put it on a dyno.
Click to expand...
I get the no racing - I'm 3hrs from any track. But you're spending money on the wrong stuff. Kind of like choosing a restaurant by the landscaping rather than the food. A cam choice should not be for sound - it should be for performance. If you've never had the car on a timed track, or even used one of the G-meters, you have no idea where it makes power, or how much. (Basing this on cars you race, that race on tracks themselves isn't quite accurate either...lol)
So before you go importing another cam, try having YOUR heads flowed, then use THAT info for a choice not based on a video game.
 
I never said i spent $0.01c on a sim product, I just told you the price tag. The internet is my friend. ;-)

I'm basing my cam choice on comparable idle vacuum (street manners) to my current hydraulic camshaft optimising average horsepower estimates/comparisons up to redline by utilising a faster rate of lift.

I am changing to a solid cam purely for the extended RPM range it allows. Not for the sound.

If i wanted sound only I'd leave the Thumpr cam in there.

I had planned to go racing on December 1st for the first time using Hyper pistons and the Thumpr cam.
But the missing ring lands told me "better luck next time"

Seeings I'm going for forged pistons and have to rebuild everything anyhow, I figured a cam upgrade wasn't a bad idea.

While my heads are not standard. they have had the smallest of small amount of work done to blend the bowls.

Yes I could get them flowed. but then bob's flow bench might be happier than Dave's etc

When funds allow, I *WILL* upgrade my cylinder heads whether it be porting them or replacing them with aftermarket set. When it comes to that I will be interested in getting them flowed.

If a 340 and 273 feel the same providing that the 340 has low compression and hobbled by small ports.... Wouldn't that mean my 10.25:1 318 (323ci) with 340 J heads would feel more like a 340 than a 273?

I honestly think it will feel like a 318, call me crazy:burnout:
 
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