No, it’s a Racer Brown cam.
Torque = Driveability ? (Engine Masters LSA shootout)
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No, it’s a Racer Brown cam.
mgoblue9798
Well-Known Member
A lot of us have overcammed engines in the past. Especially bad were the low compression small block large duration cam combos.
Compression ratio, converter, and gears all play a big part in addition to the cam. Get them mismatched and it will be a turd.
I think this is the place that most are coming from with the warnings about streetability of a large duration cam.
Does that really "kill" bottom end torque, sure CAN make it less than other combinations with same displacement. Plus HP percentage of torque down low is 19-57% so you need fairly big changes to make decent change to low speed hp, plus how long do you really spend at full throttle under 3,000 rpms.
Question is, is poor drivability from a lack of low speed torque ?
If so it is what's acceptable torque ?
As an example this discussion comes mainly along when discussing 318 hop ups to a stock running 318 with stock stall and gearing.
I bet most would say a stock 2bbl 360 would be an improvement over a stock or even mildly modified low cr 318, true ? A stock 2bbl 360 makes around 330 lbs-ft between 2,000-3,000 rpms, 340 lbs-ft peak around 3,000 rpm and 225 hp peak at 4,500 rpm. Obviously not power house but ok performance and definitely very high driveability, But those torque numbers around those rpms are very doable with a modified 318, even higher, so how can a lot people say driveability will be poor even though has similar torque numbers as a stock 360 ?
And say you do a large cam low cr 440 which will make more torque than a low cr 360 so is it impossible for a 440 have poor driveability ?
What about a /6 ? It makes terrible torque but has excellent driveability, how IF low speed torque = driveability ?
Here's a low cr 318 Base is 2bbl with headers, mod 2 adds 4bbl & spacer, xe262h cam which a lot would say xe262h is too much cam for a low cr 318.
3-8-Teen Dream
318 Long Block Bolt Ons - Tech Articles - Mopar Muscle Magazine
Here's a low cr 360 bottom blue lines stock 2bbls and manifolds.
I bet most would say a stock 2bbl 360 would be an improvement over a stock or even mildly modified low cr 318, true ? A stock 2bbl 360 makes around 330 lbs-ft between 2,000-3,000 rpms, 340 lbs-ft peak around 3,000 rpm and 225 hp peak at 4,500 rpm. Obviously not power house but ok performance and definitely very high driveability, But those torque numbers around those rpms are very doable with a modified 318, even higher, so how can a lot people say driveability will be poor even though has similar torque numbers as a stock 360 ?
And say you do a large cam low cr 440 which will make more torque than a low cr 360 so is it impossible for a 440 have poor driveability ?
What about a /6 ? It makes terrible torque but has excellent driveability, how IF low speed torque = driveability ?
Here's a low cr 318 Base is 2bbl with headers, mod 2 adds 4bbl & spacer, xe262h cam which a lot would say xe262h is too much cam for a low cr 318.
3-8-Teen Dream
| TORQUE SUPERFLOW 901 DYNO-TESTED AT WESTECH | |||
| RPM | BASE | MOD 1 | MOD 2 |
| 2,000 | 292 | ||
| 2,500 | 287 | ||
| 3,000 | 287 | 338 | 336 |
| 3,500 | 272 | 335 | 340 |
| 4,000 | 248 | 326 | 330 |
| 4500 | 218 | 309 | 319 |
| 5,000 | 188 | 285 | 296 |
| 5,500 | 250 | 258 |
| HORSEPOWER SUPERFLOW 901 DYNO-TESTED AT WESTECH | |||
| RPM | BASE | MOD 1 | MOD 2 |
| 2,000 | 112 | ||
| 2,500 | 137 | ||
| 3,000 | 164 | 193 | 192 |
| 3,500 | 182 | 224 | 227 |
| 4,000 | 189 | 248 | 252 |
| 4,500 | 186 | 265 | 274 |
| 5,000 | 179 | 271 | 282 |
| 5,500 | 262 | 270 |
Here's a low cr 360 bottom blue lines stock 2bbls and manifolds.
mgoblue9798
Well-Known Member
Can too large a cam kill bottom end torque in a poorly matched combo? I say yes. Depends on your definition of "kill" I guess.
Drivability and acceptable torque are subjective with no definitive answer that I can tell. I don't think it is too hard to recognize a mismatched combo though.
Drivability and acceptable torque are subjective with no definitive answer that I can tell. I don't think it is too hard to recognize a mismatched combo though.
Economically, the 208/214 hydraulic cam on 112 lsa .425/.435 from Delta Cams Wa. with 9.0:1 and 318 heads is a good combination. My previous truck had 204/214 with 360 heads and the same short block with less torque.
The current set up (318/208 cam) pulls a Power-Wagon 75mph at 1/3 throttle with an 800 cfm Rochester on an oem 4bbl manifold. "If" your looking to build what you already have. Spread bore carburation is the key to a good short stroke 4bbl set up.
For a similar investment, 360 with 9.0:1 (H405CP) 360 heads and the 211/218 .410/.425 Chrysler cam (4452757) on 110 is a great set up too. Both are easily built for 2k or less. My son runs the 360 combo in a 72 dart with a 2.94:1 axle and it will fry the tires relentlessly! The 345 casting 360 head from the eighties work well, have induction hardened valve seats, and they're cheap. Oem 340 valve springs are fine.
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That's all cool and all but doesn't answer the point of the thread.
Does a lack of low speed torque = less driveability ?
A lot of people seem to think so, obviously if you got a 2,000 stall and one engine makes say 50 lbs-ft less between 2,000-3,000 rpm it's not gonna be as strong there at full throttle (guess some would say turd ?) but that's an performance issue. But driveability ? (part throttle).
Koolie Kewl
Addressing the low speed drivability of a poor combination (?). For example, one combination that gave me grief was a 340 with 2 valve relief pistons,2.02 heads, Erson TQ 30 hydraulic cam, LD 340 intake with afb, 3.42:1 axle with 275/60/15 and 833 transmission. It struggled to roll over a hot marshmallow without double clutching off the light. Swapped out the Erson (pos) for an Isky 280 mega cam and Rhodes lifters then added a spead-bore Holley. Good drivability and shifted a 6700 when applicable.
Since then, solid flat tappet on the street has been the answer to rpm's and drivability with reasonable axle ratio, say 3.55:1. The 238/238 sft cam works well in the low compression (9.0:1) 360 for the street use on a 108lsa, and its good to 6k+. Surely AJ can address the engineering behind poor drivability better than I.
Compression, or lack there of is the issue (I assume). Currently I run 11:1 in my 360 with a 242/242 sft on 110 with Iron heads in my A body. It starts as easily as my Power-Wagon and drives fine off the light with a 4spd.
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Is it from a lack of torque or probably Overlap ? aka engine don't like to run at lower rpms.
Cause I bet any those cams are making reasonable low end torque.
I used to have a Suzuki Samurai I don't even think the engine was a 1L
under powered (low torque maybe 75 lbs-ft @ peak) yes, poor streetability no.He's the one responsible for my journey about low speed torque and it's effects
Aka I question his assumptions.
9secRR
Well-Known Member
Yes to large of a cam can definitely kill the performance. Look at all these TrickFlow and SM headed engines with these huge *** rollers in the 650-700 lift range barely running 10’s. Put a 600-630 lift cam in and the combo will be happy and actually perform.
BSB67
Well-Known Member
I’ve lost track, are we talking about a 318 pulling a horse trailer up a mountain pass in high gear at 1500 rpm, or a race car in the 9’s.
FWIW, my minivan is very very drivable at 1500 rpm.
FWIW, my minivan is very very drivable at 1500 rpm.
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neither
M_Body_Coupe
Well-Known Member
"streetability" to me means: tap the throttle, feel the response!
That requires a well functioning intake port setup: starting at the carburetor, all the way through to the intake valve close event, and it being supported by the remaining factors such as ignition, gearing, etc.
Here is another way of looking at it: when a smaller displacement engine (and therefore more likely producing less torque at a particular RPM) has a better throttle response, I would bet the conclusion is that is it more streetable.
That requires a well functioning intake port setup: starting at the carburetor, all the way through to the intake valve close event, and it being supported by the remaining factors such as ignition, gearing, etc.
Here is another way of looking at it: when a smaller displacement engine (and therefore more likely producing less torque at a particular RPM) has a better throttle response, I would bet the conclusion is that is it more streetable.
That is a factor, more of a performance aspect than a functional one, How much of a role does low speed torque play ?
I far as I can find a 4bbl 273 has about 250 lbs-ft @ 2,500 rpms a stock 2bbl 318 about 280 lbs-ft @ 2,500 rpm a 2bbl 360 335 lbs-ft @ 2,500 rpm and a well put together almost peak 500 lbs-ft stock stroke 360/371 make 402 lbs-ft @ 2,500 rpm.
So stock stroke sbm can make 250-400 lbs-ft at 2,500 rpm where's the line between driveability and function being less than desirable with down low torque ?
Obviously more torque more power but is the 500+ hp 371 more streetable than the rest cause it makes most torque @ 2,500 rpms ? what about a 477 hp 323 than makes 355 lbs-ft @ 2,500 rpm ?
So torque wouldn't be the biggest factor, which is what I'm seeing.
I made this mistake.
2008, I rebuilt a 360 without knowing or carefully selecting the proper pistons. I wanted to build a budget version of the MP crate 360/380.
I just didn't think things through. I used a set of basic hypereutectic pistons that probably resulted in low 8 to 1 compression, stock unported 360 truck heads and the MP 292/508 cam. It went into this car:
Yeah, it was gutless. My standard bore 360 in another car was faster by a long shot. Long duration cam that needed rpm to perform and crappy heads that were worthless past 4500 rpms.
M_Body_Coupe
Well-Known Member
I think torque/hp is/are nothing more than a static measurement. Meanwhile, "streetability" is a more wholisitc concept where that torque/hp static quantity is just an input element.
Make no mistake, this is probably one of the biggest components, but by no means the only deciding factor.
For example, my daily driver is a 2020 Subaru STI, so that's a 310hp 2.5L boxer turbo...granted it's mated to a close ratio 6 speed manual, but I'll tell ya, that thing is a LOT more driveable as compared to my 408 (6.7L) W2 stroker (about 450-500 hp? and a whole LOT more torque for sure) build which is mated to a 727 with a 4K stall converter and 4.10 gearing out back. Certainly more streetable.
OK, so with this last example I'm really deviating from the focus of the thread's discussion, but to me at least the whole combo has to be right, it has to be matched.
True, your engine only makes the HP that's required to do the task at hand which ain't much during normal driving, which is way less than any of these engines make which is another reason I find this low speed torque effects driveability false all these engines make an abundance of power to normally drive your car.
To me the core of a car being called streetable is it reasonably functional during normal driving? Could you throw your keys to anyone, your granny (especially a non car person) and they could go out and do their daily errands with no special instructions or training and it does everything they want reasonably well or at least as well as any stock A Body.
Obviously if car don't fit this description doesn't make it not a street car but to me the further away from the former the more it becomes a car that's just able to be driven on the streets.
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