You gotta shake your head sometimes when we start discussing “sound” and cam selection. There are some here who can’t accept or choose to mock (it seems) some people that are driven or turned on (for lack of a better term) by what their engine sounds like. Why is that? You like the looks of something, you like the smell, the taste you get the point. So I’m not getting why when it comes to the sound of a cam it’s such a contentious thing for some. If the car is an also ran, average or so-so then it means it must not have any radical lope, chop etc. In order to have those attributes it must perform, period? How is that determined? Is there a chart for required performance as the idle sound gets more radical? Absolute Bullshit. Talk about beating a dead horse!
Thumper
- Thread starter Wyrmrider
- Start date
-
I run that Lunati in my wife’s Challenger.
I liked the lift, the faster opening rate, shorter overall duration, etc.. looked like a nice street piece, that I figured she could start easily and idle at the stoplight. It’s pretty much all that.
Everyone was like put the 292 cam in it. As much as I like the old .509 this cam will I’m sure kick it’s @ss with the 3.23 gear I have in it, and I appreciate on longer trips.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 25,853
- Reaction score
- 13,165
I agree;
If you install 279TH7 Thumper at 102.5 per the spec you will get the following;
279/297/107/118comp/100power/ 62* Ica/74* overlap/ 74 effective.
If you take an XE274H, and install it at 104, you will get
276/286/110/118comp/101power/62*Ica/61*overlap/ 54Effective
Since the Ica's are the same, installed in the same engine, the cylinder pressure will be exactly the same.
Since compression plus power is 218 versus 219, you can roll these cams around to the same Ica and see that all the differences between these two is in the overlap
And that is where the idle-lope is generated.
Ok but between these two;
the Thumper is 227* @.050
versus 230* on the XE,
And the thumpR has .486/.473 lift
versus .488/.491 on the XE
So, the XE has the potentail to make a bit more power, with a slightly broader powerband, all other things being equal
So, it is all about the sound.
But between these two, it's pretty close in power.
However, I don't think anyone would install this XE at 104, because it knocks the Effective overlap down to 54*.. The proper install might be 108. Then you would get the following;
276/286/110/114comp/105power,Ica of 66*/61* overlap/60*effective
That 4* later Ica will cost you 6 or 7 psi cylinder pressure but the 5 extra degrees of power extraction is gonna show up as better mpgs. And of course, the true potential of the overlap can now be realized.
As for the loss of cylinder pressure, that's only a problem if you didn't have much to start with........
But hey; the XE started out with 3* less advertised intake duration......
When I look at cams, I look at what is left over for compression plus power. In these two we see 218 for the Thumper and 219 for the XE. So basically the same. These numbers are getting pretty low for a streeter. You can trade away a few power degrees to get a few compression degrees,but mostly that's a bad idea, because at low rpm, a lot of energy is going straight into the exhaust system, instead of to the crank ...... and streeters spend an awful lot of time at low-rpm, including hiway cruising. So I like to see numbers closer to 227.
But sometimes, to get it, you gotta close up the LSA, which,IMO, is not a bad thing in a streeter, if you put second gear where it needs to be.
Take this XE274H for example;
If you close it up from 110 to 106, you get the following
276/286/106/118comp/109power/Ica of 62*/69 overlap/68Effective
Waitaminuit, where have we seen 62* Ica before? Look up, waaay up, Hyup on the Thumpr, but now we have 109* of extraction, and 68Effective degrees of overlap, with compression plus power =227, a nice street number. All you gotta do is cruise at a high enough rpm to ensure the highest vacuum, lean her out and mid 20s mpg is on the horizon.
So why aren't streetcams all 106* LSAs?
IDK
The narrow 106s are purported to have a narrower powerband. So when the trans gets into second, the Rs drop to 59% and if the engine falls off the cam, you lose.
But I say Com'on, the tires are spinning all thru first gear, so put second gear where you need it to be and who cares.
So this XE274 which is [email protected] power-peaks at about 5200, and say it has a short plateau of 300 rpm so you shift it at 5500. And the Rs drop to 3245; for a powerband requirement of 2255 with a 727/904.
So put some 4.30s on that, which will put 5500 at 40 mph in first, and 60 will be 4900 in second, 5500 will be 67 mph, and the power peak of 5200 at 64mph.
What's wrong with that picture?
Oh.......... no overdrive,lol.
Well ok, put a 110Lsa in there with 3.23 gears and be slow then.
Or get a bigger engine.
Or a manual trans;
I have a 4-speed with a 1.92 second gear When the 4-speed shifts at 5500 the Rs fall to just 4015 for a powerband requirement of just 1500. So it will have no problem with a 106LSA. You auto guys just need 4000TCs to keep up,lol.
Ok so once more, apples to apples, 279ThumpR7;
to XE274H with a 106LSa. Thumpr first:
279/297/107/118comp/100pwr/62*Ica/74E-overlap
276/286/106/118comp/109pwr/62*Ica/68E-overlap
I know which one I'd buy;
and it doesn't rhyme with bumpR.
Now; to answer why the ThumpR has 297* of exhaust;
To get the 74* of overlap on a 107 Lsa, it has to be that much.
It is strictly a function of the math.
[{(Lsa x2)+overlap}x2] less the intake duration = the exhaust duration
say it was a 110cam, and keeping 74 overlap; then the exhaust would have to be 309
Say it was a 105cam, and keeping 74 overlap; then the exhaust would have to be 289
Say it was the XE274H
(110x2 plus 61)x2 less 276=286
Lets say you ordered the thumpR with the Lsa opened up to 112, you would get
279/297/112/113comp/95pwr/67*Ica/64overlap/64E-overlap.
Notice that com+pwr is now down to 208 and that mother will suck gas big time.
Let's check it;
(112 x2plus64) x2 less 279=297; Hyup it works,lol.
Last edited:
ProStocker273
MoPar N Jeep
I've been running the middle sized Comp Thumpr in a 273. With 1.75 headers 3in collectors with street tunnel ram and pair of 450 cfm Holly's. My car is around 2600lbs with a 4speed with 4.56 gears and currently 29in tall tires.
That Comp Thumpr has been a good cam for my only 9:1 tween. Car idles awesome, right at 700rpm, sounds great, and pulls to 6000rpm quickly. Motor is only 9:1 and heads have minor porting.
I choose the Thumpr because I didn't want to machine the heads for more than .500 lift. I wanted a more radical cam that would work with my only 9:1 compression. I have 155psi cranking compression with this cam.
Specs for the Comp Thumpr is a
Operating range 2,200-6100
Adv duration (IN 287) (EX 304)
Duration @ .05 (IN 235) (EXH 249)
Valve lift (IN .497) (EXH .483) with 106 LSA
I'm now building a 318 with 10:1 compression and ported 360 heads and was considering running my old cam but felt I'd be leaving to much on the table. I've been looking at the
Comp XE 285HL Hyd flat tappet or the
Comp XS 282S Solid flat tappet.
I'd be curious AJ with your math if it would show which would be better cam for a small cube manual trans combo like mine. Im doing oiling mods and prep to get this motor to rev to 7 to 7500 for peak power. Been trying to read up on adv or retarding cam timing to shift the power band up.
The XE285HL specs are 2500-6500
Adv dur (IN 285) (EX 297)
Dur @ .05 (IN 241) (EX 247) with (IN.545/EX.544 lift) on a 110 LSa
The XS282S 2500-6500
ADV Dur (IN 282) (EX 290)
Dur @ .050 (IN 244) (EX 252) (IN.520/EX.540 lift)
on a 110 LSA
I'm not sure on the intake center line of those 2 cams. Not sure how much to retard cam for the RPM range I want. The motor may be small enough that peak power will move up to the 7000rpm range with the larger cam without needing to retard cam. Either way I plan to call call luntai and comp and see what they recommend. I may go custom grind but would appreciate any further cam info. This isn't a daily driver but does need to run on pump 93.
That Comp Thumpr has been a good cam for my only 9:1 tween. Car idles awesome, right at 700rpm, sounds great, and pulls to 6000rpm quickly. Motor is only 9:1 and heads have minor porting.
I choose the Thumpr because I didn't want to machine the heads for more than .500 lift. I wanted a more radical cam that would work with my only 9:1 compression. I have 155psi cranking compression with this cam.
Specs for the Comp Thumpr is a
Operating range 2,200-6100
Adv duration (IN 287) (EX 304)
Duration @ .05 (IN 235) (EXH 249)
Valve lift (IN .497) (EXH .483) with 106 LSA
I'm now building a 318 with 10:1 compression and ported 360 heads and was considering running my old cam but felt I'd be leaving to much on the table. I've been looking at the
Comp XE 285HL Hyd flat tappet or the
Comp XS 282S Solid flat tappet.
I'd be curious AJ with your math if it would show which would be better cam for a small cube manual trans combo like mine. Im doing oiling mods and prep to get this motor to rev to 7 to 7500 for peak power. Been trying to read up on adv or retarding cam timing to shift the power band up.
The XE285HL specs are 2500-6500
Adv dur (IN 285) (EX 297)
Dur @ .05 (IN 241) (EX 247) with (IN.545/EX.544 lift) on a 110 LSa
The XS282S 2500-6500
ADV Dur (IN 282) (EX 290)
Dur @ .050 (IN 244) (EX 252) (IN.520/EX.540 lift)
on a 110 LSA
I'm not sure on the intake center line of those 2 cams. Not sure how much to retard cam for the RPM range I want. The motor may be small enough that peak power will move up to the 7000rpm range with the larger cam without needing to retard cam. Either way I plan to call call luntai and comp and see what they recommend. I may go custom grind but would appreciate any further cam info. This isn't a daily driver but does need to run on pump 93.
Last edited:
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 25,853
- Reaction score
- 13,165
@ProStocker273 that's a good question.
IDK if either of those cams are right for you. My notes suggest that 240* is gonna peak at around 5400, so Ima thinking neither is right for you.
The Mopar 292/292/108 (248@050) peaked very near to 5400 in my 367 cuber at 11.3Scr, so there's that,lol. I still spun it to 7200 cuz she was willing, and in a streeter it don't matter, cuz the tires never stop spinning in two gears; but I sure wouldna won any races. I never tracked this combo.
The power plateau of that 292/108cam was short, about 300/400 rpm but the drop -off was fairly rapid, just right for the 4-speed. But when reving to 7200 with a .73 powerband, on the shift,the Rs dropped back to 5250 which was very near to the power peak, so the car leapt ahead on the shifts; you could really feel it on the 2-3 shift. It was a lotta fun.
But I think those cams you listed are too small for a 7000/7500 shift.
The regular A833 has ratios of 2.66-1.92-140-1.00, and splits of .72-.73-.72, so
shifting at 7000(x.725) the Rs will drop to 5075. So your powerband is gonna need to be from 5000 to 7000. That's a lot. And I thing you'll need more cam. But I can't comment on how much more because my data stops at the 292 because that's the biggest I have run on the street.
_______________
I would guess, for competition, you might need at least 2 sizes bigger than 240@050. But if this is a gas engine, I sure wouldn't screw it together at 9.5Scr . Also, Ima thinking you would need a solid lifter cam. And then with solids make sure the numbers you are working with are after-lash numbers.
But then, I'm a streeter and know nothing about racing. Especially not with a 318@2600 pounds.
Call your cam-guy. He is way smarter than me.
If you could make that 279ThumpR idle at 700 with a tunnel-ram, on a 273,at 9 to 1; Ima thinking you're a pretty good tuner, because 74* of overlap is quite a bit. IIRC my 292 had 76* and it was a handful at 700.but it sure sounded good.
IDK if either of those cams are right for you. My notes suggest that 240* is gonna peak at around 5400, so Ima thinking neither is right for you.
The Mopar 292/292/108 (248@050) peaked very near to 5400 in my 367 cuber at 11.3Scr, so there's that,lol. I still spun it to 7200 cuz she was willing, and in a streeter it don't matter, cuz the tires never stop spinning in two gears; but I sure wouldna won any races. I never tracked this combo.
The power plateau of that 292/108cam was short, about 300/400 rpm but the drop -off was fairly rapid, just right for the 4-speed. But when reving to 7200 with a .73 powerband, on the shift,the Rs dropped back to 5250 which was very near to the power peak, so the car leapt ahead on the shifts; you could really feel it on the 2-3 shift. It was a lotta fun.
But I think those cams you listed are too small for a 7000/7500 shift.
The regular A833 has ratios of 2.66-1.92-140-1.00, and splits of .72-.73-.72, so
shifting at 7000(x.725) the Rs will drop to 5075. So your powerband is gonna need to be from 5000 to 7000. That's a lot. And I thing you'll need more cam. But I can't comment on how much more because my data stops at the 292 because that's the biggest I have run on the street.
_______________
I would guess, for competition, you might need at least 2 sizes bigger than 240@050. But if this is a gas engine, I sure wouldn't screw it together at 9.5Scr . Also, Ima thinking you would need a solid lifter cam. And then with solids make sure the numbers you are working with are after-lash numbers.
But then, I'm a streeter and know nothing about racing. Especially not with a 318@2600 pounds.
Call your cam-guy. He is way smarter than me.
If you could make that 279ThumpR idle at 700 with a tunnel-ram, on a 273,at 9 to 1; Ima thinking you're a pretty good tuner, because 74* of overlap is quite a bit. IIRC my 292 had 76* and it was a handful at 700.but it sure sounded good.
thesiren74
Well-Known Member
292 lunati bracket master 2 cam is completely streetable and makes great midrange power, had that 360 with a 3500 stall converter and 2.45s gears in my 74 duster and it ran 13.40s with that cam and drove it everywhere.
PRH
Well-Known Member
Your memory must be pretty short.
Mopar cam info, suggestions.
In that thread is a link to an interview with Billy Godbold, where he states he designed the XE lobes.
When the XE’s came out I was still running a lot of UD cams, and had spoken to Harold about the XE designs.
He didn’t care for them.
There is a quote in that thread from I think it’s the Chevelle forum, where he even says as much...... and that he didn’t design them.
And lastly..... again....... when the XE line came out...... UD was going strong.
He wasn’t going to be designing lobes for the competition(especially since there was still some ill will) while he was trying to grow his own company.
Billy G. designed the XE lobes..... Not Harold.
Last edited:
Wyrmrider
Well-Known Member
Aj - instead of the old 284H how about the Engle K 56
a 270 size MP
or the Purple Plus
for cams under .500
you can get a lot more power/ area/ duration @.200
Actually those thumper lobes look like good ones for the under .500 builds if you could get them ground for power instead of lope
How high do you have to rev them to get the exhaust cleaned out of the combustion chamber at overlap?
no way would I want to use one with stock exhaust- under load they manifolds will glow cherry red just like they do with a 440 magnum cam
me I'd go with the 275HL or the Howard or Lunati listed in post 7 instead of the smaller thumper
The ones in post 23 would all act bigger
Thanks PRH I missed that thread must be senile cus I later commented in it I was thinking of some old speedtalk threads where Harold discusses his time at comp
love the parts about close brutality and noise- glad they are not Harold designs
do not like that comp 268 anywhere and especially in a Mopar
Harold said his 268 chevy voodoo is up 25 hp over the comp 268
so I would think the Mopar voodoo even more so
what comp line did Harold design? In the other thread he says "268 High Energy."
now I have to wonder which one he compares to his Lunati - dosen't matter the Lunati is a better cam
edit
I evidently mixed up the HE and XE cams
There was one that we would not use with chamfered lifters or with less than good lifter bores- must have bee the Billy Extreme Energy
the other one was about as smooth as a Crane
note Evienly comp developed the Thumper lobes for endurance racing- lobe makes sense there I highly doubt they used that intake/ exhaust split and LCA though
a 270 size MP
or the Purple Plus
for cams under .500
you can get a lot more power/ area/ duration @.200
Actually those thumper lobes look like good ones for the under .500 builds if you could get them ground for power instead of lope
How high do you have to rev them to get the exhaust cleaned out of the combustion chamber at overlap?
no way would I want to use one with stock exhaust- under load they manifolds will glow cherry red just like they do with a 440 magnum cam
me I'd go with the 275HL or the Howard or Lunati listed in post 7 instead of the smaller thumper
The ones in post 23 would all act bigger
Thanks PRH I missed that thread must be senile cus I later commented in it I was thinking of some old speedtalk threads where Harold discusses his time at comp
love the parts about close brutality and noise- glad they are not Harold designs
do not like that comp 268 anywhere and especially in a Mopar
Harold said his 268 chevy voodoo is up 25 hp over the comp 268
so I would think the Mopar voodoo even more so
what comp line did Harold design? In the other thread he says "268 High Energy."
now I have to wonder which one he compares to his Lunati - dosen't matter the Lunati is a better cam
edit
I evidently mixed up the HE and XE cams
There was one that we would not use with chamfered lifters or with less than good lifter bores- must have bee the Billy Extreme Energy
the other one was about as smooth as a Crane
note Evienly comp developed the Thumper lobes for endurance racing- lobe makes sense there I highly doubt they used that intake/ exhaust split and LCA though
Last edited:
Or "3/4 Race"
BUT, that name has a history of FACT. Here's the story.
TECH QUICKIE: What is a '3/4 Race' Camshaft?
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 25,853
- Reaction score
- 13,165
IDK I never had one. But I did have a 292/108 Mopar, that by 2400 was pretty clean. I cruised at at 2600=56mph. It still sucked in the fuel-economy department,lol. And you know why? Because compression degrees plus power totaled just 212*. Even advancing it to in at 102 the Ica now up to 68*, but the power extraction now down to 100*........... just like the 279 ThumpR in at 102.5, just like the XE274H in at 104. It is what it is.
IMO a streeter looking to cruise, needs about 227* of compression plus power, to get some decent power extraction
........ unless it has aluminum heads with 11/1 compression, then just crank the cam timing to favor power extraction.
Which is what I did with a 223 Hughes cam, and everyone scorns me when I claim fuel-economy numbers too big for them to imagine.
Consider the Hughes HE2430AL, now obsolete. The specs are
270/276/110; and 223/[email protected]
in at 110, the numbers are;
270/276/110/115comp/112pwr/Ica of 65*/50* E-overlap
Notice comp plus power is 227*, no way AJ you did that on purpose. Actually no,lol, I lucked into it.
Now with iron heads, and on the street,you cannot usually make decent cylinder pressure with just 115* of comp duration. But with aluminum and 11/1, I drove the pressure to 178 psi.
And that left 112* Of power extraction. Now that is a great number. Just get the rpm up high enough to clean up the intake, but low enough to cruise comfortably in double overdrive, and excellent fuel economy is practically guaranteed.
I got a 380hp create 360, I'm pretty sure the cam Mopar choose for them was their version of a thumper cam got similar specs of other brands similar sized thumper cams works pretty good even with 2.94 gears, and does thump.
And nobody walks through the pits at the drag strip hearing cars “making popcorn“ on the return lane and through the pits and thinks they’d prefer a nice smooth idle of a stock 318 four door Volare or are worried what others will say for them wanting what they’re hearing in the pits.....
yellow rose
Overnight Sensation
I don’t. If a cam grinder brings up idle more than once I move on. If it idles butter smooth and pulls to what ever RPM I want is fine. If it has to idle at 1500 (no cam should ever need that unless you are burning fuel) then so be it.
Bighead440
Well-Known Member
'68 340 with a Lunati cam with 10* duration split at .050" and 112*LSA. We just broke the cam in so it's still idled up a bit.
Yeah. Right.
yellow rose
Overnight Sensation
I didn't say you were. I just disagreed that you never think about sound when choosing a camshaft. At some point you DO.
Anyone play electric guitar here? I like a Les Paul through a British amp, think Marshall or Orange. Anyone can buy both, tune things up, crank it up and make some spine tingling sounds once in a while. Might still suck, can’t hang with the real deals but a nice power chord or two, some single notes put together is all it takes to get “that” from the sound. Best comparison I can make. Just cause you can’t really play doesn’t mean you forfeit or forgo the pursuit of aural pleasure!
Wyrmrider
Well-Known Member
Aj post 25 that 292 MP @108 cam has to be over 300 @.006
big difference with the Hughes 270/276 @110
was that Hughes an Engle? If so a 280 @006 class cam 20 degrees less duration is a bunch
what was the lift .504?
looks like the 292 would pass anything on the highway except a gas station
big difference with the Hughes 270/276 @110
was that Hughes an Engle? If so a 280 @006 class cam 20 degrees less duration is a bunch
what was the lift .504?
looks like the 292 would pass anything on the highway except a gas station
Wyrmrider
Well-Known Member
Sound
I've done builds for absolute quiet so a stereo with classical music can be heard but still run well
and I've done stealth builds that sound stock until you really get on it
and then there are builds where you go for the most power
Want a performance sound get a 60's Howards or Clay Smith open the exhaust early and vibrate the headers
but then they (and many others) were quite brutal on the springs of the Day- Want something really brutal try an Ak Miller grind
Crane with his "computer smoothing "marketing really shook up the cam business
The lunati Bootleggers "Note: Custom grinds available for Chrysler" but why seems like a Voodoo would be better in any case
I stuck them and the Lunati Bracket master II in the list for reference
I just read in one of PRH's links that Comp's Billy Godbout learned from Harvey Crane- Well so did the owner of Camcraft- me I'd rather deal with Camcraft
I've done builds for absolute quiet so a stereo with classical music can be heard but still run well
and I've done stealth builds that sound stock until you really get on it
and then there are builds where you go for the most power
Want a performance sound get a 60's Howards or Clay Smith open the exhaust early and vibrate the headers
but then they (and many others) were quite brutal on the springs of the Day- Want something really brutal try an Ak Miller grind
Crane with his "computer smoothing "marketing really shook up the cam business
The lunati Bootleggers "Note: Custom grinds available for Chrysler" but why seems like a Voodoo would be better in any case
I stuck them and the Lunati Bracket master II in the list for reference
I just read in one of PRH's links that Comp's Billy Godbout learned from Harvey Crane- Well so did the owner of Camcraft- me I'd rather deal with Camcraft
I do. I have a 1967 Sears Silvertone Bobkat. I play it through a Pignose 60 watt tube amp. I have seven......eight other guitars. I forget. Mandolin and banjo.
-
