nasty idle cams
 

What gives a cam it's idle 'sound'? I know a tight lsa does but does more duration? Any thing else? I like a really nasty,barely able to idle,idle that rocks the car.I know a nasty idling cam isn't always the best cam for the job.Just wanting to know if it's possible to have a street/strip combo run low 10s/hi 11s and 'sound' like it runs 8s-9s.My current cam is on a 106 lsa,sounds nasty but i could live with more 'nasty' from it.

Use a cam with a "tight" LSA with LOTS of overlap and low compression ratio. Best recipe I know of for a "rough" idle. Install a Comp 292H cam into a 400 engine about 7.7 to 1 compression ratio, it will give you the sound that you are looking for....but it woln't outrun a Dodge Neon with 2 plug wires pulled off!

Seriously, tight LSA grinds with big lobes make for a "choppy" idle. We like to put a lot of compression in those engines to keep power up at low speeds.

Low 10's on the motor requires a LOT of power. You'll need near 700hp at 3500lbs race weight. Mid to high 11's takes about 500-550hp, and is a lot more realistic for a pump gas street/strip type engine.....Cliff

You could also run ported advance instead of vacuum advance at idle.You will hear "more of the cam".I'm not into the sounds fast thing ......,I'd sooner pick a cam for power and streetability not for sound.

Check out the new Comp Thumpr cams. Not a lot of reviews so far, but apparently, they manage to get some power AND that choppy idle you're looking for. But...

You can get decent idle quality and nasty sound with better than 'off-the-shelf' cams. Any good shop, like SD for example, should be able to custom spec a cam for you.

http://www.thumprcams.com/

A few questions: What size engine? Are you willing to pull the heads to swap the valvetrain? Compression? What octane fuel do you run? There are so many variables into selecting the cam, these are just the beginning. Vehicle weight, trans type, converter, rear gearing, and more. JD

Engine is a 467,6x heads by Butlers flow [email protected] comp,93 pump gas.I want upgrade to a roller,maybe solid and SD KRE heads.4 speed,3:90 rear.I'm running the CC 290b6 solid cam now.Sounds great,i get more compliments about how my car sounds more than anything else.I want to keep the sound of the 290b cam but use a roller.I kmow i should pick a cam to run hi 10/low 11s and accept whatever the idle will be.But,if a cam can be ground to give a 'nasty' pro/stock type idle and back it up with hi 10/lo 11 et's in a street/strip car AND outrun a Neon then that's what i want.Actually i like Cliff's combo running 11.30s on pump gas,but he says it idles almost stock.Give me his combo,performance with a 'nasty' idle,i'll be happy.....for a while..

"Actually i like Cliff's combo running 11.30s on pump gas,but he says it idles almost stock.Give me his combo,performance with a 'nasty' idle,i'll be happy.....for a while.."

I can turn the idle mixtures screws in half a turn and get a "nasty" idle out of it. I can also move the vacuum advance hose to a manifold source and have it idling like my neighbors 305 SBC powered pick-up truck!

My engine has a very good idle, but it has some "attitude", not completely smooth either. It's not setting off car alarms in parking lots or anything, but it does sound like there is a little something going on......Cliff

I almost used that 290b solid cam with my SD 290 KRE heads.The heads were initally set up for it.I had the cam at the time then my wife bought the heads for me for Xmas.I switched to a roller instead.With the 290b it would have made good power too....I thought maybe a little too high of revs for my engine though.Why not get the heads run 1.65 rollers and keep the cam since your cam is already broke in no worries or when you order the heads get Dave or Marcel to spec a cam for you if you wish to go roller.

I never thought about 1.65 rockers.I'm running HS 1.5 rollers now.On the chassis dyno my engine peaked at 4900 rpm,397rwhp,then nosedived.Similar to what Cliff sees with the XE lobes.I'll call SD about heads.I see guys on here running the 290b in the 10s/11s maybe i just need to tune and sort out my current combo to get the most from it.It's never really been dailed-in,just a dist.recurve.

http://www.youtube.com/watch?v=KvLwILhnkX8

Is this considered nasty?

im glad im not the only one, i had a perfectly good running motor that would burn the tires in all 4 gears, but sounded stock. now i got me a nasty 104 lsa cam for it. but i dont think i gave up anything but drivabilty and gained bit more power, i hope!!! if not im lookin at a 4k disaster lol

yeah,that's nasty nice.http://www.youtube.com/watch?v=zsl3XhHrs4s

Here's mine going on the dyno.

http://www.youtube.com/watch?v=EV5mOrODsAk Here's another for your viewing pleasure.

They didn't chain it down or even chock the wheels, I've run my cars before on a chassis dyno and we had it chained and blocked. Nice car and the cam sounds fine to me, 65 is my favorite year. I've owned 2 hardtops and a convertible.

I don't know what you are talking about, that cam sounds pretty nasty to me.

Here is mine, this is through 3" exhaust to 3" super turbos that stop right at the rear axle, I am also idling at 1300 rpms.

http://www.youtube.com/watch?v=n3IWWqsIhzA

Mark

What did it make on the dyno?

nice! Mine has a crossover and i know it gives it a smoother sound, i might take it out.

watch those 1.65 rockers with stock heads. you will probably need to "waller out" the push rod holes through the head, because the 1.65s will bottom out the push rods in the head holes at the closed valve position and they will click, sounding like the valves clicking. i had to find a 1/4" grinding ball with a 6" long shaft to reach mine, and do them individually on a mocked up motor. i like that bad idle, too, but it can be a pain for the street.

The perfect cam and exhaust is the one that can set off alarms on cars parked across the street on a 4 lane boulevard while just poking along in the slow lane...

I think a lot of people love the sound of a nasty, rough idle cam. But what causes this? In most cases your air and fuel are not properly mixing. This is fine and expected if you have a drag car that creates its power at high RPMs. I think its important to find that balance though for a street car. A rough idle creates cylinder wash at low RPMs until the motor start reaching the proper mixture. Cylinder wash will cause premature engine ware and poor street ability. My 2 cents is find the right balance between sound, power, and longevity.

Don't think I agree with that - You can still have a lean idle with a big cam. You are correct that very rich conditions will dilute the oil, but a rich idle isn't a given parameter of a tight lobed cam with a large overlap. I'm sure that there are a bunch of engines out there that fall all over themselves because of a lousy tune, but they also really sound unhealthy. A true ground pounder tuned correctly creates vibrations clear into your soul.

Actually it was strapped in the front and rear.

[email protected]'t remember the tq off hand but it was less than 500.I was expecting more from this size engine and cam.And more rpm.Not much of a power curve either,more like straight up then back down.

Run your 290b with 1.65 rockers with a set of SD KRE 290cfm heads you will have same idle more or less with high ten potential.Get some due on here to run a duno simulation....I forget what it is but I'm sure it is in the 550 to 600 hp range at around 6000rpm depending on rocker ratio.:D

My mistake, I guess I didn't see it in the video. I didn't think anyone would chance it though.
Anyway like I said nice car and I hope to have another 65 someday myself.

i dont think thats altogether right??? sure that causes a nasty idle so does unplugging a vacuum line, i think those cause the other nasty idle. theres plenty of cammed street cars running around without that problem, i think it really depends on how obnoxious a cam you cal tolerate on the street

The first roll was just to center the car up on the rollers since the car came in a little off center.

I wonder if the two-roller dyno unit had anything to do with torque being down compared to horsepower? The old Clayton dyno's had a hard time with wheel spin due to the small rollers and it wasn't unusual to have three guys sitting in the trunk during the run to provide extra traction. Could you post the results?

Ditto lust "clear to your soul":D

A properly tuned engine that has a rough idle does not have the correct fuel and air mixture at low RPMs. The rough idle is cause by poor burning of the air fuel mixture. If you cause your car to run rough to look like you have a lot of horse power, your foolish. Your giving up what your trying to advertise. Yes there are plenty of large cam street cars running around, but if they are not properly tuned to have the correct air/fuel mixture for the used power range, its only a matter of time before they need to be rebuilt. It may be 2,000, 10,000 or 50,000 miles. It won't be the optimal engine life though. Ask a reputable engine builder. I would be surprised if he recommends a poor tuned engine for a cool sound.

im no professional but, theres alot more to the rough idle than just bad a/f ratio. sure if i take a stock 400 with stock cam and fatten up the tune for a nastier sounding idle it would be foolish, but if i take that same 400 put a lil bigger lopier cam in, after fine tuning it is still gonna have a rough idle and it wont having anything to do with air mixture it will be more due to the reversion caused by the bigger cams duration and overlap. as long as you use the right gears and converter the only real sacrafice poor life expectancy of tires poor gas mileage, and some times it could get to be a pain to drive if you were gonna try and drive it all the time. the only thing that i really see being a factor of how long will the motor last is, most people with these types of motors dont just wussy foot around in them, they run the piss out of them

Like I said, it needs to be properly tuned to have the correct air/fuel ratio. I am not saying all large cams are bad. I have a 462 stroker with 585 hp at 6000 RPMs. It has a very large cam for a street car. I am only suggesting to the member that he does not sacrifice longevity for a cool sound. As long as he can maintain the correct air/fuel ratio for the RPM range that is used the most he is good to go. As far has him dirving the piss out of the car. That is hard to do when you are cruising the highway at 75 mph. A lot of damage can be done even at cruising speeds if you do not tune the engine correctly. Although there are many contributers to a rough idle, a poor tune should never be one of them. Why put thousands into a motor for poor performance.

When guys say they have a large or big cam they always refer to duration it seems.My car has large lift for a street cam in the .650's but smaller duration compared to many at around a 230/240 @.050.I wouldn't say it has a nasty idle as in rough but it sure trumpets out the back especially if its idling in park.

IMHO The car sounds great with the 290b cam! Your not going to change the impression of the average person by trying to make the idle rougher. What does an engine with the Comp 300b sound like? I think thats the part #, the one bigger in the catalog. JD

I wouldn't run the engine improperly tuned for the sake of a rough,racy idle.Performance comes first,if it sounds like a 10 sec car then it has to be able to back it up.

Exactly what valve springs are you using on those 6X heads?

What pushrods??

Stud girdle???

The 290b6 should pull strong to 6000+ no problemo.

Also,was that cam degreed when it was installed?

With the 6X heads and the compression your running,you really dont wanna go any bigger than that 290b6 cam.

Also,what sorta exhaust are you running,tight LSA cams absolutely abhor restrictive exhaust tracts,a restrictive exhaust system can cost big chunks of power with the tight LSA cams.

Can be lots of reasons for what your seeing,just gotta work thru the usual suspects in a logical way to eliminate any & all possible issues,it's a process,and it can be tedious at times,but you gotta expect to put in some work to reap the gains.

As for a SR cam to replicate the 290b6 when you upgrade the heads,here's my choice:

Brand & part no.:Comp custom high tech .420" SR lobes #51-000-5
Grind & lobe no.: AKA: the 290b6 roller "clone" cam. ( lobe # 4009/4023)
Tappet type: Solid Roller Tappet
Spec = intake/exhaust: (notes)
Adv.duration = 290°/304° (I/E split = 14°) (note: rated @ .020")
Dur. @ .050" = 254°/266° (I/E split = 12°)
Dur. @ .200" = 171°/180° (I/E split = 9°)
Lobe lift = .420"
Lift @ 1.5 rr = .630"/.630" (Gross lift) (To get Net lift subtract lash below)
Lash =
106° LSA = 106° ICL = 106° ECL

Seat events:
IO = 39° BTDC
IC = 71° ABDC
EO = 78° BBDC
EC = 46° ATDC
OL = 85°

Events @ .050":
IO = 21° BTDC
IC = 53° ABDC
EO = 59° BBDC
EC = 27° ATDC
OL = 48°

Compare that to the 290b6:

Brand & part no.: Comp Cams Part no.51-659-5 . (catalog grind)
Grind & lobe no.: Grind no.290b6 (lobe #6061/#6013)
Tappet type: Solid Flat Tappet
Spec = intake/exhaust: (notes)
Adv.Duration = 290°/304° (I/E split 14°) (note: rated @ .020")
Dur. @ .050" = 255°/266° (I/E split 11°)
Dur. @ .200" = 160°/172° (I/E split 12°)
Lobe lift = .360"/.356"
Lift @ 1.5 rr = .540"/.534" (Gross lift) (For Net lift subtract lash)
Lash = .026"/.028"
LSA = 106° ICL = 106° ECL = 106°

Seat events:
IO = 39° BTDC
IC = 71° ABDC
EO = 78° BBDC
EC = 46° ATDC
Total O/L = 85°

.050" events:
IO = 21.5° BTDC
IC = 53.5° ABDC
EO = 59° BBDC
EC = 27° ATDC
O/L @ .050" = 48.5°

Does'nt get any better/closer than that!

What's the diffence you ask???

Look at the additional lobe lift and the .200" duration numbers and you'll see. ;)

And that SR cam will absolutely love better flowing heads!!!

But I'd definitely work with the current combo some more before making that leap. :2cents:

Sooner or later though,those trips wont be able to keep up.

Bret P.

Springs are comp #995.130 closed,334open @ .550
Pioneer pshrods 5/16.I cant find the length.I had to get longer than stock because the lifter plunger was down in the body further than on the comp lifters that i was using with previous cam.
No stud girdle.Comp guide plates,7/16 studs.
Cam was not degreed.I'm suspecting this 'could be' a contributing factor.I run an E-brock geardrive with a 3 keyway crank gear.VERY hard to see the lightly stamped markings for +4,-4 or 0.There is a good chance i might have used the wrong keyway and installed it 'retarded' *4.
It does pull to 6000 and beyond with no problem,it just stops making power at 4900.
I'm replacing my 1-5/8 headers with 1-3/4.

I run 6x heads to keep a 'stock' look and i didn't have money at the time for alum.heads.I think to get low 11s/hi 10's the KRE heads would help a lot.

Jim LeHart (Mr P-body) has had very good sucess with the 290-b solid flat tappet cam. His recipie in 6X-8 heads with Comp Magnum 1.65 rockers is 150 seat pressure at 1.600" installed height, 340 lbs open. Valve size, 2.110"-5.095" long.

A fwiw, if and when the time comes and you change push rods and are using 5/16" upgrade to a thicker wall section rather than the typical .080"-.083" diameter. Manton 0.118" wall is a good one. Also Smith Brothers.

I thought your deal sounded familiar,so I went digging thru the archives last night after working on my race car,and yeah we talked about all this like last fall.

Absolutely power lurking in that exhaust IMO.

IIRC my suggestion was for headers with bigger primaries,I believe I suggested 1 7/8" with 3.5" collectors as what I would prefer to see on there,but agree going to the 1 3/4" x 3" headers is better than what you have.

I'm gonna be using 1 3/4" x 3" headers (hedman) on the 400 for my '70 Lemans/GTO race car with a very similar custon Crower solid cam (hell the back-up engine I'm building for that engine has a 290b6 ready for it),and even with what,50 some less cid I feel that size header is marginal @ best,the only saving grace to my situation is what exhaust there is will be 3" all the way back to the dumps in front of the rear axle.

And yeah,I'll bet $$$ that your cam is installed advanced,probably quite a bit.

And I'd put some stiffer pushrods in there,the pioneers are likely .065" wall,and I feel .080" wall chro-moly is the minimum,and the .118" wall pushrods are even better.

I'd also think long and hard about adding the stud girdle too.

Most combos like yours with solid cams like that peak right around or just over 5500 RPM.

Also,the chassis dyno sheet you posted showed it was a mustang dyno,and I have heard thru the grapevine that those can give hit or miss results for some,but somebody else like Harry K. would probably know a lot more about that than I do.

Oh yeah,the rwtrq was much healthier than the hp that was for sure,I think that was like 486 peak lb/ft @ the wheels,and something like 390 lb/ft average on the best run.

So that too makes me think the cam is installed advanced past what's recommended as well.

The KRE heads are always a worthy consideration when looking for more power than stock heads are typically gonna make,I'd get 'em thru SD if I were looking to buy,those guys do real good work.

Gotta go,finishing up my ignition panel installation/mock-up in the race car,and I'm burning daylight,then I shift to messing around in the garage working on misc. stuff for either my '72 firebird street car,or my brothers '68 S code 390/C-6 Ranchero GT.

:beerchug:

Bret P.

Thanks.Yes you have answered the same questions a few times for me.I WILL degree the cam,even if its 'on' at least i will have eliminated that as a problem.Not sure if i can fit headers bigger than 1-3/4,my 1-5/8 are tight in places.
I will call SD for heads.

You would be suprised how much better the big tube headers can fit on some cars.

Though often one tube on each side gets re-routed around/over a frame rail to make that happen,and the primary tubes themselves are a "slip fit" into the collector,also these sorta headers typically use a sub-flange on the head that repositions the flange bolts,so that inturn eliminates the hassle of trying to get to "that bolt".

Most folks that use these sorta headers swear they'll never go back to the "traditional" style of headers.

I'd likely be talking to Mark @ maddog myself.

HTH

Bret P.

goatman, give the hedman huslers a look, i put them on my 66 which sholdnt be any different than your 65. mine are 2inch primaries and the 8, 7 tubes run over the frame rail and thrue the inner fender back under the car and the 1 and 2 tubes run under neath the crossmember. ive never put on a set of hedders on that were easier. the only real work is you do have to cut a lil out of the fenderwell for them to run thrue. my car is a 4speed and i stil didnt have to massage the hedder to fit, probaly one of the few hedders you can buy ceramic coated and not have to ding it off with a hmmer and they are in slip fit pieces like sc mentions

Got any pics of your setup?

For sure degree the cam my 9 way billet set from Summit has markings that are off,so if you misjudge the vague markings you can be off big time.Absolutley give SD a call they helped me pick up 10 mph on my car with a head and cam swap.

have a few at home on my other computer but not on this one, but there is one picture on my album in my profile that shows a little bit of the headers, enuf that you can see how they route thrue anyway

goatman65, I couldn't find what carburetor(s) and intake manifold you were running. I'm also wondering if your ignition isn't falling off after 4,900 RPM. Have you had the distributor checked?

IIRC he's running a tri-power intake & carbs.

Cant remember exactly which tri-power intake though,for some reason I wanna say it is one of the aluminum repo pieces.

But dont quote me on that fact.

I dunno if I would feel that the ignition would cause a low hp peak myself,fuel yeah maybe I could see that,seeing as an engines power output is based almost entirely on it's BSFC (brake specific fuel consumption),and if that tanks,the power typically goes with it.

But yeah,anything is possible really,so I would'nt let anything escape my scrutiny.

I kinda ponder if he was running it with some of those tiny trips air cleaners on there,and those maybe were a bit too restrictive or something???

I dunno,but I know there's an answer for sure.

There's more power lurking in that thing right now,I'm sure of it.

Bret P.

An Idle more than this? Its not a Pontiac, but its my 74 Pantera....... Check Vids :D

http://www.youtube.com/watch?v=eNn1u9EDLEI

http://www.youtube.com/watch?v=9ECF59WNZqA

Yes i'm running a 66 repro alum.intake.I sent it to Jim at CVMS and he ported it along with enlarging the throttle bores of the end carbs.He said it flows 'similar' to the intake on Rick Hollidays GTO.The ctr. carb is a circle track carb by Jet.It flows 500 cfm.
Ignition consists of an MSD6,Blaster 2 coil and the dist was rebuilt/recurved by Larry Rowe for this engine.I did replace the points with a Crane xri unit because i wanted the rev-limiter.Larry did say the points would be just as good if not better than the Crane unit.Intial timing is 16,36 total @2500.

Dyno sheet

Only thing I dislike about the Crane XRi unit is that little potentiometer to set the RPM limit. With my eyes 6,000, 6,200, and 6,400 all look about the same when eyeballing it. Other than that, it has been a reliable unit with no problems in the 10,000+ or so miles it has been on the 2+2.

The chart looks like the results of a smaller cam. Torque peak at 3,200 RPM doesn't sound right, and I would vote that the cam is really advanced.