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chevygirl74 09-13-2007 11:23 PM

Supercharger Roll,detroit Roll,blower Surge???
What Causes A Blown Motor To Surge At An Idle?. We Have Tried Everything So Far That We Were Told That Causes Blower Surge Or Blower Roll And Still Our Engine Doesnt Do It.our Car Is A Stick But Also Tried Doing It On The Engine Dyno So We Ruled Out People Telling Us You Have To Have An Auto Because Its The Torque Converter.current Engine Is A Dart Chevy Big Block ,edelbrock Aluminum Heads 2.19/1.88 Rec Port,eagle Rotating Assembly H-beam Rods,mls Gaskets,9.5 Comp Has Weiand 8/71 With Two Holley 950 Cfm Blower Carbs,electric Holley Blue Pump, Msd Dist,6 Btm Box,coil.comp Cams Solid Roller .782 Lift .296 Dur 114 @.50 1.7 Roller Rockers,

how Is It Done What Causes It???

Things That We Have Tried So Far,,

carbs-holley Non Blower Carbs 850cfm Double Pumpers #4781 With All Of The Different Power Valves Available From Holley Including Just Solid Plugs And Many Jet Changes This Was Done In The Front And Rear Of The Carbs Jets From 2 To 12 Sizes. Also Fuel That Was Used Was Pump Gas To Torco 116 And Vp 114 And 116.

cams-comp Cams All Solid Rollers .652 Lift .262 Dur 114 @.50 And .690 Lift .274 110 @.50 And .782 Lift 111 .290 @.50 And .748 Lift .292 112 @.50 These Are Split Cams Also Tried 1.8 Roller Rockers

blower- 8/71 I Have Tried All Different Pulley Setups Under Driven To Over Driven 3lbs To 28.6 Lbs Boost We Did Loose The Head Gaskets And The Blower Ran To Hot Over 22lbs Boost.

dist- Msd Changed The Spring Weights To Make It Lighter To Lightest To Back To Where It Ran Good Again.timing Is At 35 Degrees Total Advanced

Also For More Info We Have Done This Same Setup On A 468 (except We Didnt Have Blower Carbs) And We Have A Few Other Blower Cars Here And None Of Them Will Have That Surge Idle.we Have Been To Alot Of Car Shows And Drag Races And Have Heard Alot Of Carbed Cars Surge Small And Big Block, Whether It Is The Right Or Wrong Way Are We Missing Something. We Am Experimenting And Want To Know How It Is Done. We Have Not Tried Alcohol Because We Have Heard Street Cars On Gas Surging.if Anyone Has Any Info Or If Anybody Has A Car That Does It, We Would Appreciate The Info Or If You Have Any Videos Of Your Cars Please Send To Us. Have Found Cars On You Tube To. Link To One Is Below. Thanks

Arrowhead 09-14-2007 08:47 AM

Let me get this straight, you have swapped all the parts and spent all kind of time and I'm assuming money because you WANT blower surge? To each his/her own I guess.

Reminds me of a car show a couple of years ago. A guy and his girl were cruising through the fairgrounds and they had a primer 50's type car with a huge blower motor in it. The blower surge was so bad it was snapping thier heads back and forth. I thought it was hilarious.

I thought it had something to do with big cams / loss of vacuum signal / power valves or something like that. Sorry I can't be more help.

302 Z28 09-14-2007 09:17 AM

Most blower surges are caused by either a bad idle air controller or a improperly located idle air controller. Why anyone would intentionally want blower surge is beyond me :rolleyes:


powerrodsmike 09-14-2007 09:31 AM


Originally Posted by 302 Z28
Why anyone would intentionally want blower surge is beyond me :rolleyes:


I know guys who put straight cut gear drives on...even though they suck up horsepower and aren't necessary at all, because they make that cool "gear whine noise".

It makes people look though. :rolleyes:

Later, mikey

XNTRCI-T 09-14-2007 09:56 AM

Check this thread...

400smb_s10 09-14-2007 10:50 AM

In my opinion. I think it sounds like crap. Sounds like theres a pinched gas line and its only getting little shots of gas...

But if thats what your looking for then trya lumpier cam

just me .02 cents


tubbedz 09-14-2007 01:38 PM

Supercharger Roll,detroit Roll, blower Surge???
I don't know if this helps, but on my, TH350 automatic, 671 blown SBC, I would experience "detroit Roll" at idle. After many hours of double checked timing, gaskets, etc... I tried increasing the idle feed restriction jet on my billet metering blocks. Guess what happened....the surge went away. The blower was sucking my Holley, idle feed restriction dry. So I increased the restriction jet to allow more fuel at idle. Correct me if I am wrong, but this is just my own personal experience. I am not saying this is a cure-all modification, but just an example of unique situation that I ran into and wanted to share my experience with my fellow Hot Rodders. There maybe other factors or issues that are unique to your situation.

68NovaSS 09-14-2007 02:32 PM

In the link XNCRTI posted, heed what Royce says. I corresponded with him a lot when building my car, very knowledgeable.

I have a roll in my 8-71 383 SBC, and can tune a good portion of it out by leaning the carbs. BG 750 blower carbs. Add that to the right cam duration and things can change either way.

Some like the roll some don't. One's that don't are next to me at a light after idling and loading up some, when I hammer it a little, he he, sends out a pretty good shot of exhaust, usually into their passenger window. I'll attach a link to my video, which may or may not work from my work computer, they have us blocked from the site. You can also search 'blown nova', mine's gray primer in a pretty dark garage, and yes it has some lifter noise in the video...initial adjustment on a solid roller.

chevygirl74 09-15-2007 12:44 AM

No, We Didnt Spend All Kinds Of Money And Time Just To Get That Sound,we Do Own A Speed Shop So That Helps On Parts And Fuel. And Yes There Is A Noisey Gear Drive In It To,we Like It.we Have Other Blower Cars To . None Of Them Surge Maybe There All Running To Good Lol Lol. We Were Dyno Testing And Experimenting.we Have Heard Cars At Shows And They Were Carbed And Wanted To Know How They Got It To Run That We Said Whether It Is The Right Way Or The Wrong Way Or If Some Like It Or Some Dont We Just Are Trying To Figure It Out How It Is Done,maybe We Should Ask How To Correct The Problem Lol Lol Then Do The Reverse? We Do Like The Sound And Want To Try It! We Ruled Out Power Valves And At The Last Show In Syracuse Ny There Was A Willies Coupe With A Stock 502 Stock Cam And He Had A 8/71 And Carbs And It Surged So Not Sure If Its Even In The Cam? At The New England Summer Nationals 4 Cars There Surged,that We Seen,was Probably More There. 2 Had Holley Blower Carbs , One Had Regular Holleys,one Had Demons.was Trying To Narrow It Down To Maybe Its In The Carbs? No Luck.

68novass -did You Change Anything In The Carbs ? Power Valves/jets ? What Is Your Timing Set At? Initial, Total? Msd/weights/springs? You Running A Large Duration Cam? Another Dyno Shop Mentioned To Us That The Blower Has To Be Teflon Lined, The Weiand Blower We Have Isnt.none Of Our Blowers We Have , Your Blower? Thanks For The Video And Yes We Have Seen That On You Tube Before.was Trying To Watch The Tach But Video Shuts Off There Right At The End.we Think It Sounds Good.

Would Like To Hear camaroman7d Camaro Run ,he Says His Surges And Runs Better That Way,starts The Best And He Can Tune It Out If He Wants To. Any More Idea's , Thanks For The Replies

68NovaSS 09-15-2007 10:29 AM

After a month or so I bought new primary idle air bleeds and opened them up from .070 to .080, leaned it out some at idle. Dropped the jets, pri and sec 4 numbers, that helped with the initial richness, al idle adjustments are out about 1.5 for big roll, 1.25 calms it down some. Also have new accelerator pump cams but haven't messed with them yet. These are Mighty Demons. Cam is Lunati with 50139, solid roller, Isky RedZone liftersn cam # RRA-282-290, .502 I/E. Dur 224/I 232/E @.050, advertised 282/290. I did use 1.6 rockers on the exhaust side. Timing 20 initial, 38 total all in at 2500. Teflon lined?, it';s beens o long I can't recall, I don't think so, the rotors aren't teflon stripped though. The idle when it rolls is 700/1000. Usint a MSD/BRM, no retard set. LSA 112, intake c/l 108, installs 4 deg adv.

I have three videos of Royces Camaro he sent me recorded on his cell. I converted them to .avi, two are 11 mb one is about 4 mb. Maybe I can shrink them more or convert to another type of file. I'm sure he wouldn't mind me sending them, but that's a huge file to send. Later today I will try to post to youtube, acknowledging Royce as the owner if he is ok with it. He sld the car, kept the motor is almost done building a killer '63 Skylark pro street car.

68NovaSS 09-15-2007 12:24 PM

I uploaded Royces videos to my you tube, but...they uploaded upside down!!! I may try to convert from .avi to .mov or .mpg and redo, but you can hear his motor. As I said, they were converted from a cell phone format and aren't the best around.

chevygirl74 09-17-2007 01:30 AM


bentwings 09-17-2007 09:28 AM

I guess I don't understnd why you want this motor to lope. Sounds like you have it running good. Get a Comp cam thumper if you want lope. It will about turn the car over haha.
Usually these blower motors roll at idle because they are running rich. I speed the idle up as I just don't like the things running so rich. Holes in the throttle blades let you get them closer to the idle feed where they are supposed to be. I think some blowers have variable clearances around the rotors so as the rotors turn there is more or less air going in. I like a lot of advance too and this seems to cure it some. A very hot cam makes it worse. Also 4 corner idle adjustments help. Run E-85 and they smooth out nicely.

Our FC idled at 1800-2000 and ran smooth with a 750 lift cam. Except after a burnout it would load up a little but it cleaned out nicely. It was very sharp on the throttle response.

Vortech 4.3 09-17-2007 06:52 PM

i like the way those engines sounds. its like the engine is saying " let me at it !!!"

302 Z28 09-17-2007 07:18 PM


Originally Posted by Vortech 4.3
i like the way those engines sounds. its like the engine is saying " let me at it !!!"

Yea, makes driving one on the street a real joy :rolleyes: .


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