quaddy

[bjwynd]

i seem to be running to lean in the primary ok on idle and top end but too lean at part throttle. Does anyone know what power piston spring, primary jets and metering rods i should be running on a 253 with this cam profile my jets are 70 at the moment and rods are something 49 cant remember now

Hydraulic Special

Part No: 244621
Grind No:
Engine Ident. 1969-1988 Holden V-8 253-308 CU.IN.


Valve Setting: Intake 0.000 Exhaust 0.000 HOT
Lift: Intake @ Cam 3101 At Valve 496 Rocker Arm Ratio
Exhaust @ Cam 3101.000 At Valve 496.000 1.6
All lifts are based on Zero lash and theretical rocker arm ratios
Cam timing Opens Closes Advertised Duration
at .004 Intake 35° BTDC 77° ABDC 292°
tappet Lift Exhaust 75° BBDC 37° ATDC 292°
Spring Requirements
Triple Dual Outer Inner Recommended RPM Range
Part No 99848 With Matching Components
Minimum RPM 2500
Loads Closed 105 LBS @ 1.700 Or 1 45/64 Maximum RPM 6200
Open 298 LBS @ 1.220 Valve Float 6500
Cam Timing Opens Closes Max Lift Duration
at 0.050 Intake 10° BTDC 40° ABDC 105° ATDC 230°
tappet Lift Exhaust 50° BBDC 0° ATDC 115° BTDC 230°

Remarks: Intake lobe lift at TDC = .081"

[ari666]

email these guys Hume Performance and they will send you a fax sheet asking you all sorts of q's like 1st piston stroke PSI reading, 2nd reading, vacuum@idle vac@part throttle etc

fill out that sheet and fax it back and they will send you everything you need to get your quaddy running in tip-top condition.

edit* thats a pretty big cam for a 253...

[bjwynd]

thanks mate will look into that but have done some home work and found out i should b setting at around 16 degrees btdc for that cam and will regraph the dizzy so suit and see if the prob is there

[ari666]

that cam is basically a crane 286. which i am running in my 308. good luck getting 16 deg of base into it. im pushing it with 14 ATM. in summer itll have to go back to 12. and my dizzy is graphed to suit.

whats your compression ratio?

[bjwynd]

unfortunately its only 9 to 1 i told the boys to shave the heads obliviously didnt so it wont go as hard as it should not really happy but what do u do should have been closer to 10 to 1 but runs well at 16 btdc starts fine to little bit of hesitation but starts thats if my gauge is right was saying 135 psi but motor wasnt very warm when i tested it and not shure if my rings are bedded in properly was with a push in gauge not a screw in so i might get another 20 psi out of it yet but not holding my breath as they were all within 2 to 3 psi of each other i hope so just to get the cam working properly

[bjwynd]

btw im sending my dizzy of next week to get re curved

[bjwynd]

now i might be a bit slow but y bring it back for summer dose the warmer air make the burn time quicker that at cold temp

[ari666]

yeah pretty much. pings on hot days. cold intake charge means i can cram in more fuel/air/timing, but when its hot air going in it combusts too early and pre-ignites.

mine is 10.7:1 tho. i dont think you will have a problem with pinging running 9:1 with a 286. doubt you will get it to ping at all. i tried my out with stock slightly shaved heads and it ran like crap. wouldnt ping, zero power. i highly recommend ditching that cam and going for something a bit smaller. itll mean better fuel consumption and more power. but you can learn the same way i did lol

[bjwynd]

thing that gets me is it seems to go pretty hard iv had this motor in anther car with a 2.75 diff and just wants to brake traction when you get in the cams range but a bit slow till about 1500 to 2000 rpm but i hear what you say 180 psi would be more pleasing

[ari666]

meh, psi readings are misleading IMO. a loose engine runs better than a tight one. low comp via the piston rings doesnt mean its a bad engine. just means it doesnt make full pressure when doing a comp test.

as long as all your cylinders are all around the same reading, your good to go.