meling0017

I have a new 383, 460hk stroker with Edelbrock Performer cylinder head #60899 (http://www.jegs.com/InstallationInst.../350-60899.pdf). I have big problems with the car jerking on lower speeds and found Lars Grimsrud's articles regarding timing issues and adjusting timing to 36 degrees instead of the 32 I have at present. He also states that fast burn heads should have 28-32. Does anyone know if the mentioned Edelbrock head comes under the fast burn head category. What can I do wrong if they are fast burn heads and use 36 deg. and why is the timing different for such heads?
RGS Henry

gingerbreadman1977

28-32 seems to low for any 350-383 chev to me. fast burns as a rule of thumb do like around the 34 mark but that is just a guide . cam, compression, gearing is all dependant on this. my mate has a large solid cam with GM fastburns and he is up around the 38-40 degree range so experiment with it. i have GM fast burns as well and have settled on 34-36.

dont forget timing is not all about total timing. initial timing is just as important and you may be requiring more of that while limiting your total. tell us more about your gearing, cam specs,carb etc as i dont think timing alone is your problem to create jerking at low speeds.

OzzyTom

460hp with those heads suggests you have a pretty stout cam.. possibly up around the 238~242 degree @ 0.050 lift

maybe your vacuum is down at lower rpm due to greater valve overlap... problem could be carb tuning... what carb is it? Also, are you running a vac advance canister? is it providing the right signal for your motor specs? Maybe it's just that torque doesn't become real strong till over 2500 rpm due to your combo of parts.
This was the case in my stroker.
Problem is less of an issue now as I swapped out the rear diff with a rebuilt 3.73 ratio. Now with the increased rpm (at same speeds) there's more than enough torque and motor pulls stronger without the jerking.

meling0017

Thanks so for for the replys. I am attaching the information about the engine and carburettor. I did try to increase the primary jets up 3 sizes on the carburetor but did not notice any changes. I also have the vacuum advance on the distributor. I have new adjustable vacuum advance with new different springs but have not attemted to do anything with it yet before I have some moore understanding about the issue. The gear and diff is the standard ones. Diff is 4 speed M21 with 3,36 gear.
If you can based on the below information give me some hints I would appreciate it.
Henry

BLOCK CAST # C383-6
LIFTERS HT-817
FUEL PUMP ROD Pioneer # FPR-1936
ROCKERS X Comp # 1301-16
FUEL PUMP PLATE Mr Gasket # 1514
PUSHRODS Comp # 7608
Oil Pump Drive Rod Melling # IS55G
BALANCER Professional Products # 8000
CAMSHAFT Edelbrock #2204 Roller
BALANCER BOLT Pioneer # 859012
TIMING SET Elgin # SS-3145
VALVE COVERS RPC Company #R9216
CYL. HEAD # Edelbrock # 60899
DIPTUBE Pro-Form # 66130 (RSS)
LIFTERS HL-2148 Roller Lifters
FLYWHEEL AUTO. Pioneer # FRA-159
OIL PUMP M55HV Melling
FLYWHEEL STD. PIONEER # FW 109
SCREEN 55-S1
FLYWHEEL BOLTS ATP # ZX204 (Automatic)
GASKETS X EIS-1093PT
Std. Flywheel Bolts X ATP # ZX-206
OIL PAN Silver Seal # 6503CP (Chrome)
STARTER DB Electrical # PM300
FUEL PUMP FITTING Diamond #
PILOT BUSHING Pioneer # PB-656-5
HEAD BOLTS Eng. Rebuilders # CHB-35X
400 BAL. WEIGHT Pioineer
FUEL PUMP Mr. Gasket # 7703 TIMING COVER RPC Company # R4934
OIL FILTER Parts Master # 61069
FILTER HOUSING Nickels # 43500
WATER PUMPX Eastern # 18-468 short, standard
MARCH PULLEYSX March # 20450 (Kit # 5) O
INTAKE MANIFOLD Pro-Products # 52025 polished
ALTERNATOR Pro-Form # 66445.1N
CARBURETOR Holley 670 street avanger
Power Steering Pump Durex # P-300
DISTRIBUTOR Mid-America # 618-578 tach drive
COIL PF#66958C, MSD Bracket# 8213
DIST. HOLDOWN Fred Beans GM # 10096197
Alternator Belt 54.8 inches
WIRES X Parts Master # 26907
SPARK PLUGS Champion # RC12YC
AIR CLEANER Pro-Form # 66804 14 inch
FUEL FILTERX Parts Master # GF61M
PCV VALVE Parts Master # V188
THERM. HOUSING PRO-FORM #66210

lars

In general, the more efficient the combustion chamber design, the less total ignition lead the engine will want to produce peak torque (peak cylinder pressure). Also, smaller bores require less total lead, and larger bores want more.

With that said, each engine is different, and you cannot determine the exact point without running it on the dyno to see how the engine responds to changes. I just ran a 435 with Edelbrock heads and it wanted 40 degrees total timing. I ran a 407 with RHS aluminum heads and it made best power and torque at 32 degrees (these are not "fast-burn" heads).

If you're getting "jerking" at light throttle cruise, the cause is usually over-advanced timing at that rpm. If you're running vacuum advance, unplug the hose to the advance and see what happens. If this solves the problem, shorten your vacuum advance curve and limit it to about 10 degrees. If you don't have vacuum advance, try slowing down your advance curve and limit the total advance to 3000 rpm and higher.

Lars

Bttb2

I have the same set up as you. I am having the same problems. I went to fuel injection changed fuel ratios to no avail.