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QUESTION:
Dear Professor Overdrive:
I am going to rebuild my AMC 360. I bought a Haynes manual which says the 401 has a 3.68 in. stroke. The 360 only has a 3.44 in. stroke. Could I stroke my 360 using a 401 crank and rods? Do I need a special harmonic balancer?
Jeffrey Real
Missoula, MT
ANSWER:
Jeffrey, the 401 and 360 cranks use different bearings. The rod bearings are .250 in. bigger in diameter on the 401, but the mains are the same. Check the block and cam for clearance. The bore sizes are different so you’d use custom pistons with the correct pin height, but only if the rods clear the block and cam. The harmonic balancer is the same for all 304 to 401 engines.
QUESTION:
Dear Professor Overdrive:
I’ve just finished building a supercharged small block 350 with about 9 percent boost. It’s strictly a cruiser with a mild cam, etc. The engine is on a test stand and I can’t get it to idle. When it gets close to 1,000-1,300 rpm it will start to hunt with the rpm ranging from 1,000 to 1,500 before it stops (if I don’t throttle up).
I have two vacuum secondaries on top with a Mallory Hyfire IVC ignition and a magnetic 3 wire distributor. Would incorrect valve lash help cause this?
Roger Pynappel
Truckee, CA
ANSWER:
Well, Roger, my first thought is that your carb is jetted too rich. Are your spark plugs black or tarnished brown? If these are dark, jet the carb primaries down until they are brown. On the ignition side, the motor will probably be around 35 degrees total advance. Check the total timing and check where it is coming in. Advancing too early could give the same results. Finally, if your valve lash is too tight, the valves could be hanging open. This would be evident if you are getting extra noise from the carb or header. If they are not tight enough, the pushrods may rattle and the valves won’t fully open. Finally, check for vacuum leaks.
QUESTION:
Dear Professor Overdrive:
I have a 1965 Mustang with a 289 2 barrel rated at 200 HP. I want to put an Edelbrock Performer intake and cam in the engine. Which Edelbrock carb should I use? Is there anything I should consider when switching from a 2 barrel to a 4 barrel? Also, the 289 has an EGR running from the valve cover to the bottom of the carb. The Performer has no EGR. Should I purchase a spacer, or just have breathers on each valve cover? What kind of performance gains can I expect?
Lon M. Waitman
Dayton, OH
ANSWER:
Lon, since you’re choosing a whole Edelbrock system, go with the EDL-1406 600 cfm carb with electric choke. If you have an automatic transmission you may have to use a throttle lever adapter for your kickdown linkage (EDL-1481 or EDL-1490). These adapters are only needed if you have a cable throttle system. EDL-1490 repositions the cable bracket to the carb linkage. If your system is rod linkage, you won’t need these. Also, be sure to use the appropriate Edelbrock Sure Seat valve springs for your Performer cam, EDL-5822 for a non-rotator valvetrain, or EDL-5922 for a rotator valvetrain.
The hose going from the valve cover to the carb is actually a breather, not an EGR. All you need is a PCV in one valve cover and a breather in the other. You should see a 20-25 HP gain with your high-rise manifold and 4 barrel setup.
QUESTION:
Dear Professor Overdrive:
I recently had the primary throttle shaft bushed on my Quadrajet carb. The carb worked well--except for cold-start performance. Now my stock Chevy 350 idles like it has bad valves or a vacuum leak, and the exhaust has a really bad odor. I’ve put a rebuild kit into it, including a new float, fuel filter, etc. I have changed the air horn and main body. The only thing that seems to make a difference is when I change the throttle plate. I have a good used carb on the engine and it seems fine. Do you have any ideas?
Harry Weston
Maple Ridge, British Columbia
ANSWER:
Well, Harry, with all you have done and checked, it sounds like the throttle plates were misaligned after the base was rebushed. Depending on the age and condition of the other carb parts, you might consider a different carb. If you have something available that you can try, it may point you in the right direction. Good luck.
QUESTION:
I have a Ford 351W, bored 0.030 over, roller cam with a 315 degree duration and 0.640 lift, World Products heads that have been fully ported and polished, an Edelbrock Victor Jr. intake, and a Holley 750 cfm carb.
At the beginning of the season, the motor ran well, with an average rpm of 7,500. By the end of the season, the motor has picked up a high end miss above 6,000 rpm.
I’ve tried a new MSD 6AL ignition, plugs, wires, cap, and rotor. I have even had the cam degreed, but I still haven’t eliminated the miss. What else could cause the miss? Could it be the distributor?
Bart Wilson
Hartford, KY
ANSWER:
Bart, the most common problem is valve springs. The cam size you have chosen and the rpms you are running have put great stress on the springs. You should check the pressure and installed height regularly, and replace the springs when the pressure starts dropping.
Secondly, you didn’t mention what distributor you are using. MSD makes a unit (MSD-85805) designed specifically for folks running a 351W with a Edelbrock Victor Jr. intake.
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