The whole idea about working on cars is that it’s supposed to be fun. If you think about it, the process is all about immediate gratification. There’s something that needs to be fixed or improved, and with wrenches in hand, you dive in and complete the job. It can be fun — when everything goes right. This year’s collection of 10 Tech Tips is all about helping make that process more fun and perhaps a bit less frustrating.
The issue with hot rods comes down to the immense number of aftermarket parts that must all work together. The inherent flaw here is that there’s going to be some conflict when all the different parts don’t play well together. Factory-built cars are assembled with parts designed to work together but the aftermarket is a different ball game. The key is identifying the potential problem area and creating ways to overcome that difficulty. The result is a great running car that’s a blast to drive — and fun to work on. The following is a collection of helpful hints and technical assistance to make working on your car that much more fun.
Vortec iron heads still have a place in the performance world of the small-block Chevy. These heads are inexpensive yet flow very well. But, they do have some idiosyncrasies that need to be identified. A major point that is rarely addressed is that the Vortec iron head uses a different spark plug than a typical iron small-block Chevy. The Vortec uses a spark plug with a tapered seat with a 0.680-inch thread length. A standard small-block Chevy plug thread length is 0.450.
In the accompanying photo, you can see that if the shorter plug is used in a Vortec head, the operating end of the plug will be shrouded by the spark plug boss. The result is the engine will have lower combustion efficiency which means the engine will run poorly, lose power, and demand greater ignition advance. Always use a 0.680-inch thread reach spark plug with a tapered seat on these heads. Interestingly, this is similar to the spark plug design used in GM LS engines. For reference, the standard copper core Autolite P/N for the original Vortec heads are 605 or 106.
2. Clearance Your Header Flanges
After struggling for several hours in an attempt to coerce a set of big-block Chevy header flanges to fit flat against the cylinder head, we discovered that for many Rat motor headers, the more robust header flanges crash into the head bolts and prevent the header from fitting properly. This is aggravated when using ARP head bolts as the bolt heads are slightly taller than stock versions and ARP always uses thick head bolt washers that raise the bolt head even further. The solution is easy — just use a die grinder to clearance the flange to clear the head bolts. Do this before clearancing the header tubes for the chassis as this small effort will make a big difference.
We’ve been caught in this insidious little trap on two different occasions, 10 years apart. Apparently, some engine pipe plug kits come with small 1/4-inch pipe plugs drilled with tiny 0.030-inch holes to lubricate the timing chain. The problem is that these holes are easily overlooked. If you are not paying attention, these drilled plugs can easily end up as rear gallery plugs behind the flywheel where, of course, they leak like crazy the moment the engine starts.
We discovered our error when we tried to pressure lube the engine while it was bolted on the test stand and a giant puddle of oil soon found its way to the floor. Forewarned is forearmed but you have to check — don’t assume the plugs really are plugs!
4. Throw That Curve
Did you know you can create your own ignition curve without pulling the distributor from the engine? All that’s needed is a dial-back timing light, tachometer, notepad, pen, and a friend to help with the throttle. Set up your notepad with listings every 250 or 500 rpm from 1,500 to perhaps 3,500 rpm. Remove the hose from the vacuum advance (if so equipped) and plug it.
Have a friend increase engine speed to the desired RPM and record the timing at each of those RPM points. Let’s say you have measured timing every 250 rpm from 2,000 to 3,500 rpm. While the data will offer the specific numbers, you can plot this curve on a graph using a spreadsheet program (such as Microsoft Excel, Google Sheets, Open Office Calc, etc.) which will offer a visual clue as to the distributor curve’s actual performance.
5. Holley Accelerator Pump Rejuvenation
It’s not unusual for a Holley carb that sits around for a couple of months to suddenly suffer from accelerator pump failure. The good news is that oftentimes the fix is really simple. If there is no pump shot, remove the squirter from the carb and gently pry on the anti-drain-back needle located under the nozzle. This valve often sticks and will block the accelerator pump shot.
Shoot carburetor cleaner into this area, remove the needle, and then replace it under the nozzle and check for operation. Do not check to see if it is free by pushing on the accelerator pump linkage with the squirter removed. If you do, this will launch the check valve needle where you’ll never find it (ask us how we know). Worse, it may fall into the intake manifold which will require removing the carburetor to retrieve.
If the needle valve is not stuck, then remove and inspect the pump diaphragm. The older black diaphragms can become brittle and fail to operate. You can replace them with the same diaphragm, or go with the better green diaphragm from Holley that is made of Viton rubber that is far more durable. The green diaphragm is P/N: 135-10.
This is a simple, homemade tool to help you diagnose relay issues. If you think a relay is bad you can remove the relay and use a jumper wire between the 30 terminal and its opposite, which for most automotive Bosch type relays is the 87 terminal (the one physically directly across). With the relay removed, stick the male terminal jumper wire into the corresponding pins in the relay harness.
The jumper will immediately make the circuit live. In the case of an electric fuel pump, this allows you to check to ensure the pump is operational. This simple jumper can also be used, for example, to check for electric fan operation. With relays now such a big part of late model and performance cars, this is a simple, homemade tool that costs nothing that can also save you some diagnostic time.
7. Quick Lap
Lapping valves is a time-honored technique — some swear by it, while others say it’s not necessary. The process uses a mild abrasive placed on the valve and using a lapping stick with a suction cup that grips the valve while you spin the stick between your hands. That spins the valve and grinds the compound into the valve seat.
Our buddy Don Barrington, Jr. at Barrington Machine shared a trick he learned from famous marine engine builder Don Teague. Teague uses a small cordless drill to spin the valve in the seat, which accomplishes the lapping process very rapidly and can alleviate hand cramps and sore muscles the next day.
We ran into a problem the other day that necessitated a quick fix. The brass inverted flare fuel inlet fitting in our Holley carburetor had been over-tightened so many times that it began to leak. Tightening it further didn’t help and there wasn’t a new fitting in the entire metropolitan area near our shop on the day in question. The car had to leave that day so we were forced into a makeshift repair.
For a quick, temporary repair (we recognize its hack nature), we wrapped the threads on the 5/8×18 flare nut with pipe thread tape. The sealing area is supposed to be on the inverted flare, but this quick fix moved the seal to the fitting’s threads and allowed us to drive the car until we could order the proper fitting via our favorite mail-order house.
If you’ve ever destroyed one of those very thin rubber secondary diaphragms for a Holley while trying to assemble the canister, we learned a simple trick that makes this task much easier. Sean Murphy of Sean Murphy Induction (SMI) showed us how he does it. First, slide the diaphragm rod through the housing base, and with the rubber diaphragm on the base, lightly clamp the steel shaft in a vise. Squirt WD-40 on the threads of each screw and place the diaphragm spring (Murphy likes the purple spring for most applications) in the lid.
Carefully lower the lid over the base and hand start the screws. With the diaphragm shaft held firmly in the vise, this allows you to position the lid over the base more easily without moving the thin rubber diaphragm. The WD-40 lube should prevent the male threads from catching the thin rubber diaphragm and tearing it up. This works! Of course, a Holley Quick Change kit (P/N: 20-59) is a great way to make spring changes easier since the Quick Change lid means the overall cover does not have to be removed.
10. Another Way to Remove Pilot Bushing
We recently ran across another way to press out old pilot bushings. The most popular is the grease method. There’s also the bread method where you shove moistened bread into the hole behind the pilot bushing and then pound out the bushing. On our small-block Chevy, neither the grease nor the bread techniques worked because the opening in the pilot hole was so badly elongated that the grease/bread just leaked out.
Our friend Eric Schmiege suggested employing a large tap. A 3/4-inch x 16 TPI fine-thread tap neatly cuts threads in the bushing and then, once pushed against the back wall it forces out the old bushing. We also now have a nice tapped pilot bushing that we’re looking for some other use for, since it looks so cool!
Of course, this won’t work on crankshafts equipped with pilot bearings. The bread method might work better with those. We must also include the warning that none of these efforts will work on LS engines, as the LS uses a rifle-drilled crankshaft with a freeze plug in the end to eliminate oil leaks. Attempting to push against this freeze plug will cause a massive oil leak. So don’t try this on an LS engine! Removing the pilot bearing will require a specific puller in that case.
These ten tips come from over four decades of experience. As you can tell from the pipe-plug tip, sometimes things take us a time or two to learn, but once we learn it, we happily share the knowledge, so that you can avoid the difficulties we’ve encountered. Hopefully, you find these tips helpful and stay tuned for more, because we’re always learning something new in the shop. If you have any tips of your own, be sure to share them down in the comments below.