ASK RAY

CAMSHAFT CONFUSION

Q: I have read two articles engine builds: One was lately on the Ford 351 Cleveland build in HMM(“Overachiever,” February 2022, # 222) and the other was a big-block Mopar in HotRodmagazine. Both engines were built using flat-tappet camshafts, and neither build was cheap. My question is, why use a flat-tappet camshaft instead of a roller? The last engine that I built with a flat-tappet cam was 20 years ago. After replacing two cam-and-lifter sets, I read that the modern oils lacked the high zinc and phosphate levels that were in older oils. When I replaced the third cam and lifters, I started using Shell Rotella diesel oil. The third cam has lasted approximately 20,000 miles. All the engines that I built after that have roller cams and lifters. From what I understand, a roller cam is superior and the best way to build an engine. Am I wasting money by using a roller cam?

Lee Waddington

Robinson, Illinois

A:Iagreewithyouthatamodern hydraulicrollerisabetterchoice than evenamodernflat-tappetdesign. The lobe profilecanbeoptimizedinmanyways and thereductioninfrictionisalways good.

Thereisanissuethatneedsto be checkedwhenarollergrindisinstalled, andthatiscamthrustandmovement. Thetaperedlobeofaflattappetlifter is designedtoholdthecaminplace. Controllingcamthrustisnotabigdealbut it does needtobecheckedandaddressed.

Otherthanthecostofthecamand roller lifters,Icannotthinkofanyreason why thoseengineswerebuiltusingaflat tappet.Iamnotfamiliarwiththose two enginebuilds.

HESITATING CHALLENGER

Q: I have a 1973 Dodge Challenger with a modified 318 engine backed by an A904 automatic transmission. The engine uses a Quick Fuel carburetor (QFTSS680VS), Edelbrock medium-height manifold, headers, a mild cam (I don’t know the specs), and an MSD distributor (MSD8504). The engine produces 14 inches of vacuum at 900 rpm and 18.5 inches at 1,800 rpm. The air/fuel ratio is 12:1, and the engine produces 313 hp and 351.2 lb-ft of torque. There is a full stream of fuel when operating the throttle by hand.

When I accelerate just beyond idle, I have to “feather” the gas pedal to keep the car running. If I accelerate too fast, the car will actually stall. After I get past that point it runs fine. I have had this problem since I installed the engine. Any ideas for a cure?

Ken Durst

Via email

A: In most instances, a driveability issue such as the one you are experiencing is due to a lean condition off idle. There are other areas that can evoke the same effect, such as not enough ignition advance or a PCV valve with the wrong flow rate or response.

You make no mention of the engine popping through the carburetor, but that would just confirm that there was not enough fuel if it did.

I will assume that there are no air leaks and that the float level is set properly, along with the mixture screws, especially if that carburetor has a four-corner idle circuit.

Often, the accelerator pump linkage is in the wrong hole, or the accelerator pump cam is not aggressive enough. The pump cams can be changed on many Holley carburetors, and since a Quick Fuel carburetor shares many of the design elements with a Holley, you should check these areas. The accelerator pump stroke may not have enough volume.

I would also disconnect the PCV valve from the vacuum hose and plug the hose with a bolt. Leave the valve out of the engine. Re-adjust the idle mixture and take it for a ride. If it runs much better after doing that, the PCV is wrong for the vacuum profile of the engine. I would then spend the money for the M/E Wagner tunable PCV and your issues will be over.

If this test makes things better, but not by 100 percent, then put 4 or 5 degrees more advance in it with the PCV still disabled and see if the engine likes it.

Follow these steps and you will have the engine running like a top!

CARB CLEANER OR STARTING FLUID?

Q: Hi Ray! I love your column—it’s the first thing I turn to.

I have a 1969 Chevelle 396 with a Rochester carb. I’ve had lots of trouble with fuel evaporating during the summer months. After a spin on a hot day, once I shut off the engine, you can sometimes hear the fuel gurgling like a coffee pot! It had an electric pump in the rear, feeding the mechanical pump, but as you’ve pointed out before, it can’t pump past the mechanical. I disabled the mechanical pump and just used the electrical one and voilà, problem solved.

My question is, I’ve used starting fluid (ethyl ether) in the past with success. Are there any pros or cons of starting fluid versus carb cleaner? Thanks for everything!

Kevin Konieczny

Denver, Colorado

A: Thanks so much for reading my ramblings first! I am glad I was able to help you with the fuel delivery issue.

Starting fluid is very volatile and it is very hard on an engine, while carburetor cleaner is much gentler during combustion. That is why I do not suggest starting fluid.

Starting fluid is chemically designed to allow an engine to run under extremely cold conditions since it will vaporize, where carburetor cleaner will not.

So, when it is minus 50 degrees F and you need to get the old truck started to

plow snow, grab the starting fluid. When the fuel evaporates out of your muscle car or lawn tractor, carburetor cleaner is the way to go!

TEMPERATURE GAUGE

Q: I have a 1967 Corvette with a 327. It was totally restored when I purchased it; however, the broker informed me that the temperature gauge did not work. The muscle car dealership wasn’t able to fix it even after installing new wiring, a new temp gauge, and a new sending unit.

Both the sending unit and gauge tested good prior to installation. I installed a second sending unit myself, but with the same result. The gauge will move one line from the coldest position when the engine is hot, but no further. When the 327 cools down, it’s back to the left behind that first line. It is reading something, but nowhere near an accurate temp to the gauge.

Is there a component missing in the wiring between the sending unit and the gauge? Is it a grounding issue because of the aluminum manifold? Any help would be greatly appreciated.

Mike Westeen

Via email

A: I doubt very much if it is a grounding problem with the intake manifold, but to confirm this, connect a jumper wire from the exterior of the sending unit to a ground and then run the engine to see what happens. Also, you should verify that coolant is actually reaching the sending unit—it’s highly unlikely, but there could possibly be a problem in the casting.

If this proves to be nothing, then get a cup of near-boiling water and, with the sending unit removed and still plugged in, insert the sender in the water and read the gauge.

Considering what was already changed and the tests I mentioned, if power is getting to the gauge, there are proper grounds, and any printed circuit boards for the gauges are good (if that car even has any), then I think you have either a miscalibrated gauge or sending unit.

Just because it is new does not mean it is good. I am quite sure the part is coming from one supplier overseas, so no matter where you buy it from, you’re probably getting the same unit. I have seen this more times than I can count, not with a sending unit but with many other components. One person I know went through five new ballast resistors before he found one with anywhere near the proper resistance. His car was towed home many times due to a defective new ballast.

Send your troublesome tech questions to: askray@hemmings.com or Ask Ray, P.O. Box 2000, Bennington, VT 05201

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