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Performance Q&A Questions - Performance Q&A

Kevin McClelland Feb 1, 2009
0902chp_01_z Performance_qa_questions Hand_drawn_carb 2/2

Keep Track Of Your Washers!
I really enjoy when you guys come up to me at events and comment on the topics I've written about over the years. What I find very surprising is that when I've written about making a mistake, like hurting an engine on the dyno or installing the upper control arms backwards on my wagon, it seems many of you guys can't believe I would write about it. Well, none of us are perfect.

So here I go again. If this keeps one of you from making a similar mistake, I'll take one for the team. About a month ago, Daniel and I were at a Summit ET Points race at Infineon Raceway (big surprise). During Daniel's final time trial, the engine bogged at the hit of the throttle. It was a slight bog and really didn't affect the run that much except for his reaction time. To correct this, I have from time to time run various sizes of stainless safety wire in the idle air bleeds to richen the transfer circuit of the carburetor. If I had replaceable air bleeds, naturally, I would just change their size. When I do this, I capture the wire between two flat washers under a Nylock nut on the air cleaner stud. This works very well to retain the wire for testing and semipermanent running. I knew I didn't have any wire in the bleeds when the engine bogged this time. I had run down the wire I needed and went to remove the air cleaner. The wing nut jammed on the carb stud and pulled the air cleaner stud out of the carb, even though I was using a jamb nut to secure it. After I got the lid off, I immediately turned my attention to the wing nut, trying to get it off the stud. That was my first mistake. Next, I installed the wire and noticed that I needed a washer to capture the wire properly. After rounding one up, I installed the stud, jamb nut, and washer and tested the stall in the pits. Everything sounded and looked good, so Daniel was off for first round.

By now I think you all know what's coming next. Daniel was at the head of the lanes and was next to pull into the water. I was off to the starting line to watch his race, and there was no Daniel. I turned around and there he was, pushing the car away. I ran back to the car. He said the engine was running funny, like it was loaded up, and he gave the engine a rev. Well, the rev opened the carb blades enough to let the washers through the carb and down into the No. 6 and No. 7 cylinders! As soon as he said that, the engine started knocking, and he shut it off. I knew what I had done, and I was sick to my stomach.

I'm far from proud to share these escapades with you guys, but again, if it saves you dollars and time, it's worth it to me. All I know is that I'll never run washers under the air cleaner carb stud again. I'm putting the engine back together this weekend with new pistons and rings. Luckily the washers stayed flat and never turned on end, otherwise it would have killed the cylinder heads and really hurt my wallet. My pride is already beyond repair.

Rock And Roll
I have a '55 Chevy two-door hardtop. I recently purchased a 12-bolt Moser rearend and installed it with a triangulated four-link setup from Air Ride with coilover shocks. When the old rearend was still in with the leaf springs, I had the same Budnik 17x10 rims with BFGoodrich KDW 255/45/ZR17 tires as I do now, with plenty of clearance in and out and no rubbing. The problem I'm encountering now is with the four-link. When the rearend articulates up and down, such as when entering driveways, with one wheel high and one low, there is enough lateral movement in the four-link to allow the tires to rub (inner body on one side and inner fender on the other). It's been suggested that I attach a Panhard bar from the frame on one side to the shock mount on the other side. This would require changing the gas tank for added clearance, eliminating the spare tire well, and fabricating mounts for the new Panhard bar. Do you think this would work, or is there another way to fix this? Thanks for your help.
Mike Genovese
San Jose, CA

What you've done to your Tri-5 is a very nice upgrade to the rear suspension and the power capacity of your driveline. The Air Ride triangulated four-link system uses the same geometry that many GM cars have used through the years. They have never used a Panhard bar, and you don't need to either. The triangulated link system locates the rearend by putting the bars into compression and tension from their differing angles. If you had a racing-type four-link with parallel links, you'd need some type of rearend locater, either a diagonal bar between the lower links or a Panhard bar.

The problem you are having is not the lateral movement; it's the free articulation of the rearend that causes your tires to come into contact with your wheelwells from the body roll. The only thing that will reduce this body roll is an antiroll bar on the rear suspension. Air Ride offers a very nice Musclebar front sway bar, but not a rear bar. Check with Hellwig Products for a very nice adjustable 1-inch rear sway-bar kit that mounts under the rearend for improved exhaust clearance. The bar is constructed from 4140 alloy steel and has three attachment points for the sway-bar endlinks to adjust the roll stiffness to suit your driving style. The kit (PN 5822) is supplied with all the hardware and high-durometer Polyurethane bushings.

You'll need to check out the mounting of your four-link and coilovers to see if there will be interference with the bar. Take some measurements and contact Hellwig. If you find that the bar won't get in there, check out Chris Alston's Chassisworks and pick up the universal rear antiroll bar kit, PN 6266. This kit is designed for drag cars to help control high-torque launches and will require fabrication skills to be welded into the chassis.


Speedo Me Up
I have a typical stupid question about the speedo gears in my tranny. I had to put a tranny in my '85 Z-28, so I used what I had lying around, a 4L60 out of a '93 Caprice. The problem now is that the speedo reads about 72 mph at 1,800 rpm. What gear do I need to get things right? My current combo is a 3.27:1 rear gear. The tranny tailshaft drive gear is yellow, and the speedo-driven gear is white and has 36 teeth. My rear tires are 245/50R16s. Any help would be greatly appreciated.Aaron SalernoVia email

A Speedo questions aren't stupid after you get a nice little invitation to the courthouse from your local law enforcement agency. Whenever you swap in a new transmission, you should try to steal the speedometer drive and driven gears from the original. You said you have a yellow drive gear on the output shaft. GM never had a yellow drive gear! Your '93 Caprice trans should have had a gray 15-tooth gear if it's from a passenger car or a blue 18-tooth gear if from a wagon. To correct your speedo calibration, you'll need a 38-tooth driven gear (PN 1359272) for the gray drive gear or a 45-tooth driven gear (PN 9775187) for the blue drive gear. Your driven gear sleeve will work with the 38-tooth driven gear, but if you need to go to the 45-tooth gear, you will have to swap out to a PN 25512339 to hold the larger gear.

As always, we couldn't answer any of our readers' speedo questions without the help of Ken Casey at Burt Chevy. For years I've recommended that readers bring their speedo questions to Ken. He has sold more speedo components than any other dealer in the nation. Check with him to keep the flow of gears and sleeves going. I've threatened that it will be engraved on his headstone that he was the Speedo King.


Groan No More
My '96 Impala has 260,000 miles on the clock and has never been wrecked, but it started to make growling sounds when I turned the wheel. I had the service shop replace both the pump and box with Auto Zone parts, and after the makeover the car turned hard to the right and really easily to the left. The shop then installed a remanufactured GM part, including new hoses and a belt. After all that, I'm still having the problem. Fortunately, I kept the original box and want to know where I can send it to get tested. What do you suggest? Is there any difference between the Impala boxes and others? What about a speed-sensitive ratio? Thanks!
Cliff Blacke
Via email

Boy, that's a pile of parts with the same results! We assume that the problem you're talking about is the odd power-assist. Yes, there are many differences in the boxes. There are high-effort, low-effort, and speed-sensitive ratio boxes that change the ratio with vehicle speed. Finally, the internal stops differ greatly among A-, F-, G-, and B-bodies. You're on the right track having your original box rebuilt and set for your driving preferences. Lee Manufacturing in Sun Valley, California, is the source you're looking for. At Lee, they build many Sprint Cup boxes and also boxes for many circle racers around the country, and they have the ability to custom-tune the power steering box right to your driving style. I've even had them revalve a power rack from a late-model VW bug, which is a long story for another day. Give them a call and get your original box in the mail.

Lee Mfg.

Octane Dependency
Back in the '60s I raced a gasser and have played with a '66 Nova for about 20 years. As you can guess, I am pretty low-tech. However, I have a project now that I really want to get right, and I could use your help.

The project is a '57 Chevy primarily for show, but I want good street performance too. The engine is already built. It has a 3970010 block with factory 11:1 pistons. The heads are 340292s with 2.02/1.60-inch valves. I thought I could lower the compression to about 10:1 for use with 93-octane by using a 0.070-inch head gasket. After reading one of your articles, I learned that this gasket might increase the quench area and affect performance. Will this be significant? I'm sure you will recommend aluminum heads. Are there any that will give me 10:1 compression?
Jim Jackson
Murfreesboro, TN

We sure wish we had 93-octane gas out here in California! 91 is a weak blend, and those couple of points would keep us out of our knock sensors on late-model cars. For your early iron, knocking down the squeeze a point or two is the right direction. Increasing the piston-to-head (quench) clearance is a simple way to reduce the compression ratio.

How much will it kill the efficiency or power of your engine? I don't think you need to worry about it. If you're trying to stick with the early-theme LT-1 style of small-block, stay with your iron heads. You didn't state how thick your current head gaskets are. If you're running Fel-Pro performance gaskets, they displace 8.9 cc. If you step these up to 0.070-inch gaskets, you'll displace around 15.6 cc. Finally, if you built your old-school engine true to form and used the original 0.016-inch steel shim gaskets, they only displace 3.5 cc! As a rule of thumb, for every 1 cc of change you will see 0.1 compression ratio changes on a 350 small-block. So if you have the super-thin steel shim and open it up to the 0.070-inch gasket, you should see a change in compression of about 1.2 points. At most, you will lose 3-6 percent with the point of compression change and a couple more points for the increased quench. We'd have to guess that you would see around 5 percent less power.

Since you said we were going to recommend switching to aluminum heads, take a look at the Air Flow Research 180cc Eliminator Street heads. These heads will outperform production steel heads to the tune of 70-plus horsepower! They're also available in 65cc and 75cc combustion chamber volumes. Using the 75cc chambers will allow you to run the thin (correct) head gasket to retain your quench and lower the compression by a little over a point. The production 292 iron heads have a 64cc combustion chamber. The AFR heads feature 3/4-inch deck thickness for ultimate durability and lightweight 2.02/1.60-inch valves with 8mm valve stems. They come with either straight-plug (PN 0911) or angle-plug (PN 0917) configurations. These heads will truly wake up your old-school '57 buildup. If you wish, paint the aluminum heads to match in Chevy Orange, and not many people will be the wiser.


Slight Disconnect
I have an '85 Monte Carlo SS 305 and I installed a vacuum-control distributor, a Mallory PN 8548201, and the throttle response does not respond when first accelerating. It has a pause, as if the power shuts off, then after about 1,000 rpm the car takes off and runs well throughout the rpm range. Can you give me some insight on what my problem might be? Also, it still has the factory-equipped carburetor. Could this be my problem?
William Breedlove
Via e-mail

From your information, we keyed into a couple problems. The Mallory distributor you installed is an HEI replacement-type distributor with some very nice upgrades. It features improved electronics, a High Dielectric strength cap and rotor, stainless steel mechanical advance, and an adjustable vacuum-advance can. This is a perfect upgrade to a non-computer-controlled vehicle. Your '85 Monte SS, with its 305, is computer-controlled. The computer controls the spark advance, fuel mixture, and transmission functions. You must have picked up a "check engine" lamp when you installed this distributor. With this change, you're giving the computer-controlled carburetor fits. It's probably running full rich, which is way too much fuel at idle and affecting the way the car responds to throttle changes. At wide open throttle it should run just fine.

Depending on emissions regulations in your state, you could stick with your new distributor and replace the computer-controlled Q-jet with an earlier 650 nonfeedback Q-jet, or install a Holley or Edelbrock carb of your choice. For your 305, we'd stick with a carb under 650 cfm. You could use an adapter plate to go aftermarket or change to an Edelbrock Performer manifold. The proper Edelbrock Performer series carburetor would be PN 1406, a nonemissions, electric-choke, 600-cfm carb. To mount this to your stock manifold, you'll need a square-bore-to-stock-Q-jet manifold adapter (PN 2696).

Even though Q-jets are out of production you can still get them from selected rebuilders. If you wish to stick with an original Rochester Q-jet, check with JET Performance for complete performance rebuilt Q-jets for any application, and JET can even build a custom tailored Q-jet setup for your Monte.

Finally, we didn't talk about the spark timing you may be running. If you followed the initial spark advance on the emissions label under your hood, you set the initial timing at zero, or top dead center. With the Mallory distributor you installed, you should set your timing around 10-12 degrees before TDC. Make sure that when you're setting the timing, you disconnect the vacuum advance can. This will at least make your car run the best until you can swap out for the correct carburetor. Good luck.


Blue Flame Special
I've been having issues with getting fire from my headers at wide open throttle. I'm hoping you can explain exactly which condition it is, lean or rich. My engine setup is a 383 stroker, a Comp Cams XE294 cam, Sportsman II heads, 12.2:1 compression, a Weiand high-rise intake, a Demon 750-cfm carb jetted at 73 primary with 78 secondaries, and Hooker Super Comp headers with 13/4-inch primaries leading into 31/2-inch collectors. I think they were for a circle-track application, since they come together after the flange and shoot straight out through the fenders, behind the front tires. Total length of the primaries is about 20-22 inches to the collector, then a 10-inch turndown (still 31/2 inches from the collector). It runs on 110-octane race fuel and is in my mud racing truck.

You can really only see the flames at night, not surprisingly, unless it is at WOT. At idle, there are occasionally small blue licks of flame exiting, then when I launch and all the way through the track, there are bright red-orange flames shooting out about a foot and a half. Some of the guys who race there say it is running lean and probably pulling in air from somewhere. I have yet to find a vacuum leak. Others say it is rich, burning off excess fuel. Every time I pull the plugs, they are just as they should be, depending on the day, between ash-gray and light brown. Any ideas?
Via email

Years ago we ran a 502 big-block Chevy on the engine dyno and stuffed about 300 hp of nitrous through the thing. At the time, I had the dyno facing backward in the cell with the control room window facing the engine front, and the headers came off the front of the engine. We baselined the engine on pump gas and made 670 hp, and then turned up the wick. Well, with a flip of the nitrous button, out shot 2-foot blue flames from both headers and the horsepower needle swept past 1,000 on pump gas! None of us had ever seen header flames in the dyno cell with the lights on.

Back to your mud truck. You will see flames from your headers at night. It sounds like yours may be a little excessive. The short primary header lengths aren't helping matters much. Also, with the color you say the flames are, you could be a little to the rich side. However, the amount of flames, their color, and the exhaust gas temperature are based on many things. The efficiency of the combustion determines how much fuel is consumed during the power stroke and turned into work. How much spark timing are you running? The more retarded the spark advance is, the later the flame is started and the longer it will burn. Fuel doesn't care if it's is doing work or just giving you a beautiful flame show. With your compression and race fuel, you should have somewhere around 36-38 degrees total timing. From the color of your plugs, we'd have to agree with you that your mixture is close. It's tough to set the jetting by the odometer of your truck. It would be easy at a dragstrip, but in the mud it is much safer being on the rich side.

Tell your friends to enjoy the flame show, and ask the crowd for money for the extra thrill. Guess at your track, they don't need jets flying over on the afterburners. Have fun!

Way Over Bore
I bought an engine rebuild kit from Powerhouse for a small-block 350 with 0.030-over pistons. Can a 305 block be bored to my pistons?
Allan McAra
Chilliwack, B.C., Canada

The stock bore on a 305 is 3.736 inches. Bringing it out to a standard bore for a 350 would require a 4.00-inch bore, which would remove more than 1/4 inch from the cylinder walls. Production 305 blocks will not accept that much overbore. The good news is that Gen I 350 blocks are very plentiful. Check with the machine shop where you were going to have your engine bored, and I'm sure there's a core 350 lying around or the mechanics will know were you can buy one reasonably. Sorry for the inconvenience.

Budget Builder
I'm writing in to you from the birthplace of GM and Chevrolet! I'm 23 years old and building a '72 Chevelle on a $25,000 salary. I have spent my money wisely and currently have the whole car in primer; I'm dropping in a crate engine, a fresh TH350, and all types of chrome and billet goodies. The engine is a 383 stroker with Vortec heads and 10.2:1 compression. The rearend is an 8.2-inch 10-bolt posi with fresh 3.73 gears, and I've had people tell me that I will destroy this rearend. On the other hand, the guy who built it said as long as I don't put slicks on it and really hook up, it will be fine. I won't be taking it to the track. I'm only planning to cruise it in the summer and maybe run with some guys off a few stoplights. I plan on upgrading to a 12-bolt when my budget allows but want to know if this combo will get me by until then. Thank for your help.
Paul Petronzi
Flint, MI

We have a few answers here. Yes, the rearend will live, and yes, the rearend could blow up. Doesn't that help? As everyone knows, you can break an anvil if you try hard enough.

The early 8.2-inch 10-bolts can give you very good service. As you have seen, we've built up several in past issues and they've given us great service. The gentleman who built your rearend is dead on when he says that it will live if you don't hook it up hard. Stay away from slicks and nasty wheelhop. Also, an automatic transmission helps tremendously. The automatic keeps the ring-and-pinion loaded under acceleration. Manual-trans cars tend to unload and load on every gear change and are prone to wheelhop.

If you use your brain, you should get many years of service out of your current combination and it will allow you to save for the 12-bolt you want. Enjoy the many cruise nights, and take a drive down Woodward Avenue for us!

Technical questions for Kevin McClelland can be sent to him at



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