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Techin' In With Fletch - February 2014

Dan Fletcher answers your tech questions.

Dan Fletcher Feb 5, 2014
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I’ve been writing this little ditty for quite a while now, but as I had to do once several years ago, I need to shake the trees. The inventory of quality letters is dwindling, and I need your help. If you’re thinking of a question, but you’ve been hesitant to email it, pull the trigger and send it on. Thanks!

Where’d His Power Go?

I have a 406 engine that has Dart Iron Eagle heads (2.05/1.94 valves, 64cc combustion chambers, 200cc runners), Edelbrock Victor Jr. intake, Wiseco forged dish pistons, Eagle 4340 5.7 rods and crank, Quick fuel Q Series 750 carb, and an MSD 6AL with 3 Step to retard timing for a 300 shot of nitrous. This set up is in a 1982 Cutlass that is street driven. I have a TH350 transmission and 3.73 rear gear behind the engine. My problem is the car generally runs low 12s in the quarter-mile, but now it will only run high 12s, and I don’t know what the problem is. I had a compression and leak down test done, as well as having the carb rebuilt. I also checked the plugs and wires, and everything is OK. Finally, I checked the timing, which is locked out at 36 degrees. The mark moved when I revved the engine up, which it is not supposed to do. I asked a friend about it, and he said my cam could be moving. Does that sound right to you? Would I lose power like that? The loss seems to be mainly on the bottom end.

Lastly, I’d like to know which style of rod is better, H-beam or I-beam? What are the pros and cons of either one compared to the other?
Lance Williams
Winter Garden, FL

When one of my cars does a slow down, I run through a pretty straightforward list of diagnostics. You don’t mention feeling a miss or a layover, so I’m guessing the decreased performance isn’t really perceivable going down the track. You also don’t mention whether this is with spray or not, but I’m guessing with the stated e.t.’s, we’re talking about all-motor runs.

I’m guessing the slow down has been going on for a while, so one of my first checks of cutting the oil filter apart to look for a spun bearing probably isn’t going to be applicable, but I’d still do so. Next is get the valve covers off and check lash, then compression and leak down. When nothing shows up there, I check wide-open throttle and timing. After that, I move to fuel potentials, like fuel pressure and volume. You don’t mention if you’re using an electric pump, but assuming you are, make sure you can pump a gallon in 20 seconds. Hopefully, you have a regulator that you can see going down track.

As for locked out timing moving when you rev it, with a timing chain and a distributor, ie: no crank trigger, the timing is going to retard a few degrees. My NHRA Stockers retard at least 2 degrees when I hold the rpm up to around 4,000. If this is the sort of movement you are experiencing, I’d say that’s completely normal. You say you checked the plugs and wires, but I would simply replace all of the normal ignition tune up parts, ie: cap, rotor, plugs, wires. I sincerely doubt it’s the coil or ignition box.

Potentially, you don’t have a motor problem; it could transmission or converter related. Is it consistent? Is the slow down getting progressively worse?

Regarding your question on connecting rods, I don’t think there is any cut and dry answer; it all depends on your application as to which configuration is the proper choice. Here is a link to a pretty decent tutorial on the subject from our friends at Summit Racing: www.youtube.com/watch?v=fszNIRbS8yw.

Building Blocks
A few months ago in your column a gentleman wrote in about his El Camino (I think it was) with a 1970s 454 2-bolt truck block and 1960s closed chamber heads. A few years ago I purchased a ‘66 Impala that I believe also has a ’70s 454 truck block (T1115TRH, 3999289) with late ’60s closed chamber heads (3917215, E27, GM4T). I’m curious, since his setup seems to be similar to mine, is this combination a common “old school” attempt to improve performance on the ’70s 454 smog engines prior to all the new performance stuff out there now? My engine has flat top pistons, a modest Comp cam upgrade with stock hydraulic lifters and rockers, a 750 Holley carburetor, and an aluminum Edelbrock Performer 2.0 intake. I’m running stock exhaust manifolds and 2.5-inch Flowmaster mufflers. Can you please hazard a guess at what kind of HP and torque this setup makes?
Scott Sousek
Via email

You have your info slightly off regarding the previous column’s particulars, but I’ll address your question as it stands. Sure, putting on better stock heads was, and still is, a good way to wake up a choked down piece. Your block is a ’72-78 454 2-bolt casting that came in both cars and trucks. The heads are an oval port, closed chamber that came on a ‘67-69 396 or 427 of varying hp ratings. With the upgrades that you’ve installed, I will make an educated guess that your motor makes around 350hp and 400 lb-ft of torque. I do know this much for certain, you don’t have any problems doing nice, long smokey burnouts, lol.

What’s The Diff?

I own two Chevy Caprices, a ’94 and a ’95, both with the police package and an LT1 engine. I’d like to know what the difference is between my rides and a ’94-’96 Impala SS. I’d also like to know what type of upgrades you would suggest for 300-400 horsepower for street/strip. And lastly, what is the difference between a limited slip and Posi?
Enoch Lacey
Lewisburg, Pennsylvania

I’m no expert on Caprice police packages, otherwise known as the 9C1 option, but I can do research with the best of them, and sometimes I even come up with the right answers. I wound up on a forum dedicated to the car, and a moderator there spoke to this exact topic. There are a number of outward aesthetic differences, like moldings, trim, badges, etc.; the Impala SS has a different grille, while the 9C1 has a unique front spoiler. Mechanically, the 9C1 has more body mounts than the Impala SS and different windshield wipers, while the Impala SS has a unique width rear end different from the 9C1s and normal Caprices. The SS also sits lower and has bigger tires and wheels.

As for horsepower upgrades, the LT1 in your cop mobile was rated at 260hp, and you can probably approach the 300hp mark with the typical bolt-on type upgrades, ie: CAI, headers, exhaust, underdrive pulley, thermostat/fan control, etc. If you want to make the hurdle above 300, I’d advise a camshaft and associated valvetrain upgrade. If you want to keep reaching for the stars, you’re looking at a cylinder head upgrade, more rpm, and most likely a bottom end rebuild to go with it. Edelbrock and Trick Flow Specialties have top-end kits for your exact combination that will net you major horsepower improvements—like put you in the 430 horsepower range with one phone call.

And the difference between limited slip and Posi? Nothing really, it’s just vernacular. Positraction is simply Chevrolet’s brand name for its version of a limited slip rear.

What Wheels Fit?

I have a 1968 Camaro with 2-inch lowering coil springs in the front, stock control arms, and stock multi-leaf springs in the back with air shocks. I have been thinking about installing the Hotchkis TVS 2-inch front, 1.5-inch rear drop Stage 1 kit. My question is, what size tire and wheel do you think I can use in the 17- to 18-inch range, including back space? I have a stock style Flowmaster exhaust. Can I fit 8-inch rims in front and 9- inch rims in the back? Thank you for any help you can give. I have read your magazine for years.

Doug Johnson
Via email

Simple enough question when you have a tire and wheel guy like I do. A quick discussion with Don Raiser at TCT in Buffalo, New York, netted the info you need to go with the Hotchkis lowering kit on your ’68 Camaro. The recommendation is 7- and 8-inches, not 8 and 9. Upfront, go with a 215/40x17 tire on a 17x7 wheel (4-inch back space). On the rear, go with a 255/50x17 tire on a 17x8, 4.50-inch back space wheel. This selection will give the car a pretty mean stance, and you shouldn’t have any problem regarding the exhaust.

Got a restoration question that’s been puzzling you? Send it to:
[ m ]
Super Chevy, Fletch, 9036 Brittany Way, Tampa, FL 33619.
[ e ]
[ f ] 813/675-3557



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