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Techin’ In With Fletch - October 2013

Dan Fletcher Jan 23, 2014
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Bang For The Budget

I have a ’71 Chevelle that has been media blasted, and is now in the body shop getting a makeover. The car is a blank canvas for me to do whatever I want, and like most people, I cannot decide what the best drivetrain combo to go with is. I removed a Corvette 350 from the Chevelle and I want to go bigger, but I am also into LS engines. Basically, I need help to narrow down my search for a good combination for an average budget. If I go with the old school carbureted big-block, is it better to buy a new turnkey engine? And where should I buy it? Or do I pick up an old junkyard engine and have it rebuilt? What is the best overall Chevy engine to search for that’s not going to break the bank (i.e.: older truck engines, older big-blocks specific to the Chevelle)? I also love the idea of an LS and all the easy power that could be added later and over time. But again, what is the cheapest and best bang for the buck?

I know this isn’t the easiest question, especially with all the options out there, but any and all help would be greatly appreciated so I can finally get this thing on the road and enjoy all the events you guys write about every month!

John Galas

Given your situation, which is a great one, I’d probably recommend buying a new powerplant. I’ve been in way too many projects in my life that become the epitome of “penny wise, dollar short.” Buying a core motor and going through it from top to bottom always sounds like a good idea, but it generally seems to wind up nickel and diming you to death. By the time you’re done making everything right, you’re as deep as you would have been buying new. But when I say buying new, I don’t mean lining out all the components and sub-contracting most of the work, I mean a crate motor. To me, the bang for the buck is unmatched.

I’m an old-school guy, and in my comfort zone with an MSD box and a carburetor, so I know what I’d do. If you want a nice fat block, I’d run with this 454 seen here on Summit’s website http://www.summitracing.com/parts/nal-12498777.

With that said, and as much as it kills me to say it, I think you should probably go with the LS platform. Whether I like it or not, it’s 2013 and one needs to step out of the dark ages. With your clean sheet starting point, I am going to recommend the following 525hp monster http://www.summitracing.com/parts/nal-19259233/overview/. You don’t mention where you’re located, but if emissions are an issue, they even offer a 430hp option that is CARB compliant http://www.summitracing.com/parts/nal-19257230/overview/.

Not only are the prices right, Bobby, but Summit even offers free shipping.

LS6 Head Question

I have a pair of heads that are from a 454 LS6 crate motor I purchased new way back in 1981 from the Chevrolet dealer I worked at. The engine part number is 366250. I’m wondering if the heads are worth overhauling, or should I go for the more modern iron or aluminum options available. I’m looking to rebuild the LS6 so it makes bags of torque, but runs on premium pump gas. The heads have the following markings: HI PERF, GM2T, 018\78, 6272980. Any tips you have there would be greatly appreciated.


Malcolm Harris

Certainly, there are many new options out there that will perform well. That cylinder head is a very good option, and you already own it, so I’d consider using them. But there are some issues for your particular application. As you noted, the 366250 crate motor originally came with those heads (6272990, you’re off a digit). They are a steel, rectangular port, open chamber configuration. They came with 2.19/1.88 valves and are 118cc’s.

With the dome pistons that came in your motor, the compression ratio is supposed to be right at 11:1, so you will probably have issues with premium fuel. My engine builder says he thinks it’s not really that high, and his experience is that heads generally cc bigger than advertised. However, no one wants to be forced to constantly mix race gas or add booster, so I think you’re going to want to consider changing the pistons to reduce the compression ratio to a more manageable level. Get down in the 10:1 range with no more than 35 degrees of timing and you should be worry free.

Even though those big port heads do their work upstairs, you should have more than enough torque to meet your goals. If you do decide to change to aftermarket, I’d still go with a big port, but get something aluminum, open chamber, around 120cc.

Dying Nova

Fletch, I just put a rebuilt 355 in my Nova. It idles around 1,000 rpm with no problem, but when I put it in any gear the engine dies. When I’m driving, it seems OK, but when I come to a stop, the engine dies. The various people I have asked about my problem say it could be a vacuum leak, timing, or not enough stall. Any ideas?

Roger Hackensmith

Via email

I’m thinking the people you have consulted are about a third right. Timing or not enough stall speed from converter, not so much. A vacuum leak, on the other hand, while not a 100-percent guaranteed answer, is certainly high up the food chain on the list of potential culprits.

A few simple questions to start: have you tried turning up the idle just a tad to see if it helps? Does it idle roughly? Are you using other vacuum-related functions? Do you have a vacuum gauge? With that said, get yourself a can of brake clean and start spraying around the intake gaskets and base of the carb while listening for the idle to increase. If you can find a spot where the idle jumps up, then you’ve found your leak, and most likely, your problem. Beyond that, I would do all the normal tune up type things, like replacing the spark plugs, ignition wires, distributor cap and rotor, freshen up carburetor, etc. But frankly, I don’t think it will get that far.

Which Engine Do I Have?

I have a ’73 El Camino SS with a VIN for a 454/245hp. After checking casting codes for the heads (3904390) and intake manifold (386048), I’m not able to find the block code T6F722485. Can you help me out as to whether it’s a 427 Corvette 390hp motor or one from a Chevelle. If it helps, the intake is a Holley with a Holley four-barrel carburetor.

Thank you for any help that you can provide.

Leslie Drubles
Via email

I’m afraid I’m not going to be much help, as I think you may have some of your numbers crossed. I generally like decoding questions, as its fun to play CSI Dan and figure out what is what and where it came from. The head number translates to a ’66-’67 396, either 325 or 350 hp, or a ’66-’68 427, either 390 or 400 hp. They could be from any of those combos. They are closed chamber, oval port, 2.06 intake, 1.72 exhaust, 98cc. They certainly could be from a 427 Corvette.

As for the intake and block code given, I think you have something amiss, as those numbers don’t equate to anything on my radar.

Got a restoration question that’s been puzzling you? Send it to:

[ m ] Super Chevy, Fletch, 9036 Brittany Way, Tampa, FL 33619. [ e ] questions4fletch@yahoo.com [ f ] 813/675-3559

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