Techin' In with Fletch - June 2009 (Web Exclusive)

Dan Fletcher Jun 21, 2009 0 Comment(s)

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What do you recommend as a rule of thumb for power output and fuel line size needed for supply. Also, single line and return line systems and different carburetors and their specific needs.

Chuck Hoover
Via email

Fletch:Let me start by saying that both of my race cars have #10 line going from the cell to the pump and the pump to the regulator, and #8 from the regulator to the carb. That's what I'd recommend. However, I do know of many guys who have #8 going from the pump to the regulator and #6 feeding the carb, and they seem to be OK. I'm at RWR (my Super Stock engine shop in Phoenix) as I write this, so it was easy to get some further input. A 350-inch Super Stock motor that makes 600 horsepower will run on the dyno with a #6 line, but it won't make it down the race track (#6 is equivalent to 3/8-inch). A Holley carb, due to the bowl size, has more reserve than a Quadrajet, but I don't see how you can hurt yourself by having too much volume or supply. As for the return line, as it's just bleeding off, can probably be good with #6 (I use a #8). I think anything more than 350 HP should be upgraded from 3/8-inch.

What's The Number?

Could somebody please confirm the part number on the GM large port Vortec Bowtie head? You advertised PN25534431 in a recent article. However, this number provides no feedback on the GMPP web site. Are these not yet available or is the number incorrect?

Thomas Ford
Akron, OH

Fletch:I wasn't involved with the article that you're referencing, but you didn't really think Super Chevy would steer a devoted reader wrong, did you? Here's the deal: That number was correct for the 2007 GMPP catalog. For 2008, the number has changed. The new Large Port Vortec head assembly part number is 25534446.

Have a tech question you need answered? Send it to, fax them to 813/675-3559, or snail-mail 'em to Super Chevy, 9036 Brittany way, Tampa, fl 33619.

High School Horsepower

I am currently the proud owner of a '72 El Camino. I am a senior in high school and drive my El Camino every day. I have a GM 350/290 crate engine in her with a Turbo 350 trans with a shift kit and a Posi with 3.73s in the rear. I've installed Koni drag shocks in the front and have air shocks in the rear with a low psi for better launches. The engine has an Edelbrock intake with an Edelbrock carb, which I'm planning to switch to a Holley double pumper with manual secondaries. I'm going to install an electric fuel pump (with some help from my dad) very soon and I'm saving for electric fans for the radiator. What else can I do to improve the performance of my car? I have looked into the GM Vortec heads, but that means I would have to change the intake too. I know the heads are reasonably cheap (around $500), but that's a big investment for me, especially working at Autozone. Do you have any performance tips to make my car faster on a high school budget? Thank you.

Bill O'Brien
Via email

Fletch:Sounds like you have a fun little street car. My '69 Camaro Stock Eliminator car was my high school car as well, so I feel for you. First, I wouldn't put the double pumper on a street car, but I think there are a couple cheap, basic things you can do to pick up your pick up. A higher stall torque converter can make all the difference in the world for getting your whip to leave the stop light a little more rapidly. I'd recommend a B&M Holeshot 2400, which is a PN 20412. You don't mention your exhaust system, but a set of headers, something like a set of 1 5/8-inch Hookers, PN 2451, combined with the free flowing mufflers of your choice, would greatly aid performance. As I read the specs, I think the camshaft is fine as is. Lastly, and probably most simple of all, you can throw a little nitrous at it. Something small, like a 100-horse shot. NOS makes an adjustable kit, PN 05101. It's adjustable from 100 to 150, but with the cast pistons you have, I'd stay at 100. Safe and easy, and a guaranteed gain.

Mission: Transmission

I have an '85 Monte Carlo SS with a 1970 350 engine that has in the ballpark of 350hp. I want to put a five-speed transmission in it. I was thinking about an early- to mid-'90s trans out of a Camaro would do the trick. Would one of these trans mount to the back of this '70-model 350 engine I have? I know there are some mods I have to do. My main concern is bolting it up to the early-style block.

Tobaccoville, NC

Fletch:You have no concerns. I know for a fact that a Turbo 350 transmission will bolt to a LT1 motor, because I had a fuel injected LT1 stocker with a Turbo 350 a few years ago. So if you want to utilize a transmission from an LT1 car, I'm confident that it will bolt to the older configuration small block.

Canadian Confusion

I recently built my first engine, which I put in my '81 Malibu wagon (replacing the 305 that originally came out of a mid-'80s Monte Carlo). I'm 24 years of age, and a single father of three boys, so I was working on a tight budget. I started with a 350 100,000-mile short block bored 0.030 over with hypereutectic pistons, and a mystery cam (I took a little chance on that). I then followed that up with a pair of rebuilt numbers-matching cast iron heads and a Performer intake. I reused the old Q-jet and distributor from the 305. The results I got were quite displeasing, Its soggy and it does not matter if the pedal is a quarter to the floor or all the way. It doesn't change the way it accelerates. The only thing I know to be a drawback is that I don't have the proper timing pointer so I cant get the timing quite right. Any ideas of what could be wrong would be greatly appreciated.

Allan McAra
Chilliwack, BCCanada

Fletch:I think you've highlighted several very likely sources of your problem. The carb or distributor could be completely screwed up, and the timing could be a mile off. The mystery cam scares us, too. Let's do what is cheap and easy first. You don't mention that it turns over hard, backfires, or pings, so the timing is probably somewhere in the ballpark, but it's not very difficult or expensive to get a proper pointer, so start there. Mr. Gasket makes a timing tab with adjustable pointer, PN 721-4597 for less than $10. Then take the distributor somewhere and have it spun. Again, virtually free. If everything checks out OK and the timing is right, then get a rebuild kit and freshen up the carb. Again, very inexpensive. If it still doesn't perform any better, try to borrow a known good carb from a friend. If that doesn't help, I'd recommend trying a new coil. I'd say throw a basic tune up at it, but I'm assuming you have new plugs and wires, and you don't mention a miss

A "Head" Of The Pack

I have a 1965 Chevy II Nova and have plans to put in a 327. I have been thinking of getting one of those aluminum head kits from Edelbrock or Holley. Is this a good investment? I've also been wondering what would be a good drivetrain combination with this motor? If you and your team could offer me some advice I would greatly appreciate it.

Chris Brown
Tooele, UT

Fletch: I think that those kits are an outstanding investment. By the time you have all the work done to prep a used set of heads (hot tank, bead blast, guides, valves, valve job, springs, studs, etc.), you're going to be close on dollars, and with one of those kits, you've got brand new stuff. It's a no brainer, at least to me. As for the rest of the drivetrain, you don't say if this is a race car or street car, or what you're goals are, so it's pretty hard to say. That said, I don't think you can really go wrong with a 'glide or a Turbo and a 12 bolt.




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