If the Suburban is equipped with an automatic transmission, the stock flexplate on the engine will work with your TH350 trans. If it's a stick, you'll need a one-piece rear-main, '86-and-later flexplate. The GM part numbers for this wheel are 14088765 (153-tooth) and 14088761 (168-tooth). Either wheel will work in your TH350 trans; the tooth count is based on your starter choice. We'd stick with the starter off the 'Burb because you know it's a proven unit.
Finally, for tuning we'd recommend starting with a total timing of 30 degrees around 3,200 rpm. These swirl-port heads didn't like much spark advance; 30 degrees may be a little too much, but drive the car around and listen for spark knock. Yes, we would run a vacuum advance. This will give you increased fuel economy. If you have an early-model (pre-'73) Q-jet, you will have a ported vacuum source on the front face of the carburetor body. This is where you want to pick up the vacuum for the advance diaphragm. If you run manifold vacuum to the advance unit, you may overadvance the engine at idle, and in extreme cases you'll experience an engine bog when you open the throttle too fast. This is because when the throttle is opened rapidly, the manifold vacuum drops very quickly, which retards the timing at the same time. If it's a late-model carb, you'll want to connect the vacuum line to the timed vacuum source, which originally fed the EGR valve. Try both timed and manifold vacuum sources on the late carb and choose the best drivability.
Again, don't sell yourself short. Welcome back to the game of Chevy restoration therapy! It saves us many dollars on psychiatrist couches.
Out Of Breath Q I have a '69 Nova with a 350 small-block, a TH400 trans, and a stock 10-bolt rearend. The rearend has never been touched and it has either a 2.73:1 or 3.08:1 gear. The engine is mostly stock, with a stock crank, rods, and dished pistons. The 76cc heads have been ported, and Hooker headers get the exhaust out. The cam is a single-pattern Lunati Bracket Master, 224/224 degrees duration at 0.050 inch lift. On top is a 750 Holley vacuum-secondary carb and an Edelbrock Performer manifold. Behind the engine I have a B&M Tork Master 2,000-2,300 converter. What is wrong with this combination? It was my first engine buildup, done on a shoestring budget. Some say it's overcarbureted, while others say it's not. It has been in the car for many years and was used as a daily driver. The best the car has run is in the high 14s in the quarter. What do you think the horsepower and torque figures are?
Since it's no longer my only means of transportation and is not going to be used as a daily driver, I'm converting it over to a fun weekend cruiser. I'd like to drop it down into the low 13s/high 12s. For this I've been thinking about a new engine buildup. I have a 350 block, a crank, and rods sitting around from an '86 Suburban. I plan on using Speed-Pro dished pistons, Vortec heads, an Edelbrock Performer RPM Air Gap, and a Comp Cams 268 cam. The only parts I want to use off the old engine are the 750 Holley and the Hooker headers. It will be very similar to your "Goodwrench Quest" buildup. Can I expect the same results for power and torque? My goal is 400-425 hp. What would you recommend for rearend gears, and can I keep the same torque converter and trans? Thanks for the help. Daniel Roby Via e-mail
A High 14s out of a fairly stock small-block and stock gearing isn't that bad. The main problem with your buildup is the cylinder heads. Back in '69, GM didn't use 76cc heads on the 350 engines, so this would lead me to believe that the heads are off a later-'70s or '80s engine. Yes, they may be ported, but with those large chambers and the stock dished pistons, you have around 7.8:1 compression! This, combined with the 224 Lunati camshaft, has the car basically dead off idle, and it probably doesn't really start pulling until about 4,000 rpm. Will the car even spin the tires from dead stop? If you slapped the Vortec heads on this combination, you'd be blown away by the performance increase. You'd need to swap out the inlet manifold at the same time. Just a thought for a cheap upgrade; you should see a nice bang for the buck.
For your new engine adventure, sticking to the "Goodwrench Quest" buildup will give you the performance you're looking for. Keep the compression around 9.5:1 with the iron Vortecs, and go with the Comp Xtreme Energy 268 cam. Your headers will be fine, but I really don't like vacuum-secondary carburetors. You can make them work well, but they take quite a bit of work, and you really need to understand Holley carbs to make them happy. A standard 4779 double-pumper would be a much better choice, in my book. Your B&M converter will be a little on the tight side. You could try it and simply slip back your TH400 and slide in a slightly looser converter in the 2,400-rpm range if yours is too tight. The TH400 will be bulletproof behind your small-block.
With this engine package, trans, and converter, a great weekend gear would be 3.73:1. Yes, this is right on the edge of something you'd want to drive many miles. However, your small-block will love that gearing and you'll see your high-12 goal. With a little work and refinement, you may even go quicker. Good luck with your little Chevy II.
Ram Jet Woes Q I have a GM Ram Jet 350 crate engine installed in my wife's '62 Corvette. It is one of the original MEFI 3-controlled engines and has run well for over four years and 20,000 miles. My only complaint has been that the engine always ran rich. In March 2006, in an effort to improve the mileage, I installed the GM MEFI 4 upgrade kit, PN 1249916. This kit contains a new wiring harness, computer, O2 sensor, and IAT sensor, supposedly the same electronics being shipped with all the new Ram Jet 350 engines.
Ever since the upgrade, I've had a rather annoying (and possibly dangerous) problem. When cruising at relatively low rpm (1,200-1,400) and low engine vacuum (as when climbing a slight grade), the engine acts as if it has cruise control. When I take my foot off the gas, the rpm will stay up for about 15-20 seconds before starting to fall. If I take the car out of gear, the rpm will instantly climb to about 3,000 rpm and stay there for the same 15- to 20-second period. On several occasions, my engine has hung up for over 60 seconds! Through various Internet forums, I've met several others who have experienced the same problem with this engine. Just wondering if any of your readers have experienced this problem with the MEFI 4-controlled Ram Jet and if anyone has a cure. Thanks. Charles Bernhardt Via e-mail
A Boy, engine flare can be real dangerous! My '96 L26 454 big-block Chevy truck does the same thing. This is calibrated into my truck for emissions; the need to keep the engine speed up is to run the fuel through the cat converters after a quick stab of the throttle from an idle. Your Ram Jet should have none of this in its calibration. We don't have a direct answer, but we may have some help.
Though my friends, the following information came my way from GM Bulletin number GMP07-041. The Powertrain Contact Center expanded its services to include support for Performance Parts engines and components for a Performance Parts Authorized Center Dealership and the retail, independent service center, and fleet accounts. They are there for the dealers to answer any general Performance Parts inquiries, and to provide Performance Parts technical support, which is a welcomed addition for the dealers and their customers, because of the highly technical nature of the engine packages GM now offers.
Our suggestion is to go back to the GM Performance Parts dealer where you purchased your MEFI 4 upgrade package and give him this bulletin number. Good luck, and we hope we've helped.
Get It Straight Q I want to run the large-port Vortec Bowtie heads PN 25534431, but they require self-aligning rockers. I wanted to use Harland Sharp's 1.65:1 rockers, but they are not self-aligning. Is there any alternative? Because HS is the only manufacturer making 1.65s for small-block Chevys that I know of. It's for a 406 and I want a lot of torque, so I'm running a Comp XE 274. I don't want to sacrifice horsepower with the relatively short-duration cam. Any suggestions would be great. Rocky Via e-mail
A The new Vortec Bowties are killer little heads. They are offered in small-port (185cc inlet) and large-port (215cc inlet) versions. These heads are machined for screw-in 7/16-14-inch rocker studs. Yes, you can either run self-aligning rockers or guideplates under the screw-in studs. The GM standard iron head guideplate is sold under PN 3973418; they're hardened steel and are for 5/16-inch pushrods.
Many of the late performance aluminum and iron heads have had their valves moved around to optimize their location in relation to the center of the bore. With these heads, it can be really tough to line up the rockers with the tip of the valves. Isky Racing Cams has come to the rescue with adjustable guideplates sold under PN 200-AGP. These two-piece units allow you to adjust the spread of the rockers independent of each other. After you have adjusted the rocker alignment perfectly, you can just torque down the rocker studs. We've used them in the past and like to weld the plates together to ensure no movement after you've adjusted them.