[VW@heart]

I could post a short thesis study here to be more accurate to what I’m building, but I’ll cut to my personal key points as they relate to MY application. I’m not building an engine for a 1970 Chevelle or a GMC truck either. This is for my 2500lb 911 w/ 930 four speed. The build is targeted at driving to the grocery store and being able to beat anything factory on the way. An additional comment, I also plan on pulling away from anything made in Japan with 500lbs of speakers in it.

This information is aimed at my specific application using a pre 1987 SBC and CURRENT aftermaret parts. Much of it can be applied towards other SBC and other engines for that matter. Ok here we go - In ADDITION to the basic rebuild and reliability requirements, and misc. easy to do mods this is where the fun starts:

BLOCK: Priority is in maching for correct bore size (use a deck plate) and decking for proper sealing and piston to head quench. To aid in bore strength bore min that is needed.

LOWER END rotating assembly (This is where you make your money is you have the time): CRANK - Stock forged are strong enough for any street engine I could build. The mods are lengthy, the more mods the better. The priority should be to drill the big end journals and knife edge the counter weights, remember to reduce the rods and piston wts first, then crank weight, because the last thing will be the crank counter weights losing diameter accordingly (about 5/8 of an inch!).
The simple mods can be done with a grinder. 25 hours of work will provide a smooth hi revving lower end and give 12-15 hp @ 7500, I don’t have dyno facts on what the power advantages will be in my power band. The goal is to pick up 8-10 hp at my engines peak and more importantly reduce baggage thus adding reliability. With the LARGE reduction in the rotating assembly, allowing the counterweight modified, the crank scraper’s efficiency can improve, and up to 15 hp may become available at my peak hp (vice 8-10); more free hp usually means more reliability (free meaning it is released from the moving parts). Time can be saved by using an economical SCAT cast crank, they are extremely durable, and my app will not be able to break it.
RODS-Stock rods can be reliable and handle roughly 9.5:1/350hp/6,000 rpm, correctly set and w/ minor mods this can be reliable to 400hp and 7,000 (THIS IS ALL I NEED). Do NOT USE rods with off center pin bores*, thin shoulders by the bolts heads, or improper machine of the mating surfaces (a slight angle cut adds stress). *You can spend the bank and the rod can break at the off centered pin bore on a mild engine. Stock rods run about 605-620 grams, the rod has roughly 50 grams of extra baggage. Lighten it! The weakest aspect is the bolt, once ARP bolts are used, the shoulder of the rod by the bolts will be the next weakest link, therefore shot peening needs to be concentrated in this area. The alternative is using a 608 gram SCAT sportsman style rod (can be lightened to 570). For my app using an overly strong and heavy race rod adds USELESS wt. Ultra light stock or sportsman rod will bring more efficiency in power. PISTONS – For my app forged econo Ross pistons are light and well built or KB hypereutectic cast have a good reputation in many circles (KBs have been tested well beyond my requirements). Flat tops WILL be used on my motors; the only exception may be a raised or lowered D shape. Flat tops WILL deliver more quench area, reducing octane requirements and adding efficiency. One Total Seal ring will be used.

VIBRATION DAMPER (it's not a harmonic balancer)- A damper WILL reduce power-robbing vibrations. According to dyno tests, the larger the better.

OILING: Using a high volume pump (not high pressure) and adding a few oiling mods to the block will greatly add the performance of the lubrication system. One example is drilling a small hole in the block aimed to squirt oil up under the piston skirt will reduce piston temp by as much as 200 degrees F. When required a reliably small touch of NOS may be used 75-100 hp, then piston oil cooling will alleviate any heat/endurance issues that may arise at that level of power. One note, oil pumps can cause chatter and power loss, common methods to reduce this should be utilized. Using thin synthetic oil, I tend to favor a blue printed and ported Melling high volume pump set up at 55 psi with the oil relief output redirected. This will provide more reliable, cooler synthetic oil at approx 45-50psi. Using a deep MOROSO oil pan with a sheet metal windage tray is an excellent addition and will almost eliminate a lightweight 350 SBC crank from hitting the oil in the pan, if a shallow pan most be used a mesh screen will work better vice the sheetmetal tray.

HEADS (this is where you have to decide how efficient and much potential your engine needs): My app requires an alum head. Trick flow heads have new chamber design that sets then ahead of older aftermarket heads, they hav dif runners volumes available (street or HiRPM). For my app the street heads are unbeatable at $850 a pair new, I have not seem anything older than the TrickFlow beat it out of the box on a street engine. I could run any alum head and have a good engine, but the Trick Flow gives me the efficiency potential I’m looking for. They even bolt on and perform noticeably better than Chevy’s new Vortec head. I'm considering adding a thermal barrier in the chamber, and looking for efficiency and dyno test.

CAMS/VALVE TRAINS (remember I do cannonball runs back home to the Midwest):
I’m not a fan of OVERALL valve lifts exceeding 500-525 or big durations over 230’@.050 on an SBC app like mine. I DON’T need it; it adds reliability and efficiency issues I would have to address. Buying a tried and true valve train combination will save time. If I run into good used roller cam that fits into my game plan (or can be reground to the correct lift/Dur) I use them. Quality roller TIP rockers are always used. Depending on airflow (heads) and cam lift the higher ratio rockers allowed the better. A solid bet for my app would be TFS heads and a cam made for 1.6 rockers. Use min spring tension for the lift.

INDUCTION: New designs of Holley, Edelbrock, Weiand etc will work, used alum intakes are good, Edelbrock carbs are great out of the box, old design Holleys need experienced work to run better, but aftermarket builders get goods results and will mail you a carb. DO NOTEXPECT to grab a big Holley and expect big horsepower; it almost always takes work to get good results. I prefer an Edelbrock midrange combo out of the box for my app (600-750 cfm w/ Performer RPM intake). Match porting and working the top ridge of the intake runner is not a waste of time, but can be done later as time permits. If I get the opportunity I will have my intake coated with a thermal barrier and adjust the carb accordingly (looks nice also). Don’t use crappy or small air filters. Stacks to direct the air will help efficiency

IGNITION: For my rpm range a modified HEI ignition is the dyno’d way to go, I can spend three times as much and have a better ignition at higher rpms, but I don’t need it, maybe later. Accell’s HEI or MSDs usually get the spin on my SBC. The daily use do NOT use stock soft inner fiber plug wires, use a quality spiral core. A regular plug trimmed back to the center of the electrode will work great, make sure it’s the correct heat range and a a few bucks reach in and change it out when the electrode starts to wear.

EXHAUST: For a street SBC would be 1 5/8”, a stepped exhuast 1 5/8” to 1 3/4” merged into a long collector may provide an advantage, but in the case of 911 SBC, a shorty 1 5/8 will deliver the required hp and getting a longer exhuast in may not be worth the time or money.

Has anyone noticed where Porsche puts the power peak on their “daily drivable” 930 engines? I just noticed the 1987 930 happens to end up where I plan on having my hp peak. 5,500 looks good, I should end up peaking some where between 5,400 – 5,900, the difference will of course be a TON more torque and much wider more ENJOYABLE power band.

Used in a 2500lb four speed daily driver/road runner - A reliable 360-400 hp from a 377 SBC can be achieved using the above recipe, INCLUDING the MILD cam design. As a side note, with more low end power a full bodied Chevy would be better suited with a 360-400 hp lower rpm 383 (or a long rod 400) as a daily driver/weekend "straight line" car.


[This message has been edited by VW@heart (edited 03-03-2001).]