2014 Gore Aussie Muscle Mania Car Show (12-4-14)
5.0 Litre Red Motor 308 V8
Capacity 308 ci (5047 cc)
OHV V8, 2 valves per cylinder
four barrel Rochester Quadrajet carburettor
Bore and stroke 101.66 mm x 77.77 mm
Power output 240 bhp (179.0 kW) at 4800 rpm
Torque 315 bhp (434 Nm) at 3000 rpm
Compression ratio 9.0:1
308 Path To Power: The Basics
Here’s a few pointers on how to get the most from your 308 without breaking the bank. I’ll be concentrating more on the carby 5 litre’s for now, but the same principles do apply with the EFI V8’s.
Without even thinking about cams and headwork and all the rest of the nice little goodies you can throw at an engine, make sure it is breathing efficiently and in the best running condition you can make it first. Its the little things that don’t cost much, but all add up to a generally nicer running, more flexible engine and can also promote longer engine life.
Oils Aint Oils
For the 308, I’d recommend Castrol Formula R 25W50. There are also some very good oils from Penrite and Torco in similar grade. Yes, there are plenty of other well known exotic oil brands that claim to release untold horsepower, but for the price, it is just not worth it when you are talking about a humble 308. So stick with the tried and proven.
Try to stay away from fully synthetic oils or oils that are very thin. Old holden engines aren’t designed to use them and they will likely cause premature wear.
If you have a lifter noise upstairs, there is a very good product called Nulon Lifter Free. From most reports I’ve heard, it works well to get rid of all the oil gunk and sludge in the top end and throughout the motor. The cleaner the oil system, the smoother the engine will run and you will reduce the chance of premature engine wear, which is always a good thing.
A word of warning though, I wouldnt use it on a very old engine, since the sludge buildup may be too great and there is a risk that little bits will dislodge and block oil galleries, which is very bad Be sure to read the instructions carefully if you do use the stuff.
If you have an older 308 running points, get rid of it! The standard later model Bosch electronic ignition system (i.e VL) is a very good system for a mild 308 and is an easy swap. Make sure every component of your ignition system is up to scratch. Ignition is like a chain, it is only as good as it’s weakest link, so make sure you have good leads, plugs, dizzy cap n rotor and coil. To maximise its potential even further, you can get the dizzy re-curved to suit more of a performance application.
Stick with known leads and plugs brands, like Top Gun/Eagle and NGK. Also be sure to protect the leads from any heat source, especially the extractors. Use those lead clips to neaten them up and route them correctly. Also, there’s no nead to buy fat leads, 8.5-8.8mm leads will be fine. Bigger is not always better.
There are complete performance ignition systems for the 308 from brands such as MSD and Crane, but unless you are planning big power in the future, they are not really worth the minimal gain compared to the above system. Not knocking those high performance systems though, for consistent fat spark, look no further than those two brands. IC&E also do good high performance ignition systems too.
Most standard holden air intakes are rubbish and are just designed to keep noise down. A performance air filter using a K&N element is probably the first mod you would do to free up HP, but it doesnt stop there. Cold air is your friend, and getting as much of the stuff as possible into your engine is your primary goal. Furthermore, the gains can’t always be seen on the chassis dyno, but will more than likely show up over the quarter mile.
If running a carby, not much can beat cutting a hole in your bonnet and running a conventional scoop. Furthermore, alot of people overlook this, but you can improve on this setup even further by isolating the incoming air from the scoop using a cold air box. The cold air box surrounds the carby and seals to the underside of the bonnet. This works well if the hole in your bonnet is opened up further around the filter. Perhaps the final piece of the cold air puzzle would be using a K&N Xstream top filter with this setup. You only have to look at this picture to realise why www.knfilters.com/universal/X-stream.htm
Removing the engine fan and replacing them with thermo fans is an easy way to make 5-10hp. The only real hurdle in doing this however, is that alot of people fit fans that are too small or they don’t use an engine shroud. Depending on what car you have, a set of VT or AU twin thermos is an easy and cheap upgrade. You shouldn’t have any cooling problems with these setups. Using a lower temperature thermostat can also be a good idea, and don’t forget quality coolant e.g. Tectaloy Gold. A radiator flush couldn’t hurt either. Or even a bigger radiator might be good idea if yours is pissweak.
You can’t go past a set of extractors and an exhaust system to let the bent 8 growl and make some more power.
Street Holden motors tend to like the Tri-Y design (4-2-1) extractors more so than the tuned length type (4-1), and Tri-Y’s are renowned for making more midrange grunt which helps a street car. Don’t go too big on the primaries, 1 5/8" will be more than enough. Pacemaker extractors are the way to go. Difillipo and Gonzo make good pipes for the Holden engine, but usually they cater for more street strip type engines.
With the exhaust system, alot of people go too big with the system thinking bigger is better. A single 2.5" system would be enough for a stock 5 litre, or if a cam is on the cards, a twin 2.25" or single 3" is more than enough to support decent horsepower for a 308. Although having said that, you will really need to think where you are heading in the future. If you are planning something like a stroker later on down the track, go for a twin 2.5" system or twin 2.5" into single 3". You may lose power in the short term, but you won’t have to change the exhaust when the stroker goes in later on.
If running a twin system, be sure to have some kind of merge or H pipe which helps to equalise exhaust pressure. It makes a nicer note and reduces drone too. Personally, I dont like the designs of the Merge/X Pipes on the market, simply because most of them arent designed very well. Unless you bought a merge pipe from Sureflo, use an H Pipe.
A mandrel bent exhaust would be nice to have, but the difference between mandrel bent and press bent is minimal. Although always have the tight n twisty areas of your exhaust system mandrel bent i.e. over the diff etc. I could talk endlessly about mufflers, but really, muffler choice will be dependant on how much money you have to spend. But in design, go for the Straight Thru type mufflers.
Alot of people just throw on a Holley Double Pumper and disregard the 4 barrell Rochester, but both carbies have their good points and their bad points. The Holley is relatively easier to tune and is more of a performance oriented design, but the Rochester can be made to perform on par, if not better than the Holley if rebuilt and tuned by someone who knows their Rochesters, although the problem is usually finding someone that does. The Brocky spec Rochesters are meant to be pretty good. If you want to switch to a Holley, I wouldn’t go anymore than a 600 Double Pumper or 650 Vacuum Secondary.
With either type of carby, the one thats tuned the best will outperform the other, regardless of brand. That’s one advantage of the Rochester – they tend to keep in tune better than Holley’s. Also keep the venturi’s clean by spraying them with some carby cleaner every now and then.
If you have bonnet clearance, another cheap little trick is to add on a 1 inch carby spacer to increase intake plenum volume. This usually gives more power and torque throughout the rev range. Although I would seek some expert advice on which kind of spacer would be right for your engine since there are types to suit different carbies, different manifolds etc.