31 replies to this topic

[LXCHEV]

How restrictive are factory exhaust manifolds? (ie. on a Holden V8).

I can't decide whether or not to fit extractors to my hatchback (running a good 'ol 253). I know a lot of extractor manufacturer's claim both power gains as well as less fuel usage - obviously this comes down to just how restrictive the standard manifolds are.... I'm sure some cars would be a lot worse than others, so what do people think about the Holden V8 ones???

[LXCHEV]

Hi James, thanks for the input.

Yeah a brand new, free-flowing exhaust system is on the cards, that's why I'm wondering if I should also do the extractors at the same time. (Am thinking just some off the shelf Pacemaker Tri-Y's), going into a twin 2" system.

Has anyone done this on a stock 253 before and noticed any major differences?

[TerrA LX]

exhaust isnt just how un restrictive it is, flow paths and timing of each port (in what order they intercect) and sizing is crutial to torque out put in time with rpm.
what im saying is that open zoomies work on top fuel and tri y works on the street and everything in between. (certine types of motors need more than others)
pacemakers i think would be top shelf.
beware of inferiour products as it does make a difference on which pipes meet where.

done the same job on 253 and if any thing i did notice that it was smoother alround and it did seem a bit pokier.

Edited by ALX76, 01 July 2006 - 12:25 AM.

[Peter UC]

With the extractors I would recomend 1 1/2 inch primaries instead of the 1 5/8 on the 308 extractors. Twin 2" sounds ideal.

[LS1LX]

With a 253 id wouldnt waste my time with extractors, run stock manifolds if its a stock motor, into twin 2" system or single 2.5"

[LXCHEV]

I'm not sure how long the engine will remain stock for though. At a minimum, it is about to cop a 4 barrel intake, quaddy, and electronic dizzy. (Currently running 2 barrel strommy, and points dizzy).

With these mods alone, do you think extractors would then be more beneficial, or still not worth the effort?

[TerrA LX]

imho you wont look back with a decent set of extractors.

[Struggler]

FWIW many years ago I had a VH S/LE C/dore with a 308, tri and 2.60 rear. It was dead stock. I fitted a set of extractors and it was the worst thing I could of done. Torque and fuel efficiency went on holiday below 2000 rpm, were this thing spent most of its time (due to the highway gearing).

A few years later I had another VH S/LE, this one was a 308 (Crane 276 and Performer intake), M21 4 speed and 3.08 rear. I drove it around with the fresh engine and manifolds with a 2.5" single for about a year and was quite happy. I scored a set of extractors and despite my previous experience fitted them. As this motor cruised at about 2200rpm it seemed to like the new setup. Economy even improved slightly but the performance increase was hardly noticable.

As the 253 is a bit smaller in capacity I would assume that the point of beneficial returns would be a bit higher in the rev range.

I might also add that the extractors made the engine noise a bit louder in the cabin.

[LS1LX]

The more standard you leave a 253 the better, at the end of the day you'll spend another $2-3k on it and in reality it may feel so much quicker and better but your only going to pick up 20-30hp from all those bolt ons, and 20-30HP on a 150HP engine still isnt enough.

Save the performance stuff for the SBC's, the lil 253 is going to drink the same amount of fuel as the same spec 308. Id rather drop a stock/mild $3000 308 in instead.

[gtrboyy]

When my brother had his 253 vh SLE we put extractors/exhaust on it which made it sound better but didn't give it any noticeable difference in performance,it even seemed to use a little more fuel.Having a 2.60 rear end didnt help much either.Another mate's 253 SLE had 3.08 gears,small cam,more compression & it was better on petrol but not that much quicker.

[LXCHEV]

Thanks for all the latest replies and opinions guys, some very informative stuff.

It's funny you mention that LHoon - I've decided to start looking around for a 308 to replace the 2fluffy!!! Even though the 2fluffy runs like a dream and is tuned all nicely, it's just so thirsty on fuel. I put it down to the fact that I have to work it so much to cruise around, whereas with a 308, the extra torque would move the car a lot easier.

I've been speaking to a few mates, some of which run very mild 308's backed up with manual's and they get better fuel economy than my stock 253. One car in particular makes 160 rwKw too. But a big factor in his excellent economy is the fact he's running a Supra 5 speed. That car runs 13's too.

So I am officially on the lookout for a nice stock to mild 308. The more I think about now, I can't wait! I don't want to spend more than 2K all up, running in the car. I already have a Bosch elec dizzy and a good quaddy ready to go. The hunting begins....

As for the exhaust - well I'm still undecided. I might even keep the stock manifolds for now and when the 308 goes in, see how it goes. At a minimum I'm going to replace the original system itself, esp the mufflers. Will see what happens.

Cheers again.

[makka]

the bug has bitten again hasnt it Brett!

[LXCHEV]

Yeah I went and saw Tokyo Drift last night with our car club, and afterwards I was having a good chat with a few of the boys, and somehow the conversation ended with me now wanting a 308! I AM KEEN YEAH BABY.

[LXCHEV]

A 308 would be WAY COOL!

Today I had a Mars Bar for breakfast actually, now it's all GO GO GO!!!

Come on Liam, don't be shy, you know you want to 308 your daily ride, don't deny yourself the POWER, you owe it to the torry!!! You owe it to yourself!!!

[LS1LX]

I told you, everyone tries sticking to the 253's but eventually they give in to a 308.
Everything is a straight swap.

If your going to be using 18L/100kms might as well have a 308 instead of a 253. Nothing worse then a car that loves a drink but has no performance.

Now just dont get carried away and turn that 308 into a 355 or 383, thats the next thing that worries us.

[LXCHEV]

Hmmmmmm.... 383 ....... !!! hahahahaha. It could be done. A 383 in my weekender, and a 383 in my daily!

NO WAY. 308 and no more! I will restrain myself, I promise

[TerrA LX]

if you driving a staty with a/c n p/s ill say go the 308 but if its a torry and your not happy with it as a daily then there is something wrong with your 253.

[LXCHEV]

ALX76 - I can't say that I'm unhappy with the 253 - it runs like a dream and is making good power for a stock 253, however it does use a lot of fuel, and it just does not have the grunt of a 308. In particular, when overtaking, or trying to pull out of somewhere quickly, or trying to tow a heavy trailer behind it, this is when the lack of power really shows.

LHoon - I had thought about LPG, but have since decided against it. Simply because I don't want the hassle of mounting a gas tank in the hatchback. I use my hatchback a lot, and it's excellent having so much storage space, so I don't want to take away the practicality of that by having a gas tank taking up so much room.