G'day

I was thinking today about what to do to my TP after I get a mild cam, then it hit me (sparked by another thread) TWIN CARBYS! Ok maybe a bit ambitious but it cant hurt to get some background info.

Has anyone done this before with any success?

What is involved? (Ive already got one dual webber)

What intake manifolds will fit the astron II (TR-TS version) (Part numbers???)

How much roughly would a 41/46mm webber cost (Just throwing that one out there)

Will I need to modify the manifold to make it fit the engine, and/or carbys?

How would twin carbys compare to a Turbo at 7-9psi?

Would anything need strengthening or upgrading?

My mechanic can tune a triple barrel perfectly by ear so I reckon he'd have no trouble getting the twins tuned just right. Id probably get him to install it aswell to be on the safe side. But if too much modification is involved I might shelve the idea for a while because $$$ might be a prob.

Thanx

Nobody has any idea about twin carbys?:bump:

Has anyone done this before with any success? Stock cars have come out with twin carbs before. 1st and 2nd gen honda preludes. alfa romeos.

What is involved? (Ive already got one dual webber) So you have 1 side of a twin carb setup? get the other half.

What intake manifolds will fit the astron II (TR-TS version) (Part numbers???) i dunno bout part numbers but there is a manifold u can get from a local shop here for $300. (dosent include carbys)

How much roughly would a 41/46mm webber cost (Just throwing that one out there) why go brand new? 2nd hand carbs are just as good.

Will I need to modify the manifold to make it fit the engine, and/or carbys? u cant use ur manifold u have now. u need a specially made twin carb intake manifold. if u are lucky, u will find one to fit the astron.

How would twin carbys compare to a Turbo at 7-9psi? carbys u will be pulling hard right through the rev range, not waiting for a big hit at say 3000rpm wen boost cuts in.

Would anything need strengthening or upgrading? upgrades would include high performance oil pump and timing chain (just incase). also, with twin carbys u will need a better fuel pump. get a nice torquey cam and an exhaust (go 2.25") and this will c the most out of those twins. get the head skimmed aswell to improve torque even further and help ur fuel economy. i would also slightly strengthen ur internals. ACL Duralite flat top pistons. oversized valves (to let more of that fuel flow in better, and the exhaust gases to escape.) get some head work done aswell. probably just a mild port and polish to begin. of course u wouldnt have to do all of this at the same time. maybe get those pistons put in, the carbys on and the cam in. then slowly upgrade everything from there. do all the head work at the same time etc.

Sounds complicated, certainly something to look into, especially about the manidolf, if i were to attempt something like this i wouldnt want to have a custom manifold made :nuts:

i think u can get twin webber manifolds to suit the sigma somewhere... which may or may not fit the magna for room anyway..

i hear the twin setups' are good though... apparetnly you can make abuot 140kws @ the treads in sigmas (with lots more upgrades). if you do the same in the magna you might make a little more power due to the lower drive train loss, but then you dont get as much grip :rant:

a turbo'd 2.6 for about the same cost give or take a grand would probly only get 120-140 depending on the setup, plus some lag, but probly better fuel economy.

Does anybody know what model Sigmas came out with the twin carby manifolds?

TM-SE-RED do you know the name or e-mail of that shop that sells the manifolds? Would you be prepared to pick them up and send them down to Tas for me:D?

Would it be cheaper to buy a new cam or get the stock one reground to mild spec?

Iv got extractors + exhaust, and heavy duty rockers ready for a mild cam so Im halfway there. I have no idea on costs so, what would be rough prices for: skimming the head, porting the head, oversize valves and heavy duty springs, forged pistons, and a higher flow fuel pump.

Would it be worth getting the engine bored to 2.8 or 2.9litre? Not too sure how much this would cost. Im not really serious about doing this but if there are good gains I might put some more thought into it.

BTW roughly how big do you think the pump would have to be? I would be thinking at least 1.5x the standard flow...come to think of it, what is the flow of the standard pump?

Im thinking of getting the manifold, cam, pistons, valves, springs, other carby, and pump gradually and when I get a second car and I dont have to drive the magna all the time I would take it round to the mechanic to get put together...I'll have to talk to him about the headwork...I really dont like the idea of shaving metal off:confused: .

Does anybody know what model Sigmas came out with the twin carby manifolds?

TM-SE-RED do you know the name or e-mail of that shop that sells the manifolds? Would you be prepared to pick them up and send them down to Tas for me:D?

Would it be cheaper to buy a new cam or get the stock one reground to mild spec?

Iv got extractors + exhaust, and heavy duty rockers ready for a mild cam so Im halfway there. I have no idea on costs so, what would be rough prices for: skimming the head, porting the head, oversize valves and heavy duty springs, forged pistons, and a higher flow fuel pump.

Would it be worth getting the engine bored to 2.8 or 2.9litre? Not too sure how much this would cost. Im not really serious about doing this but if there are good gains I might put some more thought into it.

BTW roughly how big do you think the pump would have to be? I would be thinking at least 1.5x the standard flow...come to think of it, what is the flow of the standard pump?

Im thinking of getting the manifold, cam, pistons, valves, springs, other carby, and pump gradually and when I get a second car and I dont have to drive the magna all the time I would take it round to the mechanic to get put together...I'll have to talk to him about the headwork...I really dont like the idea of shaving metal off:confused: .


the name of the place im pretty sure is Extreme Motorsports. i have heard they are pretty dodgy doing work to ppls cars (heard a story about them leaving a screw or some washers in one of the cylinders. yeah, not good lol) but hey, they cant stuff up a twin carbys manifold. it gets made for them anyway i would assume.

it is cheaper to get the stock cam reground, though u can run into problems. a mild cam from say Crow Cams is around $300. i got my cam reground for $140 which included $20 postage. (had to send it to brissy), but because the stock cam was shaved to mild cam specs, the tappets couldnt adjust enough. i did some research and talked to a few people and found out all u need is manually adjustable rocker gear from a sigma and this will fix the noisy tappets with a reground. i never got around to finding out how much the sigma rocker gear would b though.

prices: i got my head skimmed 10 thou for $60, and i dont think that would change if u were going to skim it 15 or 20 thou. its just the price for skimming it. port and polish... depends on how hardcore u wanted to get with it. a mild port and polish would cost the least obviously. ill take a stab and say $200+ to get it done through a mechanic. i couldnt help u with prices on the other stuff cause ive never looked into that.

im pretty sure u can only get the 2.6's bored out to a 2.8. apparently the 2.6's are just bored out astron I's (which were 2L's) so u cant do too much to the 2.6 in the way of boreing it out. it would give gains. i mean, higher the displacement the more gains u are able to extract from it. if anything, i would only bore it out to say a 2.7, but the 2.6's still have alot of potential. so get the most out of the 2.6 and if u want more, then start looking at boreing it out.

y dont u like the idea of getting metal shaved off the head? its a very effective, cheap mod. if it helps with fuel economy and torque, y not? i dont think it will really matter cause skimming say 10 or 15 thou off the head is not much at all... but wat u can ask is what u would need to do to the head bolts... whether u need to skim them aswell to compensate or wat.

hope this helps anyway, im half asleep... just got home from work.

brendan

Its not that I dont want to get it skimmed...its just that shaving metal off the engine is kinda scary. I'll get it done....I wonder how much 10thou would raise the comp? And how far can U go before theres trouble with valves and pistons getting too close.

Iv already got new rockers...Im pretty sure they're off the 3l, I'll have to check. Im pretty sure people have Used these with bigger cams and have had no trouble.

Ok Im thinking more about a parts list of everything I'll need to have:
Forged pistons (Flat top Iv heard these are what Id need....not too sure about a brand...or size)

Dual carby intake manifold (Modified Sigma manifold as the bolts dont line up, or a custom one if I can find someone to do it)

Heavy duty valve springs (Crow cams sells these Im pretty sure)

Forged Oversize valves (4 intake 4 exhaust, not too sure about a size or brand)

Valve stem seals to suit (Should these come with the valves?)

Skimmed, ported and polished head (Modified to fit oversize valves)

Mild cam (Reground... or new....I might do this mod later as it is not critical and does not require the removal of the head)

2nd webber carby (Same as the one Iv got now, have to get an exage model no)

Suitable adaptor plate for astron to webber. (Any idea where I could get one?)

Connections for a second carb (Just hoses and T connections to splice into the existing lines)

Larger fuel pump (Not too sure about the size I'll need)

New fuel filter

Head gasket

Intake gasket

5l Magnatec + new filter (Might as well do it all)

Im sure Iv missed heaps, can anyone think of anything else?

As you can see I have to do a lot of research into sizes, brands, shops, etc, any help to get me on track with these parts would be greatly appreciated. :D

I might be interested in sticking a couple of carbs in my new Magna when i get it.

that parts list dosent seem too bad. could i suggest though, getting a high performance oil pump and timing chain kit? these are 2 critical devices on the astron engine and everything else will go to hell if 1 or both of these fail with higher power going through the engine.

ive heard chrysler 360 valves will fit. not sure how much or anything though.

could i also suggest u replace all worn seals/gaskets aswell as if 1 has only a tiny leak now, this could blow out with more power going through the engine.

im not sure u would need another adapter plate as a manifold u could get (custom or from the sigma) will already be a direct bolt on to our engines (with slight modding to the sigma manifold to fit). because the manifold is designed as a twin carby manifold, u will not need adapter plates for the carb to the manifold.

a lower temp thermostat could also be beneficial, aswell as a water injection system to cool the engine down further. with a skimmed head and higher compression, the engine will produce more heat from each combustion. with twin carbs, there will also b alot of fuel getting poured in.

CAI is a must. get AS MUCH cold air as u can. a scoop would help greatly. u could also try some washers underneath the bonnet closest to the front windscreen (to lift bonnet up alittle higher) to let hot air flow out better. keeping the engine cool is a must and should not b overlooked. there is a small splash guard near the front of the car, right next to the radiator directly infront of the alternator. this can be removed with 2 or 3 bolts and will let ALOT more air to circulate through to help keep things cool. i have done this and it works very well. of course, only do enough to keep the engine cool in the climates u will experience in tassie. if it dosent get too hot, u wont have to go too extreme with cooling the engine.

brendan

I might be interested in sticking a couple of carbs in my new Magna when i get it.


????????? arent u getting an efi TN with a turbo? i hope u dont mean replacing the efi with carby's, cause that would b a very expensive, and bad idea :confused:

I thought you would remember that im gonna have a spare car left over? Ill probably keep it for awhile to screw around with.

i think aussie wants fastest carby first gen and fastest efi first gen on here muhaha :badgrin:

i think aussie wants fastest carby first gen and fastest efi first gen on here muhaha :badgrin:

he aint getting fastest carby first gen. no no... thats wat im going for. though mazzax51 looks like he'll take it out :cry:

hmmm, maybe ill go for fastest twin carby turbo on here :badgrin:

Heres a revised list:

Forged pistons (Flat top Iv heard these are what Id need....not too sure about a brand...or size)

Dual carby intake manifold (Modified Sigma manifold as the bolts dont line up, or a custom one if I can find someone to do it)

Heavy duty valve springs (Crow cams sells these Im pretty sure)

Forged Oversize valves (4 intake 4 exhaust, Chrysler 360?)
Valve stem seals to suit (Should these come with the valves?)

Skimmed, ported and polished head (Modified to fit oversize valves)

Mild cam (Reground... or new....I might do this mod later as it is not critical and does not require the removal of the head)

2nd webber carby (Same as the one Iv got now, have to get an exage model no)

Suitable adaptor plate for astron to webber. (Any idea where I could get one?)

Connections for a second carb (Just hoses and T connections to splice into the existing lines)

Larger fuel pump (Not too sure about the size I'll need)

New fuel filter

Head gasket

Intake gasket

5l Magnatec + new filter (Might as well do it all)

High performance oil pump

New timing chain kit

Water injection

I already have a scoop so I can leave that one out.

Anything else?

BTW how does a water injection system work and how much does it cost to set one up?