Sourcing a performance camshaft + Tuning advice

[Tiz]

Hi Guys,
I am building a tuned 4g52 in the UK for my 1978 Colt Sigma GE and its a massive struggle to get service parts over here for this engine let alone tuning parts so:

- I have had an exhaust flange cut so I can build a custom exhaust manifold
- Inlet manifold modified to take 38mm quad motorbike carburettors
- electric fuel pump from the bike the carbs were removed from
- Balance shaft eliminator kit from AUS ebay
- Having the head skimmed 3mm(This should bring the compression to around 9.5:1 on an astron 1 I believe)
- Electronic ignition kit
- Ported cylinder head
- 2.25 or 2.5" exhaust system with straight through silencers I havent decided on diameter yet

The thing I am struggling with is a performance cam, what would somebody recommend for this engine and where can I source one? Impossible to find over here. Are these easily sourceable in AUS or the US??


Another thing I am struggling with is a clutch, mine is goosed and im sure a standard clutch will take this power fine. I can only find 83-86 sigma 2.0 clutches over here will these fit my 78 sigma. It has what you guys call the "jap" 5 speed.


Any other tuning advice anybody can recommend would be awesome!

[krohny]

You might be best off just getting your cam reground?

[cheaterparts]

Hi Guys,
I am building a tuned 4g52 in the UK for my 1978 Colt Sigma GE and its a massive struggle to get service parts over here for this engine let alone tuning parts so:

- I have had an exhaust flange cut so I can build a custom exhaust manifold
- Inlet manifold modified to take 38mm quad motorbike carburettors
- electric fuel pump from the bike the carbs were removed from
- Balance shaft eliminator kit from AUS ebay
- Having the head skimmed 3mm(This should bring the compression to around 9.5:1 on an astron 1 I believe)
- Electronic ignition kit
- Ported cylinder head
- 2.25 or 2.5" exhaust system with straight through silencers I havent decided on diameter yet

The thing I am struggling with is a performance cam, what would somebody recommend for this engine and where can I source one? Impossible to find over here. Are these easily sourceable in AUS or the US??


Another thing I am struggling with is a clutch, mine is goosed and im sure a standard clutch will take this power fine. I can only find 83-86 sigma 2.0 clutches over here will these fit my 78 sigma. It has what you guys call the "jap" 5 speed.


Any other tuning advice anybody can recommend would be awesome!

first is this a street car or for the track or a bit of both

going down your list
exhaust I also custom made my header from 1 3/4 tube and mandrel bends tig welding them up and made the lenth 36 " and as a 4 into 1 they worked fine
inlet you will have to work that one out - I used 45 mm dcoe13 webers
your pumps and balance shaft elim is sorted
I did a couple of things different to raise the comp and improve the squish band
I decked the block and set the pistons proud of the block a couple of mm then took an angled cut around the outter edge of the piston and also set the head up on the mill and made the same angle cut in the outter edges of the combution chambers
setting the clearance of 0.050" clearance between the 2 surfaces
the head was machined a bit as well and I ran about 10:1 comp
my head porting I knocked out the guides and die ground out the lumps at the top of the port and took off the sharp edge
from the inner radius ( theres not a lot of room to improve this )
before the guide were fitted they where tapered in a lathe where they fitted though into the port to get some better flow
the seats were 3 angle cut and made as big as poss in the throut and there were right out
so only the outter 1 mm of the valve was the seat
the valves were also back cut
on my first build I got the cam reground to a 35/75 grind with 110 lobe centres ( you may find some where local that can do that )
I also fitted some double valve spings
and you will need some kind of vernier cam gear to dial the cam in - I redrill std ones on a rotary table they are simple and dont move once set up

now for some boring bits if you are going to rev it up ie some track work it will need a bigger sump ( the heads dont drain back as well as it may seam ) and the sump runs low and is ripe to suck some air though the pump
instant run bearings !
lighten the flywheel just like any small motor this makes a huge difference
fit a larger alt pulley if you are going to it rev harder

[ddt]

damn, Cheater..
That 4g52 sure got a lot of love -where is it now?

[cheaterparts]

damn, Cheater..
That 4g52 sure got a lot of love -where is it now?

I ran it around 2000 - 2001 in hillclimb and sprints but burnt a hole in a piston at Calder so it got put a side for some time
as I had an event only a short time after Calder I though a 2.6 together from an old sh!tter than had been sitting over a work bench
it was the only short engine that I had at the time , so it get stripped and washed out with a kero gun and the garden hose
dried and assembled with a new set of cast rings ( no time to bed them in so I used cast )

lucky for me I had been making up an astron 2 head for the 2 lt - a M4 magna machined 3.5 mm and ports cleaned up
and had even port matched the weber manifold in advance
than fitted to the 2.6 with dished pistons giving a 9.6:1 which was a bit low for the cam used
but I won my class with this quickly built 2.6 so the 2 lt didn't go back in the sigma

so back on topic we had a round of the Vic hillclimb champs at boisdale hillclimb ( gravel hill ) and not wonting to run my sigma with no aircleaners and set up for the black stuff
I was given a GH sigma that was a 2 lt and a mate of mine and myself ran that in fact we both did all of the practice and all our runs with the fuel that was in the car when it was given to me
total cost of the car plugs -oil and filter and an exhuast under $ 200 total
and and a joke the panel beater next door grabed the car and cut and polished it for nicks

anyway I enjoyed playing in the dirt so the GH got an engine transplant , you guessed it the old 2 lt race engine
except the flywheel was a lighter billit flywheel
and the twin webers were changed to a 34/34 downdraft weber ( ford falcon carb )
it ran that way for a while till the GH was upgrade to a cordia for my autocross work

the 2lt race engine then got a birthday and freshen up - it was advertised on this site and sold to a SG member
and thats as far as I know

by the way my 2.6 motors have had much more work than that

[Tiz]

first is this a street car or for the track or a bit of both Bit of both, wont be used on the road much so manners are not too important

going down your list
exhaust I also custom made my header from 1 3/4 tube and mandrel bends tig welding them up and made the lenth 36 " and as a 4 into 1 they worked fine
inlet you will have to work that one out - I used 45 mm dcoe13 webers
your pumps and balance shaft elim is sorted
I did a couple of things different to raise the comp and improve the squish band
I decked the block and set the pistons proud of the block a couple of mm then took an angled cut around the outter edge of the piston and also set the head up on the mill and made the same angle cut in the outter edges of the combution chambers
setting the clearance of 0.050" clearance between the 2 surfacesI dont suppose you have any pictures of this? I kinda understand what you mean but would be nice to visualise it
the head was machined a bit as well and I ran about 10:1 comp
my head porting I knocked out the guides and die ground out the lumps at the top of the port and took off the sharp edge
from the inner radius ( theres not a lot of room to improve this )
before the guide were fitted they where tapered in a lathe where they fitted though into the port to get some better flow
the seats were 3 angle cut and made as big as poss in the throut and there were right out
so only the outter 1 mm of the valve was the seat
the valves were also back cut
on my first build I got the cam reground to a 35/75 grind with 110 lobe centres ( you may find some where local that can do that )Apologies for my ignorance but what does the 35/75 stand for?
I also fitted some double valve spings Aftermarket or sourced from another vehicle?
and you will need some kind of vernier cam gear to dial the cam in - I redrill std ones on a rotary table they are simple and dont move once set upHow much would you charge to ship one to the UK or if you was feeling really generous would you take a small payment for the drawings/measurements so I could have one made up over here? No fear of me copying your work nobody else seems to tune these engines over here!

now for some boring bits if you are going to rev it up ie some track work it will need a bigger sump ( the heads dont drain back as well as it may seam ) and the sump runs low and is ripe to suck some air though the pump
instant run bearings !How would you recommend modfying it? Remove the belly pan and put big wings on it or?
lighten the flywheel just like any small motor this makes a huge difference
fit a larger alt pulley if you are going to it rev harderWhat sort of RPM are we talking here?

But thank you for all your amazing advice it was exactly what I was looking for. Would you stick with the points ignition or upgrade to electronic? Roughly what total advance figure did you end up with so I have a ball park figure to tune from i know there are a lot of affecting factors but would be nice to be in the ball park before starting rolling road sessions

Also I can find ARP rod bolts for the 2.6 but not the 2.0 does anybody know if these are the same? Also struggling to source head bolts.

I seem to read on here about the astron 1 having dished pistons mine seems to have flat tops? Does that affect any of this tuning advice or have I misunderstood which ones have the flat tops and which dont.



Thanks

[Superscan811]

Also I can find ARP rod bolts for the 2.6 but not the 2.0 does anybody know if these are the same? Also struggling to source head bolts.

Yes, both rod bolts and head studs are the same for the 2.0L and the 2.6L.

Ebay is your friend..
ARP Rod Bolts
ARP Head Studs


Cheers.

[cheaterparts]

I did a couple of things different to raise the comp and improve the squish band
I decked the block and set the pistons proud of the block a couple of mm then took an angled cut around the outter edge of the piston and also set the head up on the mill and made the same angle cut in the outter edges of the combution chambers
setting the clearance of 0.050" clearance between the 2 surfacesI dont suppose you have any pictures of this? I kinda understand what you mean but would be nice to visualise it
the head was machined a bit as well and I ran about 10:1 comp
on my first build I got the cam reground to a 35/75 grind with 110 lobe centres ( you may find some where local that can do that )Apologies for my ignorance but what does the 35/75 stand for?
I also fitted some double valve spings Aftermarket or sourced from another vehicle?
and you will need some kind of vernier cam gear to dial the cam in - I redrill std ones on a rotary table they are simple and dont move once set upHow much would you charge to ship one to the UK or if you was feeling really generous would you take a small payment for the drawings/measurements so I could have one made up over here? No fear of me copying your work nobody else seems to tune these engines over here!

now for some boring bits if you are going to rev it up ie some track work it will need a bigger sump ( the heads dont drain back as well as it may seam ) and the sump runs low and is ripe to suck some air though the pump
instant run bearings !How would you recommend modfying it? Remove the belly pan and put big wings on it or?
lighten the flywheel just like any small motor this makes a huge difference
fit a larger alt pulley if you are going to it rev harderWhat sort of RPM are we talking here?

But thank you for all your amazing advice it was exactly what I was looking for. Would you stick with the points ignition or upgrade to electronic? Roughly what total advance figure did you end up with so I have a ball park figure to tune from i know there are a lot of affecting factors but would be nice to be in the ball park before starting rolling road sessions

Also I can find ARP rod bolts for the 2.6 but not the 2.0 does anybody know if these are the same? Also struggling to source head bolts.

I seem to read on here about the astron 1 having dished pistons mine seems to have flat tops? Does that affect any of this tuning advice or have I misunderstood which ones have the flat tops and which dont.



Thanks

checked for pics of the 2 lt engine but I was slack and didn't take any back then

35/75 cam advertised spec inlet opens 35 deg btdc and closes 75 abdc and exhuast open 75 deg bbdc and closes 35 atdc
the cam lift was 0.333" and the spec @ 0.050" was 12/52

valve springs were crow items and the part number is - 5840

I'll have to check the postage to the UK - 'll try and find that out in the next couple of days

the sump - here are a couple of pics of my sump its not a lot bigger but it takes a little over 5 lts
you make note that some of the sump is forward
that was done to move the engine back and have sump clearance ( I moved the enging back 2 1/2 " )

By cheaterparts at 2008-08-09


By cheaterparts at 2008-08-09

anything say 6000 - 6500 or more

sorry I cant remember what total I was using it was prob 32 - 34 deg and with 98 oct pump fuel

now all astron 1 engines used the same size combution chambers ( same head ) so the 2.6 had dished pistons and the 2 lt had flat tops

the rod bolts and head bolts are the same - in fact the rods are the same as are the bearings

[Tiz]

Cheater, I have to say your advice invaluable. Im sure I will have more questions the further I go on in the build. I will try to keep them to just this thread along with pictures so it may help anybody in the future

If you could check postage for the pulley that would be amazing! Thank you

[Tiz]

I have heard that the nissan/datsun L series valve springs fit this engine and they are double from the factory. Does anybody know this to be true? They are a little easier to get hold of here.

[cheaterparts]

I have heard that the nissan/datsun L series valve springs fit this engine and they are double from the factory. Does anybody know this to be true? They are a little easier to get hold of here.

http://www.crowcams.com.au/media/catalo ... %20all.pdf

check out the last page sigma and L series are listed the same just the installed heigh is different
which ups the seat presure

hope that helps

[Tiz]

Just wanted to let everybody know in this saga I got "Newman Cams" in the UK to grind my camshaft for me £192 delivered with all taxes paid so a lot better than I was expecting. And Beehive valve springs, retainers and keepers are on route from the US for a 4g54 so I am sorted for valve springs.

All the other machining work is coming together well. I have finished the porting work on the head. Hoping to get it all put together for a show here in the UK called Retro Show at santapod

Wheels are coming along nicely too

[Tiz]

Well its all built and in. Just waiting on my inlet manifold for the bike carbs to be completed.