Jump to content

SC engine overhaul and opportunities


Recommended Posts

My 79 SC engine is booked in for a winter overhaul which will include some 964 cams I’ve had lying around for a while and also some port smoothing.  At some stage I will go ITBs but not yet.  I was discussing this with someone on here (you know who you are..) and he suggested that fitting a later set of SC pistons and barrels would be a very simple, low risk way of grabbing 20 or so extra bhp.  I’m wondering whether to do this, clearly leaning toward “yes” but wondered at likely cost of a used/good set and any comments on other stuff needing doing if I fit these?

Thank you

Ian

Link to post
Share on other sites

Side point - if you’re thinking of going ITBs, you ideally need some hirsute cams to fully benefit. Could make sense to do it all in one go?

Otherwise, why not 98mm and go 3.2SS

Link to post
Share on other sites
16 minutes ago, SP72 said:

Side point - if you’re thinking of going ITBs, you ideally need some hirsute cams to fully benefit. 

I appreciate you say "fully benefit" but the loss of the CIS is a big benefit. It also doesn't mean going inside the engine. ITBs and EFI can be done at any time as both you and Ian know.

  • Like 1
Link to post
Share on other sites

I understand the 964 cams that will be fitted work well with ITBs.  I’m just trying to work out if it’s worth going for later pistons and barrels and, if so, what else must I do to make them work?

Link to post
Share on other sites

Later 9.8:1 pistons and 964 cams work well with CIS but if ITB's are definitely on the horizon I would be tempted to hold back and go for something like a 10.5:1 piston with 'S' profile cams. You would retain all the driveability of a stock SC but gain an extra 60 bhp for very little extra effort. It would also allow you to match port to manifold sizes during any machining ops with the heads off. 

Also consider your CIS, these are are all getting on for 40+ years old and can work fine if undisturbed. Removal and refitting is not always guaranteed to go to plan. 

  

Link to post
Share on other sites

I already have the cams and need to limit what I spend on this project, she is watching and frowning already!  I figured I may be able to track down some inexpensive later pistons and barrels.  What about CIS, is any of it different on later SCs?

Link to post
Share on other sites

Hi Ian,

I had my 78sc engine rebuilt about 7 years ago, with a good used set of later high compression barrels and pistons, they had about 75k miles on them and measured up well within manufacturers tolerances etc. Mainly because the existing early model SC Alusil barrels and pistons were not worth saving. The replacement set were Nickasil which according to my engine builder said are much harder wearing. He also said the engine would be more “punchy” with the later barrels and pistons.

I paid £1000 for the set of used barrels and pistons (a new set of Mahle ones were £2500 at the time) including having them cleaned up by vapour blasting and faces machined etc. 

The rest of the build was standard. My 180 bhp engine was producing approx 203bhp on the dyno after the rebuild, so it would seem that you about right re the 20bhp......

Everything is standard including the cams, exhaust, CIS etc. Only change was spark plugs from standard W5D to WR3cc to clear the higher compression pistons.

Hope this helps...

cheers Phil 

ps I think you can use later SC or 3.2 barrels and pistons as they have the same bore, but please check !

 

 

Link to post
Share on other sites

No worries, might be worth ringing a few engine builders as mine came off an engine that was being built up to a 3.6 litre spec. So you may get lucky that someone has kept them on the shelf !

Link to post
Share on other sites

Could you get you cylinders bored to 98mm and fit some new JE pistons to make 3.2SS? Would likely add a lot more than the later SC setup and you keep CIS too

Link to post
Share on other sites

On the issue of cylinders, my understanding is that in Alusil cylinders, the silicon is throughout the casting rather than a thin coating and, that as long as oversize pistons are available, you can refinish the bore if needed.  This is an explanation here - https://cdn2.ms-motorservice.com/fileadmin/media/MAM/PDF_Assets/Reconditioning-of-Aluminium-Engine-Blocks_51708.pdf.  Also reflected in this thread here - https://rennlist.com/forums/928-forum/368216-preparing-restoring-alusil-bores-for-dummies-2.html (bottom of the page).  Some engine designs use Alusil liners as well but I assume ours are cast in the high silicon material. I guess the issue is much more pointed when you have a whole engine block at stake, whereas we can just replace the cylinders as needed, but it makes me wonder if we scrap a lot of perfectly good cylinders. This may all be rubbish but would be interested if there are any metallurgists or engine builders on the forum with a view. 

964 cams, the higher compression pistons and SSIs will make a very nice SC even with the CIS.  

PS The 3.2 cylinders and the 3.0 SC's are essentially the same.  However, I think SC cylinders may be grooved at the top for a sealing ring, whereas the 3.2's have a machined surface.  Not sure if this is accurate but I think so. 

Link to post
Share on other sites

Just for info....my C3 made 200bhp new, but when we did a group dyno day at AMD years ago, it made 225bhp. the only significant change according to the vast pile of receipts, was a rebuild at Dick Lovett's using 3.2 Carrera barrels and pistons, which I believe are 10.3:1 CR.

Jason.

Link to post
Share on other sites
1 hour ago, hagarep said:

Just for info....my C3 made 200bhp new, but when we did a group dyno day at AMD years ago, it made 225bhp. the only significant change according to the vast pile of receipts, was a rebuild at Dick Lovett's using 3.2 Carrera barrels and pistons, which I believe are 10.3:1 CR.

Jason.

So the engine is now a 3.2 then?

Link to post
Share on other sites
37 minutes ago, Phill said:

So the engine is now a 3.2 then?

3.0 & 3.2 both use a 95mm piston.

2 hours ago, hagarep said:

Just for info....my C3 made 200bhp new, but when we did a group dyno day at AMD years ago, it made 225bhp. the only significant change according to the vast pile of receipts, was a rebuild at Dick Lovett's using 3.2 Carrera barrels and pistons, which I believe are 10.3:1 CR.

Jason.

Any idea on the rods used to make the 3.2 pistons work?

Link to post
Share on other sites
7 minutes ago, Leicestershire said:

3.0 & 3.2 both use a 95mm piston.

Any idea on the rods used to make the 3.2 pistons work?

The cylinders are essentially the same - other than the way the cylinder and the cylinder head were designed to seal together - a sealing ring on the SC and a tapered surface on the 3.2.  You can see the groove at the top of the SC cylinder on this picture - http://assets.superstreetonline.com/f/263126426.jpg?width=&height=

The pistons are the same size but have different wrist pin sizes.  The 3.2 achieves its extra capacity because it is a longer stroke engine than the 3.0 - the crankshaft and connecting rods are different, hence the different wrist pin size. When I used Shirish's 3.2 crankshaft in my SC rebuild, because of damage to my crank. I had to use different con rods and have the pistons, originally bought for the 3.0 modified.

Link to post
Share on other sites

Got me wondering, not just about the rods, but also how the barrels seal to the head.

I also have a different crank to an SC. Mine uses the same crank as a 2.7.

I will get the file out and check for more info.

And I thought 3.2.pistons were an easy upgrade on compression. 🙄

Link to post
Share on other sites
58 minutes ago, hagarep said:

Got me wondering, not just about the rods, but also how the barrels seal to the head.

I also have a different crank to an SC. Mine uses the same crank as a 2.7.

I will get the file out and check for more info.

And I thought 3.2.pistons were an easy upgrade on compression. 🙄

As far as I know, the difference between the 2.4, 2.7 and 3.0 Carrera crank and the SC crank is the main bearings, which are bigger on the SC presumably to go with the 9 bolt flywheel.  The stroke is the same - 70.4mm.  The conrods are probably the same, but I'm not sure.  The SC is an incredibly strong and durable engine.

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...