13 replies to this topic

[Curley]

Evening all.... I've recently started a project to replace the tired 1275 that in my toy car. It's a 1972 Mini that has been stripped of all creature comforts, roll cage fitted and is used for track days and occasional B road driving. It is not a daily driver and only does about 1k miles a year. While I would like 'as much power as I can get' I also have to realistic, i don't have £15K for a full blown race engine. I'm using factory bottom end and a syncro gear box so recon I'm limited to around the 100bhp mark.

 

Below are the parts and spec I already have. I just can't decide on the cam. My engine builder has suggested 310 is too much and that I should be looking for something around the 300 mark. I originally planned on a 286 or SW7 (or SW10) but am now looking for advise from others. What do you think is something around the 290-300 range suitable?

 

• A-Plus block
• Centre main strap
• 21253 +40 high compression piston
• Standard 12G4114 rods
• Standard A+ CAM6232 Crank, wedged 
• MED ST2 Pre-verto clutch, balanced rotating assembly
• 31mm exhaust & 37mm inlet Valves on a new MPI casting
• 10.5:1 Compression
• 6 Piece SC syncro gear set
• 1:1 SC drop gears
• 3.7 SC Final Drive
• X-Pin diff

 

ps. I'm running EFI and ECU so no carbs or dizzy to worry about. 

Edited by Curley, 25 May 2018 - 10:46 AM.

[Retroman]

Looks like a decent spec for a weekend warrior

 

You can't decide on the compression before picking the cam.

 

I would be going with either a scatter 296 or a scatter VP4

 

And a lower final drive, maybe a 4.1...keeps the engine in the useful rev range.

 

PM me if you want some details

[imack]

Your engine spec isn't dramatically different to mine except mines 1380 and on twin 1 1/2" su's.
I'm running MED's Fia15 historic race cam which is arond 300 deg, in what is basically a stripped out road/trackday car.
Looks like you've got a decent head, I guess thats got offset valves going by the valve sizes, I've got the same valve sizes in my MED clubman spec head.
I think you'll need a slightly higher compression ratio though for the cam spec youve got, probably 11.5:1 or even slightly higher.
I've got a 3.44:1 crownwheel and pinion but 1.09:1 dropgears so around 3.76:1 fd so same as yours. Does give a bit of a long 1st gear with a sccr gearset, combined with a 300 deg cam and not much power low down can be tricky if you need to pull away on hills frequently. It feels pretty hard on the box from a full bore standing start with A032r's and a lsd.
You should easily get over 100bhp with a decent head, induction system and exhaust with a 286 cam which is what I had previously. The 286 was certainly a lot easier to drive on the road......but not as much fun as the fia15!

[imack]

As retro man says, I would be tempred to go for a lower final drive, I'd probably go 3.9:1.

[Allrounder]

You can get to 100bhp with just a 266 cam and the right combination of parts and the great thing is you wont need to rev it too high to get it.

[nicklouse]

i would hate to use a 296 on the road. 286 yes. done it.

[Retroman]

A 296 or 649 in 1000cc is a challenge in traffic, easier in a bigger motor, serious B road fun, should be just for the track but....

[nicklouse]

nope nope nope- i had a 286 in a 1380 3.44 FD  fine fun great on the Yorkshire roads and managed the daily commute. 296SP in the 1293 4.1 or 4.3 FD i forget nope nope nope though the EFI and ECU would make it more drivable. sorry the thought of my engine on the road is scary.

[dotmatrix]

I would not use a 296 cam in a street engine. I use one in my racer and it only begins to work above 3000rpm but perhaps this could be improved with efi.

I have never tried 276 or 286 but have tried a 266 and mg metro cam, and I would be tempted to put one of those in. also as others have said, I think you compression is a little low for a 296 cam.

[Curley]

Thank you for all the really good advise gents. What i'm reading is that 300 is a little too much for the road, great for the track, but not that helpful on the road. While I'd love to say that this car would be 100% dedicated to track and who cares about road use the truth is the Mrs and I enjoy a Sunday afternoon titting about on the B roads (that reads ruder that its meant to  ).

 

• Change the FD to 3.9
• Compression ratio will be decided by my cam choice
• I probably want a cam in the 285-295 range

 

After a long chat with Lee at MED he recommended I stay below 290, he said if it was his car he'd go for their XT over the FIA 15. I also spoke to Swiftune who have recommended their SW10. They also advised I reduce the inlet valve size 35.7 as he feared a 31/37 would be to unreliable for 'road' use.

[Curley]

After a little more searching the inter-webs I came across the attached spreadsheet. It's not mine but I have included it here for those who might find it useful.

 

Taking everyones feedback into consideration I think I'm going to go with the SW10 with a 3.9 FD. I've been told that the 21253 piston is the limiting factor to compression ratio. I note that some suggested I ran 11.5:1, have you done this with these pistons?

 

 

Attached Files

•  Camshafts.xls   46K   55 downloads

[Orange-Phantom]

Hi Curley,

Funnily enough I'm running a SW10 in my 7 port, my brother uses a 296SP in his road racer that he wins his class and beats a lot of other cars that he really shouldn't!

My thoughts are that you're making the correct choice with a SW10. The 296SP is a bit too cammy for the road in a 5 porter. It's great when you get it on cam but a bit too rough lower down.

The SW10 gives up a little on the top end for more lower down torque than the 286 as it has less overlap and only 280 rather than 290 timing on the exhaust.

Compression ratio with the SW10 should be 10.5:1 and as advised by Swiftune.

Final drive... I'm running a 3.7 and that's on a six speed. If I were running a 4 speed I wouldn't want to run a 3.9 for road use, for pure track and fun use then maybe yes.

Edited by Orange-Phantom, 25 May 2018 - 02:34 PM.

[racingbob]

296 spv4 is good cam had one in mine in Aus comes in around 3000 to about 7200 ran it with a 3.76 dif. however my head similar to yours got mg metro cam peaks at 6100 very happy with it and 3.4 diff

[Arthy]

I'm currently running a 1330, SW8 cam, MED ST1 ultralite assembly, Stage 3 Head (35.7 Inlets) by Alex at TCK, Twin HS4 (thinned throttle shaft) on a Maniflow inlet, 3.44 diff x pin, SCCR and a stock bottom end with 10:7:1 cr, and I could not be any happier with it!
 
Pulls well to around 6500 and I'm genuinely surprised at how nippy/driveable it is. Managed (just) to keep up with a modern cooper s works. He was pulling away, but I'll take it anyway! Can't imagine what any more power would feel like with a hotter cam! 

Edited by Arthy, 25 May 2018 - 07:11 PM.