8 replies to this topic

[The_Doctor]

Hi everyone,

 

I'm thinking of upgrading the camshaft in my 1275 to something like a Kent 266. I will eventually buy a better flowing head, but since they're very expensive (especially to have shipped to New Zealand) I figured I'd go with the camshaft first. With a stage 1 kit and HIF44 on an otherwise standard engine, would I see improvements? If so what sort of percentage would you estimate? 

 

Cheers,

James

[mikal]

Think it depends on what 1275 head you have. A Cooper S head flows quite well stock I believe so might work well, but a stock standard head and manifold might not give you the breathing to make much advantage of a more demanding camshaft. As far as I understand to see real gains you have to treat the whole carb, manifold, head, valves and cam as a package..

Surely there is a head guru in NZ that can trick up a head for you?.In 1984, I owned a full race rally car in Auckland and it went like the clappers (did 100 mph over the Auckland harbour bridge one night, youth being my excuse!) but as I said the whole top end of the engine was modified to get that performance.

Often wonder what happened to that car, sold it to a woman who wanted to get her 15 year old son onto something safer than motorbikes!! Was a bright red 1963 car with the works, roll cage, full gauges, timing equipment etc. Should never have sold it, hindsight......

[Earwax]

by the time you split your engine, regrind cam, change cam bearings and lifters, and whilst you are there, change anything else that looks suspect ( say rings/ bore/ etc) a head could well be cheap.. but it needs to be considered as a whole.... if i was to recommend one standalone tweak, it would be to go to 1.3 or maybe the calver 1.4 rockers, adjust your lash and timing and you will get a bit more oomph.  If i were after performance improvement i would't go with a 266, but something more akin to 276,  but (BUT for emphasis) the whole package is important - compression ratio , cam timing, valve size, inlet tract as well as exhaust.  Again, the rocker upgrade would fit in with this model, so you could leave everything alone except the rockers . just to play for a while  and then down the track , do a planned rebuild, with suited components, and just check the rocker shaft and re use the rockers 

[nicklouse]

Stop. don't do it.

 

what you are suggesting is a waste of money.

 

the cam you chose determines the CR you need. that is in part produced by the head. BUT is also determined by how much the block needs machining.

 

and as said changing the cam is an engine out and split job.( rebuild).

[Pigeonto]

Ok, I have a short answer to the original question and it is 'yes' it will. I speak from experience because I installed a 276 cam along with the proprietary big valve head.

The head then failed so I re-fitted the original, unaltered factory smaller valve head with its 9.4:1 compression just to get me back on the road. I have to say I was extremely surprised at the performance which there still was. The beauty of what you are considering is that a performance head is a bolt-on addition at any time whereas the cam change is not but once it's done you can keep adding later :- head, carbs, induction kits etc. Of course if you want to overbore/re-condition the bottom end and get the pistons flush etc then that's different but in a standard engine as mine was when the above happened, that was my experience.

All of the  responses are good advice. I am just addressing the question asked

Edited by Pigeonto, 01 June 2016 - 08:44 AM.

[Ethel]

You'll gain more from faster valve opening, low lift is when valves are the biggest obstruction. You could lose from longer valve opening lowering your dynamic compression.

If there's a kiwi machine shop up to the job I'd have thought a head would be the least complicated.

[Turbo Phil]

The primary restriction in any intake is the intake valve itself. Simply changing the cam may give some small gains as Ethel described above. If you're on a budget and can't afford a full head change, I'd go with a fairly mild cam, KC500 (MG Metro cam) or 266 and install the larger 35.6mm inlet valve and open the valve throat as per MG Metro.
This will show a decent gain for minimal cost. Depending on your current compression ratio it may be necessary to have the head skimmed to better suit the cam.

Phil.

[ACDodd]

I used to say no to this question. However cams have changed. Using the most modern profiles will give benefits in terms of area under the torque curve. The trick here is to stay mild. If you are wanting to improve on the stock profile (non mg) then I would choose swiftune sw5,piper bp255, Kent 256 or my own ACD - RT cam. If its the mg cam , then look at minispares evo 1, Kent 246, and my own ACD - RS profile. All will work better than the original factory grind.

Ac

Edited by ACDodd, 01 June 2016 - 11:20 AM.

[dklawson]

Adding my two cents....

 

I read the question as two parts:  1) Can I replace the head later and is this cost effective, and 2) can I expect any performance improvement with the stock head and new cam?

 

I will focus on question 1.  Regardless of how much improvement you get fitting the new cam to the engine before upgrading the head, you will save yourself the expense and time by fitting your new cam now.  No, you may not get as much out of it as you can but the engine is still likely to breath better and you won't have to pull the engine again later to make a cam swap.  As others have said, an unmodified big valve 12G940 head can flow reasonably well.  Using one of those should give decent performance while you save money to buy that custom head later.

 

I am not a big fan of non-standard, long ratio rocker arms as they increase the load on cam lobes and followers.  It is obviously your engine and your decision.