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MG MGB Technical - Kent 717 or Piper BP285

I know we've been here before - many times - but can anyone with experience of a similar specification engine tell me the likely effect of changing from a 717 to a BP285?

Specification is 1840cc, 9.75:1 cr, really big valve head, HS6s, Peco, Aldon dizzy, etc.

Nothing at the bottom end, flies between 3000 and 5500 rpm and then tops out. Revs really well, but seems a bit flat as it tops out. Okay on the road, but seems to run out of steam on the track (ie at full throttle in third and fourth). Could even be a timing problem but that's another story!

Thanks,

Neil
Neil Lock

Neil,

i changed to the Piper 285/2, grid from a blank and would do it again!

Engine specs: 1868, county flat top pistons, G CR 10,25:1, ralley head with larger inlet valves, lightened valve gear, fly and conrods, balanced crank, Leyland Special Tuning dizzy (6 deg. static advance) and oil pump, SU HIF6 with K&N Filters, Peco exhaust with free flow header and all the other little bits.

With the Kent grid, there was no response up to nearly 4000 rpm, with the Piper torque is there from 1800 to 6500. (Kent do some very good cams for racing but the 717 hardly performs better than the stock MG B cam)
There are two versions of the 285 made by Piper and with the /2 version power comes a bit earlier than with the 285. The B handles like a modern engined car with this improvements.

BTW, after trying to order the 285/2 from a dealer (nowhere in stock), i contacted Piper directley and had the cam delivered within less than two weeks.
Although it is no a cheap item, you should ask for one grid from a blank and avoid a regrid one.

Ralph
Ralph

Can't comment on your exact question, but I have a piper 270 cam with a stage II head and 1868cc engine with free flow exhaust. Otherwise standard and it quite happily revs to over 6k rpm. I also know of a friend with a very similar engine but with a 714 Kent cam, and he also can rev over 6k rpm. He runs an EDIS system instead of dizzy and that gave him a few hundred revs at the top end.

Iain
67 BGT
I D Cameron

Ralph,

Did you go direct from the 717 to the 285 with no toher modifications at the time ie is it a straight comparison?

Books (including Peter Burgess, confirmed in an e-mail) say the 717 is a torquey cam but it doesn't seem to work in this spec. Remember reading somewhere that it works better with a 45 DCOE, which is a more expensive but easier modification...

Neil

Neil

Neil,

i changed the cam after @ 2500 Km, as it was not able to deliver the perfomance i thought it would do. I took out the engine and removed the head and the timing cover and gears an set the cam with dial gauges (one on no. 1 cyl. one on the inlet pushrod of no. 1 cyl.) and adjusted the vernier gear to the data given by Piper in their catalogue, as the data that came with the 285/2 were those of the 285.
Two days of work but with a very satisying result.

I also read Peters book and he has done a lot on research on heads and shortblocks but does not tell everything, especially in his cam overview (think he knows why).
The decission for the Piper cam was due to the promotion of a friend from the local MG club having had very positive experience with this one, but i also tried to get an idea upon cams and asked different German manufacturers (they do not offer cams for MG's) for their recomandations and got a lot of good information from the holley catalogue where some interesting general details are explained too. So the choice for the 285/2 was the only logigal one from my point of view.
There has also been a further change in carburation. As I told you, i have the HIF 6 carbs on my engine but with BDR needles and red springs. This setup turned out to work well with the other mods done.

Ralph
Ralph

I would go with Piper. I think their profiles are quite a bit more modern than the Kent profiles. That said and you can't argue with the experiances listed above!

Sean
Sean Brown

This thread was discussed between 10/01/2007 and 12/01/2007

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