Does anyone know - are there any significant differences between the cylinder heads on 1.3MPi Felicias and the 1.4 8v Fabia engines?

I want to built a new head with bigger valves for my Fabia-engined rally car, but I only have an MPi head to hand. Just wondering whether I need to source another Fabia head to use as the starting point

cheers

James

AFAIK they're the same, James - I've had a Fabia and MPi one side by side on the shelf and couldn't tell the difference.

Are you sticking with 7mm stems? And what are you doing about springs? FYI the Motor Excel head I have is built on a 136 head - i.e. the 8mm stemmed dual valve spring setup.

they are the same casting I believe as Darren says, not sure if the older castings have more material around the exhaust ports or if it was the later one (we had two cut apart a long time ago but cant remember which way round it was now).

I've been very pleased with the performance I got out of my current (skimmed, ported) Fabia/MPi head with standard 7mm valves and the single conical springs, so all other things being equal, would happily use another. However, the Paul Ivey big valves I've got have 8mm stems. The current motor makes 117bhp with a balanced (lightened flywheel) but otherwise standard bottom end and revs happily up to 7000, though I try not to rag it too much.

So I guess the options are:

1.) Starting with an old SPi/136 head and using the dual springs

2.) Using an MPi head, modified to fit the 8mm valves (which can't be that complex, one assumes) and sticking with the conical springs

3.) Using an MPi head and having it modified both for the bigger valves and dual springs

Any thoughts?

James

I "think" the last head I had done for the slowly sideways car used 8mm stems and Pinto single valve springs. know Ken's motor is using Kent cams mini ones but was pretty expensive as he had top hats made to suit and shims under them to get the install height correct. I guess you aren't getting any problems with the conical springs tho? I think they probly allow a bit more lift before going coilbound than the double ones do but don't seem as strong pressure wise.

finding a good non corroded 136 head is going to be a challenge I would say tho so maybe getting the guides swapped from one to the other may be an option?

edit... how about getting your current 7mm guides reamed out to suit the new valves?

I had a conical valve spring break on one of the Felicias, and given the dual valve spring setup's availability and better performance it seemed the thing to go for, and then Motor Excel said their heads were based on it anyway. But this could be just prejudice because of one bad experience! I remember that Guy Croft said there was no flow difference between 7mm and 8mm stems.

Bear in mind that a 135MPi engine had dual valve springs/8mm stems so it may be possible to find a decent head in decent condition. I have one in the shed left, I'll take a look at it if you want...

Interesting - I was under the impression that all MPi heads were the same, and that the lower compression on the 135 engine came from the pistons. Is that not the case then?

No. The 136 MPi engine has the 7mm stems and conical springs. The 135 MPi head is the same as the older one - 8mm stems, dual valve springs. Go figure!

The compression does, however, come from the pistons, with the tops having an oval milled out of them on all 135 engines.

well..

heads are the same, the difference can be found on heads made in different years, not from different engines (135, 136, fabia 1.4)

I know many 136 engines with 8mm stems made until something around september 1997. Engines made after this date have 7mm stems even if it's 135 or 136 engine.

Head with 8mm stems were made only with dual springs. Newer heads with conical springs have only 7mm stems.

Now I'm running fabia head with conical springs head on my 136 engine, before there was older head with 7mm stems, but with dual springs.