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7 Port Build Spec


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#1 Baxter_MFB

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Posted 10 May 2018 - 11:59 AM

Apologies if it's been covered before but I couldn't find anything.

I'm about to start building my engine and am just wondering a few different things if anyone can help. My car will be for weekend blasts and the odd trackday, looking anything between 110-140bhp but power isn't my end goal.

I've got a Pierce 7 port head on twin Weber's, going on a 1330 bottom end. I think I'm going for the 276 cam but if anyone has any others that are better then please say. I'm just wondering what a decent max rpm would be for an engine like this and a set of pistons than will withstand it no bother.

Any other tips like what rockers and things or what compression ratio to run would be a great help.

Thanks in advance,
Sam

#2 Northernpower

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Posted 10 May 2018 - 12:25 PM

There are lots of options to look at, the main thing to remember is to put some time and money aside for a rolling road session at the end of the build. You need someone who has plenty of experience with twin webers and has a full range of chokes, jets and emulsion tubes otherwise you'll end up going back to them. One choice of cam could be this Calver one https://www.calverst...-super-sports/. You need to forget about BHP and look for maximum torque if you're going to mainly use it on the road. This cam gives as much as you're going to need and with the correct bottom end will rev quite happily to 7,500. If you haven't bought the pistons yet have a look at these, https://www.calverst...erior-quality/. Because of the material they're made from the bore can be machined to much closer tolerances. Personally I don't care for the Pierce head but if you've already bought it you have no options. With the Calver cam look to use either 1:4 rockers or 1:5. A compression ratio of 10:1 is more than sufficient.



#3 Turbo Phil

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Posted 10 May 2018 - 12:30 PM

Do you still have the small 33.3mm inlet valve fitted ? If so I would think this will limit RPM and HP potential somewhat.

Phil.

#4 Baxter_MFB

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Posted 10 May 2018 - 12:37 PM

Thanks for the replies.

Yeah Northern Power, already got a guy close to me who specialises in older engines for a rolling road so that won't be a problem. Thanks for the recommendations, I'll look into them all and as for the pierce head, one came up for sale close to me and at a bargain price, I couldn't justify spending so much more on the sc one when I've got this so cheap.

Turbo Phil, yes it's new so it'll still have the 33.3 valve and 29.2 exhaust I think it is. Will this restrict potential by much?

#5 Retroman

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Posted 10 May 2018 - 01:56 PM

Don't know by how much a 33mm will restrict it to, but in any head its the valve seat / pocket that is the limiting factor.

 

To get the figures you are after inlets of 35.5 / 36 will be enough and depending on cam/compression consider bigger exhausts too

 

The Peirce heads will take 36.5mm inlets and with the right build you will not be disappointed. You need to be on 40 Dcoe carbs.

 

You will not go far wrong with anything from KC.

 

Not sure a straight 276 will give you 110+   a scatter pattern VP3 cam will, even with only 5 ports...



#6 Northernpower

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Posted 10 May 2018 - 03:01 PM

If the head wasn't a lot of money and as you already own it I would consider getting prices for larger valves and having the ports re-worked. It will be a good investment.



#7 Baxter_MFB

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Posted 10 May 2018 - 10:18 PM

Retroman and northernpower yeah I may end up porting them out, want to make the most of the head. Thanks

RSA Mini that sounds good, I'll pm you now

Thanks again for the replies, all a great help!

#8 Ape.in.a.box

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Posted 22 May 2018 - 09:37 PM

I've got a pierce 7 port head fitted to my 1380. The main issue I've had with mine is the spark plugs. They are sods to change with carbs or in my my case throttle bodies in place... those little spark plugs don't take much to foul and stop sparking if too much fuel gets on them!




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