Technical Working the head

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Technical Working the head

Aceuno

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Jan 4, 2006
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I have a 1300 x1/9, but i stroked it and upped the bore to make it a 1602cc. I have balanced the internals, lightened the flywheel a bit. Also a nice cam.

I think its time to do something with the head as its still stock. i am running an aftermarket fuel management system with UT inlet manifold.
I was thinking gassflow and bigger valves. Getting a set of throttle bodies later in the week.

What else would you recomend and what size valve would be the best? Only the inlet valves or inlet and exhaust?
 

ABZSTILO

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Guy Croft has done some work on the SOHC engines of late, worth having a look at his website as there were a lot of piccies of SOHC head work on the site. You'll possibly getting some ideas from there, or by emailing him?

I'd have thought a port 'n' polish at least, 'breathing' is always important and I'd guess you'll want to be looking at a semi-race head for what you've described?
 

jimbro1000

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The stroked version of that engine is something of a classic combination - a nice motor but sacrificing some of the amazing rev capability.

In terms of head work you should only be looking at the inlet valves. No point going for more revs with a big overlap cam and big exhaust valves as you are wasting the strengths of the engine as it stands.

Exact sizes of valves and ports are going to depend on what cam you run and the manifold ports themselves. The head can be prepared to flow quite serious quantities of air (on a bench) but you will never be able to utilise it so no need to go mad - just get the shapes right and make sure all of the cylinders are balanced.

Guy's website has some pretty good visual guides of what can be done (look for John Valentine's engine build).
 

RS Pilot

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I had a look through Guy Crofts web site before I ported my 1500 head. It was ok as a reference but he's written it in a way where you end up having more questions than before you read it which I'm sure is somewhat deliberate!

What put me off though was the way he criticised another tuners work who used a different approach. Although he's probably right, when carrying out a critical evaluation of someone elses work, definition of why you don't think it would work would be far better than basically just saying it's wrong!

That said, the pictures did show a beautifully ported head and I'm sure it will give the desired results with those lovely pistons. My finished head was certainly nearer that of Guys rather than the original 'tuned' head.
 

sumplug

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with reference to engine builders. only buy a complete package from one. buying bits here and there will never work. a good engine builder[GC], has spent many a yr perfecting their engines. the heads CR and combustion shapes go with the cams, pistons. rods, crank etc. many and perhaps most get it wrong big time.:)
 

RS Pilot

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I agree with the whole package thing if you're not doing it yourself, I just couldn't work out why GC with such a reputation behind him would even bother to 'knock' the competition.

It is good though that he does give some tips away.

On my own engine, the next stage is to get it set up properly as it just doesn't feel as powerfull as the work carried out and the parts fitted would suggest. Finding a rolling road tuner who understands proper engines to set the DCNF's up is the first step!
 

Guy Croft

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Hello

I'd like to explain how I work. I don't deliberately hold back on info. I'm not that devious! I do the best in the time I get to write on my own website, remember that something that may seem important to you may not necessarily strike me as significant enough to write about. We sit in different chairs you see. Often I could write for hours, but I don't have that much time. I do the site on Sunday if I get time between design jobs.

The idea of the site is that if someone wants additional info they can write and ask me, which they do all the time, client or not. Re criticising people or firms in this line of work who get things wrong, it's not a case knocking others - it's exposing bad practice. Nobody respects a person who climbs on others shoulders to gain an advantage. However with my site I do try to say to potential clients that this is how it's going to be done here and because I am confident enough to be able to put the details on my website for the whole world to see, it gives clients confidence too.
A picture of how it should not be done against one showing how it should is a valuable learning tool. What you see on the site is the tip of the iceberg, believe me, there are lot of firms and individuals hacking around with engines for good money and passing things off or making a real mess of them. This is not good. I was on the receiving end of this many years ago and I don't like it. There is no code of practice in this business.
At least at www.guy-croft.com folks can get an idea of how it should look.
Was John Valentine's engine right before? No. Huge ports, low compression, low cam lift, big carbs. A recipe for a mismatch as I said to John when I stripped it. The head work was a real knife and fork job by someone who had no flowbench or dyno exp at all. Did it work, no, ask John at sfconline.org.uk or read latest Retro mag. Does it work now - well, ask him.

There are a few marvellous firms around, when I get the chance I say so too. There are also accredited experts on other engines around with years of experience and I would not for one minute try and compete with them.

Now you know I'm a member here, I cordially invite you to ask for more detail if you want to! I hope this post will not seem impersonal or curt. It is not intended to be.

Regards

GC
 

sumplug

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Guy Croft said:
Hello

I'd like to explain how I work. I don't deliberately hold back on info. I'm not that devious! I do the best in the time I get to write on my own website, remember that something that may seem important to you may not necessarily strike me as significant enough to write about. We sit in different chairs you see. Often I could write for hours, but I don't have that much time. I do the site on Sunday if I get time between design jobs.

The idea of the site is that if someone wants additional info they can write and ask me, which they do all the time, client or not. Re criticising people or firms in this line of work who get things wrong, it's not a case knocking others - it's exposing bad practice. Nobody respects a person who climbs on others shoulders to gain an advantage. However with my site I do try to say to potential clients that this is how it's going to be done here and because I am confident enough to be able to put the details on my website for the whole world to see, it gives clients confidence too.
A picture of how it should not be done against one showing how it should is a valuable learning tool. What you see on the site is the tip of the iceberg, believe me, there are lot of firms and individuals hacking around with engines for good money and passing things off or making a real mess of them. This is not good. I was on the receiving end of this many years ago and I don't like it. There is no code of practice in this business.
At least at www.guy-croft.com folks can get an idea of how it should look.
Was John Valentine's engine right before? No. Huge ports, low compression, low cam lift, big carbs. A recipe for a mismatch as I said to John when I stripped it. The head work was a real knife and fork job by someone who had no flowbench or dyno exp at all. Did it work, no, ask John at sfconline.org.uk or read latest Retro mag. Does it work now - well, ask him.

There are a few marvellous firms around, when I get the chance I say so too. There are also accredited experts on other engines around with years of experience and I would not for one minute try and compete with them.

Now you know I'm a member here, I cordially invite you to ask for more detail if you want to! I hope this post will not seem impersonal or curt. It is not intended to be.

Regards

GC
hi guy. we meet on here as well:)
your comments are spot on. in a multi million pound industry, the tuning game stinks of rip off merchants who sell anything to make a profit. some of their work ive seen is a joke. advice given out by them is usually wrong and potentially dangerous. the bolt on brigade as i call them want ousting.
the power claims they sprout about is laughable. when the cars are rolling roaded, the real truth comes out. and these are well known companies selling lots of things. the industry needs cleaning up.
magazines such as max power are to blame in a lot of ways. they encourage this sharp practice and it needs stopping.
i salute you for showing up people and guaranteeing your work no matter what. good on you.(y)
 

RS Pilot

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Thank you very much for responding, it does explain a lot when the context of the website is explained :)

You're probably right, we are looking for different things - as an engineer in the automotive engine business (turbo diesels), I like hard data to work with and I guess most of the people reading your webpage wouldn't necessarily need that.

When I was about to open my 1500 ports, I was looking for definative information regarding the full inlet track from the DCNF 40's to the standard sized valves. I had been fortunate in getting hold of a pair of alquati manifolds (the proper X1/9 angled ones) and ended up just making a steadily decreasing port, all the way to the ID of the valve seat. From my own investigation I believed the biggest issue to be in the area around the bend and valve guide where the port size decreased significantly. What I was working on was getting the port velocity to incease uniformly all the way to the valve seat however this isn't necessarily the best method and was hoping to learn this from your site.

Now if I was you, I certainly wouldn't give this information away either and thought you'd written it in way where you showed some beautifull engineering and info on how to cut metal, produce opened valve seats etc but didn't give away any of your own 'secrets' as to what to specifically do on this type of engine.

I believe my work has given some good noticeable gains however was expecting a little more.....that said it hasn't seen a dyno yet for the carburation and ignition to get set up so fingers crossed.
 

sumplug

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the inlet valves are shrouded. this area needs de-shrouding. careful where you take metal from. the flow can turn out worse then standard.:)
 
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