Interesting head info

[classicswede]

It is right and it is also so very wrong.

A head ported for max CFM is not going to be ideal for a road car or a rally car. Track car maybe. You only port a head like that for that use or if you do not know what you are doing.

Normal porting is just about allowing the air to take a smoother path at higher gas speeds. A correctly ported head is going to work all through the rev range


What the video shows is "we fitted a race ported (or just badly ported) head that did make more max HP but due to slow gas speeds lost low down and mid power meaning a original head made the car drive better)

[Bracpan]

That's true there are only basically 2 ways of making an engine produce more power, get more air into it or make it Rev higher which again gets more air and fuel into it... its all about getting as much air into it as possible so it can burn more fuel.

So was the air flow measured on both heads ? and was the carb or carbs adjusted and ignition timing to suit both heads ? Gas flowing is an art done well its worth the money...if not it just costs you money.

[Derek UK]

Both the 18 and 20 heads are notorious for having bad exhaust ports. ('75 heads are a different casting and are better but very rare) Pointless doing anything to them beyond a bit of polishing that doesn't remove any metal beyond the odd sharp edge. You have to weld up the port floors and then reshape to get an improvement and then you need to know what to remove to get the right shape. Don't port match the exhaust to the head as when the exhaust is smaller than the port it creates a back wave that helps with combustion chamber filling. Putting the F.I. head on gives you big valves but that slows the gas flow down. Big cam gives you poor vacuum at low revs so a cleft stick. A modern cam that makes the best of what you have is pricy but good value as long as the rest of the engine is in good shape. A CR of 10:1 is pushing it for premium petrol but you can chase around for 100 octane in a few places. Tesco's? Being a supermarket fuel I don't know how good the additive package is.

[classicswede]

The more duration the cam has (and overlap) the higher the compression needs to be. A common mistake is not enough compression for the chosen cam.

[Bracpan]

Who is the best on Amazon Cylinder heads ? Especially for a good torque road engine.

[classicswede]

Erland Cox is very good, lot of others in Sweden and Ben Tinus Tuning NL

[Bracpan]

Shame none in the UK. But many thanks for the info

[arcturus]

If a B18/20 just concentrate on improving the breathing,Particularly exhaust.

[Burdekin]

Originally Posted by Bracpan

Shame none in the UK. But many thanks for the info

Give Rob a call at Amazon cars and speak to him. He builds rally engines so a lot of focus on low down power. Don't know who does his heads but I imagine he'll be able to give you some advice on what to go for.

[tdz840]

Originally Posted by Khe Sanh

Give Rob a call at Amazon cars and speak to him. He builds rally engines so a lot of focus on low down power. Don't know who does his heads but I imagine he'll be able to give you some advice on what to go for.

Doesn’t Rob use Scholar Engines?