16v head on 8v block

[dubmc]

hey guys,

some of you may know from my build thread - i'm currently in the process of building another engine.

just finished rebuilding a 2l block with forgies and balanced crank.

am undecided on which head to go with - initially i was going to purchase an 8v head and port it up etc - however recently it has been suggested that i can go with a early 16v head which will bolt on directly...

i will be keeping the dellorto so will require a new inlet manifold and exhaust manifold...

essentially im after some opinions/advice with doing this particular conversion - have many people done it before? if so what are the common issues - things to look out for?

thanks.

[Valver.]

hey guys,

some of you may know from my build thread - i'm currently in the process of building another engine.

just finished rebuilding a 2l block with forgies and balanced crank.

am undecided on which head to go with - initially i was going to purchase an 8v head and port it up etc - however recently it has been suggested that i can go with a early 16v head which will bolt on directly...

i will be keeping the dellorto so will require a new inlet manifold and exhaust manifold...

essentially im after some opinions/advice with doing this particular conversion - have many people done it before? if so what are the common issues - things to look out for?

thanks.

It's done quite often, but only for forced induction applications, as the compression drops down to around 8.2:1 - far too low to achieve any level of NA performance. You'd need to drop in 16v pistons, but it's a bit late for that if you've already bought 8v spec forged pistons. At this point in time, you're better of just fitting a big valve 8v head, otherwise you'll be backtracking and spending a lot more money

[straight_fresh]

Is it the height of the head which drops the comp? Being a 2L block would the stroke be the same/similar to an abf? What if you dropped a kr head on? My mechanical knowledge is pretty limited, I can look at something, pull it apart, put it back together and make it work but the numbers and decimal points is where I get lost :/

[ozgti]

It's the piston top shape that changes compression.

[jayjay]

The lower compression is due to the extra volume contained within the domed shape of the 16v combustion chamber - inside the head. The pistons in a 16v are flat, whilst the 8v pistons have a dish in them. The 8v combustion chamber is inside the block, thus when you mate a 16v head with an 8v block, you get two effective combustion chamber volumes. Conversely, with an 8v head on a 16v block, you get 0 combustion chamber volume.

If you wanna keep your dellortos and pistons etc, perhaps try an aba or other crossflow 8v head. Would have gone that route myself if i could do it over again. All of your 8v effort won't be wasted, but biggest hurdle is sourcing a head. Everything incl. valves, lifters, cams exhaust manifold/headers etc are interchangeable with your existing 8v components.

[roccodingo]

You also need to change the intermediate shaft, crank pulley, intermediate shaft pulley, oil pump drive gear and thrust bearing / cover ( where the 8V dizzy goes) use a 16v oil pump, and have piston oil squirters preferably in the *v block your using. Then there is the different timing belt, distributor , plug leads etc... list is near endless... plus you of course need to have the 16V head, cams, sprocket etc...Exhaust manifold / extractors have a different bolt pattern and the inlet manifold as you already have indicated.

Cheaper option is to buy a complete engine IMO.

Glad to see that you have your mind working on options though

[Preen59]

You also need to change the intermediate shaft, crank pulley, intermediate shaft pulley, oil pump drive gear and thrust bearing / cover ( where the 8V dizzy goes) use a 16v oil pump, and have piston oil squirters preferably in the *v block your using. Then there is the different timing belt, distributor , plug leads etc... list is near endless... plus you of course need to have the 16V head, cams, sprocket etc...Exhaust manifold / extractors have a different bolt pattern and the inlet manifold as you already have indicated.

Cheaper option is to buy a complete engine IMO.

Glad to see that you have your mind working on options though

What Grant said..


Either buy a 16v or continue with your 8v, dude.