Combustion chamber porting? Worth or not?

kokkolanpoika · Post by **kokkolanpoika** » Sun Jan 14, 2007 4:55 pm

Hi..

What are you think about Rover v8 combustion chamber porting?
My heads are 4,6 10 bolt head, and i´m thinking to modify this combustion chamber "valve" wall area.. Slightly rounded??
And next to skim head to get correct CR ratio..

Has anyone any experience/pick?

kiwicar · Post by **kiwicar** » Tue Jan 16, 2007 11:10 am

I am unsure exactly what you intend to do but it sounds like blending and smoothing the area around the valves, a small amount would not do any harm as far as I can see, but do not take out anything that will reduce the extreamly limited squish area on that head, I am unsure that you will actually gain anything you can measure either but if it looks better it can be quite satisfying to do. The best thing to change on the rover combustion chamber is to try and increase the squish area by adding metal in the area of the plug to make a kidney shaped combustion chamber which is also more compact. I also think however that there is too much material to add for it to be practical. What you should be aiming at is a chamber like the Chevy LS1,Sb2.2(if you can change the valve angles, or the brodix/AFR/RHS designs for the small block Chevys or the later ford 302 heads, all good chamber shapes. but a long way from the rover.
Best of luck
Mike

mgbv8 · Post by **mgbv8** » Tue Jan 16, 2007 9:14 pm

If you are running high comp ratio or a bit shot of gas it wont hurt to try and gently polish the face of the combustion chamber. But beware of taking material away so you dont alter the chamber cc.
I just use very fine wet and dry paper with oil to polish my chambers a little. Then finish with a buffer brush and metal polish to finish the chambers off.
Detonation is my enemy!!

stevieturbo · Post by **stevieturbo** » Wed Jan 17, 2007 12:18 am

by all means smooth and polish....

But I certainly wouldnt use a head that has had its combustion chamber shape altered.

ihatesissycars · Post by **ihatesissycars** » Wed Jan 17, 2007 5:10 pm

Is it possible to skim and early head to bring the chamber size down to something nearer to the later 10 bolt heads?

Post by **katanaman** » Wed Jan 17, 2007 5:20 pm

skim 1mm off from standard head. Its not exact but close enough and is what Rover did themselves with the late 3.9 10 bolt heads. Not sure how much safely you can take off after that should you ever have to skim the heads again.

ihatesissycars · Post by **ihatesissycars** » Wed Jan 17, 2007 5:35 pm

So i'd in theory be able to achieve a 28cc combustion chamber?

Any ideas what c/r a 9.35:1 engine with tin gaskets and 28cc heads would have?

Post by **katanaman** » Wed Jan 17, 2007 6:03 pm

around about 9.9:1 depends if you do actually have 9.35:1 heads are usually 37cc or more not the 36 they are meant to be and the volume on top of the pistons are usually larger than they should be too. I have seen them as low as 9-9.1 never actually seen one on or above the 9.35 in standard form. I guess the tolerances are all on the low CR side. If you go this route remember and get the inlet skimmed too or it wont fit anymore with a 1mm head skim. Probably best to skim the inlet on the heads rather than the manifold. If you want more you can deck the block by about .5mm ish anymore than that and you have to start checking piston to head clearance

ihatesissycars · Post by **ihatesissycars** » Wed Jan 17, 2007 7:53 pm

Thats interesting and food for thought.

With this second engine i'm building i want to make the most out of it and not miss out on anything potential upgrades like i did with my present one.

thanks for the info!

goodsy1968 · Post by **goodsy1968** » Wed Jan 17, 2007 11:01 pm

Rover heads are easy to adjust chamber sizes compared to other heads, as there is plenty of metal to play with, 5-6 cc is possible, & reshaping them can make a big difference, especially with bigger valves where valve shrouding comes into play.

Post by **katanaman** » Wed Jan 17, 2007 11:21 pm

I should also add be very careful with valve piston clearance. There is a very high chance you need pockets when you skim stuff that much even with a moderate cam. Course you pocket your pistons and you bugger up your new found high compression so you need to skim more. Then you need to top your pistons to stop them hitting the heads f you take it off the block.

goodsy or anybody even, do you know how thick the face of the heads are? I think to get rover heads down to 6cc will need a huge amount taken off them. Or do you mean welding them up as well?

goodsy1968 · Post by **goodsy1968** » Wed Jan 17, 2007 11:32 pm

Sorry Marki, I meant taking 5-6 cc out of the original size, i.e I have taken 3.5 heads to 42cc, & 4.6 heads to 35cc without taking the squish area.

ihatesissycars · Post by **ihatesissycars** » Thu Jan 18, 2007 8:22 am

Well my heads are (stage 2) from V8 Developments and have had the chambers altered and the faces skimmed and i believe they're about 37cc already so i guess i'd need to establish how much has been taken off already and work out what is left that is available to remove.

Or start again with some 28cc heads to get my c/r up KERRRCHING!

It always comes down to not enough sodding money though eh!

chodjinn · Post by **chodjinn** » Thu Jan 18, 2007 10:19 am

I had my chambers ported/polished - but then again I'm after a low comp as I'm running turbos

Post by **katanaman** » Thu Jan 18, 2007 5:11 pm

goodsy1968 wrote:Sorry Marki, I meant taking 5-6 cc out of the original size, i.e I have taken 3.5 heads to 42cc, & 4.6 heads to 35cc without taking the squish area.

Ah lol that makes a lot more sense now.

Question still stands tho anybody know how much material is there?