The V8 Owners Forum -

Hi guys

Just trying to post a couple of pics of my ten bolt heads now ive just about finnished 'pocket porting' them. If anyone has further advice as to impovments I'd love to hear from you! Sofar I have just opened up seats and smoothed the first inch or so or the port after the valve and bulleted the std guides as they were mint. I will add a few more pics if this one comes out!

Brian

another pic

ex port

Last rover V8 my late father ever did:

http://www.mez.co.uk/westfield/09110001.JPG
http://www.mez.co.uk/westfield/09110002.JPG
http://www.mez.co.uk/westfield/09110003.JPG

Hi

Very, very, very nice! I'm a tad limited as to what I can do as I'm trying to keep as much bottom end power as poss, hence only working the area just before the valve to keep gas speeds high. I have only 'bulleted' the ends of the guides rather than grind them flush as your father did as I'm running LPG and was worried about the reduction in cooling of the valve. Am I being over cautious? As I'm new to the RV8, plus its going in a heavy ol Disco I didnt want to go too far, especially as I have decided to run with a stock cam at the moment (my aim is to get best power around 2000-4250RPM as its an auto and thats where she spends 95% of the time running!

I have so far avoided the temptation to clean up the ports further down as I'm not sure it would help and may well cost me some midrange grunt?

Any thoughts anyone?

Cheers

Brian

Brian,

Looks good and basically a stage 1 head job, should show useful gains in the region of 30 BHP on a 3.5 though would help to see a clearer pic of the transition from the seat to the throat.

A bit more compression would help with the LPG so you could have 20 thou off the heads for approx +.5/1 making 9.85 if fitted with high comp pistons and tin gaskets.

If you skim the heads you will need to check the lifter preload and shim the rocker pillars which is ok with a standard cam.

Kevin.

Hi Kevin

Thanks for info! Basically the build is a replacment motor for my 1994 3.9 discovery. I purchased a good (under 30k miles) bottom end from MuscleManta on here, its been balanced/lightened, ARP stud kit, high comp pistons with valve cutouts and the block was decked (pistons flush) along with 10 Bolt heads I'm porting here. The real aim of this conversion is to get as much tractable real world power from the engine on LPG as possible. i.e. solid tickover, power from idle (its an auto) and as much midrange as possible! (I'd trade 20 HP at 5000rpm for 10 at 3500 lol)

As far as C/R goes, having the 10 bolt heads is a bonus, musclemanta said as the block had been decked, the motor had a static C/R of about 10/1 on standard 14 bolt EFi heads. So depending on the H/gasket I use, I should get a C/R of 10/1 on composits or around 11/1 on tins. I am tempted by the tins as the higher C/R on LPG would be great, but so many people have said dont run tins as they are reknown for leaking I may well go the composit route.

To finnish the conversion off, I have bought a megajolt ign so I can get the most out of the LPG (plus two maps LPG and Petrol is handy too) and I'm losing the orginal restrictive mixer ring and have a BLOS LPG carb mixer to go on along with the mandatory K&N cone filter LOL

I will try and post a few more pics of the throat area of the ports and just want to see if I can do anymore without compromising gas speed too much!

Thanks
Brian

slightly better pic of inlet



I have left the port runners alone as the ten bolt heads have a slightly larger port already against the EFi/vitesse heads



The BLOS variable ventury mixer (think LPG S.U. Carb!) should make a big diffrence compared to the old mixer ring!

Most important, although cant be seen in pics. Is a smooth radius on the sort side turn.


basically smooth turns everywhere. No sharp turns. Overall shape can be important, but for simple stuff...just smooth !! polishing isnt important either.

As for the guides. The last ( expensive ) RV8 heads I had, they just bulleted them too. They said guide shortening made virtually no difference to airflow so wasnt worth doing.

thats great thanks! On other engines I have shrtened the guides down to the boss, but wasnt happy to on this setup so thats great to know. I have managed to put a radius on the short turn, but im having trouble finding a tool to go in the dremmel that will do a good job of it!
I never polish ports, old wives tales about uping gas speed and a rough finnish can help stop 'puddling' and break up any larger fuel droplets near the port wall. I think most polishing done on heads is really to look good so the customer can actually see something lol!

Brian

A simple carbide cutter would work. Not sure if they are available for Dremels though.

They are fantastic tools for the die grinder though

Hi

Yes, I was just looking on flea-bay again and found some 3mm shank ball and some 'tree' shape cutters that would do. So think I will invest in some! I have a die grinder, but suffer quite badly from athritus in my hands so the dremmel is easier on them, just lighter really.

Next thing is to see if anyone can help me with some ign maps for the Megajolt (petrol and LPG) to start me off and some thoughts on cam timing too. I'm using a new Std 3.9 cam for now though I may upgrade to a mild road job later. I just wonder if its worth retarding the timing a little as my main objective is midrange grunt. The engine has a cloyes roller chain with multiple timed keyways on the bottom sprocket, tho to be honest never used this system before, always had a vernier set up

Brian

I can give you maps to try when i get home, but they are for a 3.5.

I would say that there therefore means that they will have more advance than the 3.9 should, but to be honest i havent pushed any of the advance anywhere near what some people do so they should be ok.

Check the autosportlabs forums for more maps- there are a couple of 3.9s on there, and at least one guy running gas....

Hi Quagmire

Thanks for that, it would still be a good benchmark for my pertol map , I'm going to invest in a wideband AFR gauge too, so I'm expecting to be messing about with both both timing and fuel on the laptop once its running!