My BP DOHC naturally asp. engine build

[wozzah1975]

Hi All,

Newby to the forum. Thought I'd share my engine build. I am an engine specialist, and play with all sorts of breeds and engines. The aim was to build a BP engine with 220-230hp flywheel (which equates to around 145-150rwkw on the dyno I use) for my car which mainly does club sprints and hillcimbs.

First up was valves. I looked at what was available and didn't think the sizes were much better than standard, so these are Ferrea valves, the inlets are RB25 Nissan items 35.7mm, the exhausts are Nissan SR20 items 30.5mm.
Size comparison STD/NEW


Next was pistons, the one and only block I had at the time sonic tested poorly, which meant not being able to bore it very far. Good pistons at the time were expensive, and because I fully intend to build another block larger in capacity later on I opted to use Nissan CA18 pistons. These had a raised dome for more compression, and were basically a direct fit, and were a good quality unit, and bonus, they were cheap! 84mm, engine capacity 1885cc.
Pistons STD/New


Camshafts. To make the sort of power I was chasing means turning the engine to 8500+rpm. I opted for some Cosworth profiles, 264@50, 312 adv duration and .430" lift which are tried and proven in BDA/BDG Cosworth engines
Cams STD/New


I also purchased ARP head studs and main studs, ACL race series bearings and a full gasket set consisting of as steel layered head gasket.


More piccies to follow

Cheers,
Woz

[BadBong]

Looking forward to this mate, always wanted to find out what an engine rebuil entails.

Keep it up!

[wozzah1975]

Next was to get stuck into the cylinder head development, as it would need to flow well. I picked out the best head I had to start with. (apologies for quality, some of these piccies were taken a while ago)

This was the first photo, head has new inserts fitted for the larger valves, but all the guides have been removed to port it.


These are a few random shots of the portwork etc.








Had to machine the head so the cams would turn


Cheers
Woz

[wozzah1975]

More bits.
I originally purchased Carrillo A beams, but because the block tested porrly I saved them for the next block build. I opted for the Spool Rods instead, I have used these in a few other engines and had a pretty good run. They are a little on the heavy side, but for this build they're fine.


Because of the cams and valves the pistons required much bigger/deeper valve reliefs.



Woz

[Jace]

If I had the confidence and knowhow, this is what I'd be doing.

Good luck, going to be fun!

[wozzah1975]

A conversion from HLA's to mechanical bucket and shim was done, after the porting and headwork all the valve heights had changed and because I used Nissan Valves all the installed heights were completely all over the shop. I had to spend alot of time dummy assembling, measuring and machining.









Woz

[Jeo]

Following this! Nice work.

[wozzah1975]

Obviously all the standard boring, crank grinding, balancing, lightening, cleaning etc procedures were carried out to the engine. It was all dummy assembled and the deck of the block machined, then dismantled ready for final assembly.

Main studs fitted

Crank going in

Pistons and rods in

Cleaning threads for head studs

Head studs Fitted


Woz

[wozzah1975]

Head finally assembled and ready to bolt on




Woz

[wozzah1975]

Anyone that has turned a BP hard for long periods of time will know that they have a nasty habit of exploding the oil pump. There is a number of performance parts available, but I have even seen these destroyed. It was suggested to me to fit a Peterson external oil pressure regulator, as the relief valve in the standard unit isn't ample to keep up, which is why they have a problem in this area. So the original oil pump relief valve is shimmed


Woz

[wozzah1975]

Damn, those valves are monstrous for a BP head. I've never seen anything that large crammed in there. Have any flow data?

They are pretty big. They are actually slightly shrouded at the moment against the combustion chamber, but the next block with the bigger bore will help that which is the long term goal. As far as flow data, I don't have it on hand (in the middle of moving house!) but it was something like 160-170 @ 10 on the inlet and 130-135 @ 10 on the exhaust.

Woz

[wozzah1975]

Time to very carefully fit the cylinder head and all the hangons

Oil pump on


Cylinder Head on




Lightened flywheel fitted



Woz

[wozzah1975]

More bits on

Cams dialled, waterpump and belt on



Woz

[wozzah1975]

Fitted to the car and running


Woz

[wozzah1975]

First dyno run.
Few changes in jetting, and made 140kw at the wheels. Next job, new extractors and exhaust to suit, the ones fitted are way too small!



Woz