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Originally Posted by Tony 289   Hi all, thought I would say hello. Running BRA 289 built in 1984 and still running with SD1 3.5, Weber 500, Piper 270 and flowed heads. Getting slightly tired so have new RR 4.6 short engine. Any tips or views on using this and the bits from the old engine will be most welcome, especially front cover and heads. |
Just recently I did exactly what your planning to do, I'm very please with the results!
In short this is what I ended up doing:-
1. Skimmed the 3.5 (36cc) heads enough to get the CR to round 10:1 The heads already had 40 thou of them (V8 development stage III jobbies), I had another 30 thou taken off. 8 thou off is a about a 1cc reduction in the combustion chamber vol. How much you need to take off will depend on what CR pistions you have. I buretted every piston at TDC and every combustion chamber then worked it all out! (it took a while)
2. I had 30 thou taken off the inlet manifold faces but this cost a load of money due to the odd shape on the manifold (Edelbrock 180). It would have been cheaper to have the gasket faces skimmed on the heads.
3. I had the bosses that the rocker pedestals sit on skimmed 1.5mm as the valve train geometry goes to pot with high lift cams. You can see by the wear patern on the rocker pad that its a line contact at low lift but goes to a point contact at high lift.
4. Due to all the skimming the pushrords will be way too long, I used the Realsteel adjustables which are still too long. I had them shortened by 4mm. There is a small internal step in them which needs drilling a little deeper so that you can fit the ball ends.
5. Use the cam retaining plate, if your cam is not machined the except it then get it done. The 3.5 retaining method (if you can call tapered lobes that) is crap! Check the cam carfully before reusing it, there is no point in sticking a duffer in your nice new engine! (bag up the lifters so that you know which lobe they came off)
6. I used a piper vernier timing chain set, the cam retaining plate bolts fouled the sprocket so I thinned the heads down to about 1.5mm thick. RPI will sell you a modified plate but I did not know at the time!
7. You will need a spacer in front of the crankshaft damper, V8 tunner sell them for about 7 quid.
8. I used new standard lifters and a new piper 285 cam, the typhoon in my 3.5 was found to be knackered! Be careful as there are a lot of dodgy lifters about, they have not been machined correctly and fail. RPI sell standard ones made in the USA. (I don't like the leakdown lifters!)
9. If you go for adjustable pushrods set the preload to 20 thou, not 40-60 as you will get a bit more top end out of the lump.
10. You will need to pull out or cut the dowl at the back of the crank where the flywheel goes as the standard 3.5 flywheel does not have the hole. (It is only needed when the flywheel is used for timing the engine).
11. You will need a better clutch, RPI sell some sort of TVR one that works very well.
12. You will need to restrict the total advance to 28 degrees, I'm running 10 static but I'm still messing about with this at the moment.
13. The webber overfules even the 4.6 lump, a good needle is the 67x55 jobbie. It works on the 3.5 too. You need to sort this out before you run the new engine so that you don't wash the bores. Even this needle is a little out, Chedz and I have bought 2 LC1 lambda probes to fine tune the carb. I'll let you know what we end up doing.
14. My front cover fitted without any problems.
If I can think of anything else I'll let you know! I'm in Las Vegas at the mo and its 6 in the morning so my brain is not working too well!
Where abouts are you based?
Oh, by the way, the 4.6 lump will allow wheelspin in 2nd gear in the dry just by going from 1/2 to full throttle sharply !!!
Pete