An oldy resurfaces to say Hi

[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.

[oldcobber]

Hi Tony,

Welcome. Its great to here from guy`s with older Cob`s that are still around and I`m sure there will be lots of advice here soon.

Bob

[Sidecarbod]

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

[Sidecarbod]

Starting to wake up now!

If you are running an edelbrock 180 you should do the drilling mod to the stat housing AND fit a 74 degree stat.

The 4.6 lump has "issues" if its run hot!

I hope that you've got a "red grade" block (Have you got one of the cosworth blocks from RPI?)

Pete

[Tony 289]

Pete
Fab thanks for all the info. really helpful. The inlet manifold is the original I modified to take Holley etc. Its 360 and works well on the 3.5. Was thinking of getting the compression up with piston and conrod combo from JE and using the old tin type gasket. I am from the Hornchurch, Essex area. Stick on 18 always.

[Sidecarbod]

ARP head studs are a good idea but don't use the outer bolts near the spark plug holes....infact you can't has the block won't be drilled and tapped.

Only take the nuts up to the same torque as the Rover bolts.

[Sidecarbod]

Originally Posted by Tony 289

Pete
Fab thanks for all the info. really helpful. The inlet manifold is the original I modified to take Holley etc. Its 360 and works well on the 3.5. Was thinking of getting the compression up with piston and conrod combo from JE and using the old tin type gasket. I am from the Hornchurch, Essex area. Stick on 18 always.

Hi Tony,

When you say getting the compression up with a piston kit was that for the 3.5 or the 4.6 that you are building?

Hasn't your 4.6 short engine got any pistons?

I could be wrong but I don't think that you can get tin gaskets for the 4.6. Even if you could I would not use them! When you take your 3.5 heads off if its using them you'll see what I mean! (Especially if you've used the dodgy outer bolts. The gaskets will have started to go brown near the valley area, this is the start of gasket failure).

You will certainly need to get the CR up if you want the most out of the 4.6 as the 3.5 heads have larger chambers. My 4.6 lump had the high compression 9.35:1 pistons fitted but it would have not even been that lowish figure with the larger heads! (I've got the figures at home, I think it was either high 8.??:1 or maybe 9.00:1....both pretty crap!)

Like I said in my first post the problem with skimming 70 odd thou off is that it messes a few other things up that can only be sorted by more machining!

The top end BHP that you'll get from going to the 4.6 is great but the bottom end torque is even more fun, my car will pull top gear from about 1300-1500 rpm! (The 3.5 would have stalled if I tried that!)

Essex is a bit far from me, luckily for you otherwise I'd come over with my burette to annoy you!

Not sure what you mean by "stick on 18 always" ??

If you need anymore advice just post or PM me.

By the way you must read Des Hammills V8 tuning book before you build you engine, all the info I used came from that book, it is required reading material!
You should also read it so that you know about the cracked block dropped liner issues that these blocks can suffer...not nice to read but it's better to know.

When you strip your 3.5 you need to look at the valve train components VERY carefully, you maybe disappointed to find that some of the bits are worn out, stuff like rockers and rocker shafts. Your 3.5 may have been running fine but the stuff can still be worn out, it would be daft to use them if they're not in very good condition.

Pete

[Tony 289]

Hey Pete
Good stuff and take your points, just for clarification :-
Stick on 18, you are in Vegas - black jack
Yes it is red grade but LC ( was very cheap) so at least need HC pistons so thought 4.0l as the gudgeon to crown is longer so moving stroke further up the bore. The old 3.9 and new 4 and 4.6 are all the same bore so 3.9 tin fits. The reason for the smaller CC chamber was to conteract the extra thickness of the composite gasket. Therefore I figured if I used tin (thinner) the old CC combustion chamber was OK and would eliminate the need for skimming. However, all just theory until I do the calculations. Will update you when I have and may all prove futile, in which case I will follow your example. Can't wait but wife said new kitchen may take priority. Really appreciate your help, thanks
Tony

[Tony 289]

Hey Pete looks like I have got it sorted. DJE will provide new pistons and machine them to take a high lift cam (Crane 224) which will give a 10 or 10.5:1 ratio with no other mods. Quote was £360 plus about the same again for a full dynamic balance. Seems quite an easy way to go. Will check all valve gear very carefully as per your advice. fingers crossed.

[Sidecarbod]

Originally Posted by Tony 289

Hey Pete looks like I have got it sorted. DJE will provide new pistons and machine them to take a high lift cam (Crane 224) which will give a 10 or 10.5:1 ratio with no other mods. Quote was £360 plus about the same again for a full dynamic balance. Seems quite an easy way to go. Will check all valve gear very carefully as per your advice. fingers crossed.

Good one!

You won't be disappointed with the performance of your 4.6, there's a lot more stomp in them than the 3.5.

Pete