Advice on building an RV8..........

[Sunbmw]

Hi all, fairly new on here and to V8's. I am currently building a Rover SD1 which is to be a Stage rally car, it will be used for mainly Tarmac, single venue events and I need some advice on engine build.

Here are a few criteria it must meet.

I can't go over 3500 (i know that they are anyway but I can get away with a few CC, but 3.9 would be a no-no).
I would like a good few revs to use, I have been used to fairly revvy motors, 2lt Vauxhall (9000rpm) and of late a modified M3 Evo 3.2 motor (8000rpm).
It has just GOT to run downdraft induction, preferably some throttle bodies, but I just have to have that bark of downdrafts, carbs would be a last resort as I would like to have it fully mappable.

Anyway, up to press, I have aquire a new, 3.5 X-bolted block, some Group "A" rods and some Omega pistons, however, on closer inspection, these are dished crown affairs and I reckon will not give enough compression.

I will be doing all the work myself (apart from head porting) and do not have an unlimited budget, but would spend a few grand getting her right.

It would be nice to achieve 300bhp plus.

I have been a Vehicle tech all my life, and have built all manner of engines, including working for the Mitsubishi works rally team, building the Group N Evo 8 and 9 Engines, so I have some idea as what needs to be done to a competiton engine, but I am unfamiliar with the Rover lump, that is why I am throwing it out to you guys.

Thanks in advance, Lee.

[kiwicar]

Hi
To realistically achieve 300 bhp from a rover 3500 engine without nitrous or a blower will be tricky. Rover also do not rev very well so you have to take some fairly drastic measures here.
I am assuming you are not looking for normal road use here, so you may well be able to do it.
First problem is the heads, port them as far as they will go and you may get to 270-280 bhp, but at 3.5 litres you won't get more. So three options look for an olds mobile version of the engine and port the heads off that, they are not common and although the heads are more tunable very few people do them.
option 2 use Buick 300 heads skim them down as far as you can and use flat top pistons.
3 build a short stroke engine bassed on a 3.9 and use the merlin heads from real steel.
Personally I would do the last option as it may well stay together better and rev as you want.
The rest of it will need to match, I would go convert to mechanical roller cam, there is an opinion that the extra BHP you get from this (25 or so on a 3.5 over flat tappet) isn't worth the expence, however you want that 25 bhp and I don't think you will get it without. Also it should get you an extra 500 revs on the botton end of the power band and you wont have the ccs to help it. You will want 250 + degrees of duration at .05" lift maybe more and as you say throttle bodies and a good inlet and exhaust.
Best regards
Mike

[Ian Anderson]

300 from 3.5 full race engines is possible
But it will be expensive

Mate og mine in the GT40 club used to race MGB's and ran them at about 300hp (fly wheel)

Ran a holley 650double pumper into a open manifold (each runner could see the full 650cfm) Rev limit was about 6500 but he said over 5500 was not normally needed

He also said it got 3mpg so you'd better tow a tanker around for a rally!

Ian

[CastleMGBV8]

Lee.

Yes you can get 300+ BHP from a 3.5 but it will depend upon the regs you have to conform to and your budget.

The works SD1's and TR7/8's rally cars had approx 320BHP in their final spec with crossover injection, but to get there is not going to be cheap.

I'm assuming that the block you have is standard 89.9mm bore, for a high rev 3.5 you can go with the bigger bore 94mm. and use a 63mm. short stroke crank which will rev a lot better.

For high RPM (7500) use you will need in addition to your rods and pistons, a cross drilled and chamfered race prepped crank and an improved oiling system to provide 10 psi. per 1000 RPM and a light and efficient valve gear system.

Are you talking to John Eales of JE Developments, he has a lot of experience of building competitive 3.5 Rover V8 engines and has most of the parts in stock including standard or short stroke race cranks.

For the valve train I would be tempted to consider a solid roller lifter system with a custom ground cam and possibly roller rockers if the budget will allow, the geometry of the rocker gear will need work for use with a high lift cam by reducing the height of the rocker pillars by 60 thou.

Have a look at TA Performance site in the US they do a lot of special Buick parts that will fit the Rover including the roller lifters and rockers.

For the heads this will depend on whether you are restricted to standard Rover castings which can be modified?

For head work I would suggest talking to Peter Burgess who is fairly local to you.

http://www.peter-burgess.com/page34.html

If you can clarify what the regs allow we can advise better.

Kevin.

[Sunbmw]

Thankyou fellas, especially Kevin.

Regs are free, as long as I keep to within the cylinder capacity, as the MSA capped this a couple of years ago for stage rallies, you are allowed up to 3000cc with 4 valve per cylinder, and 3500 with 2 valves per cyl, apart from that, anything goes.

I work literally 35 feet away from Peter in Alfreton, I have spoken to him and he will probably get the task of doing the heads, when funds allow as he ain't cheap.

If I was to build an engine (and this would apply to any engine, not just the V8) with no budgetary constraints, my wish list would be Steel crank and rods, Omega or Cosworth intruder pistons, suitable cam/cams with a decent duration and lift, some properly worked heads, individual throttle bodies and a fully mappable ignition and fueling ECU. Oh, and I usually insist, where funds/regs allow, that the engine be Dry Sumped, but I have heard on good authority that the Rv8 is not keen on this due to crankcase breathing issues, is this correct?

Realistically, I will be looking at, as you say Kevin, short stroke, large bore block, steel rods, forged pistons, nice cam, heads done, hopefully the throttles and ECU and dizzyless ignition. I would liketo be able to build something decent for less than £5000 but not sure if this would be doable?

Anyway, thanks again guys, Lee.

[CastleMGBV8]

Lee,

To build your dream spec engine you'd be looking at around £10.000! but you should be able to put together something fairly competitive for your £5000 budget with a few compromises.

Firstly to be clear is your block a 89.9 or 94mm bore ie. 3.5 or 3.9 ?

Do you already have the group A rods and Omega pistons and what cc is the piston bowl.

What sort of figure did Peter suggest for the headwork?

Are you going to use the LT77 g/box?

I'm also thinking that even with some lightening the SD1 is not going to be that light and that it would be a good idea to retain as much torque as possible, also not sure if it is acceptable in a rally car to have a power band of say 4000-7500 RPM.

If you get back to me I'll try and work out a sensible spec for your budget.

Also sent you a PM re something else.

Kevin.

[Sunbmw]

Hi Kevin.

Right, the block is definitely 3.5, it was for this reason I bought it as 89.9mm X-bolted blocks seem rare, I also bought the pistons from the same fella (Chodjin on here), the rods are deffo Group "A" as I have weighed them at the weekend, and the pistons are Omega "316", I have no idea if this means anything, that is cast into the underside of the crown. I don't know what CC the dish on the crown is, I don't have an accurate syringe at the min to measure it, but will endeavour to do so over the weekend.

I haven't talked money with Peter yet, he quotes £1400 on his site, and I have it on good authority that no matter who you are, and where you are, he doesn't offer much in the way of discount, a fella I work with is mates with Keith who works for Peter, and even he gets charged full whack for rolling road usage!

Gearbox...........hmmmm, I would love a Tractive or Drenth, but will not be able to afford one of those for a long long while, so it looks like it will be the trusty T5 option, I will be on the lookout for one of the Glebe Transmission Sraight cut, dog box variants, I had one of the First of these in my Sunbeam, and if I am honest, it was a troublesome usnit, but I would like to think that they have sorted any issues out now.

Thing is, this is all a pipe dream at the min, I have got to get the shell sorted before I spend any oney on the drive train, and taking your advice on board, I may sell the 3.5 block and pistons etc, what do you think?

Wjhile I am on, may as well show you what the engine will be eventually destined for...................

As she was when I bought her.............



Now.................

[CastleMGBV8]

Lee,

Looks like a nice shell to build up from.

As you have a 3.5 block and the rods and pistons to match then I would use them as the basis of the engine, the longer stroke will help to retain a bit of torque. I assume the block has been fitted with the cross bolts?

Do you have a 3.5 crank?

To go short stroke, bigger bore is going to be expensive with the crank at £900 and the block around another £1500 and you would need different longer rods.

You can have a standard crank race prepped by chamfering and extendind the oil holes to increase the time the oil is supplied to the journal and this will allow higher extended RPM usage, if you have access to an engineering shop who could cross drill it at reasonable cost, this would be even better.

For the oil system use an interim front cover with crank driven oil pump but without distributor and fit the longer woodruff key to the crank (machine crank to fit) to drive the oil pump. approx £300, plus a larger capacity trap door sump for another £300


Can't see your budget stretching to throttle bodies, but if you have an EFI system you can have the throttle body increased to 71mm. the trumpet base bored out for 45mm. trumpets and the manifold ported to match the trumpet base and the modified heads. V8 Developments do these for £600-£700 a Hotwire system as a basis is better as it use the later style injectors, I'm not sure but it may be possible to bore out the Flapper manifold to fit the later injectors.

Don't forget to cost in the bearings, gaskets and an ARP stud kit to retain the heads, balancing approx £225 Real Steel are pretty competitive for parts and you can get an extra 10% discount by becoming a member for £25.

You can control this with a Megasquirt ECU from Phil at Extra EFI which will also run the ignition, approx £300.

Trigger wheels will supply alll the ignition bits have a look at his site.

For the heads your choice, you can go with Peter Burgess who will modify the heads to match your application or you could consider the Real Steel Merlin heads which at £1200 including rocker covers are good value and from evidence will flow enough for 330 BHP with a good spread of torque.

See how much that adds up to and then see what you have left for the cam and valve train components. If you set a rev limit of 6500RPM + then you could use standard rocker gear but add rocker shaft end support pillars to avoid rocker shaft breakage.

Hopefully that will provide food for thought.

Regards,

Kevin.

[Darkspeed]

6500 limit would be too restrictive, to get toward 300BHP from a 3.5 n/a then its 7500-8000 rpm and as people have indicated thats £10K plus territory unless some prime opportunities for parts come up.


Andrew

[Wotland]

Hi Lee,

Pistons you bought to Olly come from me.

They are Omega forged for Turbo/Supercharged application with 8:1 CR.

Definitively you can't use them for your 300BHP NA project.

I had one "300 BHP" 3.5 Grp A engine so will speak of my experience.

To obtain 300 BHP you need to build an high rev 3.5 with 7500 maximum RPM.

As you have already correct rods you need 12:1 domed pistons like this :



Mine waren Cosworth items (no longer available). You can always order similar domed forged pistons to Venolia in USA (Ask to have lightened pistons).

Second point is valve train weight and heads.

You need to have lighter possible parts. You can order to REC valves with 7.92mm valve stem diameter ( also use Colisbro valve guides for less friction). Don't be tempted to use larger valve with 3.5" bore. Too much shrouding effect you can't compensate by port size job.
Use titanium valve spring retainer and spend some time to study the correct valve spring to use to control high-rpm valve instability.

[Eliot]

They are Omega forged for Turbo/Supercharged application with 8:1 CR..

Well O/P says its 3.5L anything else goes - so the obvious answer to me is forced induction which will meet (and exceed) your goals and come in on budget as you dont need lots of exotica to rev it too the moon.

[Sunbmw]

They are Omega forged for Turbo/Supercharged application with 8:1 CR..

Well O/P says its 3.5L anything else goes - so the obvious answer to me is forced induction which will meet (and exceed) your goals and come in on budget as you dont need lots of exotica to rev it too the moon.

Hi Eliot, forced induction is not an option I am afraid, firstly, you have to use a 34mm restrictor with any forced induction engine, secondly, when you do have a turbo/supercharged engine, you have to times the cylinder capacity by 1.7, which would give me a capacity of nearly six litres.

I have been offered a set of domed Cosworth pistons quite cheap, but I have seen pics of them, and one looks different to the rest so I am slightly dubious. We shall see.

Thanks for the input so far guys, keep it coming....................

[Eliot]

A supercharged dakar rally raid car runs a 34mm restrictor - so dont see that being a problem!
Whats the relevance of the engine being considered larger?

[ian.stewart]

The common trick with rods was to go for Small Block Chevy rods, I think they need 0.020" taken off one big end face and the crank taken down to -0.010"
http://www.summitracing.com/search/Depa ... Rank%7cAsc
327 rods are whats needed from memory, whinh withsome searching are availabe in 0.10ths incriments, its certainly an option if using low comp pistons, with the option of the longer rod you can increase piston dwell, especially with the poor valve positioning in the bore, any little trick that helps make power in these engines is worth noting

[topcatcustom]

Whats the relevance of the engine being considered larger?

Maybe that he will be racing in a higher class with other 6l engines