piston choice, 3.9

[ppyvabw]

It was suggested I spoke to Sir John of Eales regarding pistons for my 3.9 by Chodjinn on my group A conrods thread http://www.v8forum.co.uk/forum/viewtopic.php?t=5153 (They have arrived by the way mate and they are coshar).

I'm not entirely sure what to ask for. My maximum budget for them will be around the 350 quid mark, maybe 400. He'll ask me what I want, and I'll mmmm and rrrr and sound like a right divvy so I'd like to call him and at least half know what I am talking about

It's going to be a normally aspirated engine. I want to get the compression up to about 10, but if need be I can get that up by taking some off the heads. I want to run a fair old bit cam as well so valve pockets are required, (although I can cut those, Id just rather not). A few weeks ago there were some flat top 3.9 cast pistons on fleabay made by GPM but I didn't win them, so something similar would be ideal. After market 'performance' cast pistons. Are cast omega's still available for them? I have seen them on fleabay occasionally.

I am aiming for ideally 260/270 hp out of it and occasional bursts up to 7000/7500 rpm. I may run a mechanical cam.

[CastleMGBV8]

Adam,

JE is not exactly cheap for parts, why not ring Omega direct and see what they have on the shelf, try haggling on price if they have something that will work with your rods.

I would also ring Paul at V8 Tuner and Real Steel to see what they have.

For a budget engine your RPM and BHP expectations are probably a little optimistic.

To achieve these targets you would have to spend money on improving the crank and the oiling system together with a much stronger valve train system, budget an extra £800-£1000 for the additional work and parts.

You must replace the later type vave caps as these are not safe over 5800RPM

To be realistic you can build a 230+ BHP 3.9 engine on a relatively tight budget and this will be nice to drive on the road as well as the track.

What spec heads are you planning to use?

Don't forget if you are changing the rotating parts it will need a full rebalance including flywheel clutch and front damper/pulley assembly. budget £200-£250.

Kevin.

[ppyvabw]

I'm not on a particularly tight budget, it's along term project but big outlays all at once are a struggle. That's why I don't want to spend nearly a grand on forged pistons, just some middle of the road pistons will do fine. Could stretch to 400 for pistons. I get paid once every 3 months so I can treat myself to some new toys every three months

I rang omega ages ago and they said go to john eales.

Bottom end, I have a 3.9 block with cross bolt bosses (it only has non cross bolt caps tho so if anyone has any spares, that'd be good otherwise my mate's gonna make some billet ones for me)

I will be having everything balanced etc etc.. DJE do some lightened cast flywheels. Not sure about those to be honest because they are 17 lbs and cast. I asked them, and they said they have never had a problem with them tho. Otherwise I'll get a steel one from v8 tuner and have my mate lighten that a little more. 250 for balancing will be fine.

Will be cross drilling the crank but what other work can I do to a crank to improve it? Apart from cross drilling, and squirting oil onto the cam gear, drilling holes just above the timing chain and maybe polishing the lifter gallery I don't see what other mods there are to make to the oil system without a dry sump system, or a wet sump with a belt driven pump (which im tempted by) I might fabricate a fancy sump though. The oil system in my car already has a cooler through a thermostat through 5/8ths hose.

Heads....I have some heads to practice on, so I will try and port them myself. I'll put stage two valves in, match to manifold etc etc...double springs, so will be changing the caps anyway, Chamber matching is not a problem, done that before with a burette. That's to get the compression all the same so that all cylinders are work the same so as not to stress the crank at the high revs.

I don't want to run at 7k I don't have the money, time or experience for that, just the occasional burst when accelerating and to change gear occasionally at 6.5/7k without fear of busting owt.

[chodjinn]

My advice is

a) Don't deal with DJE, he's an arse and charges the earth (personal opinion from attempting to discuss things with him on 3 occasions and being ripped off from one of his shoddy plenum insulators).

b) Get a steel flywheel, just to be safe.

c) speak to Wotland and see if he has his Group A forged cosworth pistons still, he got them from JE and the price was within you budget, plus they'd give a useful hike in CR.

[CastleMGBV8]

Adam,

If your going to have the crank cross drilled that will help the bottom end survive high RPM another crank mod is to chamfer or elongate the oil holes but not sure if that is necessary with cross drilling.

The other high RPM issues are the limited strength of the standard valve gear. the rocker shafts are prone to breakage if a lot of lift is bring used, and the minmum mod is a set of outrigger posts for the rocker shafts available fom JE. and a pair of heavy duty shafts.

Also if using in excess of .450 of cam lift you should really modify the valve gear geometry and use shorter heavy duty pushrods, I personally wouldn't use adjustables at 7000 RPM.

Kevin.

[ppyvabw]

Don't deal with DJE, he's an arse and charges the earth (personal opinion from attempting to discuss things with him on 3 occasions and being ripped off from one of his shoddy plenum insulators).

Don't mince ya words will ya Yeah there's 27lb steel flywheels on v8 tuner for the same price his cast ones are, except his cast ones are lighter. Any other suppliers of steel flywheels that are lighter than the one on v8 tuner?

Yeah I saw Dimitri got some pistons on my conrod thread but I assumed he was going to use them. I'll PM him.

Yes I was going to use outrigger posts.

I didn't know about the thing about the valve geometry though. That is something I am going to have to study. I might try and save up for some rollers, or failing that how do the steel rockers compare to the ally ones. I have heard they are not very good quality. I'll keep my eye out of fleabay Im sure I have recently seen some group A rockers on there.

[chodjinn]

what's the point in mincing or lying when money and friendship is at stake? I've given him the benefit of the doubt several times, but he's always the same. The woman that works there is the same as well, she's all knowledgable about everything, but soon as she realises you're not happy or want to talk refunds, she palms it off to Dave.

There are lighter steel flywheels out there, but some of them are small and will probably warrant a new clutch as well? How about an aluminium one?

[topcatcustom]

I'm guessing- that if you have alien main caps fitted to the engine you will have to have the block align honed...

TC

[ppyvabw]

what's the point in mincing or lying when money and friendship is at stake? I've given him the benefit of the doubt several times, but he's always the same. The woman that works there is the same as well, she's all knowledgable about everything, but soon as she realises you're not happy or want to talk refunds, she palms it off to Dave.

There are lighter steel flywheels out there, but some of them are small and will probably warrant a new clutch as well? How about an aluminium one?

Yeah, that'd be nice there's an ally one on v8 tuner that's 11lb, but it only has fixing for 10.5 inch clutch, so have 100 quid for a cover, 100 quid for a plate so over 600 quid in total, whereas I can get a steel one for a 200/250 etc...and use my current clutch cover with just a new plate which I reckon will cope with the power I want to put through it.

Does a 10.5 inch clutch fit in an lt77 bell housing?

Yeah they will need line honing. Probably would have done that anyway just to blue print the engine to perfection. One question I have about having blocks and rods honed, do you have to use bearings with larger outside diameter or do you just get say +10 bearings and they crush up? Am I being thick?

[Darkspeed]

Are/Is DJE still in business? - I went past the unit on the Nuneaton industrial estate as my office is just down the road and they/he does not appear to be there anymore - May explain a lot of the fixtures and jigs that were sale on e-bay recently.

Andrew

Sorry for the slight thread hijack

[HairbearTE]

Are/Is DJE still in business? - I went past the unit on the Nuneaton industrial estate as my office is just down the road and they/he does not appear to be there anymore - May explain a lot of the fixtures and jigs that were sale on e-bay recently.

Andrew

Sorry for the slight thread hijack

Only the other month some lucky bugger got Daves two sided 4 cyl perspex flow bench fixture which is threaded to accept RV8 heads and bored for 3.5 on one side and 3.9/4.6 on the other side.. still, at least it went to a good home

[chodjinn]

Are/Is DJE still in business? - I went past the unit on the Nuneaton industrial estate as my office is just down the road and they/he does not appear to be there anymore - May explain a lot of the fixtures and jigs that were sale on e-bay recently.

Andrew

Sorry for the slight thread hijack

Only the other month some lucky bugger got Daves two sided 4 cyl perspex flow bench fixture which is threaded to accept RV8 heads and bored for 3.5 on one side and 3.9/4.6 on the other side.. still, at least it went to a good home

Lol I have seen him selling a lot of his bits off, but even so, if you look on ebay there are still a few things from DJE through his ebay shop, but they're still silly expensive!

[ivanhoew]

these may be appropriate here ppy?

http://www.v8forum.co.uk/forum/viewtopi ... highlight=

having run this type of piston in turbocharged cars at high boost and detonation , i can say they seem to be a very strong design .

regards robert