Crankshaft and Flywheel Lightening and balance

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Khryztal

Khryztal

New Member
Posts
725
Location
Felcourt. Surrey
Morning all,

Thinking about investing some serious time and money on my 3.9V8. Just wondering about having the crank and flywheel lightened and balanced while blue printing the rest of the engine.

What I'm wondering (after reading loads of stuff about it on the net) Is it really worth it. Do you lose low down torque, How much effect on low speed do you get?

Thanks for any info
 
Depends where you want to go with it. Full balance (static = take every thing to pieces weight every thing moving and balance to smallest tollerance possible) and dynamic (drilling holes and adding weights into crank, fly wheel, and mass damper) will make a seriously nice lump. BUT you will only see results at high rpm.

Better to spend cash on better heads, and CAM. If yours is a high milage, CAM, lifters are probably knackered anyway. Heads will be coked up, so will be a massive step change in performance! You could go for a grunty configuration cam, and scare yourself all day long.

In lightening the flywheel it will make it rev quicker, but will be really easy to stall. Also if you start putting in a wild CAM (as long as you have clearance in rockers, heads) it will be a bitch to get it idling smoothly....

I had same dilema on my enigne, and basically after shelling out a **** load of cash, my engine, (nearly complete now) started as a TVR 3.9, but is now a 4.3 TVR (Tuscan challange guts) lump with all rotatives ballanced to within 1 gram.

Its got stage 2 heads (DVS) and roller rockers so should be good for 6,700 rpm and getting on for 290 - 300 BHP.

Oh Check out my profile for a couple of pictures.....

....Bit of a waste in a '73 series, but hey classic example of how a project runs away from you......

:)
 
Not looking to go stupid on the power. Would just like a nice running engine at the end.
You've kinda confirmed my suspiscions about the low down running. And seeing I green lane the classic not sure I want to lose the low down grunt and easy running.
 
Yeah figured, for off road go with cam and top end rebuild! Give Ray or shaun @ V8 developments a call he is brilliant!!!!!!!
 
It will depend how much you want to spend.
A properly blueprinted engine will run into serious money.
It should include getting every componant done.
As well as the crank and flywheel lots of other items will need work.
Con rods, pistons, pushrods and clutch to name a few.
All the valve springs should be the same lenght and strenght.
A fully blueprinted engine will have every componant checked to very tight tolerance.
 
Last edited:
yep with you on that. Looking at spending weeks doing the heads alone. Oh, and it's an auto so no clutch. But may just be doing the top end at this rate. Looking for a smooth engine not a race engine lol
 
HEADS SEATS & VAVLVES
176 Argyle St
Birmingham, West Midlands B7 5TE
0121 327 2232

Great, great company, family run business, totally passionate about what they do. They vacuum checked my (original) heads - which leaked like sieves, and after ground valves, new seats, reskimmed faces (I think they also compensated fo comp gasket). And them flow and vacuum checked.

Acctually on the car the difference was amazing - really big difference in power. I would start here. especially if you have not decoked heads all your compression will be lost as well as the acctuall detonation power...

Give him a call - cannot reccommend enough.

M
 
Going to do most of the work myself so that will bring down most of the costs. Going to replace the valve trains as they are probably worn, same with cam and bearings. I'll do the crank bearings aswell. If pistons are good I'll reuse them if not replace.
Done straight replacement a few times, so shouldn't be a problem. Never blue printed before so going to be interesting to see the out come.
Like I say, not going for a race engine just a nice smooth one.
Looking at electric fans aswell. Was toying with the idea of supercharging, but not just yet lol.
 
decent heads, cam and headers will let you see about 235hp with a 3.9L. no really point to the fancy bottom end work as the engine not going to rev much
 
Khryztal said:
Already running full stainless exhaust with tubular fanimolds. You talking about the tvr type heads? Or RPi ones?
Click to expand...


bugger RPI lol

merlin F85 heads from real steel for the best results or stage 3 heads from V8 developments or V8 tuner
 
If you are going for a man size cam, you will deffo need reduced height valve guides and more open springs, as both will hit with larger cam lift. I think std will go to 0.46" lift and machined guides + DVS (double valve springs) will go to 0.5". Also this will allow you for rev another 1K rpm.

In terms of bottom end, only mod really worth considering is sticking in a set of ARP studs. You get almost the stability of cross bolting....

Also probably not worth going for blue printing as you could find a cross drilled TVR crank from flea bay cheap. Good ones for 4.2 and 3.9 engines are cross drilled (more lub) and are very, very finely balanced! 500 Crank needs special rods and pistons. Also be carefull with 4.2 pistons as they are almost IMPOSSIBLE to find now and people are charging close to a grand for a set!!!!!

But like someone else said make sure you map out all costs as you can buy a 4.6 bottom end for approx £1500...

What induction and exhaust systems are you using?

In terms of heads,

Before you go crazy on std heads and spend loads reconing, check out V8 Dev's stage 2 heads -they flow more than most other people's stage 3 heads. V8 Dev has full dyno and balancing facilities....

..Speaks for itself really...
 
Oh other thing to look out for in rocker assemblies. Before you do anything wip of rocker assemblies, and pull back a rocker - check if there is ANY step in shaft...

...Will give you an idea on how facked lifters and cam are...
 
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