bottom end - crank and con rod mods?
Turbo Mini Forums

i have finally got my current engine running just need to get it set up properly. next year i will be looking at building a higher spec replacement engine and transmission. i hope to build it roughly to the following spec., utilising many parts that i already have

tranx sccr gearset
tranx sc drops
atb limited slip diff with 2.9 final drive
centre oil pickup
double grey clutch diaphragm
minisport ultralight flywheel, standard backplate
fast road ap clutch

a+ block bored to 1293
accralite or omega 18cc forged pistons
piper vernier duplex gears
phase 2 cam

1.3 ratio roller rockers
minisport full race stage 5 head

metro t3 turbo, ford cosworth actuator, 2wd cosworth intercooler, big bore stainless exhaust system

megajolt ignition

i make the cr to be around 8.3:1, i hope to aim to run around 20 psi of boost and hopefully it will be a fairly sorted engine. i realise that the valves in the head may be prone to cracking around the seats, but will use it and see how things go

i am unsure what to do regarding the bottom end. i have looked into this over the last few weeks, but am still unsure

i will centre strap the crank as a matter of course. i was thinking of using a standard metro turbo crank or standard mini crank and standard rods, what are other peoples views on worked crank/rods on a forced induction engine? i know it might make things more smooth on exceleration etc, but it seems a bit of overkill for the cost considering that the fi engine is relatively low revving.

are there any crank/rod workings that people would consider as essential on an engine of this spec? obviously a fully worked crank/nice rods would be nice but i need to try to keep tabs on the budget.

many thanks

Not a million miles off the spec of my engine that minus the atb, my 2p's worth, I have a more or less std bottom end only a centre strap, the general thinking is that forced induction motors dont need revs to make the power so unless your hell bent on high rpms not really any point. Only a personal preference but wouldnt use minisport for anything unless there was no other option, you may be better with head set up for fi such as one from turbo phil, benross, med or the like. Also wouldnt put a double grey in there unless your at least going to go for oil fed thrusts as the d grey loves to munch thrust washers, I currently have a single grey which seems to be holding up for now, but I think the RTS setup is a much better bet-have a search for it. If you can stretch to it binning the t3 wouldnt be a bad idea, a lot seem to be on gt17's or some other more modern turbo at the moment. And I will stand corrected on any of the above.

Hope that helps
oli

Edited by oli79 on 2nd Jan, 2012.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Forget the idea of a head from minisport, firstly its mini sport and N/A heads are a different kettle of fish to forced induction heads. I`d get a head made by one of the reputable members on here. Turbo Phil or Benross.

A turbo motor need not more than a strong and well balanced bottom end. However, that said. I would have the crankshaft wedged. Knife edged and balanced. This should help the balance of the crankshaft substantially.
Conrods, fairly critical. Given how they travel. Force racing can help you out with this one. Modified A+ conrods are more then up to any task.

Also ditch that ancient turbo! There are many better solutions available.

thanks for the input. basically i have all of these items including the minisport head. with the large cc pistons and the head the cr should be 8.3:1. with a large chamber head the compression ratio would drop too low for what im after, ie maintaining some drivability off boost. as it stands this spec would take up all of my budget. if funds allowed i would go for fully worked crank and rods. i was wondering is anyone considered any work/treatment of them essential for this build. i have all of the above parts minus the cam, rockers, pistons and the diff, taking into account the machining/gaskets/bearkings and other bits and pieces i will be stretched to spend much more on this.

also i have thought about different turbo. however i know a couple on here have made good power with the t3, it is something that i can look at changing at a later date when funds allow. if you dont mind me asking oli what does your engine drive like and what kind of power is it putting out? i originally was thinking of a fully worked crank and sc conrods, but funds jut dont allow. also if i spend so much on the engine i might end up being worried about putting my foot down in case anything went wrong and caused big damage - if you know what i mean! cheers

Forget all of the bottom end stuff other than the pidtons and invest in a better turbo.

You will see much greater benefits.

In the 13's at last!.. Just

for turboo applications, the rods and crank dont need to be worked as the engines power all in will be under 6500 rpm.

dont put you money there put it in a set of ARP conrod bolts first! you seem to have missed of your list .....any tears are caused by reusing old rod bolts.

if valve sizes over 35.6mm and 30mm exhasts are used with forced induction and the EGTs are not right, the valve seats will crack between them.

thanks for the input. i will have to get searching regarding the use of other turbos. this is something that i would be interested in persuing.

thanks for the input steve. i will be running mj and will have it set up properly, so i may just get away with the st5 head. i have it so will see how it goes i think, any problems though and i will give you a shout, i am very happy with the intercooler work that you did for me, i think it can be seen fitted on my build thread. arp bolts will be used on the rods,

so is it general consensus that good condition standard a+ crank and rods will be more than adequate for the job?

cheers, dan

YES!

i am hoping my change to a gt20 from a t3 will give more power and make it a more progressive power delivery, with the t3 the power came in one huge lump tore the clutch apart and tried to throw me in a tree

thanks for the input chaps. i will look into the turbo situation in a little more detail when i get some time over the next few weeks. cheers

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Yup, wedging is a very good idea.

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

I cannot understand why on your 24H engines

On 3rd Jan, 2012 Vegard said:
I cannot understand why on your 24H engines

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

I bet you're right :)

Coming to Avon this year V?

When is it this year? I'm afraid I'll be over earlier only.. April I think.

July