Rb25 Rebuild

[Dasmbo]

Hi and thanks for all who gave me pointers and tips for my rebuild got it started this afternoon and took it for a test drive all went well

temp normal great oil pressure for a change was suppised how well it started up and ran since i had added a couple of things once

again thanks and Jono i took a few of you hints and applied them to my rebuild thanks guys................

[Dasmbo]

Hi and thanks for all who gave me pointers and tips for my rebuild got it started this afternoon and took it for a test drive all went well

temp normal great oil pressure for a change was suppised how well it started up and ran since i had added a couple of things once

again thanks and Jono i took a few of you hints and applied them to my rebuild thanks guys................

I have uploaded a few pics of the rebuild

[The Mafia]

No worries at all mate, happy I could help.

[Rolls]

No worries at all mate, happy I could help.

Mafia, nice guy, really!

[r33_racer]

Did you check the tunnel size when torqued down with the new ARP main studs? I didnt see you mention any main tunnel honing in the machining operations or the use of a torque plate for that matter.

[Dasmbo]

Hi yes i didnt mention it i was going to post everything i had done plus cost etc.

For the boring and honing i went to a couple of engineering shops and told them what i wanted

before i decided on who was going to get my hard earned cash.

Total dollars for machining crack testing enlarging oil galleries etc including crank collar

installation was $1455.00 so made sure everything was done as required which could be

seen when assembling motor when i was double checking with plasigauges on main

and big end bearings.

I have built quite a few motors over the years for drag racing etc.and you have to use

same technique with all high output motors or it will end up as a big bang theory.....lol.

Did you check the tunnel size when torqued down with the new ARP main studs? I didnt see you mention any main tunnel honing in the machining operations or the use of a torque plate for that matter.

[r33_racer]

Yeh was just checking, as alot of people run aftermarket main studs and dont always get the main tunnel honed to bring the tunnel back to round when it distorts from all the extra clamping force.

[Dasmbo]

No probs good to see your on the ball. It would be a big waste of money if one didnt do the tunnel hone ARP stud kits are not cheap.....

Sam...

Yeh was just checking, as alot of people run aftermarket main studs and dont always get the main tunnel honed to bring the tunnel back to round when it distorts from all the extra clamping force.

[JustinP]

Sorry, can you confirm if your honing was done with a torque plate?

Thanks

Justin

No probs good to see your on the ball. It would be a big waste of money if one didnt do the tunnel hone ARP stud kits are not cheap.....

Sam...

[Dasmbo]

Hi justin yes i had the block bored 87mm and honed with torque plate got block decked the cylinders chamfered

mains tunnel closed/honed oil holes in crank radioused + crack tested and crank coller fitted ended up taking them

2+ months to do the job for me as they could not do all the machine work themselves.

Sorry, can you confirm if your honing was done with a torque plate?

Thanks

Justin

[JustinP]

Thanks for clarifying

Can anyone confirm if they have ever NOT used a torque plate when honing, and used ARP head studs, and more importantly, did they have any problems with compression due to not using a torque plate?

Hi justin yes i had the block bored 87mm and honed with torque plate got block decked the cylinders chamfered

mains tunnel closed/honed oil holes in crank radioused + crack tested and crank coller fitted ended up taking them

2+ months to do the job for me as they could not do all the machine work themselves.

[Gerg_R31]

At work with our torque plate i tested it,

honing, then measuring, then putting on torque plate then measuring again i got varied results;

Standard bolts barely made any difference

11mm studs up to 3 tenths of a thou distortion

12 mm studs up to 4 tenths of a thou

[zebra]

not as much distortion as I though there would be

[Gerg_R31]

Alloy blocks distort a shit load more

i.e gen III LS blocks, distort 2 thou with standard bolts

[discopotato03]

http://www.skylinesaustralia.com/forums/topic/378823-engine-internals-comp-ratios-general-info/page__pid__6040826#entry6040826

that i wrote up a few days ago which has the formula for working out your comp ratio which is more then grinding x amount off

Think of 8.5:1 as minimum and 9:1 as maximum, speak to your tuner, find out what ratio he is comfortable with, the turbo your running

Um , I'm not going to agree on your dynamic CR ideas but thats going to go a little OT and really deserves another thread .

Cheers A .

[Gerg_R31]

The how to work out your dynamic compression ratio isn't my idea but i was just explaining the difference between static CR and dynamic CR as someone mentioned the ITBs affect it which it doesn't. I've no idea what dynamic CR should be recommended but i am looking into it

But if you disagree then maybe you should try your best to correct me

[discopotato03]

Individual throttle valves play a big part in dynamic compression ratios because it means a engine has a lot of throttle area on a per cylinder basis . With single throttles all cylinders have to breathe through the one and you reach a stage where it can't feed them all enough to get adequate cylinder filling .

If you want an engine to breathe well - read fill its cylinders as best as possible - then individual throttles are the best way to go about it .

Look at it this way , take an 8.5 to 1 static (measured by volumes) compression ratio engine and give it individual throttles . Then take the same engine and fit your typical manufacturers single throttle and plenum type inlet manifold . ITBs give the very lowest restriction throttling because they give the least path of resistance to the atmosphere trying to fight its way into your cylinders .

Dynamic CR is all about how much air the cylinders have in them to compress , therefore if the cylinder is only 80% full its dynamic CR will be lower than if it was 100% full - for any given static compression ratio .

The way to make a less expensive to manufacture engine , ie single throttle one , feel good in part throttle conditions is to raise the static CR . In other words we didn't get as much air in as an ITB system could but what we did get was squeesed into a smaller space so the dynamic CR didn't die in the ass as badly as it could have .

Yes cam profiles play their part and the general rule of thumb is that the larger (longer) the durations are the higher the static CR needs to be in order to not lose low end torque . The reason why long period cams lose low end power is because they keep the valves open too long to allow good air trapping efficiency in the cylinders at lowish revs so the cylinder has less air to work with meaning less to compress .

The thing is that if people wish to do silly things with real long cams then its not the engines fault if it cylinders trapping efficiency is low and the static CR too low to do anything helpfull for them . Any engine is a sum of its parts and if the "system" is designed to all work together to make power over a given range then lifes good .

A .

[Gerg_R31]

I think you have volumetric efficacy and dynamic compression ratios mixed up, everything you talked about explains volumetric efficacy

Dynamic CR is all about how much air the cylinders have in them to compress , therefore if the cylinder is only 80% full its dynamic CR will be lower than if it was 100% full - for any given static compression ratio

So yeah cams will lower the CR with the intake valve closing when the piston is at BDC or the start of the compression stroke, then if you add boost it will raise the CR (rb30det 8.5:1 static comp intake valve closes at 60° ABDC add 15psi and you will have a dynamic comp of around 13.5:1)

We don't use educated guesses or "rule of thumb" when we machine and build performance motors, so for us to build even better motors that perform the best they can for what they will be used for, we have to understand and use the formulas to prevent something that will cause a problem, i.e over cammed for its purpose.

[discopotato03]

If you think about it low volumetric efficiency leads to a lower dynamic compression ratios , you have to have something in the cylinders to compress to start with .

The longer the valve (cam) timing gets the harder it is to keep the gasses flowing in the right direction at lower revs . This is obviously why engines are cranky at low revs with big cams , the valves are opened early and closed late in an effort for the engine to fill its cylinders at high revs .

Just on this ITBs tend to reduce some of the camminess (reversion) at low revs and small throttle openings because the throttle plates act as a partial barrier to reversion pulses back from the inlet ports .

To each their own , A .

[Dasmbo]

My Approx final cost for my rebuild $5,500.00 + bits I cant remember

CP Forged 8.5.1 Comp Pistons 87mm

Manley H Beam Rods with ARP bolts etc

Nitto Oil Pump & Crank Coller

ACL Bearings

ARP Main & Head Studs

Genuine Water pump Thermostat & Timing belt kit

Cometec Gasket Set

Greddy style manifold

80mm Throttle Body

All welsh plugs

H/Duty 6 Puk clutch Kit

Gearbox Bearing Kit

New Hoses

MACHINING

Block:

Decked

Bored & Honed

Crank Tunnel honed

Top of Bores Chamfered

Oil holes on Crankshaft Radiused

Crank Coller fitted

Crack tested crankshaft

Head surface ground new seals valves checked and reseated

MY INPUT

Remove all Casting flashing from inside Block

Die grind excess material around head to allow better oil return

Assemble Motor

Match ported intake manifold

Mirror Polished Manifold intake Runners

Modify pipes for manifold & blow off to suit manifold

Fit new Bearings in gearbox

Paint and install…..

Engine started pretty much straight up only had to tweak the acc valve a little and all is

Running fine Normal Temp and the best oil pressure this car has ever had….lol

I also purchased a lot of the parts from America as our dollar was $1.09 over there plus

The prices were much cheaper than in Australia

Once again thanks for every ones input i plan to have it on a tuned on a dyno after I run the engine in. Will have to find someone that can tune it with a emanage blue.