Recommended Static Cr Target For Full Time E85 Street Car.

[Ben C34]

Nope.

[Blackkers]

need higher than that for e85.

maybe in a 30psi full time track car

[XKLABA]

I have Wiseco RB25 pistons in a 30 block with a 26 head at 9.53:1 static comp ( +/- 170psi ) and have pumped 28psi into it on E80 before the rear housing choked it, going to change turbos later this year and keep pumping boost into it

Go for 9.5:1 if you plan on E85

[AngryRB]

for those people reusing stock bottom ends, have you measured the bores on the blocks? what bore size have you encountered? Wondering what the acceptable piston to bore clearance has been and weather you've had any piston slap, cause i hate piston slap and want to avoid it.

will be taking the head off my purchased rb30 and want to know what bore size is acceptable and whats a shithouse result, im assuming more than a 3thou piston bore clearance is getting unacceptable.. my old man says that the pistons will wear more

than the bore.. is this right?

sorry if this has been covered but is it ok to bolt the head on with new head gasket and do a comp test to check the ratio

and then strip and reuse the head gasket? im assuming if i got like 150psi id take it off and shave head a thou or two then

bolt it back on to get my 9.5.. but hopefully it would be up at the 170psi the first time..

Edited June 8, 2014 by AngryRB

[XKLABA]

Mine was a fresh untouched 86mm, I went 86.5mm and decked the block to 0 deck height

Piston clearance is up to the manufacture recommendation, no deers eyes what mine is set to

Doing a comp test might give you an idea of the dynamic comp ratio but the static ratio has the be measured and calculated

[Blackkers]

I guess you could compare a motor with the same head and cams if they are both timed spot on.

too many factors would make it unreliable but it could give you an idea.

I should get skyrine to do a full comp test of his fresh motor once it's finished seeing as we have the same spec ideas.

Actually if you're reading this Skyrine can you tell me which head gasket you used?

I've read that the factory HG is 1.3mm can someone confirm that? Cheers

[AngryRB]

so no ones measured the bore of there block to see if its worn? i guess ill just check a vl commodore manual then and compare, just

wondering what people have done and how much the clearance was. My au falcon has 200psi each cylinder and there supposed to be 9.6

if i have that right, so with the rb2530 im thinking that's a good guideline??? maybe someone has done a comp test and knows what it

should be with 9.5??

[iruvyouskyrine]

I measured my virgin bore RB30 block and they were 86mm+/- .1mm Also it is my understanding (happy to be corrected) that your pistons rings will wear much faster than the engine block.

I am using a 1.3mm (.051 thou) cometic MLS as that is the standard headgasket size. I have had approximately .008 thou taken off the head from skimming when I got the VCT jacket welded.

If someone can point me in the right direction on how to calculate static CR I will do it, and I will comp test it when it's all assembled

Unfortunately I am not near the car until mid July, so don't hold your breath

[AngryRB]

a quick google suggests that 0.1mm is 4thou? so will you be happy with that much clearance?

[KiwiRS4T]

sorry if this has been covered but is it ok to bolt the head on with new head gasket and do a comp test to check the ratio

and then strip and reuse the head gasket? im assuming if i got like 150psi id take it off and shave head a thou or two then

bolt it back on to get my 9.5.. but hopefully it would be up at the 170psi the first time..

My Tomei metal head gasket has been on and off 3 times now no problem. Not so sure about other types.

[KiwiRS4T]

I measured my virgin bore RB30 block and they were 86mm+/- .1mm Also it is my understanding (happy to be corrected) that your pistons rings will wear much faster than the engine block.

I am using a 1.3mm (.051 thou) cometic MLS as that is the standard headgasket size. I have had approximately .008 thou taken off the head from skimming when I got the VCT jacket welded.

If someone can point me in the right direction on how to calculate static CR I will do it, and I will comp test it when it's all assembled

The calculation is the easy part - the measurement is the hard part. Here's a guide:

https://www.rbracing-rsr.com/compstaticcalc.html

[R32Abuser]

I measured my virgin bore RB30 block and they were 86mm+/- .1mm Also it is my understanding (happy to be corrected) that your pistons rings will wear much faster than the engine block.

I am using a 1.3mm (.051 thou) cometic MLS as that is the standard headgasket size. I have had approximately .008 thou taken off the head from skimming when I got the VCT jacket welded.

If someone can point me in the right direction on how to calculate static CR I will do it, and I will comp test it when it's all assembled

Unfortunately I am not near the car until mid July, so don't hold your breath

static%20compression%20ratio%20calculator.xlsx

This is the one I created to roughly calculate mine...forget about some of the information there.

Obviously key in your inputs and it should spit out a number for the static CR....

Edited June 9, 2014 by R32Abuser

[Simon-S14]

have been thinking about building a 10.5-11;1 CR rb30, would be mint for response and e85 loves compression. i'd use a 1.06 rear housing also to free up the turbine side.

but then i just go why bother, my stocker 30e with 26 head just works so well, revs to 7400 and takes 25 psi boost, loves it

[AngryRB]

Would you say the rb30 piston is stronger than an rb25 piston? does anyone know if the ring landings are the same thickness, ive heard the 25 is prone to failure

Im thinking of using RB25 pistons and decking the block, cause my block is worn.

Edited June 10, 2014 by AngryRB

[GTRPSI]

a quick google suggests that 0.1mm is 4thou? so will you be happy with that much clearance?

How i remember it is 40 thou is 1mm so your correct in saying 0.1mm is 4 thou or 1/10th of 1mm.

[iruvyouskyrine]

have been thinking about building a 10.5-11;1 CR rb30, would be mint for response and e85 loves compression. i'd use a 1.06 rear housing also to free up the turbine side.

but then i just go why bother, my stocker 30e with 26 head just works so well, revs to 7400 and takes 25 psi boost, loves it

As much as I would really love to see it done Simon, it's a dedicated drift car, responses is but a clutch kick away.

[chairman]

rips run mid 7.5 comp to 8.0 on there rb26/30.

low comp wont have any problems spooling up / lag

over 9.0 will cause many issues

including head lifting

[Ben C34]

rips run mid 7.5 comp to 8.0 on there rb26/30.

low comp wont have any problems spooling up / lag

over 9.0 will cause many issues

including head lifting

A dedicated drag car can't be followed too closely when building a track car.

Higher comp won't lift a head. Or cause any issues. Especially on e85.

You are on your own with the low comp advice in this thread!

Edited June 16, 2014 by Ben C34

[XKLABA]

I have 9.5:1 with 28psi and the motor has been running for more then a year now and I haven't lifted a head yet, higher comp will make off boost driving a lot better though

[chairman]

fair enough