EJ235 Stroker Build numbers

[PhyrraM]

So here is what I have come up with.


Bore- 3.825”---check.

Stroke- 3.110”---check.

Rod length: 5.160”---Hrrmm
From what I can find out there are a few lengths quoted. I WANT a phase 2, 52mm, EJ25, non-turbo rod. The machinist measured mine at 5.160". Crower quotes 5.162". Pauter quotes 5.180". 5.180" is supposedly the phase 1, 48mm length --However, Crower quotes 5.185" for a phase 1, 48mm rod. Nasioc and other Subaru sites have posts quoting everything under the sun. Rods seem to come in every length imaginable, even "non-custom length" ones. Wierd.

As a side note...The builder says my rods are NOT Pauter, they are Crower. I bought them used a few years ago off of either Ebay or Nasioc. They were sold as Pauter, the boxes say Pauter. The machinist and the length say Crower. Wierd.

I'm going to go with the 5.160/5.162 measurement. It seems the most logical. Only when the shortblock is test assembled will we know for sure.

Deck height 7.904”---Most info I can find says it is 7.913. I wonder if my block has been surfaced to get this measurement? Did the machinist get it wrong? If my deck IS OEM, then the pistons will be .009" down in the bore. The .002" rod discrepancy might push them back up to .007" down. I wonder what this will do to quench? One of my main goals was to get a proper quench in an effort to stretch Cali 91 octane gas as far as possible.

Pin dia: .906”---check.

Comp ht: 1.189”---Custom piston, so...check.

Piston top volume: 26cc---OK, same deal...check.

Combustion chamber: 44cc---most folks seem to agree that the EJ20G/EJ20K heads are closer to 46-47cc. Again, I wonder if he measured wrong. If they really are 44cc, that is likely a good thing as it brings back some compression that might be lost with the rod/deck height issue.

Gasket thickness: .040”---inconsequential, looks like I need a custom gasket anyways. .040 and .051 are Cometic thicknesses. OEM is close to those also.

Gasket bore dia: 3.840---Comtic quotes a 98mm bore which is 3.858". Can't find info on OEM composite or MLS gaskets.

Deck clearance: 0---Yeah, this one is out the window unless all these descepencies really are what the builder measured.

Comp ratio looking for is 8.5-1---I'm not picky and power desired is modest, so I'll be happy anywhere between 8:0 and 9:0. More worried about quench.

So, should I be worried? All the possible errors are small, but will they add up or cancel each other? My calcs show that it's all still buildable with the C/R likely landing in the low 8.0:1 range. Worst case is that my rods are the 5.185" length and my deck is low. That would put the piston out of the block by .030" or so.

MY question, to those that have built motors before, is....Is this normal? Does everybody deal with these small +/-? I always pictured it as a science. The motor builder came well recommended. He has a good history with street and racing motors under his belt. Everything from ALS Viper motors to ProRally Subaru motors. I really do trust him until proven untrustworthy. It's just that these discrepancies have planted a seed in the back of my head, and it is starting to sprout........


Yes, I've asked him about it. Looking for outside opinions here.

[PhyrraM]

Whoops. Meant to reply. Instead I accidentally editted the original post.