I'm going to be doing an a6 cam in a b7 head with p29's and d15b rods (137mm as opposed to 134mm) which should make the rod length,stroke and deck height all the same as the d15b w more or less displacement...?Anyone here know how to calculate the compression ratio and total displacent for this motor with the 137mm rods as opposed to the 134mm stock rods. Engine specs are as follows:
-d15b7 block,z6 headgasket, b7 head, d15b rods, p29 pistons.
*We're wanting to use 93 octane for this guys car and need 2 know what the CR will be with this setup so we know which headgasket to get the CR as close to 12:1 as poss. Thanks. Leland

 

ttt

 

You can't put longer rods into a d15b7. 3mm is a huge amount to jump in length.

Go to this compression calculator and see.

http://www.zealautowerks.com/dseries.html

 

91JDMHATCHBACK:Trust me I know that 3mm is a huge jump, but the d15b is the same deck height, and has 3mm longer rods. Its known you can use the d15b(vtec) rods in a d15b7. And for anyone that wants to comment or wants a reference here's the chart:
http://www.knology.net/~jediklc/specs.htm

 

They are the same deck height but the jdm d15b uses 27mm comp height pistons so that they are flush with the deck. Using p29's will put them 2mm out of the hole.

 

The problem is I can put the b1 rods in my b7 but the stock pistons are different so I figure i'll have to calculate the b7 in the calculator with the b1 pistons in that motor to get a set of base numbers then go from there. The b7/a6 heads have the biggest cyl. head chambers of all the d's as far as I know so I'm pretty sure I can get away w/p29's without any issues its just the deck height of the a6's is 212mm as opposed to 207.45mm with the b7 so that's an issue i'll be running into with the b1 rods in the b7 block being that they are 3mm longer+ 4.55mm difference in the deck heights of the a6 and b7.

 

13.6:1 compression, will need short reach plugs, R5671A-8's likely.

Edge of piston with be .052" above deck.

Displacement won't change. Might wanna use a thick Cometic HG to drop the compression to 12.5:1.



D15B 137mm rods won't work on a D15B7 crank, will have to use D15Z1 rods.



Mine even have ARP rod bolts installed, but not resized. Some get by without it in sub 200 hp setups. I never installed then, scraping the build, others have ran it with success.

VX rods are slightly beefier than DX rods

VX vs. DX




A6 cam will be too small, will need a BIG cam to bleed off the compression at lower rpms, I was gonna use a Crane 251-0016.

Used P29 pistons on VX rods with ARP, new rings, I'm willing to sell to the right buyer.

 

Was thinking a cam such as the Exospeed "street a6" would be a nice cam for a 12:1 compression motor...Your input is deffinately appriciated bone,but what do you think about me just throwing a full a6 head on it instead of the b7 and an adj. cam gear. The a6 has better valvetrain and I have one thats in great condition, would this lower the compression ratio?...thx...

 

the b7 and a6 heads are the same. the cam and springs/retainers are different.

 

Right I knew the a6 had a better valvetrain and from what I've read the heads are identical other than that so I'd rather use the a6 head as oppossed to just swapping the cams and i'll throw the adj. cam gear on the a6 head.