A7 rods and pistons into a h22a2

spudep91 · Post by **spudep91** » Sun Mar 24, 2019 6:41 pm

Hi as above can you do this with no issues. Have a7 head. Is it worth putting the higher compression pistons in the a2 block?

Anzezaf · Post by **Anzezaf** » Sun Mar 24, 2019 9:23 pm

I believe the A7 has a larger diameter crank

Post by **Drax** » Mon Mar 25, 2019 9:02 am

I'd have to check the crank sizes between them both as I can't remember, but there's nothing stopping you putting just the a7 pistons onto the A2 rods

Post by **NafemanNathan** » Mon Mar 25, 2019 9:24 am

a2 crank is 50mm. The a7 is 55mm, so yeah, you can't use the rods.

spudep91 · Post by **spudep91** » Mon Mar 25, 2019 2:35 pm

Is it not the main bearings that are 55 mil just?

Post by **4thgenphil** » Mon Mar 25, 2019 3:03 pm

Is the main bearing that are 55mm on an a7, the rod bearings are the same.

A7 uses floating gudgion pins, a2 doesnt but if you use a7 pistons thats not an issue.

Post by **NafemanNathan** » Mon Mar 25, 2019 3:24 pm

Duh

spudep91 · Post by **spudep91** » Mon Mar 25, 2019 6:17 pm

Cheers lads. Ended up just putten a2 in with a7 head.

This is 3rd engine in the car fs. Keep doing bottom ends. Last one was are one fault run it down to min on dip stick and were going round track.

We have hondadta v3 this time to get it mapped to.
Use think youd gain much with the a7 pistons in?

Post by **4thgenphil** » Mon Mar 25, 2019 11:08 pm

If youre tuning it id drop the a7 pistons in, they are a fair rise in compression compared to ukdm pistons.

Are you running a baffled sump? Also what tyres are you running?

PerformanceAutoworks · Post by **PerformanceAutoworks** » Tue Mar 26, 2019 8:56 am

Yes you can use the H22a7 pistons and rods in a H22a2. The rod journal is the same on both 50mm and 55mm cranks.

You can't use the A7 pistons on A2 rods without significant machining to the A2 rod as A7 pistons are floating pins rather than pressed, plus the small end journal width is different.

In all cases of course, piston to wall and big end bearing clearances need to be measured