H22a7 or a8?

[Drax]

im trying to decide whether or buy a h22a7 ATR block or go with a 5G H22a8 block for the new sk2 sg2 tuner cams, valves and retainers to go into.

as far as I can tell, the atr heat should have more room for the bigger cams lobes to move and so less chance of any knocking, that correct?

That's what's tipping me over to the atr block so far, as they have the same compression as each other but im also thinking about compatibility for parts/wiring, again as far as I can tell they are a straight swap apart from the atr injectors require obd1 ecu, that correct? and is there any difference in a1/a7/a8 injectors? im thinking cant I use a1 injectors instead to save the obd swap?

im pretty sure Ill want whatever engine I go for the head skimmed, new seals etc.

any other hints/tips are grateful

[Merlin]

As far as I am aware the a7 & a8 blocks are exactly the same. I will try and find where PAW talks about them both. Compatibility wise a7 & a8 will have the exact same pros and cons as each other. I think the only difference in the a7 & a8 short blocks is that the a7 has a deeper sump.

H22a8 = P13 head same as JDM H22a, a2 and a5
H22a7 = PDE head
H22a (S-spec) = P5P head

H22a7 and H22a8 share the same bottom end - 55mm mains cranks, PDE rods with floating piston pins and PDE pistons

H22a JDM S-Spec block has relocated oil filter location and main oil galleries. Also has provision for ATTS fitment.


Internally, all the major component parts of any spec H22 will swap into any other H22 apart from of course the crankshafts - a 55mm mains crank from a7 or a8 can be used in earlier JDM A's, A2's and A5's but block mains journals and crank bridge will need to be bolted together, line bored with bearing tabs notched - which doesn't work out cheap. Obviously 50mm mains cranks cannot be used in A7 or A8

The major difference in the heads is that the a7 PDE has different casting for the PDE intake manifold compared to the a8 P13 head. They use the same cams, LMA's etc,... If you are upgrading the cams and bits the PDE head offers no advantage over the P13.

There are actually a number of differences between the P13 and PDE cylinder heads but most of them are not performance related and some of them not really worth going into.

Is a PDE head worth swapping onto a H22a, a2,a5,a8 - I'd say yes if it came complete with cams and that's all you wanted to do.
But if you were going to port it and add higher spec cams (along with valve springs and retainers) then you may as well just use your existing P13 head (of whatever year).

a1/a7/a8 injectors? the a1 will be 345cc peak and hold while the a7 & a8 will be 280cc saturated?

Edited with PAW quotes

[nitin_s1]

Same apart from intake..

[NafemanNathan]

Merlin's editted post just about covers it. Then with regards to the heads, there's no "additional room for larger cams" or anything in the a7 head. It has a mild factory p&p and the valve seats are at a subtley different angle, but none of these are going to see you oodles of extra bhp on top of the same set up in a p13 head.

[Drax]

right, so a7/8 bottom and top end there's next to bugger all difference, except a8 head will not require obd change.

(im guessing it's a no to being able to swap the injectors around from a1 345 p&h to a7/8 280 s, plus i'm guessing the 280 s are better )

what about the intake as nitin mentioned, it was going to be my next question anyway lol are they same/different mm between a7 intake and a8?

plus another quick though, I have TCS (even though its redundant atm due to the Hondata), could this cause wiring problems with a block swap as the ecu has the extra port that was had to be re-jigged for the current Hondata to work.

thanks for the help so far

[Merlin]

Both the a7 & a8 are OBDII. You'll want the PDE intake manifold as that is single intake runner and can deliver more torque, both use a 62mm throttle body but they way you are talking you'll be ditching it anyway.

[NafemanNathan]

The a7 and a8 are both OBD2, but all h22 engines can be run on either OBD1 or OBD2, you just need the injectors to suit whichever setup/ecu you have (peak/hold and the resistor box for OBD1 and saturated and no resistor box for OBD2).

Then with the inlet manifold, only the ATR has the single runner ATR inlet manifold you see many of us upgrading to. All the others run the IAB'd dual runners.

[Drax]

ok, so bigger tb (maybe skunk2 upgrade), PDE head ported to match that, doesn't matter if I go a7 or a8 as their both plug and play into the current fittings, looms etc., just means a7 has the single intake runner advantage whereas the a8 would need a skunk2 intake or a port matched atr intake?

any difference between the 345cc peak and hold and a7 & a8 280cc injectors? not that that important, just interested.
not sure if its worth upgrading the injectors and fuel rail from the 280cc.. as it's not some big turbo build.

ill buy a wideband o2 sensor, i already have the adjustable cam gears, upgraded fuel pump, and been advised to buy a fuel pressure regulator as well.

[h10ndr]

You can use 345 injectors on the atr pde head just means u use prelude intake manifold etc. My h22a7 conversion by PAW used all original prelude bits but on the atr motor inc. Obd1 distributor.

[h10ndr]

An obvious upgrade would be to mod an atr intake mani to accept 345cc injectors and tune...