Can a 7a handle a 83mm bore???

[v33sonata]

So the block is out and I am currently at 82mm but it needs to be bored again. Weisco wants me to do 83mm that its harder getting rings for 82.5mm. So is 83mm to big? I am not boosting but I have thought of nitrous, does anyone actually know anyone who has done a 83mm on a 7a motor?? I have to decide this week what I want to do........

[MisterJerk]

i found this by googling 7afe 83mm bore.

http://forums.club4ag.com/zerothread?id=37630

quick copy paste from the thread..

Re: Anyone actually bored out there 4AG block to 83mm (Davegt27) » 8:47 PM 10/23/2008 Reply Edit

yes the shop i worked at we did one i always recomend sonic checking before going big over bore as not all 3ribs have enought meat but most 7 ribs do.btw the 7afe blocks ive tested can go to 84-85mm they are much thicker than 4a series blocks


Later on in the thread.. same guy:

if you need bigger bore than 83mm i assume you are building a really big motor so why not look at doing a 7a conversion?the longer stroke add size and tourqe and when done with the bigger bores and stroke the compression ratio increases as well. from the 3 blocks i have had sonic check it looks like the 7a blocks can take up to a 85mm bore for n/a use which gives you a 1940cc motor.for those that still want more i have a custom crank machined with a 88.5mm (with the option of going89mm)stroke which with the 85mm bore makes for a 2008cc (2020cc 89mm stroke)those combos require a custom piston rod combo.b.t.y the stroker big bore combo raises the compression ratio about 3 points above where the comression ratio would be in a 1600cc motor.the 12-1 style formula atlantic piston would be 15-1 in this stroker motor.so anyone want a 2.0l 300hp n/a 10ag i would love to build one for some one...... p.s. might do it for my self as i have a finished crank sitting at my shop and a few block in stock

[ogdougynutty]

Here is my 4age bored out to 83mm with miata pistons running 11.5:1 compression. Has 1000 miles on it right now, with quite a bit of hard driving on it. Still going strong, just going to have to make your cooling system stronger due to the very thin walls.

[v33sonata]

Ya I read that already....... But it was pretty much the only thing I was able to find!

[v33sonata]

Here is my 4age bored out to 83mm with miata pistons running 11.5:1 compression. Has 1000 miles on it right now, with quite a bit of hard driving on it. Still going strong, just going to have to make your cooling system stronger due to the very thin walls.

Good to know the 4a motor is ok with 83mm so the 7a should be good too. What kinda of upgrades? That thing never got hot before..........

[v33sonata]

For anyone doing this. I had my 7a block sonic tested and I am told 83mm is fine bit anything bigger I might run into problems.

[Rogue-AE95]

"Sonic tested." Is that the same as magnafluxed?

[oldeskewltoy]

the problem may very well become how much overbore can you go and still have enough meat to "hold" a gasket....

[yoshimitsuspeed]

And the Toda stopper style gasket I can get is only 82.5mm, bummer.

I might be able to get you a custom 83mm stopper gasket. I haven't looked into it but let me know if you would be interested.
If you don't want to go full stopper I should be able to get 83mm gaskets like Cometic and probably a few others.

[ogdougynutty]

^ I am currently running the 83mm Cometic gasket, ( 83mm bore with 11.5:1 compression) But i also switched to ARP head studs, would probably switch to ARPs instead of stock head bolts.

[v33sonata]

^ I am currently running the 83mm Cometic gasket, ( 83mm bore with 11.5:1 compression) But i also switched to ARP head studs, would probably switch to ARPs instead of stock head bolts.

already have