.030 Bore on Blue Top.

HaSarcasm
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.030 Bore on Blue Top.

Postby HaSarcasm » Mon Aug 07, 2017 5:26 pm

I bought this stock 4age hoping to rebuild it so i can turbo it in the future. Now I just got the block resurfaced and clyinders bored/honed. The cylinders had alot of rust on them and the machine shop told me they had to bore .030.

Now my question is with this being my first major engine rebuild and my only expectation is for it to be a quick turbo build.

What size pistons would i need?

Would the stock rods be ok with turbo?

And would i need to get a new headgasket bc of the bore ?

I already have a TRD .8mm 16v Metal Head Gasket .

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oldeskewltoy
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Re: .030 Bore on Blue Top.

Postby oldeskewltoy » Tue Aug 08, 2017 7:01 am

.030" = .762" - Which is a bit of an odd size as you are just over 81.75mm. I would recommend you get a piston built for an 81.80mm bore, and have the new pistons fitted to each cylinder. If you need a custom piston, I can help with design, and supply.

The TRD gasket should still be fine with that bore. As to the rods, and their re-use, as long as rpm levels remain the same, and boost levels are not ridiculously high, the stock rods can be re-used (with NEW rod bolts). There are 2 types of rods that came in 4AGE engines. Earlier rods are a bit smaller @ both ends, and the wrist pins are pressed in to the rods. Later rods have slightly larger ends, have a lot more weight(mass), and do have "floating" wrist pins.

What is your desired compression ratio? What is your plan for engine management?
OST Cyl head porting, - viewtopic.php?f=22&t=300

Building a great engine takes knowing the end... before you begin :ugeek:

Enjoy Life... its the only one you get!

HaSarcasm
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Posts: 10
Joined: Sat May 07, 2016 12:07 pm

Re: .030 Bore on Blue Top.

Postby HaSarcasm » Wed Aug 09, 2017 1:58 pm

Yea im pretty sure i would need help with the supply of custom pistons. I have the early big port rods with the 18mm wrist pins .
Around how much would it be for the pistons

It all depends on the price on whats cheaper the pistons or a 4agze block with internals

Im trying to get a comp ratio around 9.5:1 - 10.5:1



Im only trying to get around 5lbs of boost nothing to serious i think stock ecu would be fine for now. I have a walbro 255 with a FPR , wide band etc

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oldeskewltoy
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Re: .030 Bore on Blue Top.

Postby oldeskewltoy » Wed Aug 09, 2017 4:10 pm

HaSarcasm wrote:Yea im pretty sure i would need help with the supply of custom pistons. I have the early big port rods with the 18mm wrist pins .
Around how much would it be for the pistons

It all depends on the price on whats cheaper the pistons or a 4agze block with internals

Im trying to get a comp ratio around 9.5:1 - 10.5:1



Im only trying to get around 5lbs of boost nothing to serious i think stock ecu would be fine for now. I have a walbro 255 with a FPR , wide band etc


set of custom pistons, with rings should run about $550-$650
OST Cyl head porting, - viewtopic.php?f=22&t=300

Building a great engine takes knowing the end... before you begin :ugeek:

Enjoy Life... its the only one you get!

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allencr
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Re: .030 Bore on Blue Top.

Postby allencr » Tue Aug 15, 2017 9:05 am

Be EXTREMELY careful getting those pistons.
I didn't think any machine shop would ever bore a block WITHOUT having a piston in their hands, WAAYY too easy to F it up otherwise. Very bad practice even if they didn't like you.

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jondee86
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Re: .030 Bore on Blue Top.

Postby jondee86 » Tue Aug 15, 2017 3:23 pm

HaSarcasm wrote:...the machine shop told me they had to bore .030.

Overbore sizes of 30, 40, 60 thou are old school inch sizes. Jap cars are metric and
oversize pistons for the 4AGE are 0.50, 1.00, 1.50 etc in 0.5 millimeter steps.

At 30 thou over you are already at 81.75 (std bore 81) so pistons are gonna cost you
no matter which way you jump. I'd say look out for a decent 4AGZE block or running
engine and start over.

Cheers... jondee86
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