Engine advice needed

[spill86]

Hi i recently decided to rebuild my largeport 16 valve as i have suspected bottom end noise. So i have decided to go and fit silvertop itbs and omex ecu from a silvertop engine i have.
I also want to use the silvertop bottom end but im unsure what pistons to use, will my 16 valve pistons fit the 20valve conrods or what would people reccomend to do to make a good engine from my 16 valve head and silvertop bottom end?

[oldeskewltoy]

(09-03-2015 12:06 PM)spill86 Wrote:  Hi i recently decided to rebuild my largeport 16 valve as i have suspected bottom end noise. So i have decided to go and fit silvertop itbs and omex ecu from a silvertop engine i have.
I also want to use the silvertop bottom end but im unsure what pistons to use, will my 16 valve pistons fit the 20valve conrods or what would people reccomend to do to make a good engine from my 16 valve head and silvertop bottom end?

Your 16V pistons MAY fit, it depends on if your 16V is before 1987. Most AE86 came with a "smaller rod" so the pistons don't always cross over.

[spill86]

(09-03-2015 09:30 PM)oldeskewltoy Wrote:  

(09-03-2015 12:06 PM)spill86 Wrote:  Hi i recently decided to rebuild my largeport 16 valve as i have suspected bottom end noise. So i have decided to go and fit silvertop itbs and omex ecu from a silvertop engine i have.
I also want to use the silvertop bottom end but im unsure what pistons to use, will my 16 valve pistons fit the 20valve conrods or what would people reccomend to do to make a good engine from my 16 valve head and silvertop bottom end?

Your 16V pistons MAY fit, it depends on if your 16V is before 1987. Most AE86 came with a "smaller rod" so the pistons don't always cross over.

Great stuff thanks for the info, i will be stripping it down in a weeks time so i will know then. The 16 valve head i have has ex and inlet port work carried out and is already fitted with mild hks cams around 264 degrees if i remember right, should i go and get the combustion chambers matched and what else would you do on a budget if you were building this engine from the engines i have, thanks for any info

[chrisd1]

You will need to match all of your bottom end for the crank, 20v will have 42mm crank, so match with pistons/rods to suit, the head will be fine! Consider upping compression a little? and do TRD headgasket too... will be a great build on ITB's and Omex!

[spill86]

(09-04-2015 04:13 PM)chrisd1 Wrote:  You will need to match all of your bottom end for the crank, 20v will have 42mm crank, so match with pistons/rods to suit, the head will be fine! Consider upping compression a little? and do TRD headgasket too... will be a great build on ITB's and Omex!

I plan to use the complete 20valve block with the 16valve head, i suppose i will know what pistons i need when i have the 2 apart, i wonder is it worth my while getting the crank lightened and balanced and anything else within reason that needs doing for a good reliable engine while everything is apart i already have a standard toyota head gasket to use thats new, would it be worth my while getting a trd gasket if i will still be using a standard piston?

[d3nso]

I would not recommend lightening the crank just balance it. Upping the compression ratio with a TRD gasket would be a good thing since you running HKS 264s. They would definetly benefit from a higher CR.

[oldeskewltoy]

(09-03-2015 12:06 PM)spill86 Wrote:  what would people reccomend to do to make a good engine from my 16 valve head and silvertop bottom end?

you might think about smallport/hi comp OEM pistons..

the head gasket will bump static compression about 3 to 4 10ths of a point, so a largeport would go from 9.4 to about 9.75 ish. Swapping in smallport pistons, and adding the head gasket you will be close to 10.6.

If you have good combustion chambers you can use the higher 10.6, if your chambers need de-shrouding, you should stick with the lower compression

[spill86]

(09-04-2015 08:12 PM)oldeskewltoy Wrote:  

(09-03-2015 12:06 PM)spill86 Wrote:  what would people reccomend to do to make a good engine from my 16 valve head and silvertop bottom end?

you might think about smallport/hi comp OEM pistons..

the head gasket will bump static compression about 3 to 4 10ths of a point, so a largeport would go from 9.4 to about 9.75 ish. Swapping in smallport pistons, and adding the head gasket you will be close to 10.6.

If you have good combustion chambers you can use the higher 10.6, if your chambers need de-shrouding, you should stick with the lower compression

the inlet and exhaust ports have had work done on them already it would be a shame not to finish off the head by cleaning up and matching the combustion chambers

how available are smallport pistons and at what price?

[harkes]

I should have some used small port pistons if you are interested?

[spill86]

(09-06-2015 05:19 AM)harkes Wrote:  I should have some used small port pistons if you are interested?

Great, i will be stripping my engine soon and i will find out what i have and let you know if i will be needing them, thanks