Getting my 61x bored out to 760, need info.

[EightySeven550]

Hey all,
I am thinking of getting my 701 bored out to a 760, what other work do I need to get done?
do i need a new head?
do i need to rejet the carbs?
New head gasket?
I have a full 760 engine can I use any of those parts? (if so what?)

Thanks all

 

[Matt_E]

Your stock 701 head will not work.
The domes are not big enough.
You shouldn't need to rejet the carbs
You need a new, 84mm head gasket.

As for boring it out, you need to have a machine shop that's comfortable doing it.
The bottom of the sleeves gets very thin, and the shop that did one of mine was concerned about keeping the boring bar centered.

Be aware that you will have only one overbore left.

 

[EightySeven550]

Would I be able to use my 760 head?

 

[Matt_E]

Yes.

 

[EightySeven550]

Now If I wanted to stay cheap (for now) can I use my 760 head gasket?

 

[Matt_E]

You shouldn't reuse head gaskets.


(Sure, go for it)

 

[wetjet701]

to get this done to a 701 motor it would kind of be expensive 61x bigbore needs to be resleaved and I believe the crank case also needs cut out get ahold of RADNEY1 at X-Scream or one of the other shops on the board

 

[wetjet701]

Oh yes you'll have to use the 760 head and please buy a new headgasket it's not good to reuse them and the carbs will need to be rejetted for the specific app.

 

[alwaystandingup]

I have 84mm pistons w/stock 701 head. You don't have to resleeve either.

 

[Mouthfulloflake]

Just save some $$ and use a 650 head then.

it will bolt on, and it will probably run, but it isnt the right part for the engine.

I have 84mm pistons w/stock 701 head. You don't have to resleeve either.

 

[alwaystandingup]

I have to run the stock 701 head because of the rules.
BTW this is on my 08 stock class boat

 

[Mouthfulloflake]

were the domes recut to be 84mm instead of 81mm?

I have to run the stock 701 head because of the rules.
BTW this is on my 08 stock class boat

 

[Matt_E]

Just save some $$ and use a 650 head then.

it will bolt on, and it will probably run, but it isnt the right part for the engine.

Oh come on.
You know you can bore out stock 61X sleeves to 84mm.
It's not a longevity mod, but plenty of people do this budget bb on the cheap and get by with it.

 

[Mouthfulloflake]

most run an aftermarket head though.

who would spend the $$ on that 84mm bore and then run a stock 81mm head?

do you use the 760 or the 701 gasket?

Oh come on.
You know you can bore out stock 61X sleeves to 84mm.
It's not a longevity mod, but plenty of people do this budget bb on the cheap and get by with it.

 

[Matt_E]

most run an aftermarket head though.

who would spend the $$ on that 84mm bore and then run a stock 81mm head?

do you use the 760 or the 701 gasket?

What do you mean, spend $$ on that 84mm bore????
It's a bore job and some used OEM 84mm pistons.
Just how much do you think that costs? :fingersx: It's a budget BB for a reason. :biggthumpup:

About the head gasket.....I'll let you think about that one for a minute. :headbang:

 

[Mouthfulloflake]

apparently your budget is greater than mine.

if I invested the $80 or so to bore a cylinder, I would use a head with domes that matched the bore of the cylinder.

What do you mean, spend $$ on that 84mm bore????
It's a bore job and some used OEM 84mm pistons.
Just how much do you think that costs? :fingersx: It's a budget BB for a reason. :biggthumpup:

About the head gasket.....I'll let you think about that one for a minute. :headbang:

 

[timbo512]

:starwars:

 

[Mouthfulloflake]

Your stock 701 head will not work.
The domes are not big enough.

:hitwithrock:

 

[Matt_E]

apparently your budget is greater than mine.

if I invested the $80 or so to bore a cylinder, I would use a head with domes that matched the bore of the cylinder.

So would I.

What were we arguing about? :dunno:

Of course you MUST use a head with the right size/diameter domes - I sort of assumed that's a given.
(Same for the headgasket)

 

[alwaystandingup]

obviously a 84mm piston is going to hit a 701 head gasket. I run a stock WBII stainless head gasket, stock 701 head(it is only a 1.5mm flat lip around the edge of the dome), and a thick base gasket and it works fine.
I didn't do this because it was cheap, I took my brand new 08 apart to do this and the only reason I went this route is because of the rules. You can bore and change gaskets, you cannot touch the head.