Stock 86gt Piston Clearance ??? With Afr 165 Heads???

1200gt · Aug 20, 2013

I have an 86GT motor in my car now with only 45K on it. I was going to swap it out for a fresh built 306 short block that I got some time ago, but have second thoughts about going to the trouble to swap-out because I can't figure out if it is internally balanced or what - it shows signs of crank lightening.... besides that, it's pre-roller so a reduced base circle came must be used to go roller - might not use it at all, which leads to my question in the thread:

My stock motor is an 1986 still in the car. I was thinking of just using this motor to slap my new AFR165's on, but was concerned about any valve clearance issues as I heard some time back that the 1986 motor has flattop pistons and needed valve clearancing. (True or False?)

I really would like to accomplish this install, and any piston mods, without pulling the motor. Is this possible?

stykthyn · Aug 20, 2013

True. The only aftermarket heads that I know of that will fit without notching are the twisted wedge heads.

mikestang63 · Aug 20, 2013

Sorry. Flat top pistons + AFR heads = BOOM . You can run the TW with the stock cam. Isky sells a tool to notch the pistons in with the block in the car if you want to go with AFR's. Here's a good tech writeup

http://sbftech.com/index.php?topic=2124.0

2000xp8 · Aug 21, 2013

I used the isky tool, while it works fine, i would not like to have to do it again and really wouldn't suggest doing it.

84Ttop · Aug 21, 2013

As ghetto as it sounds, I've used a dremel and notched the pistons in more than one shortblock with it still in the car. Before you go hating The three cars that come to mind are all still running one of which has gone 10.3x's for the last 3 years

To more specifically answer the OP's questing, Check, Check, Check! I always check PTV clearance, ALWAYS!

mikestang63 · Aug 21, 2013

84Ttop said:
As ghetto as it sounds, I've used a dremel and notched the pistons in more than one shortblock with it still in the car. Before you go hating The three cars that come to mind are all still running one of which has gone 10.3x's for the last 3 years

To more specifically answer the OP's questing, Check, Check, Check! I always check PTV clearance, ALWAYS!

I've seen guys back in the day take an old head with the valves out of the guides, glue 50 grit sandpaper to the back of the valve head, put the head back on the block with the valve in the guide for that one piston you want to notch, and spin the valve with a drill to notch the pistons. Believe it or not it worked but I wouldn't recommend that method.

84Ttop · Aug 21, 2013

mikestang63 said:
I've seen guys back in the day take an old head with the valves out of the guides, glue 50 grit sandpaper to the back of the valve head, put the head back on the block with the valve in the guide for that one piston you want to notch, and spin the valve with a drill to notch the pistons. Believe it or not it worked but I wouldn't recommend that method.

It's an interesting idea, I would like to try on a junk motor just for fun!

Rick 91GT · Aug 21, 2013

I milled out an old e7 head chamber and brazed cutters I made onto some valves and use them to cut stock pistons....works great.

Sent from my XT907 using Tapatalk 2

Noobz347 · Aug 21, 2013

Rick 91GT said:
I milled out an old e7 head chamber and brazed cutters I made onto some valves and use them to cut stock pistons....works great.

Sent from my XT907 using Tapatalk 2

PICS!

mikestang63 · Aug 21, 2013

Rick 91GT said:
I milled out an old e7 head chamber and brazed cutters I made onto some valves and use them to cut stock pistons....works great.

Sent from my XT907 using Tapatalk 2

That's some cool Mcgyver action right there.

1200gt · Aug 21, 2013

84Ttop said:
As ghetto as it sounds, I've used a dremel and notched the pistons in more than one shortblock with it still in the car. Before you go hating The three cars that come to mind are all still running one of which has gone 10.3x's for the last 3 years

To more specifically answer the OP's questing, Check, Check, Check! I always check PTV clearance, ALWAYS!

***84Ttop, you give me hope

******************************************************************************************
OK, say I go for one of the methods of notching the pistons while in the motor,
what advice can any of you, that have had success, give me to keep me on track to removing a reasonably equal amount of material?? I'd hate to screw-up a perfectly good motor....

First thing that comes to my mind is to go with the-spare-head-idea as an angle guide and maybe use a drill-stop on the drilling device of choice to meter depth??????

1200gt · Aug 21, 2013

mikestang63 said:
Sorry. Flat top pistons + AFR heads = BOOM . You can run the TW with the stock cam. Isky sells a tool to notch the pistons in with the block in the car if you want to go with AFR's. Here's a good tech writeup

http://sbftech.com/index.php?topic=2124.0

Mike I just checked out this write-up link. Thanks for posting it!

It's very good post. They also use the Isky parts to get the jobs done..... I'm going to research those parts to see if I can manage the combo when I get home tonight.

Noobz347 · Aug 21, 2013

1200gt said:
***84Ttop, you give me hope

******************************************************************************************
OK, say I go for one of the methods of notching the pistons while in the motor,
what advice can any of you, that have had success, give me to keep me on track to removing a reasonably equal amount of material?? I'd hate to screw-up a perfectly good motor....

First thing that comes to my mind is to go with the-spare-head-idea as an angle guide and maybe use a drill-stop on the drilling device of choice to meter depth??????

My guess (and it's just a guess) is that if these are the original 86 flat-top pistons (meaning motor has never been rebuilt), that it may not be a perfectly good motor.

Rick 91GT · Aug 21, 2013

On a 87+ motor I usually only remove .060" of material max...most of the time I just being it down to the stock notch depth as the depth is not the problem, the radial clearance with a larger valvw is. I set my cutters up like it is a 2.05" valve.

I use set collars on the valve and feeler gauges to set it up...

Sent from my XT907 using Tapatalk 2

Gearbanger 101 · Aug 21, 2013

84Ttop said:
As ghetto as it sounds, I've used a dremel and notched the pistons in more than one shortblock with it still in the car. Before you go hating The three cars that come to mind are all still running one of which has gone 10.3x's for the last 3 years

To more specifically answer the OP's questing, Check, Check, Check! I always check PTV clearance, ALWAYS!

Buddy of mine did the same with his set up. Ran just fine.

1200gt · Aug 22, 2013

Noobz347 said:
My guess (and it's just a guess) is that if these are the original 86 flat-top pistons (meaning motor has never been rebuilt), that it may not be a perfectly good motor.

When I say perfectly good motor, I mean it runs perfectly as stock with no leaks what so ever. Also, the motor has never been pulled apart.

Rick 91GT said:
On a 87+ motor I usually only remove .060" of material max...most of the time I just being it down to the stock notch depth as the depth is not the problem, the radial clearance with a larger valvw is. I set my cutters up like it is a 2.05" valve.

I use set collars on the valve and feeler gauges to set it up...

Sent from my XT907 using Tapatalk 2

Rick this is good info. I'm thinking 87+ pistons start out with some degree of notch.
I'd think it would be easier to notch a flattop set using the hand method because there should be less wobble effect by not experiencing pre-notch interference...
When you say you use set-collars, are u you talking about those being part of a lath of some sort, or are they pieces that stand alone as guides?

Rick 91GT · Aug 22, 2013

I put the split collar on the valve to act as my stop then use feeler gauges between the bottom of the collar and the valve guide to set my depth.

Sent from my XT907 using Tapatalk 2

Noobz347 · Aug 22, 2013

1200gt said:
When I say perfectly good motor, I mean it runs perfectly as stock with no leaks what so ever. Also, the motor has never been pulled apart.

You may want to consider a freshening up of the bottom end since you're tearing it down far enough to notch the pistons anyway.

1200gt · Aug 22, 2013

Noobz347 said:
You may want to consider a freshening up of the bottom end since you're tearing it down far enough to notch the pistons anyway.

You see, that's where it gets like the six in one hand , half dozen in another. I have the other 306 that is already built, but I just happen to NOT know how it all went together being that the engine builder died and the shop closed down.

I was thinking about having someone pull the 306 apart to get a baseline, but then, I mentioned the block is a 74 casting non-roller converted to roller thus a reduce base circle cam has to be run. I haven't heard any really good testimonies about running this type of cam. It may not be an issue being that I have no plans to race the motor.

Noobz347 · Aug 22, 2013

I'm not talking a complete rebuild or anything. Just replace the soft parts, freeze plugs, and have the bearings looked at.

Stock 86gt Piston Clearance ??? With Afr 165 Heads???

1200gt

Active Member

stykthyn

I want to measure mine. It doesn't look that tall.

mikestang63

2000xp8

84Ttop

They make new pistons every day, so why worry?

mikestang63

84Ttop

They make new pistons every day, so why worry?

Rick 91GT

Mustang Master

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

mikestang63

1200gt

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1200gt

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Rick 91GT

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Gearbanger 101

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1200gt

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Rick 91GT

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1200gt

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Stock 86gt Piston Clearance ??? With Afr 165 Heads???

Active Member

I want to measure mine. It doesn't look that tall.

They make new pistons every day, so why worry?

They make new pistons every day, so why worry?

Mustang Master

Stangnet Facilities Maint Tech... Er... Janitor

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Active Member

Stangnet Facilities Maint Tech... Er... Janitor

Mustang Master

Straight Outta Locash

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