86 shortblock. clearance issues?

[nisreo]

So I stumbled upon a post that because of true flat top pistons in an 86 bottom end, E7's may not work?

Im not quite sure if GT-40's will end up on this motor or not, but I was planning on using E7's from a 90 GT if it didnt happen. I do have the stock heads that came off the motor which are E6's correct?

Basically, will E7's, or GT-40x heads have clearance problems with a stock 86 bottom end?

Thanks in advance.

 

[skunk21]

plenty of people have swapped out the E6 heads for E7's w/o issues. I'm not sure about the gt40 valves it could be close, you would have to clay it. I would search some more on here and corral, I have read planty of post's on the E7 swap onto the 86 motor even with a B303 cam w/o issues, even TW heads with a stock cam. In the end though claying is cheap insurance.

 

[joel5.0]

E7/GT40 heads on true flattops are a hit or miss deal even with a stock camshaft. TFS TW's provide more clearance due to the valve angle design and allow the use of some aftermarket cams and provide the required PTV clearance.

 

[nisreo]

Ok then, how about this. I use the pistons out of my 90 Gt in the 86 block? yes no?

 

[Vinnietbird]

I'm using the flat tops and also an e303 cam and ported E-7 heads.No issues for a couple of years.

 

[NIKwoaC]

Ok then, how about this. I use the pistons out of my 90 Gt in the 86 block? yes no?

Why not just build up the 90's motor?

 

[nisreo]

I'm using the flat tops and also an e303 cam and ported E-7 heads.No issues for a couple of years.

yea I think ive decided to just use the flat tops, either with my e7's or gt40's. Ill check the clearances after that. Ill keep my stock cam for now for extra insurance.

Did you use a thicker headgasket or anything? Im planning on using the standard felpro one.

 

[nisreo]

Why not just build up the 90's motor?

The 90 motor is still in my car (piston rings smoked) So I really wanted to build my spare (86GT) motor so I could do a quick swap in a weekend. Rather than pulling my 90 motor out and building it and having it sit during the rebuild. I dont have a place to store the car with no motor for a long period of time.

Plus I have a good feeling the block is junk on the 90 motor due to excessive crank movement

 

[Vinnietbird]

I just used a FelPro stock style replacement gasket.I've had no issues at all,but,as you stated you'll be doing,a PTV clearance check would be good.

 

[nisreo]

Ah ok, I feel much better now. At least I know E-7's should work. Anyone run gt40X's?

 

[nisreo]

Well after alot of research here and corral, Ive found its pretty much hit or miss. I dont want to take the chance of floating a valve and there goes a fresh motor. Gonna start pulling the 90 motor on tuesday.

 

[NIKwoaC]

Well after alot of research here and corral, Ive found its pretty much hit or miss. I dont want to take the chance of floating a valve and there goes a fresh motor. Gonna start pulling the 90 motor on tuesday.

If the rings on the 90 are fried, its probably time for a bottom end rebuild as well. I don't know what your budget is though...

 

[nisreo]

If the rings on the 90 are fried, its probably time for a bottom end rebuild as well. I don't know what your budget is though...

I never really quite explanied my situation.

Im building an 86 GT shorblock (spare motor) It already has a new crank, bearings etc... Gonna be all fresh.

My 90 GT has smoked piston rings and excessive crank endplay.

I planned on building the 86 motor, intake to oil pan, on a stand so I could do a straight swap in a weekend. However, now with the knowledge that flat top pistons are a headache in terms of PTV clearance, I will tear down my 90 motor to get the notched pistons out of it. These will go into the 86 block.

So in the end Ill have a rebuilt 86 bottom end, but with 90 pistons. Gt40 heads, exploder intake,100 shot and peace of mind that I wont be bending any valves.

see my progress thread for more info if your bored.

 

[NIKwoaC]

I was reading up on some threads on the corral, and it looked to me like a lot of people were using TW heads sucessfully on 86 pistons. I'd just worry that if your 90's engine is in that bad of shape, the pistons aren't a good idea to salvage, especially if you're putting them in a fresh motor.

But its your call. I look forward to your build progress. Good luck!

 

[nisreo]

yea when I pull it apart if the pistons are damaged they obviously wont go in. we shall see