Head Gasket Size Issues

[Sandbank]

Hi Guys, hopefully someone can assist me as this is driving me bonkers.
Issue: replacing head gasket on a small block chevi 225 hp (about an 86 model I think) and the only head gaskets I can locate or have are all slightly too small (about 1.5-2mm) in size around the cyclinder bore (that is they would hang over the edge of the cylinder). I am thinking PO might have bored out the cylinder.
For the life of me I cant find the right size gasket. I have two sets spare (of the wrong size); one is a metal with a brass ring around the cyclinder hole and one is made of synthetic material with a silver metal of some kind around the cyclinder holes.
What should I do??? Any ideas??
My mechanic informs me I cant use the under size ones. The only options I am thinking are...
can I grind down the oversize ones to fit (but that would remove the metal rings around the cylinder holes). If so should I use the metal gasket or the synthetic one?
I dont belive I can use just any old gasket material and cut one out from the olds template????
Can I measure the diametre of the old gasket cylinder holes exactly and is there a supplier who I could phone to get the right one??
Thanks guys. I want to get this gasket in and all fixed so I can sell the boat as have another lined up.

 

[series60]

Re: Head Gasket Size Issues

small block chevi 225 hp (about an 86 model I think)

A little more info please. We talking a 305 or 350?

 

[Bondo]

Re: Head Gasket Size Issues

can I grind down the oversize ones to fit (but that would remove the metal rings around the cylinder holes). If so should I use the metal gasket or the synthetic one?

Ayuh,.... That is NOT an option...

My guess is, yer tryin' to fit 305 gaskets to a 350....

Let's start by ID'ing the Block 1st...

Got any Numbers,..?? Serial #s,..?? Block Casting #s,..??
What, Exactly is the Bore diameter,..??

 

[achris]

Re: Head Gasket Size Issues

Measure the bore... The label on the engine might say '228' (the only 225, GMs were in the 60s), but it might have been replaced with a 350. The difference in the bore size is about what you're talking about...

305 cu.in. (228) Bore = 98mm (3.74")
350 cu.in. (260) Bore = 101.6mm (4.00")

Chris........
EDIT: Quick-draw Bond-o got me again.... While I was looking up spec, he's off with the right answer :facepalm:....

 

[Don S]

Re: Head Gasket Size Issues

The engines long block was probably replaced at some point. All the marine accessories from the 5.0 would bolt on the 5.7 block.
Externally, the long blocks look identical.

 

[Sandbank]

Re: Head Gasket Size Issues

Measure the bore... The label on the engine might say '228' (the only 225, GMs were in the 60s), but it might have been replaced with a 350. The difference in the bore size is about what you're talking about...

305 cu.in. (228) Bore = 98mm (3.74")
350 cu.in. (260) Bore = 101.6mm (4.00")

Chris........
EDIT: Quick-draw Bond-o got me again.... While I was looking up spec, he's off with the right answer :facepalm:....

Ok try and combine a few replies into one...
Not at the boat now but I just measured the ill fitting gasket. It is 98.9mm which given the fact it is a few mm into the cyclinder would give me a 101.6mm (4inch) likely perfectly. This confirm what I had previously ascertained that it was a 350 cu.in.
Sorry dont have the model /serial No off the block but should be able to mechanic to find it tomorrow.

The serial number off the ill fitting gasket is: FEL-PRO 17020
There was no SN or it was illegible on the old gasket that was removed.

Where does that leave me...

Thanks for the reply as to ...dont even try grinding the gasket..take that option away

 

[Bondo]

Re: Head Gasket Size Issues

FEL-PRO 17020

Ayuh,.... That's a 3, 3/4" gasket for a 305cid....

Fel-pro, 17030 is the 350cid Marine head gasket...

 

[Sandbank]

Re: Head Gasket Size Issues

Ayuh,.... That's a 3, 3/4" gasket for a 305cid....

Fel-pro, 17030 is the 350cid Marine head gasket...

Thanks BondO, so if I source the FELPRO 17030 or its equivilant that should do the trick do u think) Will see if there is one local or will have to go online.

 

[Bondo]

Re: Head Gasket Size Issues

Ayuh,... I just googled yer part number to find that Info...

 

[Sandbank]

Re: Head Gasket Size Issues

Thanks Guys I appreciate the assistance greatly. Will try and locate a FELPRO 17030 or its GM equivilant #10105117. I can then end the pain...

 

[achris]

Re: Head Gasket Size Issues

If you get the casting numbers off the engine block and cylinder heads and post them up here someone will be able to tell you what engine you have....