Compression drop w/ replacement gasket on 318

Posted By: radar

Compression drop w/ replacement gasket on 318 - 02/25/10 10:45 PM

I am rebuilding a 1967 318 motor. It has the closed chamber 904 casting heads with small valves and runners. I bought a Comp 268 (218* at .050 .454 lift) cam kit. The cam wants 9:1 cr and 3.55 gears.
I have read about the replacement head gaskets all being thicker and bigger bore than the original equipment 318 steel shim. I already also bought a full felpro 318/273 gasket set with the blue head gasket. I'm assuming it is a 318 gasket set because of port sizes not bore size?

Am I in for some machining? Heads/block decked? I don't want much more than a stock build if that matters. Super budget deal.
Thanks

Posted By: 70Cuda383

Re: Compression drop w/ replacement gasket on 318 - 02/25/10 10:49 PM

Quote:

I am rebuilding a 1967 318 motor. It has the closed chamber 904 casting heads with small valves and runners. I bought a Comp 268 (218* at .050 .454 lift) cam kit. The cam wants 9:1 cr and 3.55 gears.
I have read about the replacement head gaskets all being thicker and bigger bore than the original equipment 318 steel shim. I already also bought a full felpro 318/273 gasket set with the blue head gasket. I'm assuming it is a 318 gasket set because of port sizes not bore size?

Am I in for some machining? Heads/block decked? I don't want much more than a stock build if that matters. Super budget deal.
Thanks

yup, the blue gasket is probably around .030 thick compressed.

to increase your compression, you WILL have to either

A) mill the decks
B) mill the heads
C) install different pistons with taller Comp. height
D) Any combination of the above.

keep in mind that with milling the heads/decks, the intake side of heads might need touched so the intake still fits right, and you might need shorter pushrods.

Posted By: patrick

Re: Compression drop w/ replacement gasket on 318 - 02/26/10 12:53 PM

Quote:

Quote:

I am rebuilding a 1967 318 motor. It has the closed chamber 904 casting heads with small valves and runners. I bought a Comp 268 (218* at .050 .454 lift) cam kit. The cam wants 9:1 cr and 3.55 gears.
I have read about the replacement head gaskets all being thicker and bigger bore than the original equipment 318 steel shim. I already also bought a full felpro 318/273 gasket set with the blue head gasket. I'm assuming it is a 318 gasket set because of port sizes not bore size?

Am I in for some machining? Heads/block decked? I don't want much more than a stock build if that matters. Super budget deal.
Thanks

yup, the blue gasket is probably around .030 thick compressed.

to increase your compression, you WILL have to either

A) mill the decks
B) mill the heads
C) install different pistons with taller Comp. height
D) Any combination of the above.

keep in mind that with milling the heads/decks, the intake side of heads might need touched so the intake still fits right, and you might need shorter pushrods.

the fel pro gasket that comes in those kits isn't .030 thick, it's .054" thick compressed. easiest thing to do is buy the $40 Mr. gasket .028" thick compressed gasket.

and it's actually the oil pan gasket that makes the 318/360 sets different. I can't remember if the rear main seal is the same or different between the motors, too...in all the complete gasket sets I've seen, they come with both sets of intake gaskets.

Posted By: RapidRobert

Re: Compression drop w/ replacement gasket on 318 - 02/26/10 02:19 PM

Quote:

buy the $40 Mr. gasket .028" thick compressed gasket.

Patrick is it the same # for 318 and 360? and how thick are the oe metal gaskets that come out of there (80's 318)

Posted By: mod5v

Re: Compression drop w/ replacement gasket on 318 - 02/26/10 02:46 PM

I did some resurch on this and the gasket u want is #1121G (Mr. Gasket}like Patrick said the fel-pro gasket is .053" thick.

Posted By: krw71ragtop

Re: Compression drop w/ replacement gasket on 318 - 02/26/10 02:56 PM

The last batch of Felpro's I measured were .054"-.057" thick. I purchased the Mopar set #P4120094 from Mancini and are advertised at .024-.028" compressed.

Posted By: patrick

Re: Compression drop w/ replacement gasket on 318 - 02/26/10 03:48 PM

Quote:

Quote:

buy the $40 Mr. gasket .028" thick compressed gasket.

Patrick is it the same # for 318 and 360? and how thick are the oe metal gaskets that come out of there (80's 318)

yes, same part. it's a 4.14" bore head gasket. the slight amount of crevice volume isn't going to be a big deal...
my '86 76k mile 318 had a composite head gasket that was ~.040" thick OEM...

Quote:

The last batch of Felpro's I measured were .054"-.057" thick. I purchased the Mopar set #P4120094 from Mancini and are advertised at .024-.028" compressed.

if the MP ones you bought are white, then it's a repackaged Mr. gasket gasket set.

Posted By: radar

Re: Compression drop w/ replacement gasket on 318 - 02/26/10 05:47 PM

I looked around. Mancini has the .028 gasket for $40 but is says out of stock or something on the webstore. Summit only showed an $80 SCE copper gasket which is .021. Jegs has a mr gasket #720-1135 which is listed to compress to .018 to .020.

I'm going to order a set of the thin mr. gaskets. Especially because they're only $20 at Jegs!

Anything to watch out for? I'm going to assume head and deck surfaces need to be dead flat and smooth? Are these prone to blowing easy? Do I need copper spray for them?

Thanks for all the replies Im sure this topic is beaten to death a couple times a year but parts availability changes so I really appreciate it

kevin

Posted By: mod5v

Re: Compression drop w/ replacement gasket on 318 - 02/26/10 06:05 PM

AHHH!!! I think the #720-1135 are for a big block!! May not work so good on a 318

Posted By: patrick

Re: Compression drop w/ replacement gasket on 318 - 02/26/10 07:14 PM

http://www.mr-gasket.com/CatalogsList.aspx

PN 1121 is what I used....I bought a set from summit in june. don't know why they're not listed anymore...

edit: jegs and amazon have them
http://www.jegs.com/i/Mr.%20Gasket/720/1121/10002/-1?CT=999

http://www.amazon.com/Mr-Gasket-1121-Cylinder-Head/dp/B000CMF09M

Posted By: RapidRobert

Re: Compression drop w/ replacement gasket on 318 - 02/26/10 08:14 PM

Quote:

yes, same part. it's a 4.14" bore head gasket. the slight amount of crevice volume isn't going to be a big deal...my '86 76k mile 318 had a composite head gasket that was ~.040" thick OEM....

thank you Patrick. I didn't know that my 83 318 might have a thick gasket (I was assuming thin steel). 302 heads and thinner ones should make a seat of the pants difference

Posted By: radar

Re: Compression drop w/ replacement gasket on 318 - 02/26/10 11:24 PM

Thanks fellas- I almost bought the big block set!

Nobody I can find has the thin Mr Gasket ones. They seem to be discontinued. I had turned up reports of 'national backorder' on moparts search engine but I guess it's really over for this p/n.

I haven't inspected the heads yet. If they turn out to be nice and flat I will just suck it up and shell out $86 for SCE Gaskets p/n 069152 the .021 copper ones.

Thanks again and if anybody has any other ideas I probably won't be buying the gaskets for a few weeks anyway.

Posted By: txterry2

Re: Compression drop w/ replacement gasket on 318 - 02/27/10 12:47 AM

Google 1121 mr.gasket.Found 3 sites that had them within 5 minutes,one was amazon.

Posted By: volaredon

Re: Compression drop w/ replacement gasket on 318 - 02/27/10 01:07 AM

Quote:

The last batch of Felpro's I measured were .054"-.057" thick. I purchased the Mopar set #P4120094 from Mancini and are advertised at .024-.028" compressed.

I got these P-number thin ones, thru the local dealer when I put the EQ heads onto my LA 318 a year ago; I have a Magnum 318 in the machine shop as we speak I will be trying to get another set when that engine gets back here.

Posted By: radar

Re: Compression drop w/ replacement gasket on 318 - 02/27/10 03:24 AM

I just ordered a set off amazon. Ended up being around $50 shipped. Thanks I didn't think to look there. Jegs has the p/n but it says call service rep to order. The service rep told me it's a discontinued part.

I was starting to have flashbacks to a couple years ago when everybody had 1"+ torsion bars listed for like $150 and none in stock. I ended up spending big bucks for just suspension bars. Now they're on sale for around $150. Go figure.

Anyway, thanks everybody for all the help and hopefully this thread can help the next poor sucker with his replacement gasket problem.

Posted By: denfireguy

Re: Compression drop w/ replacement gasket on 318 - 03/03/10 03:08 PM

I just ordered set off of Amazon as well. It appears that this part is discontinued. If you want a thin gasket, might be best to order one now.
Somehow I wonder if there ever will be any made again.

Craig

Posted By: Robbins

Re: Compression drop w/ replacement gasket on 318 - 01/18/17 09:30 PM

Didn't FelPro used to make a steel shim factory style head gaskets? Whether this is a good idea or not...but my dad would spray paint those gaskets with silver paint....my cousin sprays them with copper coat to help them seal.

Posted By: Baxter61

Re: Compression drop w/ replacement gasket on 318 - 01/19/17 05:29 PM

Posted By: denfireguy

Re: Compression drop w/ replacement gasket on 318 - 01/19/17 06:57 PM

First, this is a 7 year old thread that has been resurrected from the dead. And things have changed a bit. The Mr Gasket 1121G (.028 compresses) that was disappearing then is back in stock at Summit and many other vendors. Guess it was just a seasonal shortfall.
Craig

Posted By: PLUM_72

Re: Compression drop w/ replacement gasket on 318 - 01/19/17 08:42 PM

Cometic has a 4.04 bore gasket for the small block with a 0.027" compressed thickness. The trouble there is they are about $80 each.