Teach Me About Head Gaskets
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 1,223
Likes: 174
From: Fort Wayne IN
Teach Me About Head Gaskets
So I have never torn an engine down this far by myself but am learning as I go.
I have my engine torn down due to a spun bearing and will be getting to the putting things back together phase here shortly. Before I bought it, the bock was bored .030 and had a 383 rotating assembly installed in it from Speedway Motors. It does not appear it was decked. It has the stock 76cc heads on it. The head gaskets that I pulled off were 0.070 which seems kind of thick. Just looking around as the normal parts stores it seems like all of the head gaskets available are in the 0.040 range.
So what is the best way to determine what sized head gaskets would be good for this engine? The suggestions I've read are:
- Bring the piston all the way up, put a flat edge on the block and measure the gap with a feeler gauge, do the same with the head
- Put a piece of playdough on the center of the piston and then put the head back on with no gasket and turn the crank over with no cam to see how much squish you get
- It doesn't really matter that much if you're not building a performance engine, as long as you don't smack the piston into the head
I have my engine torn down due to a spun bearing and will be getting to the putting things back together phase here shortly. Before I bought it, the bock was bored .030 and had a 383 rotating assembly installed in it from Speedway Motors. It does not appear it was decked. It has the stock 76cc heads on it. The head gaskets that I pulled off were 0.070 which seems kind of thick. Just looking around as the normal parts stores it seems like all of the head gaskets available are in the 0.040 range.
So what is the best way to determine what sized head gaskets would be good for this engine? The suggestions I've read are:
- Bring the piston all the way up, put a flat edge on the block and measure the gap with a feeler gauge, do the same with the head
- Put a piece of playdough on the center of the piston and then put the head back on with no gasket and turn the crank over with no cam to see how much squish you get
- It doesn't really matter that much if you're not building a performance engine, as long as you don't smack the piston into the head
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
If it hasn't been decked...it is probably .020 in the hole. I have never seen a .070 thick composite gasket in my 30+ years of engine building.
If it is the stock heads......use a Fel=Pro 7733SH1 and spray both sides with Hi-Tack spray from Permatex......you will be fine.
If the piston is zero deck....use a 1003 Fel Pro .041 thick composite gasket.....
The idea is to have the piston .040 away from the head.....a little tighter is ok.
Jebby
If it is the stock heads......use a Fel=Pro 7733SH1 and spray both sides with Hi-Tack spray from Permatex......you will be fine.
If the piston is zero deck....use a 1003 Fel Pro .041 thick composite gasket.....
The idea is to have the piston .040 away from the head.....a little tighter is ok.
Jebby
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 1,223
Likes: 174
From: Fort Wayne IN
If it hasn't been decked...it is probably .020 in the hole. I have never seen a .070 thick composite gasket in my 30+ years of engine building.
If it is the stock heads......use a Fel=Pro 7733SH1 and spray both sides with Hi-Tack spray from Permatex......you will be fine.
If the piston is zero deck....use a 1003 Fel Pro .041 thick composite gasket.....
The idea is to have the piston .040 away from the head.....a little tighter is ok.
Jebby
If it is the stock heads......use a Fel=Pro 7733SH1 and spray both sides with Hi-Tack spray from Permatex......you will be fine.
If the piston is zero deck....use a 1003 Fel Pro .041 thick composite gasket.....
The idea is to have the piston .040 away from the head.....a little tighter is ok.
Jebby
https://www.speedwaymotors.com/Speed...ugg_q=915-2350
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
According to the paperwork the guy gave me about 10 years ago, this is what he used when he built it - and I have replaced about every one of those gaskets since for leaks
https://www.speedwaymotors.com/Speed...ugg_q=915-2350
https://www.speedwaymotors.com/Speed...ugg_q=915-2350
If you can't afford a Fel pro set....at least use the Enginetech brand......
Head gaskets and rear main seals need to be top quality, and these don't even begin to cut it.
Going from .070 to .015 will raise compression considerably....a whole point (9:1 to 10:1)....make sure you do the math on a Compression Ratio Calc to see if you can use the .015 or will you have to jump to a .041.....which is still going to bump it up quite a bit.
Jebby
Last edited by Jebbysan; May 14, 2021 at 01:11 PM.
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 1,223
Likes: 174
From: Fort Wayne IN
I know the head gaskets didn't cause a spun bearing.
The #2 main bearing had a considerable groove in it when I pulled the crank, the crank itself is not that bad but it needs polished.
I'm thinking the guy I bought it from knew enough to be dangerous and when he said it was a "built" engine he meant he "built" it in his garage and didn't do simple things like making sure the bearings were clean before he dropped the crank in.
It had a high flow oil pump in it and it had real good oil pressure, like suspiciously high oil pressure so I really had no idea what was going on inside until I finally decided to pull the engine.
Pulling that trigger was just the culmination of a lot of little problems that finally came to add up. Flywheel ring gear is worn out, 2nd gear syncro is gone, rear main leak, it was just time.
Oh and he had a circle track cam in it that sounded great but had enough overlap to asphyxiate you at idle and didn't make any real power until like 4000 rpm.
Last edited by bluthundr; May 14, 2021 at 09:23 PM.
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Cruising
Joined: May 2021
Posts: 13
Likes: 0
On every 350 based build I do now, I use Chevrolet Performance 10105117 gaskets. They are only .028" thick which would help those 76cc turd heads. They seal perfectly, and cost far less than just about the cheapest crap out there. I've used them on 13.5-1 compression engines with a 200 shot of nitrous with no issues at all. The only negative is when you have to rebuild the engine, they seal so well they are hard to remove cleanly!
I know MLS gaskets are all the rage now, but unless you're cramming 25lbs of boost in your engine, you are wasting a lot of cash.
I know MLS gaskets are all the rage now, but unless you're cramming 25lbs of boost in your engine, you are wasting a lot of cash.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
I don't see a spun bearing. I see some that had some trash go thru them. You need to pull them from the block and look at the back sides for STD, or oversize. Either way, when you put it back together, you need to measure each journal and the ID of the installed bearings to get the correct oil clearance.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
what do the back of the bearings say? make, size, date... not uncommon to see a scratched bearing like that. he coulda also bought the biggest baddest oil pump ever put in a small block because he was told it is a good idea...
Last edited by derekderek; May 15, 2021 at 10:24 AM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
This engine was put together too tight.....
You need to mix the crank to determine if it can be polished.....if not .010/010 Is the number and have a knowledgeable crank grinder do it to get you proper clearance.....good grinders know the nominal number....and they don’t leave it fat.
This one here looks like STD. Bearings and a Scat crank that was a thou fat.....pretty common....Eagle is that way too....
Who ever built this needs to quit building engines too.....so much wrong with this situation....starting with 33.99 gasket set....
Jebby
You need to mix the crank to determine if it can be polished.....if not .010/010 Is the number and have a knowledgeable crank grinder do it to get you proper clearance.....good grinders know the nominal number....and they don’t leave it fat.
This one here looks like STD. Bearings and a Scat crank that was a thou fat.....pretty common....Eagle is that way too....
Who ever built this needs to quit building engines too.....so much wrong with this situation....starting with 33.99 gasket set....
Jebby
Burning Brakes
Joined: Jan 2003
Posts: 961
Likes: 275
From: Frederick MD
Agreed, I don’t see a spin bearing here. What I do see is a motor that had a ton of trash go through it. You can’t assume anything at this point. Here is what I would do in your situation.
1. Take the block with main caps and old bearings installed. Also take the crank with and the rods and pistons.
2. Have him/her go through everything. The debris came from someplace, need to find out where. I wonder if caps were mixed up, not resized, and so on.
3. Have him/her order the parts and have them actually put the motor together, at least the short block anyways.
It’s good your asking questions and we will be more than happy to help you out with whatever you decide to do. With that said though I’m not sure this hot mess is a good candidate to learn on. Something not good happened there and it’s gonna take some doing to figure out. I’d hate for you to have a bunch of work done, you put it back together and for something minor wipe out the whole deal.
1. Take the block with main caps and old bearings installed. Also take the crank with and the rods and pistons.
2. Have him/her go through everything. The debris came from someplace, need to find out where. I wonder if caps were mixed up, not resized, and so on.
3. Have him/her order the parts and have them actually put the motor together, at least the short block anyways.
It’s good your asking questions and we will be more than happy to help you out with whatever you decide to do. With that said though I’m not sure this hot mess is a good candidate to learn on. Something not good happened there and it’s gonna take some doing to figure out. I’d hate for you to have a bunch of work done, you put it back together and for something minor wipe out the whole deal.
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 1,223
Likes: 174
From: Fort Wayne IN
So you all are right, it was not a spun bearing, the #2 main was just seized up.
I took the crank to a local machine shop to get polished, and when I picked it up, I took him the old bearings for him to look at the wear patterns and such.
What was on the engine was Clevite P bearings, standard size and when he measured the chamfer of the main journals he said they were too big for P series bearings and that was probably the issue. The sides were too tight causing the abnormally high oil pressure and causing them to heat up due to increased friction. I have ordered H series bearings for the rebuilt. Along with taking a hair of material off with polishing, he thinks that will work a lot better (but still plastigauge it to make sure.)
I took the crank to a local machine shop to get polished, and when I picked it up, I took him the old bearings for him to look at the wear patterns and such.
What was on the engine was Clevite P bearings, standard size and when he measured the chamfer of the main journals he said they were too big for P series bearings and that was probably the issue. The sides were too tight causing the abnormally high oil pressure and causing them to heat up due to increased friction. I have ordered H series bearings for the rebuilt. Along with taking a hair of material off with polishing, he thinks that will work a lot better (but still plastigauge it to make sure.)
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
So you all are right, it was not a spun bearing, the #2 main was just seized up.
I took the crank to a local machine shop to get polished, and when I picked it up, I took him the old bearings for him to look at the wear patterns and such.
What was on the engine was Clevite P bearings, standard size and when he measured the chamfer of the main journals he said they were too big for P series bearings and that was probably the issue. The sides were too tight causing the abnormally high oil pressure and causing them to heat up due to increased friction. I have ordered H series bearings for the rebuilt. Along with taking a hair of material off with polishing, he thinks that will work a lot better (but still plastigauge it to make sure.)
I took the crank to a local machine shop to get polished, and when I picked it up, I took him the old bearings for him to look at the wear patterns and such.
What was on the engine was Clevite P bearings, standard size and when he measured the chamfer of the main journals he said they were too big for P series bearings and that was probably the issue. The sides were too tight causing the abnormally high oil pressure and causing them to heat up due to increased friction. I have ordered H series bearings for the rebuilt. Along with taking a hair of material off with polishing, he thinks that will work a lot better (but still plastigauge it to make sure.)
This person ran the P bearing because it is half the cost of the H.....which I don't use anymore either....I use King now.
The H bearings went up about 70% overnight back in 07'........and they are the same damn bearing with the chamfer cut on them.....
King bearings are one of the last performance bargains left....
Jebby
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 1,223
Likes: 174
From: Fort Wayne IN
I bought the car in 06' so that guy is long gone can't can't do any more damage thank fully.
I looked at Clevite, King, and FM and it came down to what I could get (Clevite for the mains and FM for the rods.) With a combination of production being shut down for a while last year and that during said shutdown a lot of people evidently decided to tear their engines apart, there is a lot of stuff on backorder. I have a new flywheel ordered that has been pushed back for months now. Same thing for rings, I ended up with Jegs brand for those because pretty much anything else is on backorder.
The first engine shop I went to said they were 2 months out on any engine work. I got in at this other guy because he said he was actually already set up to polish some cranks and he would just slip me in too.
I looked at Clevite, King, and FM and it came down to what I could get (Clevite for the mains and FM for the rods.) With a combination of production being shut down for a while last year and that during said shutdown a lot of people evidently decided to tear their engines apart, there is a lot of stuff on backorder. I have a new flywheel ordered that has been pushed back for months now. Same thing for rings, I ended up with Jegs brand for those because pretty much anything else is on backorder.
The first engine shop I went to said they were 2 months out on any engine work. I got in at this other guy because he said he was actually already set up to polish some cranks and he would just slip me in too.
Last edited by bluthundr; May 21, 2021 at 02:12 PM.