The 360 build that has more turns than Willow Springs

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I've noticed that the range of 65-73 CCs of the #308 head show an approximate range of 3/4 point of compression from low to high.
An uncut stock block deck height should be consistent from block to block but probably varies a bit.
Pistons that sit at zero deck, .010, .015 and .020 below deck vary about .4 points.
There are a lot of variables in determining and choosing a compression ratio.
 
I have seen this on different heads of a given casting number, where they vary widely between heads. You wouldn't think 2 heads with the same number would vary that much between them unless one was worked and the other one wasn't
 
I agree. These engines were not built by NASA/Space X level protocols.
I’ll bet you could take a sample of stock engines back then and they all would vary a bit in torque and HP numbers. I think that we all have had engines that ran stronger or slower than others that seemed to be evenly matched.
The head gaskets from the previous build were the Fel Pro 8553 PT. They are listed as .047 compressed.

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It turns out I have three out in the parts shed…

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The new one measured .050 as is.

Check out how bulged out the old ones are.

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Holy crap! This is the first time I laid the old one over a new one.
The cylinder on the left in the next one is either cyl 4 or 5.

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Even it has some bulge to it.
Other side:

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The second one in is bulged. Check out THIS one….

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Why did these fail? The head bolts were tight. The heads are not cracked. The block is fine. Could it be that the guy ran it lean with too much advance? The pistons had no detonation evidence to them. I do know that this car sat awhile between drives so if he ran cheap 87 octane gas and didn’t hear it knocking, this could happen.
 

360 LA getting oil in #3 cylinder.

I knew I could count on you guys. Thanks. On to the next ordeal (for me and my arthritis) getting the headers out of the way so I can get to the head bolts. Hope I don't have to take the motor mount loose. Wishful thinking. May be Wednesday before I start that. header pipe to flange looks...
www.forabodiesonly.com

Here is a thread I started about a 74 Duster 360 my brother-in-law bought. I found the headgaskets pushed out just like yours. I had the heads resurfaced, but then decided to check the block deck surface. It was pulled up at the upper row of headbolts. I could slide a .003" feeler gauge under a machinists straight edge, laid across the deck, at the locations between the headbolt holes.
See post #79.
 
I will look at that. Thank you.
My machinist will surface the decks as part of the process he does with the engines I’ve brought to him.
 
I texted with the former owner of this engine. He and his dad used the Fel Pro .047 8553 gaskets to lower the compression a bit instead of using the common .039 ones. He didn't remember it knocking. The rod bearings looked great. That gasket is cheap in price so i wonder about it's durability with high compression. The 1008 costs over double, the 521 SD (Severe Duty) is .050 and about double the price too.
I could just go back to using the same design of pistons they had, the Speed Pro H116CP but Summit does not have them in the .040 bore size.
One alternative is these:

1990 DODGE KB KB232.040 KB Performance Pistons | Summit Racing

The compression height is .015 higher but these have an 18 cc dish. The dish makes a 1.3 point difference in the compression ratio but if the KBs are .015 taller, I think that increases the ratio by about .2, 2 tenths. This makes a net difference around 1.1 point.

The other way to go is with the standard KB 107. I calculated these numbers after a couple FABO members showed me how to compute approximate deck clearance by using the math.

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Assuming Combustion chambers on the large end (which makes sense since the engine was only rebuilt once) 72 ccs. the KB 107s 5 cc valve pockets, the .012 calculated deck clearance, a Fel Pro Severe Duty 521 SD .050 head gasket puts me right in the sweet spot.
Even if the chambers are 70 ccs, it only changes to 9.54, still streetable with 89 or 91 octane!
 
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I can see a difference in 0.039 vs 0.047 head gaskets with all else equal but I can't see 0.008 making THAT much difference
 
volaredon said:
I can see a difference in 0.039 vs 0.047 head gaskets with all else equal but I can't see 0.008 making THAT much difference
Click to expand...
I don't know why the 8553 PT is so cheap but I thought that maybe it wasn't as durable as the 1008 or the 521 SD. I'm wondering (and may never know) why the engine barfed the head gaskets given that it seemed to have a reasonable compression ratio.
This is an approximation of the previous setup:

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Like someone mentioned, it may have been the tune. It may have been the torque sequence during assembly, it may be an uneven deck surface.
It may have been 87 octane in a car that sat for 4 months.
 
In keeping with the title of this thread, I made a choice on pistons that went for the power instead of playing it safe.

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I liked the Speed Pro H116CP but the .040 size was out of stock and could take awhile. These KBs have a taller compression height so I chose a thicker head gasket..

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This does put the compression ratio in a good place, right in the middle of where I want IF the heads have not been milled and the decks cut too much.

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I am taking a bit of a gamble but this engine was 100% original when my friend rebuilt it years ago. Stock decks, stock heads. Even if I have the man take 3 thousands off each just to clean it up for a good gasket seal, I'd then have these numbers...

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Being under 9.5 to 1 with stock iron heads should still be fine with 89 octane and a proper tune.

I do have these:

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These are the 1.6 ratio rocker arms from Hughes Engines. A FABO member has a thread here about some trouble he had with them:

Hughes Engines

I don't recall that this engine had any pushrod clearance issues, but I didn't look for it either. After reading the thread, it seems that some feel that clearancing is a necessity with the LA heads. Their listing on the Hughes site doesn't state that, at least I didn't see it anywhere.
 
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Since it has been awhile since I rebuilt a "small block", I'm a bit fuzzy on the details.
This engine had 9 ARP head bolts on each side and a stock one where the "long" bolt goes. I've been wondering what may have caused the head gaskets to blow out. Some have suggested that detonation did it. Others have stated that an improper tune was a contributing factor.
What about improper clamping force?
The LA and Magnums use a 1/2" head bolt but only 4 bolts around each cylinder. The B/RBs use 7/16" bolts but have 5 bolts around each cylinder.
The ARP bolts in this engine measured between 1/8" and 1/4" shorter that the stock bolts do. That can't be good. I measured...the ARP bolts extend only 5/8" past the head surface. Taking into account the thickness of the head gaskets, you're barely exceeding the width of the bolt with the engagement of it to the block. Is that enough?
I'd think that you'd want more of a safety margin than that.
 
Kern Dog said:
That is interesting.
If I recall, this engine had the pistons right near zero deck, (Maybe .010 below deck) the pistons have 5ccs worth of valve reliefs. With a 63cc chamber, what is the compression ratio?

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Even if I have it wrong and am .020 below deck...

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Over 10.25 to one with iron heads on no better than 91 octane?
Click to expand...
The compression ratio has little to nothing to do with detonation or head gasket failure. That's attributed to excess cylinder pressure and heat.
 
I've estimated what the CR was before. It was in the low 9s so I agree, there was something else going on.
 
Kern Dog said:
In keeping with the title of this thread, I made a choice on pistons that went for the power instead of playing it safe.

View attachment 1716361504

I liked the Speed Pro H116CP but the .040 size was out of stock and could take awhile. These KBs have a taller compression height so I chose a thicker head gasket..

View attachment 1716361505

This does put the compression ratio in a good place, right in the middle of where I want IF the heads have not been milled and the decks cut too much.

View attachment 1716361509

I am taking a bit of a gamble but this engine was 100% original when my friend rebuilt it years ago. Stock decks, stock heads. Even if I have the man take 3 thousands off each just to clean it up for a good gasket seal, I'd then have these numbers...

View attachment 1716361513

Being under 9.5 to 1 with stock iron heads should still be fine with 89 octane and a proper tune.

I do have these:

View attachment 1716361517

View attachment 1716361518

These are the 1.6 ratio rocker arms from Hughes Engines. A FABO member has a thread here about some trouble he had with them:

Hughes Engines

I don't recall that this engine had any pushrod clearance issues, but I didn't look for it either. After reading the thread, it seems that some feel that clearancing is a necessity with the LA heads. Their listing on the Hughes site doesn't state that, at least I didn't see it anywhere.
Click to expand...
I won't comment on that member's woes with the rockers, but I will say Hughes makes some nice pieces.
 
Kern Dog said:
I've estimated what the CR was before. It was in the low 9s so I agree, there was something else going on.
Click to expand...
Something caused detonation. Oil in the cylinders, water.....something that doesn't compress.
 
I keep thinking that if the factory thought that shorter head bolts wouldn't affect durability, they would have used shorter bolts than they did.
 
Small blocks have always been known for head gasket issues if the cylinder pressure get to high whether through parts selection, detonation, boost, NOS, whatever... Like many Fords the ten head bolt pattern puts four bolts around each cylinder... Big blocks have 17 bolts which puts five bolts around each cylinder... O ring receiver groove in the block use to be the accepted fix for running higher cylinder pressures...

Upgraded head gaskets & studs help...
 
I have never had a head gasket failure in anything. I've had oil leaks, vacuum leaks and water leaks at water pumps but my luck with head gaskets is good.
I'm not one to claim that I've built hundreds of engines but I've built a few Chevy 350s, a 400, a few 440s, a 383, three or four 360s and done numerous engine swaps.

I'm thinking of adding this to the build:

Cloyes Gear 9-5387 Cloyes Replacement Timing Chain Tensioners | Summit Racing

The intake is heavily stained so I will paint it either dull aluminum or the same orange the engine will be.
The car it was in had an electric fuel pump so this engine had no fuel pump eccentric on it. I lost the Woodruff key in the end of the cam so I'll need to source that. I did take pictures of the other 360/5.9 that is getting rebuilt here at the same time...

FPE 1.JPG


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Yeah, that is right.....Rich and I are building similar engines at the same time in the same shop out back....

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If your machinist skims the decks & surfaces the heads, chase the threads & use a quality gasket & you should be fine... You don't know enough about that engines past life to know why it failed.. possibly tune, possibly assembly errors...

Before I accept that it was just a regular tuning issue I'd be suspecting the guy tried nitrous.. More engines are hurt by first timers playing with nitrous without learning enough about it first than guys who seriously run nitrous...
 
The car didn't have nitrous. This is the car it was in:

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I did the body and paint on the car. I used to be good friends with the father of the owner. Politics pushed us apart so sadly, I don't talk to him anymore.
I get along fine with the son though.
Mike didn't drive this car much. His tuning skills were fair but he isn't as big of a gearhead as some of us are. He didn't care to work on the car much so when the head gaskets blew, they swapped a stock rebuilt 360 in the car and stashed this one away.
 
So it was built in 2012-13... How long did it run before it lost the head gasket? Sounds like the heads didn't get torqued properly or those bolts caused issues... One thing when you run ARP or any other premium bolt, they have a higher torque spec, if you use the stock torque spec you never actually properly stretch the fasteners which can lead to a premature failure...

But like I mentioned earlier, pretty common problem on smallblocks...

Blown Head Gasket
 
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