Head gasket questions, GC heavy duty gasket

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Alvon Elrod
Posts: 3
Joined: June 22nd, 2006, 7:35 pm
Location: Ventura, CA

Head gasket questions, GC heavy duty gasket

Post by Alvon Elrod » February 23rd, 2010, 6:36 am

I purchased a GC heavy duty 1.8L head gasket, and plan to use it on my current engine rebuild (Fiat 124 spider, blown head gasket after 21K miles, probably result of continued detonation with compression that is too high -- 10.6:1 CR --, and using standard head gasket). I am very impressed with the construction of the design features of the gasket for reinforcing the fire rings. Seeing this head gasket gives me good confidence that the rebuild will be substantially stronger that my original build using a standard head gasket. I was planning to machine the domes of the Mundial 8 mm domed pistons down to 6mm, to bring the CR down to a more manageable level, about 10.1:1. However, I see that the heavy duty head gasket is thicker than standard (about 1.83 mm compared to 1.4 mm for standard), which would give an equivalent volume change as removing 2 mm from the piston domes. My questions:

1) Are there any special head or block preparations recommended for the GC heavy duty head gasket? Any copper spray or other product recommended?

2) Torque to standard 61 ft-lbs? Re torque later?

3) What thickness does the gasket compress to when torqued? The standard one that I removed is about 1.22 mm, where before installation was about 1.4 mm. I'm guessing that the heavy duty gasket would compress from the 1.83 mm down to about 1.7 mm or so??

4) My calculations show that the CR with the new heavy duty head gasket will result in about 10.1 - 10.2 if I leave the 8mm domed pistons as is, depending on the compressed thickness of the head gasket. Would you agree that this reduction in CR may be enough to possibly cure the detonation problem, or do you think I should skim the piston domes some to lower the CR even more. I had detonation mostly at 2000 - 2800 rpm under load, even with premium fuel with octane boost additives.

Thank you for your time. I'm providing more reference info below, if needed or interested.

Alvon
_________________________________________________________________________________________________

Engine details: (built in Dec 2005, Jan 2006) (click on picture links to enlarge)
Elrod Fiat 124 Spider 027A, small.jpg
Elrod Fiat 124 Spider 027A, small.jpg (317.19 KiB) Viewed 8324 times
1.8L block
85.0 mm bore
Removed all galley plugs for cleaning, including crankshaft (installed threaded plugs)
Standard size rod and main bearings.
8 mm domed Mundial pistons, standard rings, piston crown is level with deck at TDC
2.0L Beta cylinder head, 52.5 cc's combustion chambers
Standard size stainless steel valves, intake and exhaust
40-80 intake camshaft, 3 mm valve face clearance from piston (dry build check), valves shimmed to about .011" clearance per cam manufacturer (PBS engineering)
70-30 exhaust camshaft, 4.5 mm valve face clearance from piston (dry build check), valves shimmed to .019" clearance per PBS
Cam driven distributor, 28 crank degrees advance at 3500 rpm, Crane fireball 700 electronic conversion, stock coil with external ballast resistor
Experimented with idle advance from 0° - 10°, set for about 5° at 800 rpm (33° total at 3500 rpm)
1438 cc flywheel, lightened (original drive train in 1970 Fiat 124 spider)
Weber 40 IDF's 13/15's with 32 chokes, waffle manifold, Pierce Manifold foam air filters with wire mesh domed housing
Standard 4:2 exhaust manifold from 1608 engine, stock 2:1 down pipe and stock exhaust tubing and muffler
Adjustable cam wheel pulleys, dialed to 110° intake and exhaust
In-head thermostat, 190°
Electric fuel pump, regulated to 3 psi
Crankcase vapors vented overboard, through a catch can to trap droplets
Everything was balanced, balanced, balanced!

Measurements used in determining Compression Ratio:
a) Cylinder head chamber volume 52.5cc
b) Head gasket volume, 1.22mm thick, 85.8mm dia. 7.05cc
c) Ring lap volume, 11mm crown to ring, 84.5 mm crown diam, 0.93cc
d) Dome Intrusion, 8mm domes 15.08cc
e) Valve reliefs below crown 1.23cc
f) Crown height above deck 0 mm
g) Volume of Crown above / below block (85mm, crown height) 0.000cc
h) Combustion volume, 85mm 46.63cc ( a + b + c + e - d - g)
i) Swept volume, 85 mm diameter x 79.2166 mm stroke 449.51cc
j) Compression ratio 10.64 (i / h + 1)

Engine ran very strong from the beginning, though had some pinging with accelerating under load at lower rpms up to about 2800 rpm. Experimented with adjustable cam wheels and distributor initial timing to try to eliminate detonation, but did not ever completely resolve the issue. Resolved to use premium gas with octane boosters, but still did not resolve the problem. I merely became careful with my driving style to avoid loading the engine at lower rpms. After about 10K miles, noticed that the car was not as strong when climbing steep grades. Compression check showed no problems. Leak down test showed that cylinders 2, 3, and 4 were showing some leaking from bore to bore. No water leaks or oil leaks, likely fire ring leak only. Car still ran quite strong (stronger than most others that join our Fiat gatherings), so I decided to live with it and keep a close monitor (actually drove across the US and back in 2008 with the engine in this condition). In the Fall of 2009, we went on a weekend outing with a large group of Fiats, which included a lot of spirited mountain driving. We traded cars around for the experience, and I'm guessing that my car was possibly exposed to more detonation than it normally did with me driving. Actually, I think the others driving my car babied it pretty well for me, since I had asked them to be careful about the detonation problem at lower rpms. Also, it had another peculiar behavior at high altitudes. It would tend to get flooded when coming to a stop sign and letting it idle -- maybe a carburetor float setting or leaking float valve, though it didn't have this tendency at lower altitudes. The next day, the head gasket completely blew out between cylinders #3 and #4 while on a casual drive joined by 2 other Fiats (Pierre Benniston and Steve Bedillion), headed to the Best of France and Italy show in Los Angeles. We got the car back home, then went on to the show. Upon disassembly that evening, we found the fire ring between #2 and #3 was more than 50% shot also, as expected. The seal between #1 and #2 was good. The engine had about 21K miles on it.

Other than the head gasket, the engine looked very good inside. Flatness check on the block and head surfaces showed absolutely flat (.0015” shim wouldn’t go under a straightedge anywhere). The main bearings look new, and can be reused. The rod bearings are shiny, and will be replaced. I will rebuild with lower compression to try to eliminate detonation problem. I will try total seal rings this time.

The valve stem guide clearances were higher than I would expect (cast iron guides). All were about .003" to start with. The exhaust stem clearance increased to about .013". The intake stem clearances increased to about .017" except #1, which was .022". The increased clearance was pretty much in all directions, not just side to side. I had been using a set of very strong 'racing' valve springs, with about 50% higher spring loads than stock, and possibly this had something to do with the valve stem wear. Possibly the intakes had higher clearance due to running a too-rich fuel mixture. Some of the valve shims were showing signs of pitting, probably from the high spring load, though the camshafts looks fine. I will be switching back to stock valve springs, and changing out the valve stem guides, possibly to bronze.


One discovery that was particularly interesting during engine tear down was a large amount of metal blobs welded to the side of the cylinder bore in cylinder #2, above the top compression ring. I had driven the car back home after the blown head gasket, about 8 miles. I know, I know, was not a good idea, should have had it towed, but the car would actually run if I kept the rpms above 3500 rpm, so I did it. Let's just say I was keen on getting down to the BFI show in LA as planned, and didn't want to wait the hour or two to have it towed. It made all kind of racket under load, but sounded normal when decelerating. I kept a close eye on oil pressure and water temperature, which stayed normal, so I just continued to drive back home, while friends Pierre and Steve followed closely with their cars in case I had further issue.

That evening, we removed the head, and found the fire ring completely blown between #3 and #4 as expected, and only partially blown between #2 and #3. I believe all the welded metal in the top of cylinder #2 came from the chunks of fire ring from between #3 and #4, but it is hard to imagine how it got there, unless it was some sort of reversion flow through the exhaust manifold, since #2 and #3 are connected together in the exhaust manifold.
#1, from front
IMG_7799.JPG
IMG_7799.JPG (82.52 KiB) Viewed 8324 times
#2, from front
IMG_7798.JPG
IMG_7798.JPG (88.05 KiB) Viewed 8324 times
#3, from front
IMG_7797.JPG
IMG_7797.JPG (80.99 KiB) Viewed 8324 times
#4, from front
IMG_7796 (2).jpg
IMG_7796 (2).jpg (137.85 KiB) Viewed 8324 times
Last edited by Alvon Elrod on February 24th, 2010, 1:43 pm, edited 2 times in total.
'70 124 spider, 1.8L modified engine

Guy Croft
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Location: Bedford, UK
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Re: Head gasket questions, GC heavy duty gasket

Post by Guy Croft » February 23rd, 2010, 9:24 am

Alvon, greetings

This is a nicely crafted post but Photoshop hosting is not acceptable and doing so is in violation of Protocol 3.

http://guy-croft.com/viewtopic.php?f=13&t=1194

I have no wish to appear overbearing but with a firm to run and especially with a book to finish I do not have the time far less the patience to wait for Photoshop hosted photos and navigate thru them with all the associated adverts for white teeth etc.

Please use the site uploading service which is accessible by editing your post and scrolling down to the upload attachement section.

Thank you for your continued respect for forum rules.

GC

Alvon Elrod
Posts: 3
Joined: June 22nd, 2006, 7:35 pm
Location: Ventura, CA

Re: Head gasket questions, GC heavy duty gasket

Post by Alvon Elrod » February 23rd, 2010, 12:36 pm

Please accept my apologies for violating the pictures guidelines. I will review the guidelines and edit the post appropriately.

Alvon
'70 124 spider, 1.8L modified engine

Guy Croft
Site Admin
Posts: 5037
Joined: June 18th, 2006, 9:31 am
Location: Bedford, UK
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Re: Head gasket questions, GC heavy duty gasket

Post by Guy Croft » February 23rd, 2010, 7:17 pm

Alvon, hi

thanks. Here is an attachment with instructions on how to fit & tighten the GC supplied head gasket. Read carefully and I will take any questions after, OK?

I've read your careful post as fast as I can, sorry if I miss anything. Major computer problems have set me back all day so here goes.

Too high inlet air temp could detonate it and you're inducting at underhood temperature. Not good. 10.6/1 would NOT blow the early gasket ordinarily if torqued up right and then retorqued (stone-cold) but overheating inlet air could cause the problems you've seen. Too lean could do that too, as could plugs too hot, I'd be on race plugs NGK B9EGV on that motor. Overkill? No, you cover every angle when you tune a motor, looking back you'd figure the same I think. Fitting them categorically rules out plugs as probable cause.

Ignition timing OK, chokes too small, need 34s but 32's not the cause. I would be concerned maybe about the mufflers. Standard, sure - but new or old? I can tell you that I would not be using them in any case because you could have way high back-pressure. That can cause chronic heat build-up in the ex port region and the chamber too. You need one or two straight thru 2.25" bore big oval mufflers on that engine. One for performance or two for quietness but the more silencing the more back pressure.

Your ignition is developing peak way too early, 33deg total at 3500. The 1800 124CSA top mounted distr peaked 34-36 at 3800rpm (Marelli S144BA) and worked fine but yours peaking at 3500 doesn't sound good to me. I don't know the characteristics of your distr but I can tell you every other TC with a distr peaked at 5500. I ran 200bhp 2 liter units with that and would never run what you've got. That your engine was pinging around peak adv may be a clue.

Remember that if the cause is not ID'd the GC gasket will blow too, or if not the gasket maybe a piston will end up with a hole in it, the extreme pressure has to go somewhere.

This is all I can manage just now after a very difficult day, hope it helps some for now,

G
Attachments
Gasket & Bolts.doc
(32 KiB) Downloaded 620 times

Alvon Elrod
Posts: 3
Joined: June 22nd, 2006, 7:35 pm
Location: Ventura, CA

Re: Head gasket questions, GC heavy duty gasket

Post by Alvon Elrod » February 24th, 2010, 6:08 am

Thank you for your review. I will study each of your points in more depth, using my Croft Workshop manual, and try to post a few more pictures when I get a chance. I'm thinking that my first priority should be to curve the distributor to lay the advance curve down a bit, so that it doesn't advance so quickly. The distributor is a Marelli S144CBY (also marked with 401 R1 P1 5L). I have seen several different distributor advance curves in the workshop manuals, with specs all over the map, so it's good to know the curve that has worked well for you with this type of build. It's been modified with a Crane Fireball pickup, but the centrifugal weights and springs are as they are when I got it, which I assumed was stock. I'll see if I can dig up some stronger springs and / or find a place that can change the advance curve for me.

I'll look at ways of cooling the intake air (remove the hood!!) and opening up the exhaust, also.

I have been using NGK BPR6ES and 7ES plugs, and they seem to burn about right. I'll see if I can find the plugs that you mentioned. If anything, I've been tuned a little too rich, rather than too lean, which may be why I have rather high valve stem wear on the intake valve stem guides. People that follow me have commented about a rich mixture aroma coming from my exhaust. I have an assortment of jets to experiment with on the carbs, and will look into getting the larger chokes.

Thanks again for reviewing my info.

Alvon
'70 124 spider, 1.8L modified engine

Guy Croft
Site Admin
Posts: 5037
Joined: June 18th, 2006, 9:31 am
Location: Bedford, UK
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Re: Head gasket questions, GC heavy duty gasket

Post by Guy Croft » February 24th, 2010, 9:00 am

OK, good. I'm glad we have got started on this.

Rich mixtures and HC engines need LESS advance than lean ones by the way than lean (OE production settings) and low CR. I imagine the problem with your distr to be worn springs because I think you've got the right static (10 deg at 850) but peak is coming in way too low.

GC

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