Cracks between head bolts and coolant passages
- Thread starter CudaRay
- Start date
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What years are the 318 blocks with the headbolt cracks?
Specific to just a few years?
Talk was 318 engine production went to Mexico mid 1981, possibly they made a better block and hence cured the cracking problem?
Don't know, but maybe someone here does?
Thanks
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Specific to just a few years?
Talk was 318 engine production went to Mexico mid 1981, possibly they made a better block and hence cured the cracking problem?
Don't know, but maybe someone here does?
Thanks
☆☆☆☆☆
CudaRay
Active Member
The blocks I have and have been finding with cracks are 82 (two of these), 84, and 85. My 76 318 (which threw a rod after getting too hot, the whole reason for this build) does have a beefier design than these 80s blocks.
This is a 76 318 block out of a W 100. This is the type of block you’re looking for if you don’t plan on running a roller cam.
CudaRay
Active Member
Thats the exact block I took out of the car, much beefier (included a picture of my findings after removing the heads on said block). But to reuse it, I'd need to tear it down, bore it, and buy new pistons. Nearly $800. I've found an 84 block in great shape 4hrs away, I'll probably be picking that one up this weekend.
NC Engine Builder
Grumpy Old Man
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A 84 block will likely be cracked too. Any of those blocks from 80-88 are paper thin throw away garbage in my opinion.
jos51700
Green Bearing thread connoisseur
I'm not super close, I'm near Kansas City, but I have a complete 5.2 that ran when pulled a decade ago. I'd make you a deal on the block, or the whole motor. It's super easy to add a carb intake to a Magnum and replace a LA engine, and they have several advantages.
It's been in storage for ten years, but it was stored for a year in an area where there was high humidity at times (not all the time). I have not turned it over in about 3-4 years. I had the exhaust and intake stuffed, but haven't spun it over.
It's been in storage for ten years, but it was stored for a year in an area where there was high humidity at times (not all the time). I have not turned it over in about 3-4 years. I had the exhaust and intake stuffed, but haven't spun it over.
Not to mention there's ZERO effort to REPAIR the actual problem. Cast iron cracks just keep getting bigger and thread sealer does nothing to stop it.
CudaRay
Active Member
Assuming this other 84 block I found is crack free, is there any reason not to go ahead with it at this point considering I have the blueprint and parts ready for assembly? I'm hearing that 80s blocks aren't worth a dime, and at this point it's either buy the block and have a running car this weekend, or return all my parts and sit around hoping for a 70s block shows up.
I remember reading something that somewhere around 1980 they started wanting any 318 that came apart to seal the head bolts when reassembled.
There was a spec, I don't remember the number but the "before" blocks had blind head bolt holes where the "after" ones went into the water jacket. If you could stick the screwdriver in past a certain amount you were to use sealant.
Seems I also remember seeing stickers on some valve covers warning of the same sort of thing. I'm guessing that all or most of the cracked ones the head bolt holes were not bea that went into the water jacket
There was a spec, I don't remember the number but the "before" blocks had blind head bolt holes where the "after" ones went into the water jacket. If you could stick the screwdriver in past a certain amount you were to use sealant.
Seems I also remember seeing stickers on some valve covers warning of the same sort of thing. I'm guessing that all or most of the cracked ones the head bolt holes were not bea that went into the water jacket
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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If you want power out of a 318, yur gunna have to increase the Cylinder Pressure anyway, and that's gunna take high compression pistons. So IMHO, just bite the bullet and rebuild the one you already have.
Cams only increase the Power at higher rpms. For a street driven vehicle, that's NOT what you want.
What you do want is Power at lower rpm, and cylinder pressure will get you that.
If you build yur 318 at a nominal 8/1, and add a decent cam then you will also have to buy a convertor and gears, to get the rpm up to where the power starts. Which is also gunna cost money, and is IMHO, way less satisfactory.
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CudaRay
Active Member
Unfortunately a rebuild on that one is 100% out of the question. Between the machine shop, pistons, rods, etc, it's going to put me about double my budget with the rest of the build.
It seems like the trip to Mexico coincides with the cracked blocks.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Well then, you need to also reevaluate your 300hp expectation.
Cam , headers and 4v ought to get 250+ pretty easy. Good enough to get well into the 14s with stock converter and 3 series gears in an Abody
I would endeavor to find a good 5.9 Magnum core. But that said, Magnum heads are bad about cracking. There are still some used engines out there with cross hatch still evident in the bores, but those days are drawing quickly to a close. I wouldn't be sittin around on my laurels. I'd be lookin hard.
CudaRay
Active Member
Could you tell me what I'd need to change for that magnum? After doing some research earlier, I see that I won't be able to use my performer intake on it, and I assume I'd have to get a different cam. I am open to going this route as there are several sub 100k mile 5.9 and 5.2 magnums near me for decent prices.
I would simply get a stock 5.9. If you have access to some under 100K, then they are likely still in good condition. I would simply bolt on an Air Gap intake, 650 AVS2 and some headers and put a good ignition on it with a good loose curve. You'll be happy.
Thanks
The '89 to '91 TBI 318 roller engines I have had good luck with. Convert them over to 4 bbl.
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JDMopar
Well-Known Member
If you can find a good, low mile Magnum, you can get one of these inexpensive intakes that will bolt to a Magnum or LA. You will need an oil pan from a 360 LA car oil pan for either a 5.2 or 5.9 Magnum to install it in an old Mopar. A 273/318/340 oil pan will not work on a Magnum motor, only a 360 car pan.
That's the one I was talking about! Thanks, Jackie!
Swinger 340
Well-Known Member
I drove 4 hours for a perfect fender and 4 hours back. PERFECT!!!!!!
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