mercruiser 4.3 thermostat housing

ste80

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Can someone suggest me also where to buy nee head bolts? I sow this online but is for car and they ask car type :) are same? Do you know this seller? Have you got any other place where i can buy and theu would send to italy?
Thanks again all for the help you are all nice 🙏
 

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Lou C

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If you can order from Summit Racing or Jeg's either one is a good source. I bought a set of ARP head bolts at a local speed shop. The bolts are not marine specific, basically the only marine specific parts on this engine are the head gaskets (to prevent corrosion with raw water cooling) and the core plugs in the block (not steel but brass, or stainless steel, same reason, corrosion). Block, heads, etc are the same as auto parts, the cam may be a marine specific cam, or a truck/RV cam. Of course the carb, fuel pump, starter, alternator, & distributor all must be marine certified parts.
If you haven't installed the bolts yet, I would advise making sure that the threads for the cylinder head bolts in the block are really clean, so that your torque readings will be accurate. I used a thread chaser to clean the threads, then brake cleaner and compressed air.
 

ste80

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If you can order from Summit Racing or Jeg's either one is a good source. I bought a set of ARP head bolts at a local speed shop. The bolts are not marine specific, basically the only marine specific parts on this engine are the head gaskets (to prevent corrosion with raw water cooling) and the core plugs in the block (not steel but brass, or stainless steel, same reason, corrosion). Block, heads, etc are the same as auto parts, the cam may be a marine specific cam, or a truck/RV cam. Of course the carb, fuel pump, starter, alternator, & distributor all must be marine certified parts.
If you haven't installed the bolts yet, I would advise making sure that the threads for the cylinder head bolts in the block are really clean, so that your torque readings will be accurate. I used a thread chaser to clean the threads, then brake cleaner and compressed air.
thanks, they are car spare parts, wich model i have to look at? i try on jegs but model is 96-2014 ( i think they are little bit longer from description also if i think there was not difference
for the thread i was thinkig to pass the thread maked in all thread before assembling,
what u think?
 

Lou C

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What I did was use a vehicle model that this same engine came in, mine's a 1988 V6, so I used a 1988 Chevrolet Blazer S-10 to find the right ones.
I like using a thread chaser, it is a safe way to really clean the threads, you can find thread chasers on Amazon.
If you can figure out which age range your engine is, that will help. The way to tell is to find the casting #, then it can be looked up on the net. Here's a few pix to show you....4.3L casting numbers & serial number.jpg
 

alldodge

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Note: ARP makes good bolts but if you use ARP then do NOT use the Merc manual torque spec, use only to torque spec that come with the bolts
 

ste80

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What I did was use a vehicle model that this same engine came in, mine's a 1988 V6, so I used a 1988 Chevrolet Blazer S-10 to find the right ones.
I like using a thread chaser, it is a safe way to really clean the threads, you can find thread chasers on Amazon.
If you can figure out which age range your engine is, that will help. The way to tell is to find the casting #, then it can be looked up on the net. Here's a few pix to show you....View attachment 404773
thanks. on jegs they have this, they mention 1996 ( my should be 1995 ) but should be same he said should be same
1736540496007.png
 

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ste80

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Note: ARP makes good bolts but if you use ARP then do NOT use the Merc manual torque spec, use only to torque spec that come with the bolts
what about torque on this? the problem is that the size is not perfectelly same, mercruiser has 3" +1,750+3.750 ( thy are 1,5-2mm longher and one 2.2 mm shorter) what do you think? 1736540683579.png
 

Lou C

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remember yours is a Pre-Vortec, the Vortec started in '96, so make sure they know that, the bolts could be different as well as the torque specs.
 

alldodge

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what about torque on this? the problem is that the size is not perfectelly same, mercruiser has 3" +1,750+3.750 ( thy are 1,5-2mm longher and one 2.2 mm shorter) what do you think? View attachment 404776
Regular head bolts will stretch under torque and this is why there are different torque requirements for different lengths of bolts. ARP are much harder and for the most part will not stretch under load.

Just using numbers off top of my head
Merc says torque in 3 steps to 125 Ft Lb
ARP says torque in 3 steps to 70 Ft Lb

If you torque the ARP bolts to 125 you just might pull the threads right out of the block. My bud and I did this very thing on a 454 rebuild. It came with the sheet telling us what to do and we said we don't need to stinking instructions, we have the manual.

We then bought a threaded insert kit to repair block
 

ste80

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remember yours is a Pre-Vortec, the Vortec started in '96, so make sure they know that, the bolts could be different as well as the torque specs.
1736541737529.png

this is if i put chery S10 that was manufactured in 1995 ( should have the 262 block)
 

ste80

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Regular head bolts will stretch under torque and this is why there are different torque requirements for different lengths of bolts. ARP are much harder and for the most part will not stretch under load.

Just using numbers off top of my head
Merc says torque in 3 steps to 125 Ft Lb
ARP says torque in 3 steps to 70 Ft Lb

If you torque the ARP bolts to 125 you just might pull the threads right out of the block. My bud and I did this very thing on a 454 rebuild. It came with the sheet telling us what to do and we said we don't need to stinking instructions, we have the manual.

We then bought a threaded insert kit to repair block
thanks the issue is clear, but if i do not use the arp, but if i use other make like the make that Lou C said? Wich torque shuld i have to use? is better to use old bolt at this point just to avoid issue?
thanks
 

alldodge

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thanks the issue is clear, but if i do not use the arp, but if i use other make like the make that Lou C said? Wich torque shuld i have to use? is better to use old bolt at this point just to avoid issue?
thanks
If new bolts do not come with instructions then follow the Merc manual
 

ste80

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If new bolts do not come with instructions then follow the Merc manual
Perfect i eill buy new then. The problem is that in italy is not so easy.
You know this company?
 

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Lou C

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That is correct about the ARP bolt torque specs, I used theirs not Merc's or GM's. The GM spec is 65 ft lbs, the ARP was 70 ft lbs
Torque for the intake manifold bolts on the Pre Vortec was 30 ft lbs
 

Lou C

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Perfect i eill buy new then. The problem is that in italy is not so easy.
You know this company?
Sorry don't know the company, but the main thing is that the threads are nice and clean. As long as they thread in well, they should be OK. Make sure to follow the torque spec pattern, etc. Since some of the bolts bottom out in a cooling passage, I used Permatex Aviation on the threads on mine.
Those look like they already have sealer on them, the ARP ones come with a tube of sealer you put on the threads.
 

Scott06

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Thanks so much oil sending unit you mean the one that goes here in the picture?
Not even thread sealer?
yes that hole but I think AD meant do not use so much sealer on the end wall gaskets for the intake that it gets down in the hole for oil pressure switch. Some folks just use RTV sealant on ends and it can squeeze down in the oil passage.
 
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