mercruiser 4.3 thermostat housing

[Scott Danforth]

Did you get a marine gasket set?

 

[Lou C]

They look like the Fel Pros I install do when I did mine 7 years ago, also for the Pre Vortec not Vortec….

 

[ste80]

Those restrictors are for the exhaust crossover in the intake to warm the base of the carb & auto choke spring. The restriction limits the flow to keep from overheating the carb base….

thanks so much. so should i keep it on ? or better should i install it? thanks again

 

[ste80]

Did you get a marine gasket set?

it should be. i the garage where they did the machining of the head and cilinder they bought all the set. actually here in italy this motor is not common for car because we don't use such engine like in USA so it is more common i think to find the marine one than car oune. tomorow i also check on the box what is mentioned

 

[alldodge]

The marine gasket set would not have those items in it, because salt water woukd eat them up in no time. Not knowing more info I would suggest not using them

 

[Lou C]

That’s an exhaust passage restrictor not a water passage so it’s fine to use as is. I did when I did mine 7 years ago….

 

[ste80]

Yea it seams to be gas in that holes.
This are the gasket, cheking online they are maine

 

[Lou C]

The exhaust crossover was used on the pre Vortec engines because these engines were originally designed for carburetor fuel systems. As such there was a need for a way to bring heat into the intake manifold to prevent carburetor icing and to provide heat to operate the auto choke thermostatic spring or hot air tube. On the Vortec engines the exhaust crossover was eliminated so those engines have to use a carb with an electric choke. So that’s why there is that passage now why there is the restrictor is to heat the carb enough but not so much that you get vapor lock on a hot day. Some in very cold climates might remove the restrictor to provide more heat. In racing applications it is often blocked off to provide cooler fuel to the carb. So it’s a bit of old tech left over from the earlier days of the small block Chevrolet….

 

[ste80]

The exhaust crossover was used on the pre Vortec engines because these engines were originally designed for carburetor fuel systems. As such there was a need for a way to bring heat into the intake manifold to prevent carburetor icing and to provide heat to operate the auto choke thermostatic spring or hot air tube. On the Vortec engines the exhaust crossover was eliminated so those engines have to use a carb with an electric choke. So that’s why there is that passage now why there is the restrictor is to heat the carb enough but not so much that you get vapor lock on a hot day. Some in very cold climates might remove the restrictor to provide more heat. In racing applications it is often blocked off to provide cooler fuel to the carb. So it’s a bit of old tech left over from the earlier days of the small block Chevrolet….

Thank so much. So in my case that i normally use boat in summer, maybe is better to keep it on, avoiding extra hot in intake manifold. What do you think?

 

[Lou C]

When I replaced the cylinder heads on my engine like 7 years ago I put the restrictors in and it's been totally fine. Our summer temps are 80-95*F so the restrictor allows the auto choke to work properly but it doesn't get so hot that I had vapor lock during hot restarts. At the beginning of our season and at the end it can be as cool as 50* F so it is nice to have the auto choke working
properly. If you have a Holley or Edelbrock carb this doesn't matter because they use an electrically heated choke but my engine came with the Quadrajet that uses the manifold heat to heat the thermostatic spring to open the choke as the engine warms up. Just like our Chevrolets and Oldsmobiles way back in the '70s lol.

 

[ste80]

When I replaced the cylinder heads on my engine like 7 years ago I put the restrictors in and it's been totally fine. Our summer temps are 80-95*F so the restrictor allows the auto choke to work properly but it doesn't get so hot that I had vapor lock during hot restarts. At the beginning of our season and at the end it can be as cool as 50* F so it is nice to have the auto choke working
properly. If you have a Holley or Edelbrock carb this doesn't matter because they use an electrically heated choke but my engine came with the Quadrajet that uses the manifold heat to heat the thermostatic spring to open the choke as the engine warms up. Just like our Chevrolets and Oldsmobiles way back in the '70s lol.

thanks. temperature here is almost same in summer. i had a weber 4 barel carburator with spring. ( i sow that maybe is possible to use an electronic choke as optional but i'm not sure, and at the moment it is with thermostatic spring ( and i think i will leave the thermostatic spring) so is better to keep the restriction then.

 

[Lou C]

tks;
that gasket are the gasket between heads and intake manifold. in the pack i had this 2 metal restrictions but in the efi if i remember wel it was not any restriction. ( this LX was not mine and i bought already disassembled so i don't know haw it was.

keep in mind there are 2 different intake manifold designs for the GM/Chevrolet 4.3 V6. There is the pre-Vortec (up to and including 1995) which has 12 bolts holding down the intake manifold and has the exhaust crossover in the intake manifold. Then there is the Vortec (1996 and up) which has only 8 bolts holding down the intake, and no exhaust crossover in the intake manifold. Your EFI "might" be a Vortec, it is important to make sure you are using the right intake manifold for the heads that are installed on the engine. The pic of mine that I posted is a 1988 which is a Pre-Vortec with a 12 bolt intake and the exhaust cross over .

 

[Lou C]

Mercury Marine MerCruiser 4.3 L 262 V6 GM Vortec Engine 4 barrel intake manifold | eBay

Shelf 23-15-1-A. I will do my best to resolve the issue.

www.ebay.com

this is a Pre-Vortec intake you can see the exhaust cross over in the pix where it is turned over....

4.3L 4BBL Cast Iron Intake Manifold Vortec 4.3 V6 mercruiser volvo penta marine | eBay

Fits years 1997-present. This is an 8 bolt Vortec intake manifold. This intake is manufactured of the highest grade cast iron. New 4 Barrel 4.3L Vortec marine intake manifold assembly.

www.ebay.com

this is the Vortec intake manifold, no exhaust crossover....

 

[ste80]

The one that i'm repearing now is not efi (efi is my old one and the one where i took the thermostat).
The one that i'm rebuilding is a 4.3 lx 1996 , on head is mentioned vortec, it has the shaft balancer but i think is actually what you call prevortec. My head is the 181 (final) my intake manifold has 12 bolt

 

[Lou C]

The balance shaft was added a few years before they started using the true Vortec cylinder heads. To add to the confusion GM changed to these plastic valve covers that say Vortec on them even though they weren’t using the Vortec cylinder heads yet…….that could be a 1994 or a 1995 model year engine…engine looks very good, nice paint job?
Are you in Italy? I think I see a FIAT in the background!

 

[ste80]

But what is the real difference between old head and real vortec?
Thanks i'm painting all components before assembling

You have a good observation, yes i'm in italy and that is my baby i rebuilt this car 12 years ago it was totally destroied now is the weekend car

 

[Scott06]

But what is the real difference between old head and real vortec?
Thanks i'm painting all components before assembling

You have a good observation, yes i'm in italy and that is my baby i rebuilt this car 12 years ago it was totally destroied now is the weekend car

The non vortec and true vortec heads the intake and exhaust ports and combustion chambers are designed for better airflow and make more power. The easier way to tell is the intake manifold bolt pattern.vortec heads use 8 vertical head bolts instead of 12 angled into the cylinder heads. Ona 4.3 the vortec heads add about 20 hp.

the engine you show in the photos with vortec on the valve cover does not have vortec heads as shown by the intake bolt pattern. GM used the engine name vortec prior to introducing what became vortec heads in 1996.

 

[Scott Danforth]

cool little Fiat

 

[Scott Danforth]

history lesson on the "vortec" name. for many years, GM (and many others) did not want to pay royalties to Sir Harry Ricardo for the better combustion chamber shape used today.

Vortec was a sales name given to the V6 about 1985 when the 4.3 was released. as Scott mentioned, the heads came in 1996

the Ricardo combustion chamber, AKA Vortec head chamber was not used until the reverse flow LT1 Gen 2 SBC when the patent ran out. then in 1996 the "vortec heads" were released for the Gen 1 SBC family.

 

[Lou C]

But what is the real difference between old head and real vortec?
Thanks i'm painting all components before assembling

You have a good observation, yes i'm in italy and that is my baby i rebuilt this car 12 years ago it was totally destroied now is the weekend car

Yep the Vortec heads are designed for more efficient combustion and add about 20 hp. The FIAT reminds me of the air cooled VW Beetles we all drove back in the 70s as broke college students….