For the front coolant lines i'm tapping 1/2 NPT and going with AN-10 fittings and hose. I will plumb them to the coolant/thermostat crossover tapped holes on the front of my Weiand carb intake. For the back i'm using the stock 1/4 NPT and teeing the two heads together. Then bringing a single line to the front and tapping a hole in the coolant/thermostat crossover for that.

As for motor build i'm going comp extreme XS262S-10 solid cam with the upgraded springs. I will also pocket port the LT1 heads and maybe cleanup the port runners. The LT1 heads will be milled for 10.2:1 for whatever pistons i find in my mystery 305.

I'm not looking for a big monster motor, just something that is fun and can hold me over till i an engineering job and get an LS1. I mainly went with LT1 heads because they are light and cheap, along with the added benefits of a better design.

This is what me and Mike (Stekman) came up with. Thanks Mike!!

 

The only thing questionable, to me, at this point, is the water pumps pressurized return line (green). I am unfamiliar with those style of pumps. Does anyone know for sure if that port is a pressurized return?

 

 

By the looks of it, the green line is where the heater hose would go. Or at least thats where the heater hose routing was on earlier SBCs.
Guys would sometimes connect the two heater hose ports to delete the heater. But the ports could also be plugged.

Question: What is the purpose of the blue line?
It seems unnessecary to me.

It seems like the diagram in the 5th post on this thread has all the hoses that would be needed.
My reasoning behind that is because the SBC1 has no functioning coolant outlets at the rear of the head. There are coolant ports at both the front and rear, but only the front ones flow.
The coolant ports are cast into the heads at both ends so the heads will be interchangable R&L.

Perhaps I'm overlooking something, correct me if I'm wrong.

 

I also took that fact (that Gen. I heads from factory do not have rear ports), however, consider the size of the front ports, then consider the volume capable of being flowed by dual -10 or -12 AN lines (whatever Leigh thinks). I don't think they will flow as much as the cast ports, so I suggested a rearward draw as well to help "alleviate" some coolant. That is why I suggested the "blue" lines (they would tee up and draw from the rear coolant crossover- or similar- holes).

 

Probably not a bad idea.

So, never having seen an actual set of LT1 heads, I gotta ask.
Are the 1/4" npt fittings (shown in the pics) on both ends of both heads?

Is the heater deleted on this car?

 

I do not know about the hole being drilled on either head, would be nice, though, if it were. That would give a nice starting point.

From talking to Leigh on Yahoo, yes, heat has been deleted; part of the reason I went and suggested the green line (on the assumption that was a pressurized return port on the front of the pump).

Final sizes are up to Leigh, but here is what I have suggested:

-12 AN for the front of the heads to the intake (red lines)
-6 AN to a tee fitting, merging to an -8 AN that leads to a drilled and tapped hole in the intake (blue lines)
-10 AN or a 5/8" heater hose for the pressurized recirculation line (green)

Again, final sizes are up to Leigh.

(edit: that is his engine in the pictures, so you can see the lack of heater)

 

Yes there is a 1/4 NPT port on each end of the head on both of them.

For the rears i want to use the 1/4 NPT to AN-4 or AN-6 teed to a block (still can't find 6-8 t) or something with with 6 or 8 out.

The fronts i want to use 1/2 NPT to AN-12 or 10. But the limiting restriction for both is the NPT ports.

Heat is gone so the green line is to bypass the thermo when its closed. We still have questions about that setup though, not knowing what the pump does.

We will findout a lot more about this whole thing when i start pulling it all apart.

 

I'm pretty sure you could put a plug in there at each end of the green line.
Sometimes if a guy had a heater core leak, or for some other reason wanted to delete the heat, just putting a hose right there where the green one is would be the solution. The thing is, plugging the ports was a better solution. It eliminates a hose that's basically non functional.
As always, with everything I say... get a second opinion.
Unless otherwise stated

You could get a 1/4" npt brass T for that rear hose, if all else fails.

 

The problem as i understand it, is when the thermostat is closed, coolant has a tough time flowing. Since the coolant is not flowing through the radiator, the coolant is not flowing in a cycle. The green line lets coolant bypass the radiator when the thermostat is closed.

This is my understanding. Right now i have the intake plugged along with the pump and it seems to work fine so...

 

I always thought that the small hole underneath the pump mounting area on the block (pass side) is a press relief/bypass to prevent too much pressure from building in the block and holding the thermostat shut.
The way I see it is, when the heater is off, the valve is shut and the coolant flow through those lines is completely blocked anyhow. Which would have the same effect on the pressure in the cooling system as plugging the port.
I've never tried plugging those heater hose ports, cause I like heat.
That's why I suggested getting a second opinion.
But I have seen hot rods and racers that had those heater hose ports plugged, so I think it's probably okay.

 

To me, I see it like this: The engine is warming up, the thermostat is closed. The pump forces coolant through the engine, etc. Fluid gets pretty much a single pass before it rests in the intake. If that hole were plugged, this coolant would just sit in the intake doing, well, not it's job. If it were to be hooked up to the pump, it would draw coolant back around and recirculate to more evenly "distribute" the heat, until the thermostat opened.

In your case, Streetiron, the pump would push coolant around, but when the coolant comes to rest in the intake, there it sits, builds pressure, than hits the bypass. That means that the coolant around the heads is heating more than the coolant at the intake, where the thermostat is reading. That's fine for a race car, but for a daily driver, excessive metal heat isn't the best thing. With the pump hooked up, while the pressure may be topped, coolant still has circulation throughout.

That's my view.

 

Good point
Having the hose connected definitely would have a circulating effect, which probably wouldn't do any harm, other than to just add one more hose to the engine compartment.
But I can't help but wonder if it's needed, because it seems like when the coolant flow to the heater core is stopped, it would be no different than having the ports plugged altogether.

It would probably be a good idea to play it safe, and run it with the hose connected and mod it later when/if the full story is known.
It's probably the easiest thing under the hood to change, besides the radiator cap.

 

Actually, it's a very good point, Stekman.
Because without some sort of bypass there, when the thermostat is closed, there'd be a bunch of coolant stalled in the heads until enough heat reached the thermostat to cause it to open.
So now I'm puzzled. What is the factorys solution to keeping coolant flowing past the thermostat when the thermostat is closed and the heater is off?
Does the valve to the heater core not close completely?
Is there another bypass within the heater system?
Or does the bypass system in the block allow coolant to move past the thermostat when the heater hose valve is in the off position?

 

I don't think there is an actual valve in the heater core lines or heater core. I believe that there is just a door in the HVAC system that blocks air from going through the heater core and producing heat into the car.

This is what i get from my Chiltons without actually knowing.

 

I just went out to the garage to look at a block to try an get to the bottom of this.
I never actually studied the coolant path of the bypass system til just now.
The coolant bypass in the block is routed to return coolant from the pass side head directly into the waterpump outlet that goes to the lower radiator hose.
Something that could be very useful to know when swapping LT1 heads, because I'm not sure the LT1s have that hole in the heads.
As far as whether or not that bypass would provide enough circulation past the thermostat when it's closed, if the heater hose ports were plugged is still unknown.
I could swear that I've seen SBC heater systems that have a valve on the hose. But too, it's possible that that valve doesn't close completely, permitting additional circulaion.

 

There is an actual valve plumbed into the line that goes to the heater core. Under normal conditions, though, I think it is always open, and like Leigh said, a flap blocks off air from the heater core. When Max AC is turned on, then vacuum is supplied to the valve, effectivly closing it. I just don't know where it goes to.

I'm not the most fluent with the factory routing....

 

The hole in the heads that routes to the bypass is at the front of the head on the pass side, about 1-1/2" below the bolt hole that's furthest to the front.
Heres a pic

https://www.thirdgen.org/techbb2/sho...ight=LT1+heads

Go down to about (I lost count) the 42nd post

 

Ah ok. I kind of figured it went back to an iron part. Figured it was the head, since I've never seen a block tapped for such a thing.

 

I always wondered what that hole was for.
Prolly ought to run the green line just to play it safe.
Or get a heater.

 

What are we talking about now, can you link the picture to here. I'm lost i don't know what the hell you guys are talking about.

 

Leigh, just follow the damn picture!!

 

https://www.thirdgen.org/techbb2/sho...ight=LT1+heads
Go down til you get to the full size pic that shows the LT1 head gasket laid over the gen1 block.
That's the pass side, and right below the bolt hole, there's another hole. That hole feeds to another hole that's at the bottom of the waterpump gasket area (sbc1) from there, it goes to the big radiator hose outlet on the waterpump, and to the radiator bottom hose.
It's the coolant bypass system.

 

this one https://www.thirdgen.org/techbb2/att...postid=1053752

There is no hole there in the LT1 heads

 

Leigh, you don't have a heat setup. None of that pertains to you. Just follow the idea in the picture we set up.

 

I'm just curious, i want to know is this specific to the LT1 waterpump and the 2-way thermostat?

 

You guys are thinking way too into this.

I'm basically using the setup that Millican has diagrammed on his site (www.lt1intake.com) for coolant flow. However, instead of teh coolant lines coming from the intake, they are going to come from the front of the heads.

Then, I may connect the rears of the heads and run a line back to the radiator, or I may run it to the remote t-stat housing, and locate the coolant temp sensor in the head instead.

Tomorrow I'm going to go to the store and pick up some fittings that will fit into my remote t-stat housing and figure out what size hose and fittings for the heads I'll use from there.

As for the heat, I was pretty sure there was a valve in the line itself to decide whether or not to flow heat through the heater core. I thought that's what the coolant diverter valve was for. It has 3 coolant lines running to it and a vacuum line, on a stock TPI motor anyways. I thought this always blocked coolant from travelling through the heater core unless the heat was activated. I would think this could possibly pro-long the life of the heater core by reducing the coolant flowing through it all the time.

 

Nope... This one
https://www.thirdgen.org/techbb2/att...postid=1052586

I should have shown it that way yesterday, sorry about the confusion.

The hole below the front bolt hole is the one I was referring to.
It's routed to the lower radiator hose.

 

FWIW, the LT1 heads had a design combustion chamber volume of 54cc. Of the two different pairs I've actually checked, the chamber volumes were slightly under 54cc. Further, while TPI 305 heads had a design volume of 58cc, all 305s did not have those heads. The '416 and '187 heads were 58, but some swirlie heads on 305s were up to 64, and some '70s heads were as large as 76cc.

Cast iron LT1 heads can be welded rather easily using a high nickel filler material, and the weld strength will usually surpass the surrounding iron.

 

Alright i have been thinking about this alot , and i have come to the conclusion that our original setup may not be the best.

I am thinking that the thermostate bypass that we have plumbed into the water pump from the intake may be too big and take to much coolant from the radiator. I think it is still a good idea to have it but i want to make it small 1/4npt to AN-4. This way coolant is still flowing by the thermostat when it is closed but not too much.

What do you think of this new setup, i know your going to be smacking your heads, "why oh why." But i just want to come up with something that will work relatively well.

 

There are numerous possibilities as to what would work, IMO
As far as what would be best, it's guesswork. And experimentation might be the answer to finding the optimum setup.
I think that if you hooked it up the way it's shown in the diagram, and then changed it around little by little, you might find that there's a way that works best for your application.
Put an accurate mechanical temp ga in there, and log the results you get when you change things around.
Then you can tell us whats best.

 

Whatever you want Leigh.

 

So does it really matter, thats all i really want to know?

 

Connect all the lines shown in the diagram and use rubber heater hose, then put a temp ga into the fittings in each head, and another close to the thermostat.
Then do a series of tests, restricting the hoses by clamping on them, and find out what the results are.
After that you'll know what's best
Til then connect all the hoses. Too much coolant is better than not enough.

Nobody here knows what's best, you're the first guy to do this!

 

Ok i will try putting some thermocouples or something in each line and measuring the temps.:lala:

 

There yuh go!!

Just think of what fun it'll be...

 

Back to the compression ratio, it was calculated to be 9.8:1 with pistons 0.040" down from the deck at TDC? Are you sure it's 0.040"? Because I thought 0.025" was standard for all Chevy small blocks. That might actually increase your compression a little more than what you might think. But if they're aluminum heads, you might be okay. Try it and see.

 

I posted some calcs earlier using this calculator
http://kb-silvolite.com/calc.php?action=comp

Based On
3.736 bore
3.48 stroke
53cc head vol
5cc valve relief
.040" gasket

Did one calc with 0 deck, and another with .025 deck and got 10.4:1 and 9.8:1, respectively.

Possibly you assumed that my .040" figure meant the piston was .040" below the deck, when it's actually piston to head clearance with -0- deck and a .040 gasket.

 

Yeah I did. Okay.
0.040" quench is about ideal, isn't it? You might get your best power numbers like that.

 

It's a good number to shoot for. But it's not a good idea to make any assumptions when you're trying for a true zero deck. There can be variations in the below deck clearance that could put the pistons above the deck if you just go by the advertised numbers.
As a rule, it's advisable to preassemble if you want -0- deck.

 

I'm going to measure everything, and modify the heads accordingly, for an average of exactly 10.2:1. I'm going to get as close to 10.2:1 on as many cylinders as i can.