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  #16  
Old May 23rd, 19, 06:24 PM
Alan71 Alan71 is offline
 
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Ok thanks!
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  #17  
Old May 30th, 19, 09:37 PM
Elvis Elvis is offline
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Default Re: I canít find a whole lot on my engine

Quote:
Originally Posted by Big Dave View Post
The only other option with a one piece rear main seal small block is a 5.0 liter or a 305 with a tiny 3.736" bore that a 2.02" valve would hit the edge of the block it is so tiny.

Big Dave
But you can fit a 1.94/1.50 setup in that bore.
Bill Mitchell's World Products used to make something called a "305 Torquer" cylinder head that did that.
It addressed the old trick of putting 305 heads on a 350 to create a cheap and easy way of getting 10:1 c.r., due to the 305's smaller combustion chambers (55-62cc with 58cc being typical).
The problem was those heads were fitted with smaller valves and smaller ports, so RPM was limited.
The 305 Torquer put regular 350 valves and ports into a head otherwise setup to sit on a 305.
That way you gained power from the increased c.r. but didn't lose anything due to valves and ports.
IF you put those heads on a 305, you'll actually get a little bump in power and RPM, due to larger than normal valves and ports.
I remember one magazine tested them to see what the increase was and they realized something like a 13HP increase in peak power and a more nicely shaped power band for street use.
In the article they showed the head, from the bottom of the block, as installed and the valves filled up almost all of the bore.


Elvis
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  #18  
Old May 30th, 19, 09:52 PM
Elvis Elvis is offline
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Default Re: I canít find a whole lot on my engine

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Originally Posted by Big Dave View Post
Unless it is a billet steel custom ground can (and few of those engines retain a stock mechanical fuel pump) you use a stock fuel pump rod made out of mild steel to ride on your cast iron cam elliptic. Since your engine was out of an EFI truck it won't have the rod installed (nor a bushing or a machined hole in the crank to support a manual trans). The truck it came out of had a low pressure electric fuel pump in the tank (17 psi for TBI; 48 psi for port injection).

Big Dave
That's a high pressure fuel pump, Dave.
Low pressure pump is the type like Alan mentioned. 5-7 psi.


Elvis
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  #19  
Old May 31st, 19, 11:39 AM
Big Dave Big Dave is online now
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Default Re: I canít find a whole lot on my engine

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Originally Posted by Elvis View Post
That's a high pressure fuel pump, Dave.
Low pressure pump is the type like Alan mentioned. 5-7 psi.


Elvis
I was referring to the in tank electric pumps. TBI is a low pressure pump, as the injector compresses the fuel in the throttle body for final atomization. The High pressure pump is controlled by the return valve on the fuel rail as to pressure but the sequential in port injectors where only open and closing not squeezing the fuel so they used a high pressure pump. That was before direct injection EFI was introduced which has to now overcome 170 psi dynamic cylinder pressure before the fuel is injected (atomized since liquid fuel won't burn only gas vapor will ignite).

The mechanical (bolted to the block) fuel pumps are controlled by the return spring pressure and for stock are set to 4.7 psi. I have not seen a stock pump that outputs fuel at 7 psi because that would cause most carburetors to flood. The fuel is not pressurized by the arm moving up on the eccentric, but by the spring pushing the fuel out from under the diaphragm as it resets the arm. The spring sets the pressure in stock style pumps. Not going to talk about the other mechanical fuel pump used by mechanical fuel injection (alcohol or nitromethane cars) as it gets very complex rapidly depending upon injection system and pump size, but pressure is important to keep the engine lit under load.

In a Holley brand carburetor the float generates only enough pressure applied against a .0.137 inlet seat to close it against 7 psi. 7.01 psi will force it off the seat and flood the carb. only a newb would attempt to run 7 psi with a carb because there are bumps in the road that would allow the fuel to blow off the needle and seat. That is unless you are building a custom carb with a bigger float, or a longer float arm to apply the buoyancy of the float against the needle on the seat (you could also restrict the diameter of the seat allowing in less gas to fight the pressure). Seven psi is the maximum allowed and pressure doesn't make more power, or add to reliability.

I have a half inch diameter fuel line fed to the inlet of my Dominator carb with the fuel pressure set at 4 psi. I have never run out of fuel since i changed over to a single Aeromotive A1000 fuel pump (had twin Holley black pumps before).



Here is the 305 bore with a 1.95 inch intake valve installed. I can see lots of valve shrouding with this set up which might make a 1.72 inch intake a better choice.


No body will run a 305 or a 396 because the bores are too small to make any power. The bores shroud the valves which adversely affects the ability to breathe. Bigger bore is always better.

Big Dave

Last edited by Big Dave; May 31st, 19 at 11:51 AM.
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  #20  
Old May 31st, 19, 02:59 PM
Elvis Elvis is offline
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Default Re: I can’t find a whole lot on my engine

The in-tank pumps have always been high pressure, since they do the job of both delivery pump and injection pump.
At a time when all pumps were low pressure engine driven pumps, the in tank pumps FOR FUEL INJECTION (because there were in-tank pumps before FI became common place, and they were low pressure pumps, too) were always considered high pressure.
Nowadays, its so common place no one really thinks of them as "high pressure", because the comparative has been obsolete for so long now, you have to think about it before you realize there is a difference (of course, if you're under 30 or 40 years old, you're too young to realize the difference, or remember that there is one).
Of course, for us guys who work with the older platforms and remember when that was THE platform that denotes a "vehicle", its a no brainer.
For years, my every day vehicle was an 80's Mazda truck and sometimes I would tell people about the time the gasket behind the fuel pump (cam driven, mounted on the head) leaked and I had to change it (because it precluded an engine rebuild that occurred not too long after) and whenever I told that story to a younger person I always got the same response...isn't the fuel pump in the tank?...then I have to explain to them how things were, once upon a time. It always reinforces the fact that as every day passes, I become more and more of a dinosaur.
Where's my shawl and my walker, right?
Don't get me started...anyway, yeah, there's a difference and its ok if you mix them up. No one's perfect. We all make mistakes from time to time. =)

As for the valves, you're changing your story. Originally, you said one couldn't use a 2.02" intake valve on a 305 because the bore is too small and you're right about that.
Now you're saying the 1.94" intake valve that was used for years on SBC's shouldn't be used due to valve shrouding. Make up your mind, what would you like to chat about?
You can use that head on a 305 and you will gain some HP. It was tested and the results were published.
I believe it was an issue of Super Chevy, or possibly Popular Hot Rodding from back in the early-mid 90's.
I will side with your assessment that the intake is shrouded a little, but I've seen worse.
People still run 396's and 305's and they do just fine.



Elvis

Last edited by Elvis; May 31st, 19 at 03:40 PM.
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