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Just bought a 521


mainer311

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The TDC must be set with the timing pointer. Lobes at 10 and 2 just confirms compression stroke and not the exhaust stroke TDC (there are 2 on a 4 stroke engine) and is no where near accurate enough.

 

If you did use the timing scale at 0 (zero) the cam timing is perfect.

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Well, stupid me broke the stock steel tubing for the manifold coolant return line. I heat it up red hot and tried bending it and it cracked, so I made a whole new line out of 3/8” heating oil fuel tubing. It has a flare fitting on the manifold and just slides into the stock rubber elbow on the pump side. I  then cut the ugly orange plastic off of it.


1J6Ka9S.jpg

 

I used a “P” clip on the stock front stud to support the middle.

 

rLTLUt5.jpg
 

I then managed to stretch my NOS PCV hose over to the new location on the Offy manifold. There’s a closer fitting, but it’s on the primary side in the back. I’d rather have  it in the middle where it’s evenly distributed by the cylinders.


y9loeMP.jpg

 

I was asking about the fitment of the RockAuto radiator hoses a while back. Well, the lower Gates brand one fits awesome with the aftermarket radiator.

 

jAOWwUN.jpg

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Weber showed up today. I turned the studs to the right length and loctited them into the manifold. Then I threw the carb on to make sure it fits.

 

T7qA2PC.jpg

 

Of course, the install kit doesn’t come with a gasket that works, so I may just cut my own. One question though for any Weber gurus out there. This Offy is a split-plane, so I want to make sure the two circuits are separated, however this DGV has two holes in the middle. Is it okay to plug these?

 

pj4vizs.jpg

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I wouldn't. Probably for intake vacuum to operate the power valve. The Hitachi uses a hollow mounting screw. Which when rebuilding can be put back in the wrong place. My 710 was this way and when fixed makes a huge difference when passing on the highway.

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7 hours ago, datzenmike said:

I wouldn't. Probably for intake vacuum to operate the power valve.


I had to scour the net for a while, but I found that the power valve vac port is to the outside edge of the secondary venturi. So now I’m wondering if these are just for casting purposes. I wish I could see to the bottom of them, but I can’t. Either way, these holes are going to sit directly on the rib of the manifold that separates the two circuits. 

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@datzenmike I got a reply back from Weber. I think his grammar is worse than that of Ratsun!

 

"these of no concern

if you chose to seal them with a gasket which is common

however in common plenum manifolds ( large open Tub plenum if you will)
they are used for things like additional timed vacume or power break
fittings and PCV."

 

So, it looks like I'm just going to seal them over. He even said that on the DGV, most of the time the cast cylinders aren't even finished, so they aren't even cross-drilled or anthing.

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30 minutes ago, wayno said:

So they are saying one can use something on that carb for a PCV or drill and tap something for a PCV???


Yeah, I think I figured it out. Basically they use an intermediate spacer plate that is drilled and tapped for 1/4 NPT from the side, and then use a special gasket that redirects those ports. The guy was rambling on about “preconfigured kits,” and how certain carbs come with special adapters and additional machining if it’s required. He said in the K657 kit, those two ports are unfinished. The crappy part is that I’m adapting it to this Offy manifold, so half of the parts in the kit don’t work anyway. The good news is that it’s already jetted to all of the right specs, which I verified.

Edited by mainer311
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50 minutes ago, mainer311 said:


Yeah, I think I figured it out. Basically they use an intermediate spacer plate that is drilled and tapped for 1/4 NPT from the side, and then use a special gasket that redirects those ports. The guy was rambling on about “preconfigured kits,” and how certain carbs come with special adapters and additional machining if it’s required. He said in the K657 kit, those two ports are unfinished. The crappy part is that I’m adapting it to this Offy manifold, so half of the parts in the kit don’t work anyway. The good news is that it’s already jetted to all of the right specs, which I verified.

 

 

What jets might that be?

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10 minutes ago, d.p said:

Mainer didn’t you say you had no interest in a Weber because it sucked in hot air off the engine?  Something about the cooler air from the stock intake was superior??


I could have sworn that was you.  

 


Yes, and I still think the same thing.

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So, now the fuckin accelerator pump linkage hits the intake manifold and the carb won’t bolt on w/o the linkage preventing the secondary from opening all the way. It appears that a phenolic riser is supposed to be under the carb so that everything lines clears. I guess I know what I’m doing tomorrow.

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33 minutes ago, bilzbobaggins said:

What jets might that be?

 

See below. The only difference was that the idle jets were 55/55, so I bought a 50 and swapped it into the secondary side.

Main Venturi: 26/27 

Aux Venturi: 3.5/3.5 

Main Jet: 140/135 

Em Tube: F50/F6

Air Corr Jet: 165/160 

Idle Jet: 55/50

Pump Jet: 50

Needle Valve: 2.0

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17 hours ago, mainer311 said:

I picked up an air horn from Pegasus Racing for the DGV. For the money, it’s a pretty nice piece of machined aluminum, and full radius to boot.

 

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Be careful not to disrupt the airflow with a filter that's too short. The lid of the filter needs to be at least 3/4" above the velocity stack, or you may as well not even use it.

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