[tremo]

Is it normal for a '70 factory cast iron 4-bbl manifold to have the PCV port capped? I'm nearly done building a 400ci and plan to use the manifold pictured below.

As you can see there is a cap fitting right next to the "GM 2". Now my existing 350ci manifold has a 90 degree fitting in this same location with a vacuum line going down to the valley pan PCV valve and into the grommet.

I believe the car previously had a QuadraJet installed. It's the Chevy version (side angle fuel inlet), but since I purchased the entire motor disassembled I'm not 100% sure what was on the motor before they tore it down. I plan to use a Holley 4160 750cfm with vacuum secondaries. I would imagine that regardless of the carb, having the PCV valve installed and working properly is a good thing.

As such, I'm wondering if I need to remove the fitting off my 350ci manifold and install it on the 4-bbl manifold and/or the reasoning behind capping the PCV port in the first place?

Thanks!

Jim.

[shaker455]

Someone capped it and it was not the way it came from the factory.

Yep! by all means use your PCV

[Held for Ransom]

Doesn't even look like a '70 manifold (I think that's a '72 unit). Remove the fitting from the 350 manifold and use that. I don't know what you will use for the throttle bracket.

[tremo]

Thanks guys! I've removed the elbow fitting from my 2-bbl manifold and will install it on the 4-bbl.

HFR, what are the diff's between a '70 and a '72 manifold that could cause me some grief using the Holley 4160? Thought they started adding the EGR stuff around '72 and obviously this manifold doesn't have that.

Ah, I just zoomed in on the picture (the engine is at the shop) and see "J151" stamped right next to the thermostat opening: 10-15-71. So, I guess the question becomes what (if anything) do I need to worry about when using this '71 manifold w/ my Holley?

Also, why wouldn't my 350ci throttle bracket work? Looks to me like it'll bolt up the same??? Just trying to eliminate any headaches before we install it and fire 'er up...

Thanks for any advice!

Jim.

[JSAauto]

The holley bowl looks like it will hit the 90 degree fitting. You may need to use a carb spacer to get the carb higher so it wont hit the fitting.

The throttle cable brackets are different from a 2bbl to a 4 bbl. I think one says H-2 and the others say H-4. The distance from where the cable mount is from the ear of the 2bbl carb is different from the 4bbl. You may be able to use a hammer and smack it to get the right pull on the carb.

[mchell]

Interestng that only one side of the water crossover is drilled and tapped. All the 71 manifolds I have seen have both sides drilled and tapped. I would guess a 72 also........

[WARPed]

1973 is when the EGR was used. Functionally the 1967-72 intakes are the same the cast part number ending in 068 is a 70 intake.

[tremo]

Thanks all!

JSAuto, excellent point. Hadn't even thought about the bowl hitting the 90 elbow for the PCV. Fortunately I plan to use a 3/4" square-bore (carb) to spread-bore (manifold) adapter. I took a quick measurement of the elbow and it'll be close. We'll see. Thanks for the details on the throttle bracket too. Yet another area that may require some tweaking and/or a bracket change for the Holley.

Aside from using a QuadraJet (more expensive to rebuild on my budget vs. a new Holley 4160), I could not find a *new* spread-bore carb - Holley, Edelbrock, etc. Hence the adapter.

Q: What do you guys think about using a square-bore to spread-bore adaptor? The Holley carb installation guide says they don't recommend them ("...since adapters may have an adverse affect on cylinder-to-cylinder distribution and ultimately, total engine performance."), yet #17-6 is listed as a recommended accessory for the #4160 on Holley's site?!

mchell, yeah I also thought it was odd that only one side was tapped. Looking my two barrel manifold, the right side (not tapped on the 4-bbl) is the water temp sensor and the left side is for a 4-port vacuum "manifold".

The vacuum source port hose leads to the base of the carb, another port leads to the distributor vacuum advance and the other two are capped. Since the 4-bbl seems to have the left side tapped for the water temp sensor, instead of the right, I'll use it instead and simply use the Holley for the other vacuum lines.

WARPed, the casting number is 485912. Any ideas on the year? (I thought the date code of J151 was the month & year?)

Good stuff, thanks again!

Jim.

[rolling money pits]

(I thought the date code of J151 was themonth & year?)



october 15th, 1971.

maybe a month later, november, i thought the factory skipped a letter somewhere.

[WARPed]

The date code makes it a 1972.