[JIM68]

What's the difference between spread bore and square bore intake manifolds and carburators? I've got this intake (from a 275hp 327) What is it?


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1968 Coupe, 327/210hp project in process.
PS/PB, Factory AC

[CamaroNOTcamero]

its a spread bore, spread bore's are for Q-jets and they have two big rear holes and two smaller front ones spread apart. square bores are usually just two open halves (for dual plane) and a square flange.

[Eric68]

Jim - I noticed you've posted a number of nice pics and graphs on this board. How do you post a pic? I've never been able to figure it out.

Thanks

Eric

ps. your manifold is a spreadbore - spreadbore just means that the secondary barrels are larger than the primaries. Squarebore means all four barrels are the same size.

[JIM68]

Eric 68,

the hardest thing about posting pics is that you need to have them saved somewhere else on the internet. Like if your internet provider giives you 10MBs of wed space... you need to find out how to upload to those spaces them link to them in your post. Check this page out: http://www.camaros.net/forum/ubbcode.html
There are some free web space site on the net if your server doesn' give you any. I don't know of any off hand, but just search for those family photo sharing sites.

Thanks for the info guys!

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1968 Coupe, 327/210hp project in process.
PS/PB, Factory AC

[This message has been edited by JIM68 (edited 01-26-2002).]

[Eric68]

Thanks Jim - I'll give that a shot sometime. I do have about 5mb of space through my ISP and have been playing around with it a bit.

[Sleepy-69]

That appears to be a '184' intake from a 1969 Chevy sb. It has the blocked oil-fill, recessed choke coil mount, open-exhaust ports to the carb...which by the way,..don't run this without a heat baffle (between the carb and the intake) which blocks this heat from boiling the fuel in the carb. I learned this the hard way...as I do most everything.

[bonecrusher67conv]

Intake with the last 3 digits of 803 was for late 66 to mid 67 327/275hp or 350's.

Anyone using two metal rods to plug up the exhaust crossover under the front of carburetor on this manifold? I've been thinking of blocking these two 7/16" sized exhaust ports off completely.

[JIM68]

The intake in the picture is a "3919803"

Anyone object to me blasting this manifold with aluminum oxide? Or should I use glass beads?

And what should I do about this whole exaust heat ordeal? Is it a serious problem?

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1968 Coupe, 327/210hp project in process.
PS/PB, Factory AC

[This message has been edited by JIM68 (edited 01-28-2002).]

[This message has been edited by JIM68 (edited 01-28-2002).]

[bonecrusher67conv]

Ok, I felt uneasy about shooting numbers off the hip/memory. So, I have the book open right in front of me and these are all numbers for cast iron rochester 4bbl.

I was wrong about the 67, instead the 4bbl rochester intake is 3905393. I should have went to the shop, there is one of those sitting on a shelf.

For 68 the 3919803 is the 4bbl rochester intake. For 69 it was 393927184 (300hp) or 3958626 (250hp) or 3987361 (300hp).

Sorry for my bad memory glands.

[bonecrusher67conv]

To glass bead the manifold it will take forever unless you have an industrial blast cabinet.
You won't have any problem blasting it with aluminum oxide or even sand. Since it is not an aluminum intake you don't have to be so gentle with it and glass beads just don't cut through rust like aluminum oxide does.

FOr the bottom heat shield, that will pop off relatively easy by taking a chisel and pounding under the 4 rivet heads. Just hold the chisel at like a 60degree angle to the rivet head and hammer away.
To reattach the shield, it makes me uneasy to reuse the rivets. So, what I've been doing is tap threads into the rivet holes and then use short hex head bolts to secure the heat shield. Since the holes are so close to the edge of the sheet metal, you just bend up the corners of the shield so they act as a lock against the hex head.

The only reason I mentioned blocking off the small exhaust cross-over holes, was that I'm thinking the extra heat added to the carb during hard summer driving has a tendency for the heat to evaporate gas off and make starting harder after parking it for a few minutes. At least my car anyway. By no means is this a huge problem, it just causes a little extra cranking and time to figure out if you are flooded or fuel starved.


[This message has been edited by bonecrusher67conv (edited 02-03-2002).]

[JIM68]

Thanks guys, I've access to a blasting cabinet and all the taps known to man, so I'll definitely be putting your tips to use.

[JohnZ]

Tap the holes at the ends of the "heat groove" for pipe plugs - you do NOT want that functional, even with the stainless heat shield gasket required - even with the shield, that design fried thousands and thousands of Q-Jets and rendered them not only unusable, but unrebuildable as well; GM stopped using that design in '69 after the biggest carburetor recall in history.

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JohnZ
CRG
'69 Z28 Fathom Green

[JIM68]

Are we talking about the heat groove holes at the arrows?

I guess I'll plug them too, maybe throw a weld in there... but tapping and plugging seems best.

thanks a million

[Sleepy-69]

John-Z is absolutely correct. It took me forever to diagnose problems caused by the described exhaust heat (perculating fuel in the fuel bowl, rough idle, no power, backfiring, etc).

Another solution I did to correct this problem is to sandwich two of the thin stainless heat shields between three gaskets (Fel-Pro #60043...good thick reinforced gasket), and since, I've had no problems on a 69 SS-350 car. After the engine is good and warm, the carb is very cool to the touch. The heat shields seem very effective.

Good luck!