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Author Topic: 1968 Camaro 327/210 - I want to convert to 4 barrell carb/intake  (Read 7139 times)
texasappraiser
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« on: July 13, 2006, 02:19:19 AM »

My '68 Camaro 327/210 is very original except for dual exhausts. I would like to put on a 4 barrell carb and intake manifold. But I want it to be the correct intake/carb for my '68. Not aftermarket. Anyone have Chevy #'s that could help? Will it match up with the stock heads? Thanks.
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CNorton
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« Reply #1 on: July 13, 2006, 06:07:29 AM »

The most common GM 4-barrel manifold for a 1968 327 has a casting number that ends with "803."  I'm unable retrieve the rest of the number for the time being (probably later today) but no doubt someone else will have it handy.  The 803 manifold will mount an appropriate Quadrajet carburetor and help you achieve a cosmetic transformation to a 327, 275 horseower combination.  Unfortunately, the 210 horsepower, 2-barrel heads won't do much for the added flow.  The casting number for a commonly used 1968 head will most likely end with "462" (again, I'll have access to the complete number later today).  The "462" has larger valves and ports that will match the manifold.  There are several other castings that would help you achieve a mechanically correct change-over but many of those numbers incorporate accessory-mounting bolt holes in the ends of the heads.  The correct head for 1968 would have the traditional "double-hump" casting mark and no holes.  If you are successful in locating an 803 manifold and 462 heads the rest of the swap will involve locating fuel lines, linkage, air cleaner parts, and miscellaneous hardware to get it all looking and working right.  It's a relatively simple changeover but a little more complicated than it appears at first glance.
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KevinK
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« Reply #2 on: July 13, 2006, 06:26:13 AM »

 I have a '68 327/275hp (hence Q-jet carb) and here are some numbers that are/would be factory correct:
If you're planning to change the intake (and carb) alone that should be fine,...but I've listed all the numbers anyway.

Intake = 3919803 (for 4 barrel, ...Q-jet)
Heads = 3917291 (for a 275hp motor)
                ...I just read CNorton's post (good info by the way), ...but wanted to add. The '462' (3890462) head he mentions is slightly earlier than the '291' head. The '291' head was used late '67 and all of '68. (Ref.  Colvin's By the numbers) ...The only visible difference between them is that the '291' head has the temperature sending unit boss in the head itself (where in earlier applications (ie. the '462') the sending unit was located in the intake.  This brings me to the point, ... that the Intake manifold (#3919803) will not have a hole for temp sending unit.

Carb = 7028212 (Quadrajet for a 275hp motor)
Dist = 1111297

...again, ...these numbers are correct for a 275hp car, ...if you're just wanting to add a 4 barrel carb, ...the intake # (3919803) is all you'd need.

Kevin
« Last Edit: July 13, 2006, 06:46:02 AM by KevinK » Logged
rich69rs
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« Reply #3 on: July 13, 2006, 10:05:42 AM »

Went just the opposite of the way you are going. When I purchased my '69RS (Base 327/210 Hp) coupe in Nov 1991, it had the incorrect 327 engine in it. The intake manifold on the engine was #3919803 with a 4BBl Rochester QJet. As mentioned above, this intake was for 1967-68 327 CID engine, 300/350 Hp. I recently sold it to another 68 Camaro driver who is doing the same thing that you are doing - 2 BBl to 4 BBl conversion.

If the heads for '68 327/210 Hp engine are similar to the 3927185 heads used for '69 (and they probably are), the valve sizes are 1.74" dia. intake, 1.54" exhaust. Although the 4Bbl "803" intake will have more capacity, the heads will still be the flow restriction and I don't believe that you will get the extra punch that you are hoping for.
 
For my car, I did the exact opposite - originality was key to me, so I wanted the 2BBl setup. The '69 327/210 2BBl engine that is in my car now runs and performs better than the engine originally in the car because everything works well together. When I had the correct '69 327 engine rebuilt in 2005, I enlarged the intake valves in the "175" stock heads from 1.74" dia. to 1.94" dia. and installed a slightly different cam to help the low end. Engine has very good low end torque and response. 2 Bbl just dies about 4200 rpm. But then I'm not going to run the car that hard. With the Powerglide and 2.73:1 rear end, cruising a 70 mph is about 2400 rpm - and the car goes 0-60 reasonably well.

If you install the "803" intake or any similar intake, please note the post below from JohnZ regarding this type of mainfold. The "803" intake that I sold had the hot slot.

 Re: Q-Jet swap problem
Reply #1 on: 07 January 2006, 09:52:55

--------------------------------------------------------------------------------
Can't help you with the mismatch issue, but if your intake has the "hot-slot" like the one in the photo below (that's an intake for a Holley, but the same "hot-slot" design was used on many cast-iron Q-Jet intakes), I recommend plugging the holes at each end of the slot with core plugs as shown in the photo. That slot is connected to the exhaust crossover passage, and allows hot exhaust gases to heat the carb base at cold start for improved atomization of the air-fuel mixture, with a stainless steel heat baffle to protect the carb base from direct impingement of the hot gases. Unfortunately, that heat also fries/distorts the carb base and can cause the bottom well plugs to fall out of the Q-Jet float bowl, resulting in engine fires. GM recalled millions of Q-Jet-equipped cars with this "hot-slot" design in 1969 due to the fire problem, and abandoned the "hot-slot" design in 1970.

 
 
« Last Edit: July 13, 2006, 10:27:30 AM by rich69rs » Logged

Richard Thomas
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texasappraiser
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« Reply #4 on: July 13, 2006, 11:26:16 AM »

Thanks for the replys!
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nuch_ss396
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« Reply #5 on: July 13, 2006, 02:32:19 PM »

Guys,

Isn't there also a cam difference between the 2-bbl & 4-bbl 327 engines?

I've been into big blocks for far too long, so the small block stuff has blurred a bit.
We did this very same 2-bbl to 4-bbl thing as kids all the time. Caming always seemed
to be the limiting factor there.

Perhaps some of the SB guru's here can comment further.

Steve
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69 SS 396, Hugger Orange, D/80, D/90
Chambered Exhaust, N/66, THM400, 3:73 posi

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CNorton
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« Reply #6 on: July 13, 2006, 07:57:43 PM »

The camshaft specs were the same in both small blocks.  Intake lift = .390; Exhaust lift = .410.
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opelitis1
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« Reply #7 on: December 05, 2008, 05:27:49 AM »

Hope I am not hi-jacking the thread a bit, but, I always wondered what that slot was for and now I know...  Gonna check my intakes and plug up the holes on the fire slot designed intakes... Were 69/70 intakes the only ones with this hazard??
Over the years we buy and sell stuff w/o really knowing all the ins 'n outs ... so to speak.
Thanks for this valuable potential life-saving info...
Ted
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KurtS
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« Reply #8 on: December 05, 2008, 03:50:46 PM »

As discussed here, http://www.camaros.org/forum/index.php?topic=4688.0, the 2 barrel carb has plenty of flow. Though the 4bbl looks cooler, it won't necessarily run faster.
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Kurt S
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brad68RS
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« Reply #9 on: November 24, 2010, 08:10:00 PM »

Hey texasappraiser! if you make or have made the swap from the 2 barrel to the 4 barrel would you like to sell what you took off?
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