When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Having a valve job done on my L76. Contemplating an intake manifold change at this time instead of the aluminum stocker. Only 2 concerns, however. All attachments mount same position as stock and no additional height for hood clearance. Anyone here have an experience they care to share? I could go either way. Performance improvements a plus of course.
Most if not any aftermarket intakes are just copies of GM designs and most only offer performance at higher RPM Find a better problem to add performance
Most if not any aftermarket intakes are just copies of GM designs and most only offer performance at higher RPM Find a better problem to add performance
Hi rpm is where an L76 spends most of it's time......Just toying with the pro's and con's. Factory carb and cam will nicely support additional intake related performance gains.
Having a valve job done on my L76. Contemplating an intake manifold change at this time instead of the aluminum stocker. Only 2 concerns, however. All attachments mount same position as stock and no additional height for hood clearance. Anyone here have an experience they care to share? I could go either way. Performance improvements a plus of course.
The biggest bang for the buck would be to skip the valve job on the stock heads and spend the money instead on a new set of the Trick Flow DHC heads. These will greatly out-perform your stock heads, and visually they look just like the stock heads (painted Chevy orange, of course).
The best stock intake is the one used for the Z28 and LT1 engines. These intakes have better flow than the L76 intake, and if you choose carefully (paying close attention to the placement of the thermostat housing), you can have very similar appearance to the L76 intake and complete compatibility. A less expensive option would be an Edelbrock intake, but the appearance does not quite match the stock L76 intake.
Regarding hood clearance, the attached chart shows a comparison that I put together a few years ago. Your stock L76 intake matches the 4.19" height of the L79 intake. The 4.69" height of the Z28/LT1 intakes is marginal for the C2 when used with the 1966-1967 air cleaner. On some cars it fits, and on others it interferes just a little bit. You can add some shims to each body mount to gain some hood clearance.
The 327 (.040) in my car is running the Trick Flow DHC 175 heads and an Edelbrock 2703 intake manifold with oil fill tube. The oil fill tube that comes supplied with the 2703 manifold is a bit chintzy. A chrome factory style oil fill tube was ordered up as a replacement. The factory style tube fit had a nice firm feel to it seating it into the hole in the Edelbrock manifold.
Slightly taller than the factory 490 manifold the Edelbrock 2703 fit under the stock hood was acceptable. A drop base air cleaner will be required. A 2 inch tall drop base air cleaner as installed. It did restrict air flow. The air filter top was modified to accommodate more air filter media that was installed to help carb air flow.
The 1968 Z/28 intake is the best choice. The fittings for heater hoses, temp sender and thermostats housing are almost identical to the L76 intake. I bought a 69 Z/28 intake which works but you can’t use the thermostat housing on the L76. I also had a machine shop take 1/8 off the intake to help hood clearance. After getting the intake on I would have been find. Here is a picture.
The 327 (.040) in my car is running the Trick Flow DHC 175 heads and an Edelbrock 2703 intake manifold with oil fill tube. The oil fill tube that comes supplied with the 2703 manifold is a bit chintzy. A chrome factory style oil fill tube was ordered up as a replacement. The factory style tube fit had a nice firm feel to it seating it into the hole in the Edelbrock manifold.
Slightly taller than the factory 490 manifold the Edelbrock 2703 fit under the stock hood was acceptable. A drop base air cleaner will be required. A 2 inch tall drop base air cleaner as installed. It did restrict air flow. The air filter top was modified to accommodate more air filter media that was installed to help carb air flow.
John
I agree that the Edelbrock 2703 with the front oil fill tube is about the only option for buying a brand new intake that has the oil fill tube.
Regarding factory aluminum intakes, if you look at just the flow characteristics, there were really just two basic designs:
1) The aluminum intake used on C2 engines from 1963-1967 (3794129, 3844461, 3890490)
2) The much improved aluminum intake used on the Z28 and LT1 engines from 1967-1972 (3917610, 3932472, 3959594, 3972110, and service 3972116, 14044836)
While there are several different casting numbers within both generations of intake, the only differences were things such as the placement of the thermostat housing and oil fill tube. For example, careful study will reveal that on some versions the thermostat housing was centered, while other versions had the thermostat housing moved off center and rotated. And, some versions have the oil fill tube tilted toward the driver side, while others have it tilted toward the passenger side. Some versions provide a "choke stove" on the passenger side of the carb, while others don't. And some have the boss for the oil fill tube but it is not bored out.
All of the original production castings are pretty expensive ($500+) if you want one in good shape. The service castings for the second generation intakes are usually less, since they are not desirable for a numbers-matching restoration.
So, if you want a replacement for your L76 intake that flows better and still looks stock, I think the second-generation intakes listed above are what you have to choose from.
With all the above being said, I want to reiterate the comment I made in post #10 above. You wont get much bang for the buck by changing the intake. You would be far better off changing to the Trick Flow DHC heads that look stock.
Most of the intake comparisons in car magazines show only small variations of 10-20 peak hp over the various manifolds tested, and this testing is usually done with open headers. The high restriction of your stock sidepipes will greatly decrease any performance benefit you get from changing the intake. I doubt you will be able to feel the difference.
The stock L76 intake was a "performance" intake in the 1960's, but better "performance" intakes have come out since then. The problem is that they are only slightly better, and without a low restriction exhaust, the power increase will be very small.
Very good gouge, Joe. I like it when people know what the heck they're talking about. I thank you.
Hi Don:
I'm not sure what "gouge" means in this context, but it sounds painful. I'm just trying to be helpful.
If you still have time to call off the valve job and buy the Trick Flow DHC heads instead, your engine will look bone stock but you will feel the increase in power, even with the stock sidepipes. The benefits of the improved heads will be noticeable throughout the entire rpm range. While the sidepipes will limit the power gain at high rpm, I think the gain will still be enough for you to feel it there too.
BTW, if you look at my post #42 in the following thread, you will see some more info about how the Trick Flow heads compare to stock heads:
02-04-2024, 05:04 PM
Contemplating a Change......
Better flo = more go . 
