On the L-69 & LG4 engines, are the factory intake manifold bolts all the same length, or were some shorter than others? I can't remember.
I know about the potential pushrod interference issue for cylinders #4 & #5, but the added thickness of the lifting brackets on the corners would necessitate a slightly longer bolt.
I bought a set of ARP intake manifold bolts for SBC and they were only 1 inch long. They also came with washers. Well my intake manifold is 5/8" thick which would leave only 3/8" of threads, add the washer and the thickness of the intake gaskets and that would leave almost nothing. I sent them back and ordered a set for BBC which are 1-1/4" in length. So now I'm wondering if I should I have kept the 1-inch bolts as well and used both lengths...

 

The factory intake manifold bolts for the Chevrolet L-69 and LG4 engines typically have varying lengths. These engines were used in various applications, and the intake manifold bolt lengths could vary depending on factors such as the specific intake manifold design, cylinder head type, and any added components like lifting brackets or spacers.

Given that you mentioned the possibility of added thickness due to lifting brackets, it's possible that some bolts might be shorter to accommodate these brackets. Using longer bolts from a BBC (Big Block Chevrolet) set could potentially work, but it's essential to ensure that they don't bottom out or interfere with any internal components within the engine.

To be sure of the correct bolt lengths for your specific setup, it's a good idea to consult the factory service manual for your particular vehicle or engine. The manual should provide detailed specifications for the intake manifold bolts, including their lengths and any specific recommendations for your application.

 

The intake is the same thickness at all holes. The bolts all could be 1¼" if there was nothing else there. But there is, so a couple of them are longer (1½"), and one or 2 are studs with provisions for a nut. Pretty sure the front driver's side one is like that, for an AC bracket.

Be careful not to use bolts that are too long. The center 2 on each side go all the way through to the rocker gallery and are DIRECTLY in line with push rods, therefore a too-long bolt can bind them up. The other 4 holes are blind and often full of rust and crud down in there since they are on either side of water jackets, so a too-long bolt in any of those can bottom out and break, strip, etc.

 

What the heck was all this garble? Post #1 from a Chinese bot network or something? Whole bunch of regurgitation ending with "consult the factory service manual". Not helpful at all. At least couch potato had a useful answer.