What is the correct fuel inlet orifice size within the brass "T"? I have seen larger size about 3/16" and smaller ones about an 1/8".Which would be correct with a Holley 4555?
Greg
Greg
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Re: 70 LT1 Brass Fuel Line "T"
Greg:
I measured the one on my LS-6, it is 5/16's. -
Re: 70 LT1 Brass Fuel Line "T"
Greg-----
I don't understand what you mean by "fuel inlet ORIFICE size". There is no "orifice", per se, in the fuel inlet block. The fuel line that connects at the inlet is 3/8". The tubing nut that attaches the tubing to the block is determined by the size of the tubing (which is 3/8"). The tapping in the block is determined by the size of that tubing nut.
There may be some minor differences in the size of the hole behind the tubing nut tapping, if that's what you're referring to, but the block used for a 1970 LT-1 was, by no means, unique. This block, GM #3886153, was also used for 1966 L-72, 1967-69 L-88, and 1970-72 LT-1. A different block of a different configuration was used for 1971 LS-6, though.
Curiously, the GM #3886153 block was NEVER available in SERVICE. For SERVICE, the part was GM #3866924. I don't know how that part differs. It may include a minor difference in the size of the hole behind the fuel inlet nut tapping. Nevertheless, the blocks are externally identical, I believe, and either one are 100 % functional for the applications.In Appreciation of John HinckleyComment
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Re: 70 LT1 Brass Fuel Line "T"
Inside the threaded area of the "T" block the size of the hole opening diameter differs from one block than the other that I had seen.The amount of fuel delivery is the real question.Smaller inlet hole less gas?
I never noticed this before until I looked at others.I am thinking maybe big block motors required the larger inlet than small blocks.What is your thoughts on this?
GregComment
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Re: 70 LT1 Brass Fuel Line "T"
Greg:
That is what I measured for my LS-6.Comment
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L88 has 3/8 inlet 5/16 outlets *NM*
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Re: 70 LT1 Brass Fuel Line "T"
Greg----
As I mentioned, the blocks used in PRODUCTION for 1966 L-72, 1967-69 L-88, and 1970-72 LT-1 were all of the same part number. Therefore, as far as GM was concerned, they were all the same. Even if some of them had been made slightly differently as to "orifice" size, this had absolutely nothing to do with application. The assembly line workers would not inspect parts of the same part number to determine "orifice" size.
If there are different "orifice" sizes that exist, then it's due to one of several things:
1) There were other part numbers used for other Chevrolet applications;
2) There were slight manufacturing differences between the original parts;
3) There were differences between the PRODUCTION and SERVICE parts. As I mentioned, the PRODUCTION part was never available in SERVICE. However, as far as GM was concerned, the PRODUCTION and SERVICE parts were equally functional for all catalogued applications;
4) There is a difference between the originals and later-manufactured reproduction blocks.
In any event, if the smaller "orifice" block concerns you, just drill out the "orifice" to the size you think it should be or the size you want. Very simple.In Appreciation of John HinckleyComment
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if the block is brass
and you want to redrill it to a larger DO NOT use a twist drill as it will grab and you will have a mess on your hands. brass should be drilled with a straight fluted drill bit so it does not want to "screw" itself in the brass piece like a "twist drill" will do. sometimes in a pinch you can take a "twist drill" bit and grind a negitive angle on the tips to prevent it from grabbing the soft brass material but this may not work all the time.Comment
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