71 LT-1 Holley baseplate dilemma

[Mike E.]

At some point in the past, a PO bought a very pretty ebay list 4801 Holley. As I prepare to use it, I find that the boss that should be tapped for the vacuum to the PCV valve is not drilled and has no metal tube in it. I have a couple of questions that I'd love to have answered: 1)can I simply drill the hole in the boss and secure a metal tube in it? I don't have an appropriate Holley to look at and compare. 2) If the answer to (1) is yes, what is the OD of the hole/metal tube? 3)Does anyone know a ready source for the correct baseplate or tube? P3132587.jpgP3132588.jpgP3132590.jpgI have no idea why my post added the 4th pic separately, but it won't go away. Pics 2 and 3 are the baseplate boss from the outside and then from the underside.

[Phil A.]

Re: 71 LT-1 Holley baseplate dilemma

Mike, I just colored and restored my 4801 and it is the original carb. It appears you could drill through the base plate with no problems. I think Chicago Corvette was selling the nos base plate at one time for the 4801. I would have to measure OD of the hole/tube when I get home this evening. By the way the carb I have says 4801, 082,3989021, made with in 2-3 weeks of yours.

[Dick W.]

Re: 71 LT-1 Holley baseplate dilemma

Reverend, refresh my memory. Is the tube pressed in or does it have a nut that screws into a fitting on the base? Old memories are gone

[Paul O.]

Re: 71 LT-1 Holley baseplate dilemma

Mike

That is a pressed in tube here is a photo that I think is correct.

[Dave S.]

Re: 71 LT-1 Holley baseplate dilemma

At some point in the past, a PO bought a very pretty ebay list 4801 Holley. As I prepare to use it, I find that the boss that should be tapped for the vacuum to the PCV valve is not drilled and has no metal tube in it. I have a couple of questions that I'd love to have answered: 1)can I simply drill the hole in the boss and secure a metal tube in it? I don't have an appropriate Holley to look at and compare. 2) If the answer to (1) is yes, what is the OD of the hole/metal tube? 3)Does anyone know a ready source for the correct baseplate or tube? [ATTACH=CONFIG]51554[/ATTACH][ATTACH=CONFIG]51555[/ATTACH][ATTACH=CONFIG]51557[/ATTACH]I have no idea why my post added the 4th pic separately, but it won't go away. Pics 2 and 3 are the baseplate boss from the outside and then from the underside.

Mike,
Do these help.???

[Phil A.]

Re: 71 LT-1 Holley baseplate dilemma

The tube is pressed in and it is a 3/8 OD .377inch. You probably could rob a tube off any other old holley 4bl that wasn"t worth saving. By the way what head markings are your 71 intake bolts and thermastat housing.

[Timothy B.]

Re: 71 LT-1 Holley baseplate dilemma

Mike,

FWIW, that tube may even still be available from Holley or Chicago Corvette Supply.

[Mike E.]

Re: 71 LT-1 Holley baseplate dilemma

Thanks for the help, guys. I have the tube coming from everybody's ebay friend, Gray Gracy

[Timothy B.]

Re: 71 LT-1 Holley baseplate dilemma

Mike,

I can't give the dimension of the hole to drill but I would not undersize it. Mic the tube and drill to that size and get some loctite and install. You will not have any problems with that and it won't budge using the loctite.

You may want to remove the base and check the top and bottom for flatness just to be sure all is good.