What size tap for a header bolt hole in block - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Mrturner1 · 03-05-2016, 04:15 PM

Anybody know off hand

**'68OrangeSunshine** · 03-05-2016, 04:59 PM

3/8-16 UNC on the L6

franken · 03-05-2016, 05:00 PM

There are no header bolt holes in the block.
Try 3/8 coarse.

**'68OrangeSunshine** · 03-05-2016, 05:01 PM

I think he meant the head.

Mrturner1 · 03-05-2016, 05:07 PM

Quote:

Originally Posted by '68OrangeSunshine

3/8-16 UNC on the L6

Is L6 a 70' 350?

**'68OrangeSunshine** · 03-05-2016, 05:43 PM

Quote:

Originally Posted by Mrturner1

Is L6 a 70' 350?

An L6 is a 250 or 292. You got a V8. I don't know, in that case, it might have a smaller diameter. My SBC uses 7/16 bolt heads on the manifold exhaust holes, IIRC. 3/8 bolts have 9/16 bolt heads. Sorry I don't know it offhand.

Metaldoc · 03-05-2016, 06:41 PM

3/8-16 nc on exhaust bolts, header bolts have a smaller head but still have that thread.

**special-K** · 03-06-2016, 11:36 AM

^^^ Correct, now that we know what you have.

03-05-2016, 04:15 PM	#1
Mrturner1 Registered User Join Date: Nov 2015 Location: Colfax California Posts: 1,644	What size tap for a header bolt hole in block Anybody know off hand

03-05-2016, 04:59 PM	#2
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,436	Re: What size tap for a header bolt hole in block 3/8-16 UNC on the L6 __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

03-05-2016, 05:00 PM	#3
franken Registered User Join Date: Jun 2013 Location: Somewhere Posts: 3,102	Re: What size tap for a header bolt hole in block There are no header bolt holes in the block. Try 3/8 coarse.

03-05-2016, 05:01 PM	#4
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,436	Re: What size tap for a header bolt hole in block I think he meant the head. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

03-05-2016, 06:41 PM	#7
Metaldoc Registered User Join Date: Apr 2015 Location: Ayr Ontario Posts: 1,122	Re: What size tap for a header bolt hole in block 3/8-16 nc on exhaust bolts, header bolts have a smaller head but still have that thread.

03-06-2016, 11:36 AM	#8
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,852	Re: What size tap for a header bolt hole in block ^^^ Correct, now that we know what you have. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~



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