manifolds/headers - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**kwmech** · 12-08-2005, 11:31 AM

No not the debate. A little brief history. 69 GMC 1 ton dually. Factory 350/400 converted to 400 small block with a serpentine set-up. I moved the engine back 1'' with the big block stands and am going to use the big block fan shroud. Seeing as how I have a large dimple in the engine stands, looks like plenty of room for some later model exhaust manifolds so the plug wires can come across the top. Any ideas on which cast iron manifolds will fit and get dececnt flow. I have been looking at the later model truck that has the O2 hole in the left side. (will be going to tbi this following summer) Any other ideas? Thing is, I do not want to keep running around buying manifolds to see what fits and doesn't. Some of these have to be special ordered. I may be open to some headers but will prefer the cast irons.

mblackburnjr · 12-08-2005, 05:09 PM

I can attest that you dont want circa '84 monte carlo manifolds. The drivers side dumps right on top of left hand dipstick blocks...

**kwmech** · 12-08-2005, 09:26 PM

I was considering something later model with the O2 sensor hole, probly something after 86 or 87 maybe.

**kwmech** · 12-09-2005, 12:19 AM

102 views and 1 reply. Somebody should have an idea, or am I the only one to put a small block on big block stands

mblackburnjr · 12-09-2005, 12:23 AM

My manifolds may be a little later, i was just guessing. It seems like i saw an o2 sensor.....anyway, just keep the dipstick thing in mind if you have to search out a pair.

Tim240Z · 12-09-2005, 02:22 PM

The L31 manifolds will NOT fit, so take those off your list. The headers rest on the frame before the engine mounts are within an inch or so from the pads.
FWIW, I tried the manifolds from a 99 suburban, OBS with the 5.7L Vortec.....
Sorry I can't help with something that actually fits.....I would look towards the F-body and corvette manifolds as those engine bays are tight, so the manifolds tend to be very compact.....and generally flow fairly well...

Tim

**basketcase** · 12-09-2005, 02:39 PM

If you can find something that fits don't worry about the O2 sensor. You can weld a bung in the front pipe for that. Most GM cars were in the pipe in the '80s anyway. Summit and any header company sells the bung. I used '81 Corvette manifolds on mine. They do require the plug wires to be run underneath as stock. They are a stainless tube shorty header and look nice with the heat shields and AIR tubes removed. Just weld up the holes. They are the same comfiguration as the old ram horns with a center dump.

Tom

**kwmech** · 12-09-2005, 09:18 PM

Thanks Tim240z, I'll look in that direction,

Basketcase, I know about the weld in bung, I was wanting to put the shorter wires above the manifolds. That way I do not have to worry about the plastic clips burning/breaking and the wires falling into the hot manifold, everything up top and easier to service.

Thanks for the replys guys.

DangerBoy · 12-10-2005, 07:42 PM

I'd go for a nice set of shorty headers. You should have plenty of clearance even with the engine moved back an inch.

**kwmech** · 12-10-2005, 08:18 PM

Not exactly crazy about the header idea, but that is how it is looking at the moment, probably a good pair of ceramic coated ones.

Tx Firefighter · 12-11-2005, 07:36 AM

I'd look at 73-80ish truck manifolds. They are the down low type that allow the plug wires to come in from the top. Beware though, there are two types. One type has the three legs that bolt to the head, and the other type has the three legs, but connected by a small bar. GM found that the manifolds would warp and the three legs would get out of alignment with each other. They added the bars on later ones to keep them all in alignment and stop the warping problem. What I'm saying is that the earlier ones sometimes look fine, but when you try to bolt them to the engine, you can't get some of the bolts started due to the warpage.

Tx Firefighter · 12-11-2005, 07:40 AM

Here's two pictures to clarify what I'm talking about. Notice the bar on the ones in the first picture that is missing on the second picture. You want the bar.

Russell · 12-11-2005, 01:58 PM

I wish they'd have used those bars on the 87+ manifolds! Them things warp something nasty, I had to make a hydraulic spreader just to get them back onto my 89, and now they leak real bad too

Tx Firefighter · 12-11-2005, 02:09 PM

Good idea Russel.

I didn't think of trying to make one. I bought mine off the Snap-On truck.

12-08-2005, 11:31 AM	#1
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,573	manifolds/headers No not the debate. A little brief history. 69 GMC 1 ton dually. Factory 350/400 converted to 400 small block with a serpentine set-up. I moved the engine back 1'' with the big block stands and am going to use the big block fan shroud. Seeing as how I have a large dimple in the engine stands, looks like plenty of room for some later model exhaust manifolds so the plug wires can come across the top. Any ideas on which cast iron manifolds will fit and get dececnt flow. I have been looking at the later model truck that has the O2 hole in the left side. (will be going to tbi this following summer) Any other ideas? Thing is, I do not want to keep running around buying manifolds to see what fits and doesn't. Some of these have to be special ordered. I may be open to some headers but will prefer the cast irons.

12-08-2005, 05:09 PM	#2
mblackburnjr collector of vintage rust Join Date: Apr 2004 Location: southern ohio Posts: 421	Re: manifolds/headers I can attest that you dont want circa '84 monte carlo manifolds. The drivers side dumps right on top of left hand dipstick blocks...

12-08-2005, 09:26 PM	#3
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,573	Re: manifolds/headers I was considering something later model with the O2 sensor hole, probly something after 86 or 87 maybe.

12-09-2005, 12:19 AM	#4
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,573	Re: manifolds/headers 102 views and 1 reply. Somebody should have an idea, or am I the only one to put a small block on big block stands

12-09-2005, 12:23 AM	#5
mblackburnjr collector of vintage rust Join Date: Apr 2004 Location: southern ohio Posts: 421	Re: manifolds/headers My manifolds may be a little later, i was just guessing. It seems like i saw an o2 sensor.....anyway, just keep the dipstick thing in mind if you have to search out a pair.

12-09-2005, 02:22 PM	#6
Tim240Z Senior Member Join Date: Jan 2005 Location: LAX area, So Cal Posts: 499	Re: manifolds/headers The L31 manifolds will NOT fit, so take those off your list. The headers rest on the frame before the engine mounts are within an inch or so from the pads. FWIW, I tried the manifolds from a 99 suburban, OBS with the 5.7L Vortec..... Sorry I can't help with something that actually fits.....I would look towards the F-body and corvette manifolds as those engine bays are tight, so the manifolds tend to be very compact.....and generally flow fairly well... Tim __________________ 1972 Suburban C20 454/TH700R4, eaton-corporate 4.10 (looking for 3.7) Sold: 71 Cheyenne 20 Installed a 99 5.7L L31/4L60E from Suburban 1500 (2005)

12-09-2005, 02:39 PM	#7
basketcase Senior Member Join Date: Oct 2001 Location: Edgerton OH USA Posts: 632	Re: manifolds/headers If you can find something that fits don't worry about the O2 sensor. You can weld a bung in the front pipe for that. Most GM cars were in the pipe in the '80s anyway. Summit and any header company sells the bung. I used '81 Corvette manifolds on mine. They do require the plug wires to be run underneath as stock. They are a stainless tube shorty header and look nice with the heat shields and AIR tubes removed. Just weld up the holes. They are the same comfiguration as the old ram horns with a center dump. Tom __________________ '69 swb stepside in progress. '59 Corvette lifetime project

12-09-2005, 09:18 PM	#8
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,573	Re: manifolds/headers Thanks Tim240z, I'll look in that direction, Basketcase, I know about the weld in bung, I was wanting to put the shorter wires above the manifolds. That way I do not have to worry about the plastic clips burning/breaking and the wires falling into the hot manifold, everything up top and easier to service. Thanks for the replys guys.

12-10-2005, 07:42 PM	#9
DangerBoy Registered User Join Date: Nov 2005 Location: Springville, Ca Posts: 270	Re: manifolds/headers I'd go for a nice set of shorty headers. You should have plenty of clearance even with the engine moved back an inch. __________________ 2002 S10 ZR2 for the dirt. 1968 C10 shorty for the street. She said the truck would be the end of us. I still have the truck!

12-10-2005, 08:18 PM	#10
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,573	Re: manifolds/headers Not exactly crazy about the header idea, but that is how it is looking at the moment, probably a good pair of ceramic coated ones.

12-11-2005, 07:36 AM	#11
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: manifolds/headers I'd look at 73-80ish truck manifolds. They are the down low type that allow the plug wires to come in from the top. Beware though, there are two types. One type has the three legs that bolt to the head, and the other type has the three legs, but connected by a small bar. GM found that the manifolds would warp and the three legs would get out of alignment with each other. They added the bars on later ones to keep them all in alignment and stop the warping problem. What I'm saying is that the earlier ones sometimes look fine, but when you try to bolt them to the engine, you can't get some of the bolts started due to the warpage. __________________ I'm on the Instagram- @Gearhead_Kevin

12-11-2005, 07:40 AM	#12
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: manifolds/headers Here's two pictures to clarify what I'm talking about. Notice the bar on the ones in the first picture that is missing on the second picture. You want the bar.

12-11-2005, 01:58 PM	#13
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Re: manifolds/headers I wish they'd have used those bars on the 87+ manifolds! Them things warp something nasty, I had to make a hydraulic spreader just to get them back onto my 89, and now they leak real bad too __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap) Last edited by Russell; 12-11-2005 at 01:58 PM.

12-11-2005, 02:09 PM	#14
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: manifolds/headers Good idea Russel. I didn't think of trying to make one. I bought mine off the Snap-On truck. __________________ I'm on the Instagram- @Gearhead_Kevin



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