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Lumps for a GMC 302? #63111 02/03/11 04:45 PM
Joined: Feb 2011 Posts: 7 NorCal Q quicksilver02 OP Active BB Member
OP quicksilver02 Active BB Member Q Joined: Feb 2011 Posts: 7 NorCal	Does anyone make bolt-in lumps for a GMC 302 head? I've looked at the lumps on both Tom Lowe's and Larry's (Twisted 6) websites, but they seem to be only for the Chevy 6's. - Nate

Re: Lumps for a GMC 302? quicksilver02 #63126 02/04/11 11:32 PM
Joined: Oct 2007 Posts: 5,015 Likes: 47 Northern Nevada Beater of the Pack 1000 Post Club
Beater of the Pack 1000 Post Club Joined: Oct 2007 Posts: 5,015 Likes: 47 Northern Nevada	I don't know of anything like that for the older engines. The port design is totally different. The 302 ports are huge. Lots of old timers preferred the smaller ports for street use. "I wonder if God created man because he was disappointed in the monkey?" Mark Twain

Re: Lumps for a GMC 302? Beater of the Pack #63133 02/05/11 05:44 PM
Joined: Sep 2008 Posts: 3,669 Likes: 42 N. Georgia CNC-Dude #5585 1000 Post Club
CNC-Dude #5585 1000 Post Club Joined: Sep 2008 Posts: 3,669 Likes: 42 N. Georgia	The lumps would have to be T-shaped because the port is shaped similarly. This would make the insertion of them impossible because the width of the lump will be almost 3 times wider than the port opening. Class III CNC Machinist/Programmer

Re: Lumps for a GMC 302? CNC-Dude #5585 #63246 02/11/11 04:14 PM
Joined: Feb 2011 Posts: 7 NorCal Q quicksilver02 OP Active BB Member
OP quicksilver02 Active BB Member Q Joined: Feb 2011 Posts: 7 NorCal	Originally Posted By: CNC-Dude #5585 The lumps would have to be T-shaped because the port is shaped similarly. This would make the insertion of them impossible because the width of the lump will be almost 3 times wider than the port opening. Good to know. I don't have my 302 head yet, so I haven't been able to look at the port shape to see this for myself. I had thought that I read of others using lump ported 302 heads somewhere, but maybe I was mistaken. - Nate

Re: Lumps for a GMC 302? quicksilver02 #63249 02/11/11 05:16 PM
Joined: Sep 2008 Posts: 3,669 Likes: 42 N. Georgia CNC-Dude #5585 1000 Post Club
CNC-Dude #5585 1000 Post Club Joined: Sep 2008 Posts: 3,669 Likes: 42 N. Georgia	Im not saying it cant be done, it just will take some thinking to work it out. Maybe even a 2 piece lump.... Class III CNC Machinist/Programmer

Re: Lumps for a GMC 302? CNC-Dude #5585 #63253 02/11/11 07:01 PM
Joined: Jan 2005 Posts: 2,123 Likes: 3 Hempstead, Long Island, NY P panic 1000 Post Club
panic 1000 Post Club P Joined: Jan 2005 Posts: 2,123 Likes: 3 Hempstead, Long Island, NY	I agree that the short side radius is bad, which will (probably) be helped by a curved floor. If a lump was made in symmetrical (L&R) pairs they would look like an upside down "L". Each could be rotated 90° and inserted, then locked together. However: there's no existing head bolt to attach either one. I don't see any easy method here? Any insertion also decreases port area somewhat, so this may work best on the large port heads such as the H.

Re: Lumps for a GMC 302? panic #63282 02/14/11 10:25 PM
Joined: Nov 2006 Posts: 217 Kansas City, Missouri R Ron Golden Contributor
Ron Golden Contributor R Joined: Nov 2006 Posts: 217 Kansas City, Missouri	Quick, I got my 302 head to flow 250+ cfm by using 2.02/1.60 SB Chevy valves. That much intake flow is enough to support 500 HP. The real problem is the sorry-ass exhaust port (end port)that only flowed 144 cfm. You need to have your cam ground with some extra exhaust duration. The actual porting was minimul but the combustion chamber needs to be modified or you can't get the intake to flow. If you email me (goldenri@aol.com)I'll send you a picture of the combustion chamber modification. By the way, what are you going to put the Jimmy in? Ron

Re: Lumps for a GMC 302? Ron Golden #63283 02/14/11 10:28 PM
Joined: Feb 2011 Posts: 7 NorCal Q quicksilver02 OP Active BB Member
OP quicksilver02 Active BB Member Q Joined: Feb 2011 Posts: 7 NorCal	Originally Posted By: Ron Golden Quick, I got my 302 head to flow 250+ cfm by using 2.02/1.60 SB Chevy valves. That much intake flow is enough to support 500 HP. The real problem is the sorry-ass exhaust port (end port)that only flowed 144 cfm. You need to have your cam ground with some extra exhaust duration. The actual porting was minimul but the combustion chamber needs to be modified or you can't get the intake to flow. If you email me (goldenri@aol.com)I'll send you a picture of the combustion chamber modification. By the way, what are you going to put the Jimmy in? Ron Thanks Ron. I'll shoot you an e-mail as I'm definitely interested in the pictures. I'm going to put the Jimmy in a 1935 Ford 1/2-ton pickup that I'm building. It's a bit of a rust-bucket chopped cab right now, but I'm trying to save it and make something fun. Still on the fence between naturally aspirated and forced induction, which will really affect what I should do with the head. - Nate

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