3.1L Heads

Beholder88 · 08-27-2008, 07:22 AM

Is it possible to mod some heads from a 3.1L motor so I could put them on my 3.4, and still have a 3.4? The heads are from a 2000 Malibu, and I have a 2000 Alero. I would like to go all out on the heads, but I don't want to lose any Cubic Inches. The 3.1 was a "J" code engine if that helps. Any ideas?

cherrington17 · 08-27-2008, 07:53 AM

isn't the 3.4 a bored out 3.1?? so the heads would be smaller... if i understand correctly.

Vtolds · 08-27-2008, 08:41 AM

I had a friend once mount the heads and intake from a 3100 onto a early 90's 3.1 MPFI motor in a Beretta. But I have no idea if the 3100 and 3400 parts and interchangeable.

Beholder88 · 08-27-2008, 10:01 AM

I'm not sure if the 3.4 is a bored out 3.1, or if it's the same block and just stroked. I've heard from numerous people that the heads are the same. If you look on Wikipedia, the big change from the 3.1 to the 3.4 was in the heads. It was supposedly an "advancement" in technology or whatever. I dunno, I'd like to find some use for these heads, before I decide to just sell them outright.

CactusWill · 08-27-2008, 01:28 PM

It may just be a longer stroke like you just said. I used to know which way it was at one time but I don't remember now.

01OldsAleroGt · 08-27-2008, 01:47 PM

the 3.4 is a bored out version from the 3.1 now stroke... im not 100% percent sure..

surreal_awakening · 08-27-2008, 02:00 PM

Go to http://www.60degreev6.com and they have specs for all of the GM 60* V6 engines so you can compare.

Beholder88 · 08-27-2008, 03:52 PM

Damn! It is the bore that's the difference! The 3100 has an 89 mm bore and the 3400 has a 92 mm bore. Guess that means I can't use the heads from my 3.1 on my 3.4. Does anyone think they could be dished out? I couldn't find specs on the stock heads anywhere. I'd have to see the difference in cc's. I know the intake valves are the same, I'm not sure about the exhaust.

kwhauck · 08-27-2008, 10:41 PM

just get some 3400 heads to work on ya cheap ass.......

WhiteV6 · 08-28-2008, 07:26 AM

They are identical heads on a 2000 3100 and a 2000 3400. You can look at the casting numbers. Those should end in 170 casting number

The 94-99 3100 are 1.72" intake valve and the 00+ 3100 and all 3400 are 1.76" intake. That is the main difference. All are 1.42 exhaust. 28.6cc combustion chamber is what you are working with for the combustion chamber.

Beholder88 · 08-28-2008, 07:47 AM

Thanks, I'll check the casting numbers when I get a chance. It would be nice not to have to spend big money on new heads when I've got a set lying around anyway.

Beholder88 · 09-11-2008, 10:07 PM

Which numbers are the casting numbers? I see some that are under the valve covers.

guiguilandry · 09-11-2008, 10:43 PM

I would port match them for the intake and exhaust if you have them sitting in your garage.. if done correctly, it will help

WhiteV6 · 09-12-2008, 02:22 AM

Yes, on the exhaust side of the head, below the valve cover. What are the last 3 digits.

Do not gasket match the exhaust.

Midgear · 09-12-2008, 08:47 PM

3500 heads = sex

wasn't there an argument about ported 3400 heads having less flow than stock 3500 heads?

kwhauck · 09-12-2008, 10:03 PM

I believe the argument was a stock 3500 head and stage 1 port, but i'm pretty sure that in extreme (read stage 3+ port) that 3400 heads are still superior.......

WhiteV6 · 09-12-2008, 10:43 PM

3400 heads can be ported to outflow 3500 heads, but that is not really important unless you have boost.