3.1 to 3X00 Head Swap Questions

[TazMan]

Okay so I have a 1995 3100 Buick Century that I am getting rid of and I would like to take the top end off for my 1992 3.1l Grand Prix. After searching around I found a site, http://www.domesticcrew.com/660/ that has a great explanation of how to do this swap to a J-body. There are a few things however that it says to do for the J body that I am not sure also apply to the W body Grand Prix. Now it looks to me like I can use my old 3100 push rods. The instructions say I have to use custom pushrods because in 1996 they changed to pedestal mounted Roller Fulcrum Rockers arms with a 1.6:1 ratio and my Buick is a 95. So does this mean I can use my old pushrods? It also says you have to change the front timing cover. Now I for some reason was under the impression that the 3.1L J-bodies were rear wheel drive cars and that was the reason for this step. Is this the case? Or maybe I need the 3100 cover to fit the 3100 power steering pump? And lastly, It talks about drilling a whole to use the 3.1l CTS. Can I somehow splice in the 3100 CTS and not have to drill a hole? I'm working on a budget of almost zero and I'm a bit uncomfortable with having to drill into the cylinder head. And my last question is about the computer. Will the car run alright without having to reprogram the computer? I am a complete newbie and until 2 weeks ago I knew nothing about these cars so any info is appreciated. Anyway thanx everyone for reading!

[IsaacHayes]

lol, there are no modern RWD v6 GM cars except for firebird/camaro's. (not counting the cadillac CTS).

You can put a new connector on your wires to use the 3-wire CTS from the 3100. The 3 wire sensor does both the engine temp for computer and your gauges. Check www.3400swap.com for more info on that one. Your computer should be able to run it just fine. Not sure if 95 3100 has the 3 wire CTS. My 94 has 2 sensors, one in the head for the gauges, one in the thermostat housing for the computer. Not sure which year they switched to the 3 wire.

[bszopi]

Here is an old article from a previous version of the site that obviously needs to get put back up on the site. I'll try to do that this week. But for your reading pleasure, here you go:

"Gen 3 Pushrod Top End Swap






The 3100 and 3400 engines are called Gen 3, because they are the third generation pushrod 60V6 engines. The reason for the swap is simple. Flow and design, both of which the gen 3 trumps all previous gens. The iron heads dont have splayed valves, D shaped exhaust ports, or in some cases even the larger valves (1.42/1.72). The Gen 2 Aluminum head engines are the most popular to do this swap, but no matter what you start with, the same steps apply. The Gen 3 parts have D shaped exhaust ports for increased flow, and the 3400 and 2000+ 3100 heads have a 1.76" intake valve which increases intake flow.

The intakes are also very important. The iron heads had a decent intake manifold setup, but the gen 2 aluminum intakes are pure BS. Sad but true, you are going to need boost to overcome the design flaws. With larger ports and equal length runners, the gen 3 intakes are far superior. The 3400 and 3100+ have even larger intakes, which you can check out here. There are some complications with the changes made over the years with the gen 3 heads and intakes however, so lets address these first.

Complications, its not always plug and play
Much of this information comes from Chris Williams, who was the first to do this swap as far as we know (corrections?) There are some platform specific details that we are hoping the owners will share with us to add at the end. As it sits, this information is based on a swap into a 93 Grand Prix 3.1. Before I get too far ahead of myself though, lets talk about the intake and head changes over the years.

The 94-95 3100 intakes and heads are the easiest to use for the swap because the heads still used the stamped steel 1.5:1 ratio rocker arms and the plenum will allow you to use the EGR your computer was programmed and wired for. The downside is that these intakes were the early revision and do not have the larger gen 3 ports and runners. Increases over stock are still awesome so if you want the easiest swap path, grab these.

In 96, the EGR changed which means you will have to either disable the EGR in the computer, block the EGR off and pray for a no code situation, or make an adapter plate so your old EGR will work with it. The heads are still stamped steel and not roller rockers unless you are lucky. We believe the W body line may have them though. That applies to the 3100 only, as the minivans started getting the 3400 engines in 96 and these had the larger runners AND roller rocker arms. Sweet deal, so you may as well go for the 3400 if you are going to mess with the EGR. 96-99 are the same for the EGR, and 97 should be the start of the 3100 heads getting the roller rocker arms. The roller rockers got the 1.6:1 ratio however and you may have to get custom length pushrods to match up with them. No big deal, just have to measure for this

2000 got another EGR change, so its the same situation as the 96-99. The 3100 now has the same heads as the 3400 (1.76" intake valve) and the 3100 intakes are identical tot he 3400 as well (larger ports/runners). There is an issue with the coolant line that goes under the TB into the lower intake however. Instead of a screw in type, they are now pressed in. Create your own threads, or just avoid these lower intakes.

If you didnt check out the link to the intakes before, now is a good time to check it out because another issue comes from the rocker arm to lower intake manifold clearance. Brad already found this out the hard way so you can learn from his ordeal. Roller rockers really shouldn't have this issue, nor the older rocker arms without the tab over the oiling hole from the pushrod. Basically this was added in the 94-95 engine rocker arms to help direct oil to the pivot ball. If you are getting the heads and intakes from the same engine and using the rocker arms from that setup, this is a non issue.

Alterations to do the swap


These are Chris' words on the swap.

Biggest issues with the swap:
Power Steering Pump - youll need to get one that matches the motor.. 94-99 for any car with the 3100. It would also help to get the lines since they route differently

front timing cover - If you use the 3.1 timing cover, youll need to modify it to fit the steering pump (shave 1/4" off the back where the PS pump mounts) newer 3100 timing covers have a thinner mount to compensate. Youll also need to make sure you get a 94-99 PS pump pulley.

Throttle cable- This will be a little more difficult for you, there was never a 3100 in a cav so GM didnt make one. Youll probably just have to modify your existing one (they connect to the throttle body differently than with the 3.1)

coolant temp sensor - 3.1's use a coolant temp sensor screwed into a corner of the rear head.. 3100 heads (at least 96+) dont have the hole for this so youll need to mount it somewhere else. Im thinking of putting it in the thermostat housing pipe.

Rear Manifold to Downpipe junction - Depending on what year heads and exhaust manifolds you get, youll need a matching downpipe flange.. 3.1 downpipes will not bolt up, plus youll need the composite donut for the same year

Engine Mounts - My Grand Prix uses the dogbone front mounts, so i ended up grinding quite a bit off one of the head mounts so the thermostat housing pipe would fit.

Heater Bypass pipe - 3100's use a different routing method for the metal pipe going across the front of your motor for coolant bypass. I ended up cutting mine off after it comes out of the water pump housing, and meets the 3100 pipe which runs inbetween the plenum and lower intake, then just used a small length of heater hose to connect the two.

As far as Sensors, your gonna reuse all of your old wiring since all sensors are retained. You will however need to lengthen the TPS and IAC lines for the throttle body about 5" each. You will need the 3100's vacuum lines, if you dont have them I have a spare set (ordered 2 sets accidently) that i can sell you for cheap. Youll need some misc bracketry to mount thinks like the MAP sensor and purge solonoid.

Id suggest mounting the DIS pack in its stock location so you dont have to lengthen the wires.

If there are any questions, please post them on the forums and I will update this page accordingly."

[TazMan]

Hey great article! It pretty much answered all of my questions. I was just a little confused about this paragraph about the intakes.

"If you didnt check out the link to the intakes before, now is a good time to check it out because another issue comes from the rocker arm to lower intake manifold clearance. Brad already found this out the hard way so you can learn from his ordeal. Roller rockers really shouldn't have this issue, nor the older rocker arms without the tab over the oiling hole from the pushrod. Basically this was added in the 94-95 engine rocker arms to help direct oil to the pivot ball. If you are getting the heads and intakes from the same engine and using the rocker arms from that setup, this is a non issue."

Now I am getting the heads and intakes from the 95 Century so this means I wont have any issue with this right?

Also a company called Standard Abrasives make a DIY Head porting kit that can be had on ebay for about 50 bucks. Any idea how difficult this would be to use for a first timer?

[IsaacHayes]

Right, if the heads and lower intake came from the same car, then there wont be issue. It's when you are using heads and a lower intake from different motors/years/etc when you could run into a clearance problem.

Porting takes a long time, and forget it unless you have an air die grinder and a huge aircompressor (like one of those units as tall as you). If you don't know what you are doing you can actually hurt velocity and loose performance. You want them to flow well, but also keep the velocity up. I would only attempt it if you have read lots of articles and know the specifics of the v6 heads on what needs to be done and what needs to be left alone.

I have a meduim sized air compressor and I get about 5secs of real use out of my air die grinder. So it's taking me a long time to just open up the the little metal around my 3500 upper plenum. 1/4" thick. I'm just gasket matching and bell mouthing it, so not much I can screw up there as far as hurting flow. Should be a faste easy job, but without the right tools, it sucks. I might consider porting more on things if I had the proper tools, and a long reach bit for getting into the lower intake and heads. I'd likely just enlarge the taper going down the lower, and then gasket match the lower opening and the opening of the heads. I'd rather do just a little to improve flow with port matching, than try to be radical and end up hurting velocity by opening up something that I shouldn't.

[TazMan]

The site about the DIY head port and polish was http://www.sa-motorsports.com/diyport.shtm I meant to put the link in the last post but forgot. It says you can use an electric die grinder if you use some sort of speed regulator (I was thinking a heavy duty dimmer or a modified old sewing machine pedal I have). To me the instructions looked really good but I've never done this before so I wouldn't really know. I was really hoping to get a bit more out of these heads before I put them in but having never done this before if you think I'm more likely to hurt the heads, I'll definitly take your word for it. Bummer. Anyway I just thought you might be interested in the link. Thanx everyone for all the great info. If not for you guys and this site I would have NEVER had the nerve to attempt something like this but the heads are almost out of the 3100 and SO FAR it really hasn't been as difficult as I expected.

[IsaacHayes]

Well, you can always experiment. I don't know if you would notice if it hurt performance or not wihtout going to a dyno, but you would have done that work for nothing. But you might do a good job and come out ok. Don't let me discourage you, but just giving you warning to be cautious!

You will need custom length pushrods, I don't know the links. www.domesticcrew.com has a good section on hybrids (like what your're doing) but I don't remeber them listing the pushrod length. Also it will depend on if you have roller or stamped rockers in those 3100 heads.

I'm using a 2 speed craftsman dremel tool, and it's hard. 15,000 rpm is the slow setting, and if you aren't carefull the almuminum will "melt" and coat your bit, causing you to just polish your work or smear the metal around.
Aluminum is soft, and sticky sort of like grinding lead. Also it gets hot, hotter than an air grinder since the motor is making heat, and that makes it even worse. Also, if the bit grabs something, it will take off and jerk out of your hands and skip out and over the flat surface where the gasket goes, and whoops, now you've got trouble. An air die grinder will just stop spinning if it grabs something or gets stuck, and after you let off the trigger, it stops almost instantly, where as an electric one will keep spinning with torque....

I used a lot of masking tape around where I wasn't touching on the gasket side. I've had a few accidents and the several layers of masking tape has saved me.

Thanks for the link BTW. I'll be reading it!

[TazMan]

Yeah I don't know about the port and polish. I was leary about trying it anyway. The site gives flow tests and says on a 300HP motor you could expect to see about 19 more HP. Now to me that means maybe 10HP most on this motor (thats just my assumption so please correct me if I'm wrong), and thats done by an actual shop which means I would have to do it perfect for that 10HP gain.

As far as the pushrods go, www.domesticcrew.com says you have to use custom pushrods because in 96 they switched to Pedestal mounted Roller Fulcrum Rocker arms with a 1.6:1 ratio. Now The article above says from 94 to 95 they were still using the stamped steel 1.5:1 ratio rocker arms in the 3100's. Since it is a 95 does this mean I can use the pushrods from the 3100? Also, lol try not to laugh at me but is there a way I can tell for sure if they are roller rockers by looking at them?

[bszopi]

Unfort, that article is old and wrong. We have since found out that all 3x00s (stamped or roller) were 1.6 ratio rockers. As far as being able to tell the difference, yes. It is very easy to tell the difference between the 2.

[IsaacHayes]

Either way I belive you need custom rods. As Brad said they are both 1.6 ratio.

Roller will have a bearing in the center of the rocker, and non, well it will just be a stamped peice of steel.

[TazMan]

Well thanks again guys for saving me from using the old pushrods and screwing up something else. After some searching here it seems I need a measuring pushrod. I found thishttp://store.summitracing.com/partde...5&autoview=sku at summit racing but have read alot of posts about finding one short enough for our engines so I was wondering if anyone knew if this was the correct part. Also when I measure, obviously I have to turn the engine to a certain position for each pushrod. I have no idea how to go about doing this. Am I looking for TDC at a certain cylinder or am I just sticking in a pushrod, turning the engine till that pushrod is in a certain position and then measuring the distance to the lifer with the test pushrod.


Now should I be just adding these questions to this post like I've been doing, or should I be starting a new thread with each one? Sorry for all the stupid questions guys and thanks so much for having taken the time to answer them.

[bszopi]

http://60degreev6.com/showthread.php?t=32167&highlight=measuring+pushrod

Look to the bottom of the thread for pushrod lengths. And keep posting in the same thread since it is all pretty much related. No sense have 4-5 different posts about basically the same thing, only a different part of it.

[TazMan]

Thanks for the link. I actually saw the post while searching about the pushrods but there were some contradicting answers on the question. First someone said you have to measure to get it right. Then someone answered with actual measurements. Someone else then followed with different measurements. Someone at the top even said they used their old pushrods. I've heard using the wrong size pushrods can cause disaster in the engine so I was gonna buy the pushrod checker just to be safe. Will such small size differences be a problem and if not can you recommend whether I should be going with the the bigger or smaller sizes? Here's the posts with the sizes:


"if your useing gen3 rockers with the gen 3 heads on the gen2 block(hybrid)
the measurements are:
6.26" exhaust and
5.95" intake"

AND

The measurements I had were 6.275, and 5.94 inch

Others I know have measured:
6.250 and 5.950 inch
6.260 and 5.94

[TazMan]

Also the pushrods come in 5/16 in., 3/8 in., and 7/16 in. diameters, and it says you have to specify the tip style for your Engine. What diameter and tip style would I need?

[IsaacHayes]

Hmm. I was wondering that too. www.pushrods.net is that where everyone likes to get theirs?