Gen 3 2.8L or not...

[sanjay]

Snag those quick! lol


I've seen a hybrid using 3.1 flattops and a H272 cam so i'd imagine it would be ok. Keep the cam duration resonable and you shouldn't have problems.

I could tune out my startup issues in the cold but since It's seen snow twice in 3 years it's really not needed. In the summer it fires right off and runs great.


for the timing chain, get a GM set for a 99 or older 3400.

Yeah I hope I can get those pistons but I have to buy a car so no spending till I get the new ride.

Can you explain why the pre 99 GM Timing set is a better choice??

Considering my target power level am I right to assume that a set of 3400 M2 injectors & the stock 89 fuel pump will do the trick??

The 11.5:1 CR is based on a FWD head gasket right??

[Superdave]

the CR calc on this site comes up with 12.5:1 using the .060 gaskets. Yah, stock 3400 injectors, '00+ FPR and the stock fuel pump should be fine (if it's healthy).

Here is the chain differences..



you tell me which one looks stronger :P

[95Grand-Am]

What are the spec on the flat top 2.8L pistons? The specs that I have say they will be .047" in the hole. Using the .040" gaskets should give you 11.97:1 with a quench of .087".

[Superdave]

the flat tops should go to 0 deck or very close. .0097 rings a bell but that might be the 3.4 flat tops. check the CR calculator on the left.

[IsaacHayes]

My guess on the chain is the smaller one maybe is more flexible with the smaller links, and maybe quieter. Maybe not as strong, and GM figured even being less strong it would work fine for a stock engine, while being quieter than the old style.

[sanjay]

the CR calc on this site comes up with 12.5:1 using the .060 gaskets. Yah, stock 3400 injectors, '00+ FPR and the stock fuel pump should be fine (if it's healthy).

Here is the chain differences..



you tell me which one looks stronger :P

Wow, is all I have to say..

As for piston specs well I was under the impression that they were stock replacements.

Ok I'm picking up my new car tomorrow so that leaves me with some good news and soem bad news.

Bad news first, it isn't the 89 Z24 I was looking at so this motor project is dead before it even got off the ground. I'd still like the discussion to continue and maybe benefit someone else who wants to try a Gen 3 2.8.

Now for the good news. The car I got is an '01 Grand Am GT. If 660 parts I have for sale don't sell they may make their way onto my new car when it coem time to do the intake gaskets.

I'd like to thank everyone who helped and responded. I'd like to try this out soemday, maybe in the Grand Am with a switch over to a 5 Speed in the future but for now because it's a shared car it will remain stock..ish..

[ghrarhg]

Well if I can find a 3400 cheap and soon, I'll be adding that plus a cam to my 2.8 turbo 5 speed.

[sanjay]

Good news!! I got fed up with the Grand Am and replaced it with a 94 Z24. The motor has a slight miss at idle and a major miss under load. No codes but it has a lot of oil in the intake. The PCV has been changed but the hose is now broken. I have a feeling the 2 problems are related so instead of fixing the 3.1 the 2800 project is now back on. Unfrotunately it won't be as glorious as I had originally wanted it to be.

There are certain restrictions that must be followed now such as:
Must run with a 3X00 swap chip or require very little modification to the tune
Must not make enough power to overpower a stock clutch (the one in the car is brand new) so that means stock 3400 cam, throttlebody & exhaust manifolds.
Stock fuel pump, 3400 M2 Injectors

Budget..this has to stay close to what it would cost me to fix the 3.1. Absolute max for this project is $500 and that has to include the 3X00 swap mount and the chip & adaptor.

The only parts I still need to get my hands on are:
3100 block (trade for my spare 3400 block)
2.8 Crank (On the way..I think)
2.8 RWD or FWD Pistons (need to buy)
Various gaskets & bolts (Need to buy)

26915 springs & the lifter spring mod will be done.

The 3.1 has an FFP pulley on it so that will be recycled I will most likely use the Alum flywheel off my 3400/3500 project.
3X00 starter had to be able to turn it over easily, even in the coldest weather.
My only variables now are compression and port work and exhaust size. If I can easily tune for 11.??:1 comp with the stock ecm then I'll go with the RWD pistons. I really don't know how far to take the port work. I only need enough flow for a stock cam and possibly a 62mm TB. As for exhaust size I believe I'd want to stay on the smaller side of 2.5" to keep the torque up since I will be losing torque over the rev range with the decrease in displacement. 2.25" I think will do..

I can't stress more that this HAS to be reliable and have no tuning issues. There can be no question if this will work of not before beginning. I can't be running into an custom machine work with the exception of maybe cutting down the pistons for a lower comp. I want to use as many off the self parts as possible.

I'll be taking my 3400/3500 project off the stand and starting this as soon as my 3100 block gets here. Probably the second week of August and hoping to have it installed by the end of August but most likely mid September.

I'm am more than happy with the power output of the 3.1 so I'm not looking to make a ton more power here. 160 Hp will be more than fine with the increased higher rpm flow of the Gen 3 top end. I'm also hoping to get my fuel economy to 500KM a tank. It's around 400 now with a proper running 3.1..

[Superdave]

a 3400 swap chip should run it ok, and i'd use the flat top pistons for sure. More compression will give you a bit more torque.

I have a feeling that you'll go past the $500 but not by much. It's going to be very rev-happy, 1st gear will be fun. hehe

[IsaacHayes]

2.5" will still be good for your power range. But if you already have 2.25" that would be ok too.

If you want reliable don't put the UDP on...

Port work, open up the top manifolds (upper/lower) and taper them down. Heads don't do much to them, you can do a minor gasket match and clean them up and make them all equal, but unless you know what you are doing, it's best to not touch them as you can hurt flow more than increase it.

62mm TB should work well with a rev happy 2800.

If you have a 3.1/3400 crank you can put that in the 3100 block if you wanted a straight 3100 too.

Anyone else have input of RWD pistons on stock cam? I wonder how well that would work.. EDIT Superdave says go for it!

I've always wondered how a gen3 top end will perform on the short stroke crank. I think what would be really neat if one had the money/time would be a 3400 block with the 2.8 crank and 3500 heads... That would be a 3.0/3.1L big bore high compression cammed screamer, with good mpg.

[sanjay]

a 3400 swap chip should run it ok, and i'd use the flat top pistons for sure. More compression will give you a bit more torque.

I have a feeling that you'll go past the $500 but not by much. It's going to be very rev-happy, 1st gear will be fun. hehe

Since I'm sticking with OBD 1 I'll eventually be getting a diagnostic cable so I can datalog if problems do arise.

Yeah I'll probably go past $500 but I meant I didn't want to spend more than $500 more to get the remaining parts. The 3100 I'm getting is apparently complete and the guy wants $100 for it so I'll see if I can talk him down to $75. I have no idea what condition or what year it is yet but I'll find out soon. I'm suppose to be getting the 2.8 crank for free and I have to buy the pistons. How much could used pistons possibly cost?? After that it's just head gaskets and head bolts front mount and chip + adaptor. Everything else I already have.

Why can't multiple quote?? Anyway...

I'm not sure what size the current exhaust is but it's leak free and still good so for now it's staying.

I think I'll be ok with the UDP. I don't see this engine revving muck past 6000 RPM.

I was considering the 3100 crank but then it's pretty much a stock 3100. Yeah it will work great with a stock chip but what would be the point of this thread. A 2800 sounds more interesting. I also think a 3100 stock or slightly modded would be pushing the limit of a stock clutch.

I'll find out more about the 3100 tonight. Hopefully its a large port so I can sell the top end and put the money back into the motor...

[IsaacHayes]

The J bodies got 2.25" exhaust stock I hear. My Beretta got 2" press-bent with the stupid 1.60" inside down pipe.

2800 sounds cool for sure. I'm interested in hearing how it runs. Are you going with large port 3x00 heads and intakes? I take it you have a 3400 top end for it.. What manifolds will you use? I hope at least 3100 manifolds. The 3.1 manifolds are really small. W body 3100 manifolds flow better than L body 3100 manifolds (rear is larger), but the downpipe is off to the side instead of in the center. 3400 manifolds flow even better with the short runner on the back. 2005+ 3400 manifolds are even better as they are bigger inside the same as the 3500 log manifolds. And anything else is better of course.

[sanjay]

The J bodies got 2.25" exhaust stock I hear. My Beretta got 2" press-bent with the stupid 1.60" inside down pipe.

2800 sounds cool for sure. I'm interested in hearing how it runs. Are you going with large port 3x00 heads and intakes? I take it you have a 3400 top end for it.. What manifolds will you use? I hope at least 3100 manifolds. The 3.1 manifolds are really small. W body 3100 manifolds flow better than L body 3100 manifolds (rear is larger), but the downpipe is off to the side instead of in the center. 3400 manifolds flow even better with the short runner on the back. 2005+ 3400 manifolds are even better as they are bigger inside the same as the 3500 log manifolds. And anything else is better of course.

I believe the earlier J bodies got 2.25" and the later years got 2". Either way it doesn't matter. The exhaust on the car is a multi repair cobble job so it's probably 2.25" crush bent piping.

I have will be using large port 3X00 heads and 02 3400 ex manifolds, both ported. Later 3400 ex manifolds are possible if I can score a set for 50$ or less.

The latest news on the motor is that it's an 01-02 3100 with bottom end issues. I'm hoping for a spun rod bearing not a main bearing...

[Superdave]

I'd use 3500 exhaust manifolds like we did on Redbird's 3500. they're badass.

2.25 would be plenty for this setup.



Abob is driving his 3400 '89Z on a stock clutch. It will slip under load but for daily driving i'm sure it's fine.

[carbon]

I've always wondered how a gen3 top end will perform on the short stroke crank. I think what would be really neat if one had the money/time would be a 3400 block with the 2.8 crank and 3500 heads... That would be a 3.0/3.1L big bore high compression cammed screamer, with good mpg.

I don't think you could short stroke the 3400 with the 2.8 crank... the pistons have a different pin height besides the longer stroke. I don't think the 3.4/3400 pistons would come far enough up the bore to make compression...