97GST Rebuild Questions

[prophecymiller]

Ok guys, I am thinking about rebuilding my motor some time in the future. I want to buy a shortblock that is rebuildable and do it slowly over the next year or so and then swap it in. Here are my questions...

1. My car is a GST, so do I need a 97-99 GST motor or would any 7bolt work?

2. What are your opinions on keeping the 7bolt vs. swapping in a 6bolt? If I kept the 7bolt I would take it to Jack to have him put some magic in it to fix cw issues:)

3. How would using the 2g pistons and then getting some forged rods work if I'm not pushing any more than 300hp and revving to 7500? Is that necessary?

4. Whats the going price(if any) on a rebuildable short block and head?

I have read about the answers for all of these questions already, but I figure I will ask someone who is more knowledgable before I buy anything so I know I'm not getting misinformation;) Thanks guys and let me know what you think???:)

Steven

[drcustom]

1. My car is a GST, so do I need a 97-99 GST motor or would any 7bolt work?

Any 95-99 motor will work. The 92-94 7 bolts swap in just the same as the 6 bolt motors.

2. What are your opinions on keeping the 7bolt vs. swapping in a 6bolt? If I kept the 7bolt I would take it to Jack to have him put some magic in it to fix cw issues


You get a little bit of goodness out of the 7 bolt because of the lower rotating mass. If you were pushing 400hp I'd consider the 6 bolt. The 6 bolt is a bit stronger, but not by much. I've done a few of the swaps. Another option would be the 7 bolt 1g motor. The heads are also swappable if you prefer one over the other.

3. How would using the 2g pistons and then getting some forged rods work if I'm not pushing any more than 300hp and revving to 7500? Is that necessary?


For this, I'd definitely suggest a stock motor however you go. 300hp is nothing for these.

4. Whats the going price(if any) on a rebuildable short block and head?

I've got a 6 and 7 bolt for $200, but honestly I think that you could hold off and find one cheaper. They're available if you're looking to buy right away though. I've also got a stock 2g 7 bolt that was running fine, but overheated. The headgasket was replaced, but they installed the timing incorrectly, damaging the valves. I'd like a little more for this, but it would be a great crankwalk fix candidate and probably wouldn't need much to rebuild.

[D Walker]

Stock rods are forged, and with ARP will handle 400-ish to the wheels just fine. A decent"upgrade" would be stock EVO 7-up rods.

defiitely use the 1G head

[prophecymiller]

Thanks for the replies fellas. I've got hks 264/272 combo that needs to go in and they are for a 2g so I suppose I need to stick with the 2g head? It's tapped for the 2g cas also.

I also have a pretty small turbo (fp big28), so would a 1g head be necessary? Or would the 2g head be better since the exhaust gas would flow faster? I know there are a billion threads about head differences on small turbos but I always see differing opinions on it? Thanks

Steven

[drcustom]

Thanks for the replies fellas. I've got hks 264/272 combo that needs to go in and they are for a 2g so I suppose I need to stick with the 2g head? It's tapped for the 2g cas also.

I also have a pretty small turbo (fp big28), so would a 1g head be necessary? Or would the 2g head be better since the exhaust gas would flow faster? I know there are a billion threads about head differences on small turbos but I always see differing opinions on it? Thanks

Steven

The cams will work with either head.

For you it sounds like the 2g head would probably be the way to go. It's a slightly better design that's a little more efficient, and gives you a little more power down low. It's not a big difference, but 300hp isn't too much to ask from it. If you're pushing 400 or looking to drag the car more than drive it I'd consider the 1g head, but you loose a little for everything except the top end.

[D Walker]

Incorrect- you do not "lose" anything with a 1G head, but you gain big-time when you start wanting to make power. We do not have N/A cars, we are relying on a turbocharger to provide power and the better you make the motor flow at all times is going to be better, especially since none of us run these things at 2k rpm. We are all revving the piss out of them, so "upper end" power is what you need, which is exactly where the 2G sucks the biggest. I have a mildly ported 1G head on my "big" turbo car and it made over 200whp on 3- yes THREE lbs of boost. If you are "concerned" over "losing" bottom end grunt simply use a Cyclone manifold and control the changeover and you will be fine. The largest drawback to the 2G head is the 2G intake manifold, which sucks beyond belief.

[drcustom]

Incorrect- you do not "lose" anything with a 1G head, but you gain big-time when you start wanting to make power. We do not have N/A cars, we are relying on a turbocharger to provide power and the better you make the motor flow at all times is going to be better, especially since none of us run these things at 2k rpm. We are all revving the piss out of them, so "upper end" power is what you need, which is exactly where the 2G sucks the biggest. I have a mildly ported 1G head on my "big" turbo car and it made over 200whp on 3- yes THREE lbs of boost. If you are "concerned" over "losing" bottom end grunt simply use a Cyclone manifold and control the changeover and you will be fine. The largest drawback to the 2G head is the 2G intake manifold, which sucks beyond belief.

I think we're getting into 'prove it with a dyno territory' :D I tend to have a really bad habit of coming across like I know what I'm talking about, and you must be wrong...definitely not the case. I've been working on DSM's for about 8 years and my friends were running 12's when I started helping them. For that reason, I get pretty set in ways of thinking, but I'm always open to new ideas...I just need numbers to back them. I've found that no matter how much it makes sense that things will work, they sometimes don't. Conversely, no matter how bad of an idea something can be, it can really surprise you. With that said, I've been wrong and surprised many times, but I like to think those days are behind me (I'm sure they're not, I just need to see proof before I change my mind)...

There's no question the 2g head has a few advantages. Port volume and bowl size, port taper and angle of entry, and the short side radius (and maybe some other things). The 2g head wins out on all of these, and I don't know of any disadvantages...until you start talking about a lot of power. The only scenario where the head starts to be a problem is when you're trying to flow a lot of air. I don't think the HKS cams come close to being problematic. In fact, I think you might even lose a little power due to the 2g head being a superior design...but I think the proof is in the numbers, or at least a side by side comparison.

I see where you're coming from on forced induction. I agree some of these things are less important for us, but I can't let go of the idea that what is good for an n/a car will also be good for a turbo car. My understanding is that the 2g heads promote atomization and keep the fuel in suspension longer than the 1g head, both things that have nothing to do with flow itself. I'm pretty sure these qualities will beat out the 1g head, especially at lower speeds, low to mid rpm's, and around town driving. When you're trying to make power these are definitely advantages, and at 300hp or so I have a feeling quality still wins over quantity. When getting closer to 400hp where the 2g heads are really at risk for choking then I'd say just get the air in there however you can and use a 1g head.

Before I bought my car it dyno'd 370 whp with a stock 2g head, an 18g, and supporting mods. I plan on knocking on 400hp's door and I'm still on the fence on whether or not to use a mildly ported 1g head - but I'm leaning towards it. I'm willing to give up a little around town comfort and gas mileage (another 2g head benefit) for that extra that you get on the top end, and I might upgrade before too long. I would definitely prefer using a 2g head but I don't have the time/money to port it enough to let it breathe.

Simply put, the 1g heads aren't a bad design, but around 300hp I think the 2g head will outperform the 1g head. We might be in gray area here, but I think the 2g head will outperform (the design is more similar to the evo heads, so it's not like it takes a whole lot to get some power out of them). I get the idea this guy isn't planning on revving the piss out of his motor, and I'm thinking that maybe for the last 2-3k rpm is where he'll see restriction - if anything that's even significant at 300hp.

On a side note, I used a 2g head on my last car and portmatched it for a 1g manifold. I can't say for sure how it performed at higher power levels but with a 14b I at least 'though' it was definitely an improvement over a 1g head.

And if we needed to start another fire, I once heard the cyclone actually dyno's 3hp over the stock 1g manifold. I'm with you in thinking it's only providing low end, but I've got a cyclone mani just sitting here until I actually see proof either way.

[D Walker]

ok- well see thats the difference between legend and facts. Over 300whp (or 30-35lb/hr) UNLESS its been ported to hell the 2G head sucks- on the flowbench, on the dyno, and pretty much everywhere else. It might have a somewhat broader curve because there is slightly better low-velocity flow, you give up far too much once you are building boost and trying to flow air. If you have the money or the tools/knowledge then you can MAKE a 2G better, but unfortunately most people do not have access to either. The 1G head will make more power stock for stock, period. While the 2G head is a "technically" superior head, it is only "technically" superior once you spend lots of money to make it as good as a 1G head in the first place. No one has ever shown me a dyno sheet with a 2G head that made as much or more power until it has had a lot of work done to it. I could probably dig up a fair amount of data and dynosheets however, of where a car with a simple 1G head swap, with everything else staying the same, made more power than it did before.
As far as flow numbers, the 2G head isnt even in the same ballpark as the 1G head, and is nowhere near an Evo 8 style head. Consider the Evo8 head the best of both worlds- extremely large ports with great design.
If you search carefully you should be able to find the flowbench results of the cyclone manifold VS both the 1G and 3G intakes, with numbers for both runner configurations. If memory serves it has the same numbers as the 2G with the long ports with similar velocities and was within IIRC 3cfm of the 1G manifold on the short runners and high port velocities. To me this is the best of both worlds and allows me to run the Cyclone and have the "low-end" of the 2G head/manifold and the "top-end" power of the 1G head/manifold.
I have seen a couple of 2G heads ported (butchered) to fit the 1G manifold, and I remain convinced that without proper knowledge this is an exercise in futility and will likely lose more than can be gained.

[D Walker]

My understanding is that the 2g heads promote atomization and keep the fuel in suspension longer than the 1g head, both things that have nothing to do with flow itself. I'm pretty sure these qualities will beat out the 1g head, especially at lower speeds, low to mid rpm's, and around town driving. When you're trying to make power these are definitely advantages, and at 300hp or so I have a feeling quality still wins over quantity. When getting closer to 400hp where the 2g heads are really at risk for choking then I'd say just get the air in there however you can and use a 1g head.


I really want some proof/tech data on this, as the injector angle on the 1G head I believe promotes much better "tumble" which is what keeps the fuel suspended and gives the 1G head a HUGE advantage in regards to knock prevention and the ability to make power safely.

[drcustom]

I really want some proof/tech data on this, as the injector angle on the 1G head I believe promotes much better "tumble" which is what keeps the fuel suspended and gives the 1G head a HUGE advantage in regards to knock prevention and the ability to make power safely.

You're right, I'm mixing things up here...

I'm not sure about how the injectors come into play, but the sharp turn on the 1g head does promote better atomization through tumble. My understanding is that same turn can also bring the fuel out of suspension though?

I could be wrong about the details, I'm no engine tech. Just going with what I've heard. I'm not sure what evo version I was looking at, could have been a much earlier than the 8, but aside from the injectors being in the manifold, the ports and design looked a lot like the 2g ports.

[D Walker]

The Evo3 head is pretty much identical to the 2G head, with the largest difference being the intake manifold and turbo giving it more power over the 2G. An Evo 8 head has ports about equal to the 1G in size and all the "refinements" of the Evo3/2G head.

[Kibo]

As far as flow numbers, the 2G head isnt even in the same ballpark as the 1G head, and is nowhere near an Evo 8 style head.
OEM DSM head flow comparison (http://members.cox.net/abelracing/tech/HeadFlow/index.htm)

According to this, the 2G head intake ports flow more than either a 1G or Evo head at low lifts, but rapidly lose out at higher lifts. The Evo intake ports really don't look that great in comparison to a 1G head, so there must be more going on than a simple flow chart shows.

[prophecymiller]

Cool, this is a good read:) . I am thinking of going with the 1g head/cyclone mani combo from what you are saying Don. I like the idea of keeping the low end velocity and also getting to see the difference in top end of a 1g vs. 2g head. I also can actuate the solenoid with the nitrous controls in DSMLink right?

So from what you are saying Kibo, the 2g is better for stock cams, but since I will have hks, they will be negatively affected by the 2g head? What cams were you using when you put down 370hp Drcustom? Maybe the 2g head is the way to go if I was going to stick with the stock cams?

My next question is what about ceramic coating the piston tops? I know this is generally used on higher power motors, but I figure it cant hurt and is not too expensive I don't think. I have run across some diy ceramic coating that I also might try out for my exhaust mani, turbine housing, o2 housing, and the first two or three feet of my exhaust...How do you think that would turn out as far as results? I want to start running e85 and am going with either 780 or 880 pte injectors so I have some room to work with. Thanks

Steven

[drcustom]

What cams were you using when you put down 370hp Drcustom? Maybe the 2g head is the way to go if I was going to stick with the stock cams?

I think you're on to something here . My numbers came from a stock motor (upgrades were injectors, fuel, turbo, intercooler, etc.). Cams, head, and all internals were completely stock.

I can't find the numbers, but I think the lift is about 10mm, and with a rocker multiplier of *I think 1.7*, those HKS's should put you around .500" lift -which has obvious disadvantages for flow. I'm not sure on the numbers of the stock cams though.

Regardless, I'm still under the impression that the 2g head does a better job of getting the air into the motor (at least at lower power and lift levels anyways). The entry angle it steeper which appears to have some pro's and con's, but I get that's ultimately best for efficiency and performance. Maybe with a forced induction car things like this matter less, I'm really not sure.

In short, I remember thinking the 1g cams got more air in (quantity), but the 2g head did a better job of getting less air in (quality). I'm really not sure at what point it's better to switch over from the the 2g to the 1g head though. Maybe doing nothing else but swapping in the HKS cams puts you at a disadvantage with the 2g head. Maybe anything above stock power levels give you a disadvantage with the 2g head. Maybe 300hp is the point where the two meet. Maybe we should actually put the heads up against each other...we could compare the 1g and 2g heads. :D I don't think you'd be unhappy with either decision though.

I've got a project car that I'm throwing together...if someone had a stock 1g and stock 2g head we could compare...but they'd have to both be known good and not be trashed. I'm looking at going with a stock or near stock setup, so we could get a baseline for lower power. On my other car (the one that ran 370hp) I'd consider doing the swap there as well, but I won't be touching that car for a month or so...we could compare the baseline to this if we really wanted to get serious.

That ceramic kit sounds pretty neat. At 300hp I really wouln't think twice about the pistons though. The stock pistions will take you over 400hp without too many concerns, running them around 300hp should give you plenty of overhead. It wouldn't be a bad thing, but you could probably spend the money somewhere else where it could be more useful or make a noticeable difference - even if it's cheap, I don't think it will matter either way for your setup. As for the rest of the parts you mentioned, it might help a little with longevity, and if the price is right why not.

[D Walker]

Well I know for a fact the Evo8 head flows more than a 1G head pretty much everywhere, so that comparison is likely done using an e3 head, which is pretty much identical to the 2G head. Also, that test doesnt give enough information- like model of machine, test procedure, etc. There are LOTS of ways to influence flow numbers, so more specific information is needed.

[Kibo]

I can't find the numbers, but I think the lift is about 10mm, and with a rocker multiplier of *I think 1.7*, those HKS's should put you around .500" lift -which has obvious disadvantages for flow. I'm not sure on the numbers of the stock cams though.
The lift on the HKS cams is nowhere near .500". HKS 264 intake will have .392" lift, HKS 272 exhaust will have .379" lift, all with stock 1.7 rockers. That's compared to .366" / .343" for a stock C/D combo.
Well I know for a fact the Evo8 head flows more than a 1G head pretty much everywhere, so that comparison is likely done using an e3 head, which is pretty much identical to the 2G head. Also, that test doesnt give enough information- like model of machine, test procedure, etc. There are LOTS of ways to influence flow numbers, so more specific information is needed.
Don, I'd love to see some data if you could find it. Agreed, the link I provided is low on information, but it's all that I've seen.

[D Walker]

I had a stock E8 head flowed on a Superflow 110 flowbench and while I no longer have the data sheets to give all the information, I will say the stock e8 head exceeded my expectations and I wanted desperately to figure out a way to adapt it to a 1G :)

[Kibo]

I had a stock E8 head flowed on a Superflow 110 flowbench and while I no longer have the data sheets to give all the information, I will say the stock e8 head exceeded my expectations and I wanted desperately to figure out a way to adapt it to a 1G :)
Any luck? :D

Only mildly related to the conversation, I'd like to get my hands on a MIVEC cam sprocket and tie it in to a DSM ECU. :)

[drcustom]

The lift on the HKS cams is nowhere near .500". HKS 264 intake will have .392" lift, HKS 272 exhaust will have .379" lift, all with stock 1.7 rockers. That's compared to .366" / .343" for a stock C/D combo.

I found a place that lists the HKS's lift (264's and 272's) at 10.3mm intake, 9.8mm exhaust. That's .4055" and .3858" respectively. With 1.7 rockers, that puts those at .689" and .655"!? Maybe the quoted lift factors in 1.7 rockers, or am I just looking at this wrong?

[Kibo]

I'm going from the numbers I've seen elsewhere on the web, like here (http://www.dsmsource.com/forums/archive/index.php/t-56156.html). In either case, the lift numbers take the 1.7 rocker ratio into account.

[prophecymiller]

I know I'm digging up an old thread here, but what would be the advantages of using evo8 rods and pistons vs. 2g internals??? I've been reading about them but are they worth the extra money, or would it just be better to put the money into making the stock parts better, or maybe some head porting?

I also am wondering if the added compression of the evo pistons would be a bad thing since I'm front wheel drive:confused:

[drcustom]

If you're going to spend any money on pistons, definitely go with something aftermarket and forged...then you can pretty much select the exact compression you're shooting for.

Not so long ago I picked up a brand new set of Wiseco's for about $300 - the deals are out there.