6 bolt swap auto or 7 bolt

[dsm1212]

alright so im looking to build a motor for my 97 gst auto. i wanted to go 6 bolt but it seems like it is a difficult swap to do in an auto from what i have read. So im wondering if i should just go with a 7 bolt because i have searched and it seems like crankwalk is almost impossible on a auto is that correct? well give me your input.

 

[4g64fiero]

Man this is a can of worms.

I like the 7 bolt head design, I like the girdle the 7 bolt has on its mains stock. I am building a 7 bolt this time currently. If you rebuild the engine in the future correctly, with everything accounted for(how your going to drive and what its going to be used for) you should have no issues with the 7 bolt.
There are plenty of 1000whp evos around(although the thrust bearing design of the evo 7 bolts is more like the 98+ eclipse engines, and the operation of teh clutch is reversed as to not put presure on the thrust bearing).

I say stick with the 7 bolt/fwd a/t combo. Its underrated. Lets part to break and parts to build an a/t to ipt standards are cheap relative to its manual counterpart albeit theyre harder to work on.

 

[oVaBoost]

yes the 7 bolt will crank walk on auto but more common in 5 speed. well since you wanna build up the car i would do 6 bolt and will hold more power.

 

[dsm1212]

yes the 7 bolt will crank walk on auto but more common in 5 speed. well since you wanna build up the car i would do 6 bolt and will hold more power.

how much more power im not looking to be at like 800 hp maybe 400 tho have to get a bigger turbo than this t28 i have now.

 

[4g64fiero]

Stock 7 bolts have seen 600hp.

6 bolts have stronger rods stock, but thats it. Everything after that is subjective and opinion.

 

[oVaBoost]

Stock 7 bolts have seen 600hp.

6 bolts have stronger rods stock, but thats it. Everything after that is subjective and opinion.

And they dont crankwalk But I think what most people dont know is when you dyno an auto and you know you have a setup for 400hp is that the auto tranny puts down different #'s than a 5 speed. If you want 400 hp you need lots of $$$ and time.

 

[dsm1212]

And they dont crankwalk But I think what most people dont know is when you dyno an auto and you know you have a setup for 400hp is that the auto tranny puts down different #'s than a 5 speed. If you want 400 hp you need lots of $$$ and time.

what do you mean by this?

 

[4g64fiero]

what do you mean by this?

He is refering to the fact that the auto transmissions have a little more parisitic drain on the power output of the engine in comparison to the manual transmission. From what I have witnessed it is not as dramatic as he claims but it really depends on the setup. The m/t only has a 5 hp advantage over the a/t stock. The same could be said for AWD vs. FWD.

An a/t awd 1st gen at slightly stripped can get you in the 10s with 430 hp.

 

[dsm1212]

i didn't think it was to drastic a difference. i will be looking into a built tranny most likely by IPT if i will be pushing that much HP

 

[JusMX141]

6 bolts have stronger rods stock, but thats it. Everything after that is subjective and opinion.

What about the 6-bolt's 7.8:1 compression ratio? You're forgetting that as the 4G63 progressed throughout the years, the compression ratio gets higher and higher.

If you like less off-boost torque and less ability to spool turbos of any size (not a good idea for an auto) in exchange for a tiny bit of ragged-edge tuning forgiveness, then the 6-bolt is for you.

 

[Burnett03]

And they dont crankwalk .

ANY motor can crankwalk, no motor is immune to it.

 

[JusMX141]

I was talking about certain advantages one motor might have over the other. Compression ratio falls into the "subjective" category.

In that case, the bigger 1G rods are heavier and rob power....that should fall into the "subjective" category as well.

We're talking about benefits of 6-bolts over 7-bolts as they're assembled from the factory. As they are, the 6-bolts have a lower compression ratio which will cause the O.P.'s car to feel more sluggish...that's fact, not opinion. It's not like we're discussing turbo sizes or oil viscosities here- those would be considered subjective topics.

 

[oVaBoost]

ANY motor can crankwalk, no motor is immune to it.

yes but most common on 7bolt motors

 

[dsm1212]

so im thinking i will be going with building a 7 bolt, i like how it feels now with the t28 at 25psi. i just want to go bigger. I deffinetly don't want to have less tourque. I thought about building a stroker but i think that would be almost worthless since i am FWD.

 

[Winglessflight]

I wouldn't say "worthless". That's far from true. It just depends on how you design your setup. A 2.4 is going to give you a lot better off boost response (depending, of course, on compression) which is great for street driving and gives you an off boost advantage, and spool your turbo faster. Just learn too feather the throttle when boost hits if you spin. You were going to have to do that anyway, regardless of what size block you have. Your advantage with the auto is you can concentrate more on throttle control than shifting, making your fwd less of a handful, more reliable and durable (if taken care of properly), and less "driver error" excuses down the line. And if you really wanna stir things up, get some slicks, a higher stall converter, and brake torque the pants off that thing... .

 

[the_mork]

I would say grab the IPT shift kit and end clutches and call it a day for your transmission, if it breaks then replace it with something more beefy but our transmissions as they sit (after taking care of out crappy end clutches and valve bodies) are pretty stout. Installing either kit does not require dropping the tranny.

As has been stated (and perhaps resolved) sticking with the 7bolt IMO is a good choice because the extra work of putting a 6bolt into an auto car is not worth the minimal potential gains and comes with its own can of worms and disadvantages.

 

[dsm-onster]

The stock 6bolt record is 600whp. It's a worthwhile swap.

You can have 2 6bolts for the cost of forged internals for the 7bolt. You have a little less work involved upgrading the internals of the 7bolt.

 

[dsm1212]

thanks for all of your help i think that i will just build a 7 bolt now i just have to decide if i want to go with the 2.3 and a bigger turbo or stay 2.0

 

[mountaineerjeff]

my .02 is to stay with the 2.0
it has plenty of power for a DD

 

[Nihad]

Stay with the 2.0 its alot cheaper...

 

[dsm1212]

well i want to stay with a 2.0 but i kinda want a bigger turbo but don't want to have to sacrafice the quick spool time but i don't want to stay with a 2.0 and a smaller turbo that falls on its face around 5000 rpms

 

[4g64fiero]

The stock 6bolt record is 600whp. It's a worthwhile swap.

You can have 2 6bolts for the cost of forged internals for the 7bolt. You have a little less work involved upgrading the internals of the 7bolt.

Are you saying 7 bolts are more expensive to build than 6 bolts?
Theyre not.
7 bolts eagle rods:
EXTREME PSI : Your #1 Source for In Stock Performance Parts - Eagle H-Beam Connecting Rods: Mitsubishi Eclipse 7-Bolt 92-99
6 bolt rods:
EXTREME PSI : Your #1 Source for In Stock Performance Parts - Eagle H-Beam Connecting Rods: Mitsubishi Eclipse 6-Bolt 90-92

Most parts are the same price.

If your saying you have to build a seven bolt to hold what a 6 bolt will hold, thats true, but that built 7 bolt will be WAY stronger than the stock 6 bolt so its apples to oranges. I dont see a reason to swap to an engine just for the stronger rods when he is going to build it with forged internals in the future anyways.

AMS has an evo 8 they had for sale that they made 600 hp on the stock internals as well. IIRC you can take ALL the internals from an evo8 and stick them in a 7 bolt as long as you use the correct thrust bearing design for the block your swapping to. But, that wouldnt make sense to do when the stock 7 bolt eclipse internals should technically be stronger since they arent lightened.

 

[easy]

didn't they take care of the biggest crank walk problem in the 98+ 7 bolts by going with a different thrust bearing...

 

[Burnett03]

yes but most common on 7bolt motors

Your point is? You said a few post above that 6bolts don't walk, and well that isn't true.

 

[dsm-onster]

Yes crankwalk is overrated. Yes it is, by far, much more common with the 2g 7bolt up through 1998, I believe. It may be just money, but some just don't want to risk their built motor costs (forged internals + machining) with the realistic (not overrated) chance of crankwalk. The benefits of the girdle and other factors should be weighed in. . . But not in this person's case. He doesn't "need" a build.

Are you saying 7 bolts are more expensive to build than 6 bolts?
Theyre not.
7 bolts eagle rods:
EXTREME PSI : Your #1 Source for In Stock Performance Parts - Eagle H-Beam Connecting Rods: Mitsubishi Eclipse 7-Bolt 92-99
6 bolt rods:
EXTREME PSI : Your #1 Source for In Stock Performance Parts - Eagle H-Beam Connecting Rods: Mitsubishi Eclipse 6-Bolt 90-92

Most parts are the same price.

If your saying you have to build a seven bolt to hold what a 6 bolt will hold, thats true, but that built 7 bolt will be WAY stronger than the stock 6 bolt so its apples to oranges. I dont see a reason to swap to an engine just for the stronger rods when he is going to build it with forged internals in the future anyways.

AMS has an evo 8 they had for sale that they made 600 hp on the stock internals as well. IIRC you can take ALL the internals from an evo8 and stick them in a 7 bolt as long as you use the correct thrust bearing design for the block your swapping to. But, that wouldnt make sense to do when the stock 7 bolt eclipse internals should technically be stronger since they arent lightened.

He said that he was looking for about 400whp. If he were building with forged internals for insurance at this level, then he'd be better off with the 6bolt WRT cost. We all know the 6bolt will laugh at 100whp more than his goal.

Arn't stock evo8 rods forged? You can say that evo8 internals are lightened. Does the weight reduction of those particular parts cancel the benefits of forging those particular parts?

The girdle helps with a jumproping crank that doesn't rear until far after you stretch 6bolt or 7bolt rod bolts with their respective reciprocating assembly.

Yea, I agree it would be a waste to build a 7bolt block when he can swap in a block that can handle 150whp more than his goal and still be reliable. The 7bolt can handle more than his goal. So if he wants insurance, how much should he really spend?

I'm not comparing any tangible thing. I'm comparing mod paths. He asking which direction to go in. I'm suggesting a particular path that will benefit him financially. He will spend less money and have plenty of durability. 99% of us on here want no more, or can really cope with no more than what the 6bolt block can handle. And the op wants about 150whp less than what they can reliably tolerate. That's plenty of head room.