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]

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.


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.

Oh ok i see what your saying. If I was going to stick with 400hp I'd stick with the 6 bolt to.

As far as evo internals go, I double checked and yeah the evo 8 and up have forged rods, thats good to know.

 

[dsm1212]

so what your saying is if i go with a 6 bolt i can use stock pistons and rods and be able to hold 550 HP before needing to go with forged internals, but if i go with a 7 bolt im going to need forged internals in order to get to my 400-450 hp goal?

 

[dsm-onster]

You can push the 7bolt to 400-450whp. Some break. Many don't . . . It's a reliability thing. Your goal doesn't leave much room.

I REALLY like, I mean REALLY TRUELY like a built 7bolt. You have the girdle and larger bearing "pad" in the journal. Not to mention the extra bolt on the FW/FP comes in handy at really high HP. The headbolt holes are meant for smaller bolts/studs, but that can be easily remedied.

In your case. I would run the 7bolt or swap in a 6bolt. Swapping in the 6bolt will insure reliability at your goal and then a little more. If however you want more than 500whp in the near future, jsut build the 7bolt. The above guys are very correct about how durable a built 7bolt can be.

 

[TSIMonsteR]

Remember, if you go 6-bolt in an A/T, you'll need one of these IPT Performance Transmissions Torque Converters and Transmission Parts for Ford, GM, Chrysler, and Import vehicles

I vote 7-bolt with 2G pistons and 1G rods. Cheap, and works. The 6-bolt and 7-bolt bare block with the same internals will make the same power with the same durability.

Crankwalk is overrated. Half of the reported "cases" aren't crankwalk at all.

 

[90T5I]

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

yes very true but the 7 bolts are prone to it. 6 bolt is a god among motors. and i always prefer a m/t it jst feels nicer

 

[dsm-onster]

Remember, if you go 6-bolt in an A/T, you'll need one of these IPT Performance Transmissions Torque Converters and Transmission Parts for Ford, GM, Chrysler, and Import vehicles

I vote 7-bolt with 2G pistons and 1G rods. Cheap, and works. The 6-bolt and 7-bolt bare block with the same internals will make the same power with the same durability.

Crankwalk is overrated. Half of the reported "cases" aren't crankwalk at all.

That's another good option. He can even upgrade to the arp rod bolts for $40ish more. That would make for a STRONG high rpm capable motor. He will have to get the big ends of the rods bored anyway, so a line hone for using different rod bolts should be included in the costs for modifying the rods with or without the bolt upgrade. How much does a decent machine shop charge to modify 2g rods and install 2g pistons? I've never done this to my builds.

 

[dsm1212]

i think that i am going to go ahead with building a 7 bolt and i think that i want to run an FP 3052 to get to my goal. which should leave room if i decide i want 500+ right? but because its a bigger turbo i was thinking about the 2.3 build but earlier i was hearing its not worth it. I really just want to have decent spool up with a lot more top end.

 

[AWD_Hybrid]

300-400 higher stall & all brazed up, will solve the spool with the bigger turbo.
The stator-sprag press fit is a weak spot, I will be dowel pining future cons.
I modify the 2nd gear band to handle 500hp+ w nos. Can't breakum so far.
The bigger turbo will push torque more, but 252s still drop off in speed climb.
Cheers !

 

[gsxeclipse97]

Well I like the saying that "if its not broke don't fix it." A 7-bolt is plenty strong for the numbers that you are wanting to push. I say save your money on the engine swap and but the money towards reaching your goal and doing all the required work that would make it more reliable with the stock motor.

 

[deflator]

i think that i am going to go ahead with building a 7 bolt and i think that i want to run an FP 3052 to get to my goal. which should leave room if i decide i want 500+ right? but because its a bigger turbo i was thinking about the 2.3 build but earlier i was hearing its not worth it. I really just want to have decent spool up with a lot more top end.

Don't forget about traction. With FWD, faster spool might actually hurt you more than help when you break traction when the turbo kicks in hard. A larger turbo, with slower spool, will give you more torque under the curve. Stay 2.0 and build the head to rev higher.

Oh and if you go 6 bolt with an atx, you'll need the Kiggly adapter kit from IPT. Don't forget a big trans cooler either!