Reduced compression

[carsonlhammond]

https://www.summitracing.com/parts/mah-2242190020

So I called summit and they can’t get them, mahle has discontinued all variations of the reduced compression idi piston. But I REALLY want to Get my hands on some. There are a “couple” threads on here discussing boost and compression and obviously this is the best way to solve the issue VS milling the pistons. It says that it will give you around a 19.7:1 cr. Does ANYBODY know where to get something like these? Does anyone have an old set around they’d like to sell? They were supposed to be used in blocks that had been milled .010 and so the wrist pin holes are machined .010 higher in the piston. In theory this would let you run a cam with even longer durations and lifts without piston on valve romance. Who makes custom pistons? Maybe they could make a set. Anyway thanks for any feedback!

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[Thewespaul]

They can be found on rock auto but decompression is the easiest way to ruin performance in an idi. The stock cam and valvetrain flow phenomenal for the stock horse power rating, and with an upgraded turbo these things don’t seem to have airflow as the limitation but rather fuel.

 

[carsonlhammond]

But if I were to say build a strictly track engine where power until boost doesn’t matter as much as a street truck?

 

[79jasper]

Not to mention dealing with the hard starting to follow.

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[carsonlhammond]

I guess I should clarify. I want to build a high output engine. Like 400+. I was thinking of buying one of your pumps Wes and I was hoping you could steer me in the right direction to build something like that. These pistons I thought were a good start. Then possibly an r&d cam. Maybe you have a better option? Please enlighten me as you seem to have the know how to build something capable of that.

 

[Thewespaul]

But if I were to say build a strictly track engine where power until boost doesn’t matter as much as a street truck?

How much power do you want to make? Even the biggest pump Ive ever made to date(db4 conversion) only made enough fuel that just an s300 frame turbo could digest it, even with a stock IDIT bottom end it will handle it fine. Removing compression in these engines is removing efficiency, they need it.

 

[Thewespaul]

Oops you beat me to it, Id say 400hp paired with a stock rebuild on a IDIT, add studs and springs and call it good. Fuel you would need either a hot big bore db2 or a smaller db4, I have a set of competition only injectors that I could use some more data on.

 

[carsonlhammond]

I have a turbo block that needs to be re-ringed and re-bearinged. I would be happy to do some testing. What would you looking for in terms of data? Would the truck need to be street legal or can I get away with green stickering it? I want to build a pull truck so I’d like to keep it off the road. What pump would you set me up with to match?

 

[YJMike92]

https://www.summitracing.com/parts/mah-2242190020

So I called summit and they can’t get them, mahle has discontinued all variations of the reduced
compression idi piston. But I REALLY want to Get my hands on some. There are a “couple” threads on here discussing boost and compression and obviously this is the best way to solve the issue VS milling the pistons. It says that it will give you around a 19.7:1 cr. Does ANYBODY know where to get something like these? Does anyone have an old set around they’d like to sell? They were supposed to be used in blocks that had been milled .010 and so the wrist pin holes are machined .010 higher in the piston. In theory this would let you run a cam with even longer durations and lifts without piston on valve romance. Who makes custom pistons? Maybe they could make a set. Anyway thanks for any feedback!

You must be registered for see images attach

Looking at the summit page the ship date from Mahle is 8/22/19. I guess you could get a 7.3l engine to rebuild. the pistons are still available for that application.

 

[Thewespaul]

I have a turbo block that needs to be re-ringed and re-bearinged. I would be happy to do some testing. What would you looking for in terms of data? Would the truck need to be street legal or can I get away with green stickering it? I want to build a pull truck so I’d like to keep it off the road. What pump would you set me up with to match?

Id like to see how they do matched with a pump built to their spec. The pump if setup on the bench with an aggressive delivery valve setting that better matches a low pop pressure injector like the 3M injector is designed for, it could be the ticket for getting a lot more fuel from these rotary pumps. For 400hp, a very rowdy db2 could be built to support it, but if you wanted to do any more than that a db4 would be the way I would go. With the db4, I could see room for over 500, if we're building a pump with an ag governor, and not worried about having a quiet, smokeless idle like I do in the street pumps.

 

[carsonlhammond]

What are looking at in terms of price for this setup? Also what turbo would you recommend?

 

[Thewespaul]

I’d really like to see how far my T04Z drop in turbo for the idit could be pushed:https://classicdieseldesigns.com/co...roducts/cdd-62-62mm-drop-in-093-factory-turbo

That would save you some time and money not having to go to a different turbo kit. The max effort db2 would likely be around $1600-2000 by itself, and the db4 would be $2700-3300. If you wanted to buy the pump, injectors, and turbo combo from me I would do a package deal for $3500 with the db2 and $4500 for the db4.

 

[carsonlhammond]

I’d be very interested for that price. I’d do the 3500 dollar option but it’d still be awhile before I’m ready to take the plunge. That seems extremely reasonable

 

[IDIBRONCO]

and not worried about having a quiet, smokeless idle like I do in the street pumps.

Is this kind of like the IDI version of the head turning idle you get from a lumpy cam in a gas hot rod? That was the first thing that came to mind when I read this.

 

[jaluhn83]

Best solution is probably just to have the pistons milled. Plenty of thickness to take a bit off without issues, and ceramic coating will help with gear flux