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13B NA Rebuild as turbo engine ?

Old 07-28-18, 02:46 AM
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13B NA Rebuild as turbo engine ?

I have an 86 FC 3s with an NA engine.
I am wondering if it can be stripped and rebuilt into a turbo engine.
Are the housings the same or adaptable ?
Can I reuse the rotors ? Can the compression be lowered ?
I have a 375WHP FC turbo at abou 15PSI and want to convert the second engine/car to be similar or higher HP for track use only.
Engines are hard to find here so as I have this one is why I am wondering if I can convert it.
Thanks for your help guys.
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Old 08-04-18, 12:27 PM
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The main internal difference is the rotors are higher compression. 9.4 vs 9.0. Higher compression rotors can be used for turbo charging but you have to retard timing a bit as it will be more knock prone. Also you'll want to swap out the exhaust sleeves for the turbo version as the there are diffusers to quiet the exhaust pulses. Lastly S4 side plates don't have much material around the upper dowel pin areas so highly boosted engines can crack in that location.
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Old 08-04-18, 01:34 PM
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Re 13B NA Rebuild as turbo engine ?

Thanks t-von
I have been doing lots of reading with a view to extending the dish on the S4 NA rotors to match the dish on the S4 Turbo rotors lower the compression as we would want to run boost up to low to mid 20s PSI .
As the NA and turbo rotors are supposed to be the same weight as stock it seems logical that extending the dish in the NA rotors would mean they are then lighter so I am now wondering if removing that material (we could probably do that ourselves) would then necessitate having the counterweights lightened to match which I think we would need to get professionally done. If so with the other mods needed to the NA engine to turbo it I am starting to wonder if simply selling our NA engine complete and sourcing another turbo engine, probably from over East would end up no more expensive than modifying the NA engine
Our current engine has run at low 20s PSI but we keep it down to about 15 PSI and have no problems but is is fully dowelled. Was dynoed at about 16 PSI to 375WHP . We also try to keep RPM no higher then 7500 rpm.
Might not be as kind to the second engine so re your comments on the weakness in the S4 side plates, I have read in a few places that the S4 engine will run to around 500 HP on stock dowel pins. So I am wondering if fully dowelling the engine is neccessary. What do you think ?
At what sort of power level and boost level do the side plates become vulnerable ?
Are S5 plates stronger ?
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Old 08-13-18, 08:53 AM
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S5 plates, yes are inherently stronger. The dowel landing around the rear upper dowel is much thicker than the S4. But, from what I've seen full dowel on a block will increase the strength, but it may equal out to a set of good shape used S5 irons. Now, I've had a pretty awesome conversation with the Goopy guys, and really, you don't need to extend the dish on the rotors, doing so will just require greater balancing and more work. By using the S4 NA rotors and focusing on the tune, you should get just as good returns from them as Turbo rotors. Save your money. Apparently lots of the drag racers use S4 NA rotors stock (maybe balanced a little better) but have a rockin *** tune and put down 1000+hp with Billet plates.

You don't always have to throw away what you've got to make power. Just utilize it properly.

-Tim
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