To Turbo or Supercharge

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Killer6 said:
Draw-thru carb vs mpfi, the turbo body heats the inlet air even w/o boosting, draw-thru w/alky will help cool it. I have no idea what the OP is envisioning here, so just bringing some info to light. 400 hp isn't that lofty an output achievement, but durability as You say, is going to require a lot of attn.
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Draw through should not even be considered at this point in the evolution of turbochargers and how awesome off the shelf blow through carburetors have become. Draw through stuff is ancient technology and gives you no ability to intercool at all. Durability aside (but also very important) 400 hp from a slant IS a lofty goal. There’s only a handful of people that have done it.
 
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TT5.9mag said:
All you gotta do is search for it. Are you insinuating that it’s easy and lots of people have 400hp slant 6s?
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Depends on exactly what your talking about, durability and or 400hp?
Not saying it's easy but 400 hp doesn't sound like a pie in the sky number especially if going the turbo route. As for can the bottom end take it, I would believe so unless you point out some weakness?
 
I would supercharge it, between the two options:
- the dreaded turbo lag. Always worse with a smaller engine. 225 ain't that big, 440 is big, nearly twice the size.
- simplicity. Having to cobble together an exh system for a turbo.
 
The /6 head is the greatest weakness when it comes to power, a fully built na /6 power limit seems around 300 hp. Most warmed over /6 probably lucky to make 200hp.
 
273 said:
Depends on exactly what your talking about, durability and or 400hp?
Not saying it's easy but 400 hp doesn't sound like a pie in the sky number especially if going the turbo route. As for can the bottom end take it, I would believe so unless you point out some weakness?
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I don’t think the bottom end is a problem at 400hp. I do think it will take more than 14 psi or so to get to the 400hp mark and it’s been proven time and time again that the slant head bolt arrangement and size is just not up to the task. Like I said twice now, it IS doable and I hope the op does it. But you ain’t gonna screw a slant together with shelf parts and cram 15 pounds in it and have a reliable 400hp.
 
Bewy said:
I would supercharge it, between the two options:
- the dreaded turbo lag. Always worse with a smaller engine. 225 ain't that big, 440 is big, nearly twice the size.
- simplicity. Having to cobble together an exh system for a turbo.
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Turbo lag is simply a matter of sizing the turbo correctly. It was a big problem for OEMs back in the day but we have ceramic dual ball bearing turbos and billet wheels and all kinds of fancy crap now that makes lag a thing of the past. The OPs goal will be harder and require more boost from a supercharger than it will from a turbo. Hands down a turbo will be the easiest route, but I agree probably the most involved fabrication wise.
 
273 said:
The /6 head is the greatest weakness when it comes to power, a fully built na /6 power limit seems around 300 hp. Most warmed over /6 probably lucky to make 200hp.
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It's not luck, and any decent attempt at making power will be about that, a serious plan for a really hot one will easily exceed that. Mine fell just short of 200, and it was under-carb'd, at 196hp. :thumbsup:
 
Killer6 said:
It's not luck, and any decent attempt at making power will be about that, a serious plan for a really hot one will easily exceed that. Mine fell just short of 200, and it was under-carb'd, at 196hp. :thumbsup:
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Did you have to do any porting?
 
Killer6 said:
It's not luck, and any decent attempt at making power will be about that, a serious plan for a really hot one will easily exceed that. Mine fell just short of 200, and it was under-carb'd, at 196hp. :thumbsup:
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I just mean a lot of heads have decent amount if untapped power waiting for basic hop ups yo unleash it, the lowy stock 318 head can do 300 hp with mild and a least 325 hp wild setups before porting etc... From what I understand the work done to the /6 head is gonna make the build hp wise.
 
273 said:
I just mean a lot of heads have decent amount if untapped power waiting for basic hop ups yo unleash it, the lowy stock 318 head can do 300 hp with mild and a least 325 hp wild setups before porting etc... From what I understand the work done to the /6 head is gonna make the build hp wise.
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Yes, the head had 1.74/1.41 valves in it, & I pocket ported it. It was done with no flowbench at the time, so I was conservative with My approach, I know now it had room for much more improvement.
 
Dedicated cams for power adders are usually ground on wider LSAs to reduce overlap. Otherwise, the power is flushed out the exh during the o'lap period. Turbo cams often have less exh duration [ than the intake ].
 
Bewy said:
Dedicated cams for power adders are usually ground on wider LSAs to reduce overlap. Otherwise, the power is flushed out the exh during the o'lap period. Turbo cams often have less exh duration [ than the intake ].
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Thank you for that info. What about lift? How would this affect a supercharged engine ? Do I need to be careful with lift. I have a 440 lift cam now but was looking at some of the Cams with big lift 500ish and 112 LSA
 
Slant 6 Nick said:
Thank you for that info. What about lift? How would this affect a supercharged engine ? Do I need to be careful with lift. I have a 440 lift cam now but was looking at some of the Cams with big lift 500ish and 112 LSA
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It depends on what You mean by "be careful".
Anything much past .460" will require machining the guides down for seal/retainer clearance, which the shop can do easily, & You should go to a modern PC type seal when thats done. If it's a 198 or 225, & low enough pistons for boost, the valves won't even be in the same zip code as the pistons so no interference to worry about there. Particularly if You're staying with wide LSA's. Guide ht. & proper valve springs are Your big musts there. Remember to add some extra seat load above the cam requirements for the boost, the more psi, the more You need to add when selecting a spring.
 
Killer6 said:
It depends on what You mean by "be careful".
Anything much past .460" will require machining the guides down for seal/retainer clearance, which the shop can do easily, & You should go to a modern PC type seal when thats done. If it's a 198 or 225, & low enough pistons for boost, the valves won't even be in the same zip code as the pistons so no interference to worry about there. Particularly if You're staying with wide LSA's. Guide ht. & proper valve springs are Your big musts there. Remember to add some extra seat load above the cam requirements for the boost, the more psi, the more You need to add when selecting a spring.
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Thank you for the advice! Will def keep that in mind.
 
I've thought about going with a home brew draw thru on my recent/6 build. True, measured, 8-1/2:1 CR, ported and shaved head, oversized SI valves (1.70/1.44) Oregon 819 cam (no overlap with this cam) and Aussie head gasket.

this is in a D150 with a 727, and 3.21s different purpose than OP. Was thinking about 8 lb or so limit. "Hey, it's a truck"!
Was looking into possibly using a turbo off of a lebaron or shadow. Yeah smallish I know but I'm not building a racer.
 
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