I'm in the process of having Dyno Don upgrading my TPI 350 motor. Right now I'm around 400HP with a dyno'd 322RWHP. Figuring a 20% drive train loss. See signature for future mods.

I'm running the factory TPI plenum that came with the car. It has been modified for a 58MM throttle body and port matched. I'm running an Edelbrock TPI manifold that has been Extrude Honed and port matched. I have SLP runners that are siamesed. Existing mods are in the signature.

Question is can I reach 450HP at the crank with my future mods? Here they are and my estimates.

1. Bore the block .030" to 355CI. That should be worth 6HP.
2. Swap out the cam to the XFI 268. Should be worth 18HP.
3. Change to Dyno Don 1 3/4 inch headers. 7HP
4. Change to MAP, proper tune, efficient 3.5 intake track. I figure 10HP
5. Porting my Trickflow heads. 7HP

 

Definitely, freshly bored motor, XFI cam, ported heads. Should do it.

And the headers would add some good upper RPM horses becuase your engines begging for a little better breathing.

 

i dont know man... its gonna come down to your tune.

making 322 rwhp is impressive enough with tpi... u might be pretty much nearly maxing out the TPI setup u have now. make sure your heads can flow good enough.

450 crank hp on a 350 is pretty stout for any combo. i think you might see 420hp. thats still very impressive for TPI... the most i ever seen so far...

many say you cant get 300rwhp outta a TPI setup without BIG cubic inches.


i'd advise going 383 if your gonna rebuild...

 

I don't want to rain on your parade because us SLP tri-y guys have to stick together... oh wait, you're ditching them
Anyways, I think your 20% drivetrain loss is bogus. Don't believe for one instance that it's a percentage, because it isn't. The only thing that is a percentage is the drag induced by the extra side loading (friction in the bearings)... everything else like the weight of the drivetrain is a FIXED hp loss. Example; 200hp engine loosing 40hp to the wheels isn't going to be 80hp lost with a 400hp engine! It'll be more than 40hp, but not by much, something around 42-43hp.
Trust me on this, it's straight from SAE papers and actual personal hands on testing that I've done.
You trapped higher than me, but not by much, and my engine without any accessories is rated at 330hp flywheel... not sure where that leaves you.
I think your goal of 450hp crank, if you want to say CRANK, should be measured on an engine dyno and not derived from chassis dyno. A more reasonable request would be to ask for 400rwhp .
I think it's possible with TPI but it's not smart. Put the TPI in a truck and install something that moves more air = easier horsepower. You wouldn't install a 400cfm 2 barrel carb on a 450hp engine... or would you?
Another little bit of info; big cubes doesn't = horsepower, it just shifts your powerband down in the RPM range. So if you've only got a couple gears for the 1/4 mile then you want big cubes, else go with a lighter rotating assembly like a punched out 350. By being lighter you can rev the engine higher and pump that much more air. It's like free HP . If you ever notice, the big cube engines with heads like AFR 190's aren't any faster than the small cube engines with the same heads . HP is all about how much air and fuel you can get into the champer OVER TIME. Rev the 350 higher and make the hp you want!
Good luck and with dyno don porting those heads you would be looking to replace the LTR TPI

 

its common knowledge that u can make more hp with more inches... the combo wont need as big of a cam and use less rpms so its more streetable

 

I will change the goal to 360RWHP. That can be measured. I agree on the power loss through the drive train is subjective with many factors involed. Also the .030" boring will unshroud the valves just a wee bit more.

Other Trickflow heads that have had the porting done have flowed in the 260CFM range on the intake and over 200CFM on the exhaust. These are with the 195CC intake.

The car is a fully loaded GTA with all accessories on board and fully California smog compliant. Curb weight is 3510 pounds. Just need 38 more RWHP.

 

what was the lift range on your heads? where is that peak flow at? if you are making more flow at higher lifts than the zz9 cam u have now, then definately look to gain some power by goin to that 268 cam. they got abit more lift than the zz9 if i recall right

 

You CAN make more hp with more displacement but that is if you equip the engine with better air flow heads. The funny part is that when guys build bigger cube engines they also install rather large cams... because when you've got that much low speed torque who's missing it? The result is more hp from the "inchs" when infact it isn't just the inchs.

 

another thing to be said is the ci vs rpm. - It doesn't mtter how big a cubes you run, you can turn as high of rpm as your heads/cam will feed it too. My 355 turns around 72-7300, my old mans 445(100+bore 427)9600 in low gear. I help crew a 540ci blower motor turning 9k ...if you can feed it it shall happen...- ci only makes more power if you feed it more.

the only thing that beats cubic inches is cubic dollars...

and to get back on topic(sorry) - yes, I think your list of future mods will get you there. - You REALLY outta look into the "FIRST" intake though...

 

The XFI268 cam with 1.6RR has a lift of .565" on the intake and .570" on the exhaust. My current set up with the 1.6RR has .518" on the intake and .528" on the exhaust.

Here is what is interesting. The XFI cam has an advertised duration of 268 on the intake and 274 on the exhaust at .006". The ZZ9 cam is advertised at 282 and 287 respectively. So the XFI cam might have a better idle and more vacuum at idle. Also the "dwell" time that the intake and exhaust valves are open are quite a bit larger than comparable cams.

 

Welllllll............... Your HP goals are rather easily obtainable. The real question is WHERE do you want this HP to be on the power curve?
If you can get 800HP at 7,000 rpm, will that really help you?

This could open a really long discussion, maybe later.

OK, one thing to check out right away is a good set of self aligning alloy roller rockers, really strong pushrods, maybe a high grade roller cam lifter. Make sure the valves are polished and "flowed" too. I'd also get some titainium keepers/retainers.
Lowering the mass of the valve train and the inheirent friction of a pushrod/rocker arm valve system is always more HP on the crank!
Go over your ignition! 1 degree of timing error is 10% HP loss at optimum tune! Heavy duty timing gear, roller bearing distributor shaft, high tolerance billet dist housing...alll good.
A really good high powered ignition system will squeeze all the HP that's available. Jacobs, MSD have some of the best options.
Try a set of those multiple tip spark plugs too!

Personally I have found that the best power curve will have lots of low end across the band. The more area under the curve, the more available power.

Good luck!