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365 hp / 428 lb. tq. from 350 TBI??????

tiger9297

tiger9297

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Have a '90 K5 w/ TBI and looking to do an engine rebuild. I'd like to stick w/ TBI for ease and cost but I really want more power. IIRC Holley claims up to 275 hp w/ their 670CFM TBI unit. These guys claim waaaaaay more than that and it looks like they are using mostly stock stuff (470CFM I think). Check out the 350TBI stages I and II. How are they getting these kinds of numbers out of these engines? :confused: http://350chevys.com/index.html
 
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http://350chevys.com/350_tbi_stage_2.htm

That one you are questioning?

I wonder a bit about the compression ratio claims...9:1 w/76CC heads seems a bit optimistic without some exotic pistons, most flattop pistons I've seen for 350's bump compression to that level with 64CC heads. I could of course be wrong, some folks that spend more time building engines than I can probably comment. I'll go check out speedpro's pistons and see what I can come up with, they may make them.

I'd like to see cam specs too...it's a roller cam, but that sort of power with stock heads (mid generation, whats that??) indicates to me the cam is going to be really wild.

Not saying it can't be done, but that is a lot of power for a TBI engine. I don't see anywhere they mention all the upgrades necessary for that type of power, I can't imagine slapping that engine into a stock truck and expecting it to be perfectly fine.

Edit: Federal Moguls site deserves an award for about the most worthless ever. :) I can't find an electronic catalog at all there, so no idea on the pistons.
 
I am not an experienced engine guy at all but it seems to me that no matter what you did to the bottom of the engine you would not be able to get enough fuel and air through a TBI to support that kind of power. I doubt they are just flat out lying. I'm sure they have dyno numbers to prove it, but just seems like something is missing.
 
That's why I wonder why there is nothing mentioned about what needs done to get that power with TBI. Stock injectors alone would be problematic at that level I assume...
 
If they used speedpro H100cp pistons the CR is listed as 9.4 for a 64cc head and 8.6 with a 76cc head. This piston is a flattop with either 2 or 4 valve reliefs in it. I wonder if they aren't using a desktop dyno program to figure hp and tq numbers. I think those numbers are about 50 points in both sides. I'm not real experienced with a tbi setup, but I know big cams give them problems. Also wonder how they deal with detonation problems on iron heads and 9.4 compression ratio's. Or are they expecting the computer to back the timing off all the time to reduce the pinging.
George
 
I have a friend that uses a turbo city modified tbi to support his 383HT motor and it runs great. Turbo city claims to do this setup all the time with no problems. As a note of experience go with a modified gm throttle body over the holley, simply better units. While you're looking search for tbichips.com it think is right, tons of info on how to get power out of these units.
 
The turbo city ones are just bored out stock 350 TB's. Find a 454 TB and it flows as well as the holley ones(both have the same size bores). You can also increase fuel pressure, up to a point, to handle more HP. The best places to find out TB info are camaro web sites, like "thirdGen.org" and stuff. Some of those comaro guys really get them TB to perform, at least compared to stock.
 
How are they getting these kinds of numbers out of these engines?
Click to expand...

They are not. At least not with any 2-barrell TBI. They could get these numbers with a square flange 4-barrell TBI, which is what they are probably not bothering to mention.
 
275hp impossible with a 670cfm throttle body? come on guys, that is highly possible. i've built several 350hp engines with a 600cfm carb. 670cfm is 670cfm, be it a throttle body, a carb, or a pair of carbs.

for an easy way to get that kind of power....
www.cfm-tech.com
not just a bored out throttle body, contoured venturi, spaced injectors, and a more contoured air cleaner, its not that hard to believe at all.
 
They may have in fact gotten these numbers from one of their engines but I will bet it was put together alot more carefully than the other ones probably with some extra little steps too. Dyno numbers can be manipulated pretty easily. A shop looking to get max power out of there motor can tune the motor for the dyno you usually don't get that kind of power out of every one of their motors mabey they have found the "demon tweak" who knows I think you would probably get a good motor and one that made alot of power most poeple think their motors make more horsies than they really do anyway I would bet your engine would be anywhere from 5-15% off those numbers
 
I'm considering a rebuild too , but I'm going to put a new cam, and headers on and see how that works first.
 
275hp impossible with a 670cfm throttle body? come on guys, that is highly possible. i've built several 350hp engines with a 600cfm carb. 670cfm is 670cfm, be it a throttle body, a carb, or a pair of carbs.
Click to expand...

Yes, everybody agrees with this. The numbers this company is claiming is 365 HP, with TBI, which is what the debate is about.
 
with a stock TBI, i'd agree, impossible. but, those are heavily modded TBIs, not your run of the mill production line unit.
 
What TBI are you talking about? Did I miss something on that page that detailed what setup they used to achieve those numbers?

It looks to me to be deceptive at best. To a layperson looking to replace their TBI motor, looking at that site I'd just assume that it's for my TBI truck, and is a drop-in replacement for my stocker. Nowhere do I see larger throttle body, larger injectors, chip tuning, etc. as being requirements to make the power they claim.
 
I'll bet those details would come out in the ordering phase....You would think there would be a disclaimer though....

That price is $500 - $700 more than the lesser TBI version, wonder what all the extras include?

I would think that the stock heads would have a hard time supporting this also....
 
dyeager535 said:
What TBI are you talking about? Did I miss something on that page that detailed what setup they used to achieve those numbers?

It looks to me to be deceptive at best. To a layperson looking to replace their TBI motor, looking at that site I'd just assume that it's for my TBI truck, and is a drop-in replacement for my stocker. Nowhere do I see larger throttle body, larger injectors, chip tuning, etc. as being requirements to make the power they claim.
Click to expand...

My thoughts exactly. I have emailed and called (left message) but have not gotten a response yet.

Not only does it appear that they are using the stock TBI, but it also appears that they are using the stock heads too. Additionally, on the Stage I engine they are in fact using the stock intake manifold. The Stage II uses and Edelbrock manifold. I have had so many people, much more knowledgeable than I, tell me that you can do whatever you want to the bottom of the engine but as long as you have the stock TBI,manifold, and heads you simply will not see a significant increase in power. While I am questioning these engines I can say, on an optimistic note, that if they in fact are getting these numbers I'm all over that. My '90 K5 would "wake up" with that engine.
 
the 454 tbi's are ok but take tweeking to make work. There aren't provisions for kickdown brackets for the tranny and the IAC wiring is different IIRC
 
There's another guy on ebay called extreme-fi that has a 382tq long block for 1999.00. He says that if you buy his motor and the 399.00 tbi package it will make the numbers.
 
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