My current Engine

* CSB 355cui
* GM FastBurn "Swirl Port" 64 cc 1,55/1,90 valves
* Claimer Hypereutectic Pistons (Total Seal rings)
* CompCams XR270HR-10 http://http://www.compcams.com/Techn...0HR-10_001.asp
* Stock TBI Intake
* Compression 10,7:1
* Hedman hedders 1-5/8'' Tubes 3'' Collector

*Adjusted TBI unit
*High volume/pressure fuelpump

 

I don't have dd, but I can tell you that stock tbi intake is killing you!

 

I have the same thougts about the Intake...

But it burns rubber with 2,73 in the rear anyhow

One thing that is for sure is that the engine consumes a lot of air.
If i rev the engine with the stock snorkel aircleaner from the 305 it sucks the lid down at least 2" :P

Would be fun to know what the current setup performs.

 

According to Comp Cams Cam Quest software, with a high flow dual plane (an RPM air gap or the like) and a 750 cfm carb, you're looking at:
367.2 HP@ 5000 and 439.5 FtLbs@ 3500.
The TBI unit you are using will make more torque at lower RPM's but less overall power in the mid-to-high RPM ranges.
This program seems to add torque to the bottom and steals hp from the top when using the TBI unit. It also lowers the entire useable power band by 1,000 RPM. Very interesting!
TBI results:
345.6 HP@ 4500 and 485.7ftlbs@ 2000RPM

Johnny Blaze is most likely correct! However, that torque output at 2000 is quite impressive! No wonder you destroy the tires with that 2:73 gear!

 

You're not still running that stock air cleaner are you?

 

Hehe no, the stock aircleaner is replaced

 

First of all, which Fast burn heads? Are they truly swirl port (191, or 193 casting number)? I'll assume that they are.

Fast355 has made big power even using the factory intake manifold, so the claim that it is limiting your output is IMO unlikley.

The stock unported heads aren't helping you any, because you have a fairly hot cam and a good exhaust... and your combination is aimed at the range where those heads really are a flow restriction.

On the power estimate, IMO if you had enough fuel delivered (I'll comment on that below) AND if you had a good ECM tune (a stock chip will not work well, if at all), then I'd ceiling the power at around 310 hp and the torque at 380 ftlbs. I used the term ceiling because the stock unported swirl port heads are a flow restriction in your case with your cam, and using the D. Vizard cfm flow rule-of-thumb of 2*cfm (a 350 assumed), and using 178 cfm as the max intake air flow speed for 193 casting swirl port heads (data from Fast355), you'd be limited to 356 hp. I don't think you'll get there however.

356 hp doesn't equal 310 (my guess) because a sbc TBI unit with two 1 and 11/16" bores (42,6 mm diam each bore) is going to become a flow restriction itself once the power goes past 300 hp.

I think the intake manifold can support flow (and power) above that, but the sbc TBI units won't. I also don't think machining them out to a larger bore, or using the 50mm bore big block TBI unit is really required because I skipped over fuel and only briefly mentioned tuning.

Two sbc injectors will have a tough time supporting over 300 hp, nevermind 350+. You need, at the very minimum, copcar injectors orTBI injectors from the 454 TBI, and you probably need to raise the fuel pressure as well. There is a often quoted formula for fuel delivery, BSFC, number of injectors, rpm, and VE that I won't repeat... but you need to use it to (a) size the injectors you need and (b) choose the right fuel pressure. You didn't specify these things, so you need to check them. You did say "adjusted TBI unit" but adjusted could mean different things ("ultimate mods", bore area, fuel pressure, injector spacers, TBI spacer... etc) so I'm being specific on issues of the flow area (bore) and the combination of injector size (lbs fuel/hr) and fuel pressure.

Lastly -- ECM (chip) tuning. All of the above is non-stock, so you MUST use a custom tune to get the engine to run well at all loads and speeds. I cannot stress this enough --- listing the parts above only tells you what you MIGHT make for power; tuning decides how close you will really get.

Fast355 has made a lot more power with the swirl port heads, after he ported them, using the factory intake manifold, and a similar cam. But he also had the correct injectors, proper fuel pressure, a high-demand fuel pump, and very good ECM chip tuning. Search for his posts for more details. Lo-tec also made 250+ fwhp (my estimate) using the same stock heads and a smaller cam, so I don't think my guess is unreasonable. FWIW, HTH.

 

I think the only reason the computer analysis showed 345 HP and 485 ftlbs is because the program estimates the cylinder head flow to be 219 CFM.
I completely agree with 2hp per CFM.
2 times 219 is 438, but the program also knows that the complete combination of his particular parts is not capable of making a full 438hp.
I also agree that these numbers assume a PERFECT tune.
You are absolutely correct to assume I have no ACTUAL flow data for his particular heads (all are different). I just selected "Fast Burn" from the cylinder head flow data's drop down menu, and it did the rest. I'm sure Comp Cams did some research before posting all the flow ratings. Then again maybe there are a few different styles of Fast burn heads and they just picked the best castings to add to their program-I dont know.
If you have actually flowed your heads, I would be willing to enter the information manually to see what the results are. So far, in my experience, as long as the data entered into this program is correct, the output is suprisingly accurate.
Just trying to help.