Originally Posted by gofastz
a fac LT1, puts out 300hp rite? the one we have our hands on has Alum heads, they any good?? what did the car run down the Qt when it was new? and now we are looking @ a hot cam kit 525", and some headers with 15/8 or 13/4 primaries with 3" ex to a flowmaster, how much HP would that combo breing, and how fast would it do n a Qt??
Yes a factory LT1 was rated at 300 horse with aluminum heads. The cast iron headed LT1 is from an Impala not a Camaro or Corvette. The Camaro is high 13 low 14 second car as comes out of the box. The LT4 head is a better breather with raised ports but uses the same chambers with slightly larger valves it's rated at 330 horse, but the other changes with a cam, 1.6 roller lifters and retuning the EFI obfuscate what the changed heads actually contribute to the increased power over the LT1.
I have a Franken mouse that uses a stock bore, 4 bolt, 880 Vortec truck block with an LT1 cam running the valves thru 1.6 Miller roller rockers. It uses Gen II LT1 heads modified to conventional coolant routing and milled to 50 cc chambers, the SCR is hair under 10 to 1, they use Manley Race Flow Valves, the springs are Howard?s Zero Tolerance Electro Polished 1.25" Drop-Ins. Other than that the heads are stock. The pistons are Keith Black hypers, std bore with a 19 cc D cup relief. The crank is the standard GM forged truck for one piece seal that came in the block. The rods are Howard?s Sport Lite 6 inchers. Induction is built from 1991, L98, TPI modified to fit into a GMPP LT1 spread bore carb intake. It uses a 650 Holley throttle plate on a 4 hole aluminum block to support the TPS and other injection sensors. The MAP sensor is relocated to the right head in a vertical position to mount on the revised coolant return off the front of the head, ala, Smokey Yunick/Moroso return of the 1970s and 80's. The front end is converted to V-belts to make space for the coolant returns. The water pump is a long style, conventional rotation Edlebrock. The back of the heads are vented from the std LT1 banjo vent to the forward coolant return adapters to prevent air or steam pocket formation above the upper rear portion of the number 7 and 8 combustion chambers. The SBC is known to The ignition is a small cap outside coil, HEI from a 1995 350 TBI equipped pick up it retains the computer generated advance. The computer has a custom prom from Fastchip, done about 7-8 years ago. The headers are Sanderson shorties made for the S truck V8 swap. Exhaust is 2-1/2 inch H pipe duals thru dual cats (it has to and does SMOG) and Thrush glass packs. This thing is closing in on 200,000 miles of use so it has proven to be a very reliable configuration.
This engine dyno'ed at 398 Hp at 5800 RPM on the crank when it was new. The test used the installed headers to a 2-1/2 inch Y pipe with a 3 inch exit, no cats, no mufflers. As installed it has cats and mufflers. The exhaust has morphed into 2-1/2 inch primaries with an H cross over to a pair of CATCO cats It comes off the cats at 2-1/2 curves up under the truck's bed reduces to 2-1/4 and passes thru a pair of long Thrush glass packs, then over the axle and out under a rear valance panel.
Experience would tell me that your installation would do better with 1-3/4 to 1-7/8s equal length headers into 3 or 3-1/2 inch primaries. Performance wouldn't be much improved with out more rear gears. I run 3.08s on the rear and it is a bit doggy at 70 where it's only turning 2000 RPM, the engine doesn't come on super strong till it gets to 3000 then it plants my butt to the seat. But since it has to commute long distances in heavy traffic along with the power it had be decent on fuel mileage, which it is pretty good running 17-19 in the winter and 20-22 in the summer. When it was young, it would turn about a 12.9 quarter but has serious traction problems so more suspension and tire work that it never got would certainly make it faster.
I would highly recommend d dished pistons. The factory slugs use a round dish which pretty much eliminates anything you would be pleased to call squish and quench. These functions are big time important in extracting maximum power and holding off detonation. So you've got to think of the pistons as part of the combustion chamber shape with a great deal of control over the flame travel.