Road Racing GT2 Fiero engine suggestions

[GT2 Gordon]

I've been road racing a 3.5 (2005 G6) for 2 years and it has been great thanks to this forum. Street strip cam, 65mm tb, headers and a Haltech ECU. No issues with the engine. I'm guessing maybe 275HP at the crank?? Rev limit set at 6500.

For next year I'd really like 325Hp at the crank to compete better with the Corvettes, BMW's and Porsche cup cars.

This is what I'm thinking. Any suggestions are welcome:

7250 rpm rev limit ( So I can avoid shifting into 4th in 2 places. typ shift before 7000)
3.4 block - Line bored
3.4 crank with scraper
SBC rods
11.5 pistons
Fully ported 3.5 heads, LIM and UIM
Racing cam shaft (4500-7000 power band) and proper valve springs
Keep the stock 3.5 rockers arms???
Same 65mm TB
Stock Hyd roller lifters with LS lifter springs ( Will these last at 7250 rpm's for long periods?)
Proper length stronger push rods
Better fuel injectors
MLS head gasket

Do you think it will make close to 325HP at the crank???

Thanks

[1988GTU]

7250 rpm rev limit ( So I can avoid shifting into 4th in 2 places. typ shift before 7000)
SBC rods
11.5 pistons
Fully ported 3.5 heads, LIM and UIM
Racing cam shaft (4500-7000 power band) and proper valve springs
Same 65mm TB
Stock Hyd roller lifters with LS lifter springs ( Will these last at 7250 rpm's for long periods?)
Proper length stronger push rods
Better fuel injectors
MLS head gasket

I would go with the above with added valve springs fitted to your needs.

Using the 3.4 block & 3.4 crank would be not my choice. Stay with the 3500 100%

[SappySE107]

No available pistons, rods, or crank scraper. Its cheaper to do a 3400 for racing than a 3500. Custom cam for racing but I wouldn't shoot for over 7000 without going solid lifter. You can, and its quite possible that it works but for sustained usage, id shoot for 7000 unless you are open to the idea of more issues. Power depends on your exhaust setup at this point. Good tuned headers will be 325 crank capable.

[Guest]

Going to this level custom pistons would be a given anyway, which many manufacturers would be capable of producing, Probe Industries is one company that comes to mind that makes pistons based on dimensions, not necessarily application, for their full custom pistons (at least they used to, even if they don't there are other companies that will). Rods can be adapted from other engines, and that selection should be made before the pistons are, due to the possible need to change the wrist pin size. Crank scrapers are for the most part over-rated, especially in an engine with a properly designed windage tray and has very little clearance between the crank/rods and the block, that the 3500 has. If you REALLY want one, they are pretty easy to make, it just takes time to get the clearance correct.

Some people might say that the smaller rod journal of the 3400 is better suited to high RPM, but I don't think that the 3500 rod journal size is really going to be an issue to 7000 RPM. You may find that you might have to turn the crank down a bit to suit an off the shelf rod anyway, or just a rod that will fit.

I agree 1988GTU, staying 3500 is how I would proceed, due to the better crank, which even if reground to fit a small journal would still be stronger and take the higher revs desired here. I also agree with Sappy on the switch to solid lifters for sustained high RPM use, takes the variability of the hydraulic lifter out of the possible problem equation. This would also require a change to an aftermarket adjustable rocker, so that lash can be set properly, and adjusted as the engine runs in.

Is this in a 2005 G6, or is it a swap into a different chassis?

[ericjon262]

there are rods that fit a 3500 crank available on the shelf they're for a 3800 and will require custom pistons.

http://www.summitracing.com/parts/esp-5967b3d/overview/make/buick

[niceguy]

Any pics of your curent setup and vehicle?

[Will'sFiero]

3.4 block - Line bored
3.4 crank with scraper

Any reason you can't go with the LZ4/LZ9 block & heads? 99mm bore and bigger valves with better ports. Big bore and big valves is the bestest formula for big airflow and big power. Heck you might only need ARP rod bolts to spin an LZ4 shortblock to 7000...

[caffeine]

Especially considering the factory 3900 redline is 6400 rpm

[GT2 Gordon]

Sorry for the delay I was out of town. Thanks for the ideas.
I would love to use a LZ4/LZ9 but the SCCA rules don't allow it. The rules state the last engine I can use is the LX9 and I can't mix and match to an earlier year.
I also figured out the power to weight rule favours the LX9 3.5l so I will try and make that work instead of the 3.4L.
I will change my goal to 7000 rpm to stay with Hydraulic lifters with whatever springs are required to keep things simple. ( I need to keep things simple)
Propose using a "Steel crank" turned down for 2.1" chev rods.
Propose using Manley rods 6" that weigh 558g compared to stock PM at 634g
Propose using 12:1 racing pistons with thin dome ( since I'm not turbo) at 336g compared to stock 369g
Propose using race piston pins at 87g compared to stock 141gs
1) This saves 978g of weight + steel machined off the balance side
2) This reduced stress on the bearings at high RPM
3) This eliminates the need for mass added to the crank to balance which I want to avoid.

And here is a picture of the race car.

[Guest]

if you have a 3.5 g6 block now, why would you go to a 3400 block? Stay with the 3500 bottom end. Some 3500 bottom ends have a forged steel crank already, and the 3500 rods are strong enough to handle 7k rpm. only thing I would do with the rods is to install arp bolts.

There is a guy on here who did a built up 3500 and made 275 whp through a 5 spd getrag so thats definately over 300 crank hp. If you have a cam already, I say a fully ported set of 3500 heads, plus some headers if you don't have some already. That should get you close to 275 whp.

saving 978 grams is a lot of money, and thats only about 2.1 lbs of saved weight. You could save more by buying a aluminum flywheel from WOT tech. I think that weighs about 6-7 less than factory steel flywheel.

I find it odd that the rules will allow a 3.5 lx9 motor, but not a 3.5 lz4 motor. lz4 has bigger valves, bigger intake runners, and a 75mm tb intake opening from the factory. BCC sells a ls1 tb 75mm adapter to bolt on which has 10mm on your current intake. install your cam in that lz4 and you can prob do 300+ crank hp without porting the heads. lz4 heads have 1.7 rockers too. If the lz4 could be used thats how I would go.

[Will'sFiero]

Sorry for the delay I was out of town. Thanks for the ideas.
I would love to use a LZ4/LZ9 but the SCCA rules don't allow it. The rules state the last engine I can use is the LX9 and I can't mix and match to an earlier year.
I also figured out the power to weight rule favours the LX9 3.5l so I will try and make that work instead of the 3.4L.
I will change my goal to 7000 rpm to stay with Hydraulic lifters with whatever springs are required to keep things simple. ( I need to keep things simple)
Propose using a "Steel crank" turned down for 2.1" chev rods.
Propose using Manley rods 6" that weigh 558g compared to stock PM at 634g
Propose using 12:1 racing pistons with thin dome ( since I'm not turbo) at 336g compared to stock 369g
Propose using race piston pins at 87g compared to stock 141gs
1) This saves 978g of weight + steel machined off the balance side
2) This reduced stress on the bearings at high RPM
3) This eliminates the need for mass added to the crank to balance which I want to avoid.

And here is a picture of the race car.
[ATTACH=CONFIG]8330[/ATTACH]

The LX9 block comes from GM with 2 mm bigger bore than the 3400 block so definitely go for that. Will LZ4/LZ9 heads fit that block? Can you use them?

While nifty, I don't think you need to do aftermarket rods.
If you still feel the need, Chevy 4.3 ninety degree V6 uses a 2.250 journal, so rods for that engine are already the right journal size for the largest journal 60 degree engines and just need to be narrowed. Those rods are set up for .927 Chevy piston pins, so you'll have to specify that for your high compression pistons.

For reducing rotating weight, you're better off spending money on a super light clutch like a Tilton dual (or maybe even single) disk 7.25" unit.

Keep piston to head clearance in the .035 to .040 range by appropriate selection of gasket and piston compression height. If possible, order gaskets with gasket bore as close as possible to block bore to minimize crevice volume.

What intake manifold will you be putting on top of the heads?

[ericjon262]

buick 3800 rods also have the right journal size and don't have to be narrowed. the down side, they are on the other end of the spectrum, being a little bit narrower than stock. my rods are eagle H beams for a 3800.