gregl316

iTrader: (1)

Well it's been awhile but my build is done. Thanks to the help of all you out there. Now I want more power!!!!

I have a crate motor from GM. A 330hp vortec heads. I have done everything to get the HP numbers up. But I am putting 252 to the wheels.
Now I have a 5 speed and the 700r4 is gone. My question is...is there a way to get 50 to 100 more to the ground and what do I have to do? Can a TBI do it? I have a lot of money tied up into the unit. Or do I just need to stop dreaming and put a carb on it?

I'm thinking heads and a cam but... the dyno/tunner guy said I can't support it. The TBI is built buy a guy off here. It is 46mm w/68# injectors sitting on a GM Perf. TBI intake. I also put in a Vac AFPR. With a performance TPI fuel pump.

Thanks for the help

Schurkey

Nitrous.

WHICH 5-speed? Will it take more power, or will it **** gears?

Fast355

iTrader: (2)

TBI can and will support the power just fine! Just needs a good intake under it, plenty of fuel pressure, and some decent tuning. 46mm bored TBI flows around 580-600 cfm dry @ 1.5 in/hg pressure drop. Seeing that you have a 5spd and I am guessing 7.5" 10-bolt you are probably only losing 15-18% power through the driveline. You are making 296-307 HP as you sit.

What does your exhaust system and intake consist of?

gregl316

iTrader: (1)

Yea it is a T5 5-speed, and a Moser 12 bolt rear end with 3.73 Wavy posi.

As far as the engine I have the GM performance intake and SS shorty headers a 3" exhaust with a SS Magna flow muffler. No cat.

Schurkey

Ahh. You can expect it to shatter. The typical "World Class" T5 needs to be installed with wing-nuts so it comes back out for repairs easily. I guess the aftermarket has internal parts made from hardened unobtanium; but that gets expensive in a hurry.

jokerZ71

If this is the GM 350 HO,that cam would be the next thing to swap.IIRC,it's a flat tappet.Switching it over to a roller of even similar specs & more modern profile would make substancial difference.That intake isn't doin you any favors either.You're nowhere near the limits of the Vortec heads,so,they are not holding you back @ this point.That cam ,however'is not letting them perform as well as they could.Also,I seem to remember GM uses a fairly thick headgasket on that on the HO for 9.1:1.You could pick up some gains from a thinner gasket & getting the compression up some.

Fast355

iTrader: (2)

I think that engine has the normal .028" compressed gasket used on the Vortec truck engines.

http://www.carcraft.com/techarticles...mble_pie_tech/

http://www.carcraft.com/projectbuild...ckage_install/

http://www.carcraft.com/techarticles..._block_engine/

jokerZ71

According to GM spec sheets,it uses #12557236,which is a .051 gasket.It is listed for use on the 350 HO & the ZZ4 crate engines.

gregl316

iTrader: (1)

So a roller cam, and rockers along with thinner head gaskuts? I have put new head gaskuts on it allready. I just didn't know what to be careful for when buying them.

What about a new tune? How much Hp will that free up? Which cam? That is a lot cheeper then new heads.

Will the TBI keep up with the new demand?

jokerZ71

Are you currently running on a stock tune?If so,you will definitely see some gains from tuning.Do you not know what thickness gasket you used?The heads are not the bottlenek @ this power level.

gregl316

iTrader: (1)

No it has a custom tune on a dyno. No I don't know the thickness of the gaskets. The drivers side is orig. and the passenger side is just one I bought at Napa.

FRMULA88

what are your power goals?? 2 65# injectors can only support so much.
and with 252 to the rear wheels you are at the limit..

I don't care what the so called "experts" on here tell you..
The OEM TBI system is a LOW PRESSURE system.. and was designed for fuel economy / emissions not High Performance.

You can crank the fuel pressure to the moon.. the 65# injector is rated for 65#/hr of fuel @ 13 PSI... You still only have 2 of them. Increasing the pressure to 23 PSI does not double the volume of fuel the injector can flow.

Listen to your dyno guy / tuner a carb will perform much better for way less money or spend the coin on a 4 injector TBI system.

FRMULA88

65 *2 = 130 # hr of fuel..

1 hp = .5 # of fuel per hour (BSFC)

130 / .5 = 260 HP


to support 300 flywheel hp with just 2 injectors they would need to be 93#

you also do NOT want to exceed 80% injector duty cycle.


based on fact not fiction:

http://www.witchhunter.com/injectorcalc1.php

FRMULA88

remember increasing the fuel pressure can increase the flow rate but it is NOT a 1:1 ratio going from 13 to 26 psi only changes flow rate from 18 to 25.5

and keep in mind the increased flow rate is still limited by the injector duty cycle which should not exceed 80% for safe operation..


that being said a 65# injector is only rated for 65# @ 80% duty cycle... increasing fuel pressure is like a dog chasing his own tail... there is not much to gain by doing this alone..

Fast355

iTrader: (2)

You do realize that Mercury Marine had a 496/502 with a single TBI using 2" bores. 405 HP @ 4,600 and it had 61# injectors at 30 psi. The used dual TBI units on a supercharger on a low compression 454 and built a 575 HP @ 5,000 rpm TBI big block.

The intake manifold choice and exhaust will choke the engine well before a 46mm TBI unit will.

gregl316

iTrader: (1)

My TBI is custom built and shaved. It has 68# injectors and is 46mm. The intake is a GM Performance and I had it matched to 46mm. I am running a vac. ref. FPR with a max of 25 psi. I have headers 1&7/8th" w" 3" out to a Magnaflow muffler with dual 3" outs. I have all MSD ign.

So a roller cam and lifters will help? What about 1.6 rockers?

thomas1976

I have no personal experience with a 350ci 330hp crate engine, only read from feedback on the internet that they are overrated and the part holding it back is the tiny cam.

It does not take much to make 300+rwhp with a DIY 350ci and TBI.
I am using a 46mm TB with 2x 80#/hr injectors and a DIY ported performer tbi intake (that is still restrictive, dropping from 98 kpa key on engine off to 89 kpa @ 5600rpm), and still certainly making 300+rwhp.

I guess that if you go with something like comp cams 8-500-8 or up (501, 502, ...), tune and fuel the set up you will be braking easy in the 300+ rwhp too.

1.6 rockers will probably not make a huge difference.

FRMULA88

There you go comparing apples to oranges again. these are not OEM injectors, parts or fuel pressures used in factory 3rd gen.

you also forgot the details that they needed DUAL TBIs.. (that's uummm 1,2,3,4 injectors) and a blower just to make 575 HP with a big block which is pretty un-impressive because that can easily be done with a 1000 CFM 4150 Carb, or a Dominator and no supercharger.

LOL my small block makes 669 HP with a "primitive" carb and 6.5 PSI of fuel pressure and NO blower.. which really makes that big block a dog by comparison.

There is nothing factory OEM about my setup either but as long as we are comparing apples to oranges I might as well contribute.

FRMULA88

Yes a better cam will help but will still be limited by

the 2 injector TBI system
the crate engine cylinder heads

Cylinder head technology has come a long way, even for Gen1 SBC.
2 injector TBIs stopped being using by the OEMs in late 80s-Early 90s there a reason for that. LOL

Fast355

iTrader: (2)

DOUBLE

Fast355

iTrader: (2)

You act like this stuff is hard to obtain. Every 350 TBI pickup truck, SUV, or van used a 61# injector. The marine regulator is practically identical to the 94-95 TBI 454 regulator. Every TBI truck used a 454 TBI unit. A single 2bbl 454 TBI unit is good to over 450 HP.

575 HP is impressive when its happening at 4,800 RPM on pump gas and can run WOT all day long. Marine engines are different animals that car engines.

I do not know many pump gas NA 454 engines that make 575 HP under 5,000 rpm and can run flat out for hours at a time.

Fast355

iTrader: (2)

You do realize that the crate motor heads are 062 Vortec castings. They have made 450 HP unported.

FRMULA88

Only a neophyte would compare a marine engine to an automotive one.

WOT at 4,800 RPM right... that is no where near the actual RPM limits of the engine which is more like.. 6500+ RPM

Marine engine RPM limit is dictated by the propeller (there is no transmission or differential) and the CAMSHAFT for a marine engine has totally different lobe profiles than one used in car.

Apples... Oranges... got it!?

The heads may have that potential but not with that setup up... you need to burn more air/fuel to make more HP>>>

Fast355

iTrader: (2)

He could swap a 4bbl dual plane and a 750 cfm 4bbl on that setup and NOT make 10 RWHP more. Its the cam, dual plane intake, and shorty headers that are limiting the engine.

Actually if you cannot get the correlation between marine and automotive and the differences that is on you. Its still a 575 HP TBI engine that is nowhere near maxed out. Mercruiser made a 502 with a single 2" bore TBI using a tiny cam, small oval port heads, and restrictive marine exhaust that made 405 HP @ 4,600 as well. That alone tells you that a single 2" bore 2bbl TBI unit will not be a restriction on a 400 HP smallblock.

FRMULA88

Made,,, as in "past tense" what is Mercruiser doing today in the 21st century?!

Perhaps you should have been on the development team for the Hellcat Challenger..
Those engineers must be stupid for not using 2bbl TBI to make 707HP with 6.2 litre small block hemi.

I had Holley 4Di on a "puny" N/A 383 SBC pump gas engine and that made 465 HP @5800 RPM. That was over a decade ago... 405 HP out of a 502 big block is nothing to brag home about... then or now.. LOL

You can keep on dreaming or living in the past but the simple truth is 2 injector TBI "high performance" systems died a long time ago.

I welcomed the 21st century and look forward to picking up my new hellcat in the near future.

Fast355

iTrader: (2)

And carbs died longer ago!! Hell Nascar doesn't even use them now.

Mercruiser builds their own monster now days that is loosely based off a big block and a 32v ZR1. Its an absolute monster, they left anything GM is building today in the dust! All aluminum, 4.57" bore and 4.21" stroke, 4 valves per cylinder, 7.8:1 compression, dry sump oiling, and a pair of turbos. 1650 hp and it has a Gm bellhousing pattern.

FRMULA88

right.. and it's for sale to the general public: I got news for you pal. this is what the "average joe" can buy from them.

http://www.mercurymercruiser.com/mer...selector.aspx?
most you can buy is 450 HP...


BTW when NHRA goes to 100% EFI you can say CARBs are dead.
And even then Carbs are still the affordable choice for the sportsman racer or pleasure driven vehicles.


Anyone else want to feed this troll? because I am done here.

Fast355

iTrader: (2)

Actually I am not the troll that rolls around these boards, slamming TBI everytime a question comes up on what to do to make more power out of one. His current setup does not have much to gain with a carb swap. Unless he swaps heads the TBI will cover his power needs.

gregl316

iTrader: (1)

So with just a cam and some roller rockers I can boost my Hp? Won't I need bigger injectors and of course a new tune.

Tell me which cam and lifters. Should I get rockers and a timing chain too? What about thinner head gaskets too?

Thanks

Fast355

iTrader: (2)

To support up to 400-425 HP at the flywheel you really only need the 30 PSI regulator spring and a different intake manifold. The GMPP TBI Vortec intake just does not breathe well compared to a 4bbl carb dual plane or a 2bbl single plane.

Cam, Rockers and springs will boost your HP dramatically but you need to pick the right one. Years ago Car Craft tested the 330 HP 350 HO and added a few different cams. IMO the best cam profile they tested was the LT4 Hotcam, but that being said it is an older grind and some similar aftermarket grinds will easily outperform it.

I would use new GM LS7 lifters and the GMPP roller conversion package. To go from a flat tappet cam to a roller you will need a timing chain as the bolt circle is smaller on a roller cam to clear the camshaft retainer plate behind the cam gear.

Thinner headgaskets work great at improving quench and making a touch more power so long as you use a rubber embossed shim gasket that is .016" compressed. To use these the block and head must be very clean and very flat.

gregl316

iTrader: (1)

That sounds great.

So intake, cam, lifters and gear. Maybe there's a kit out there from GMPP.

Where should I look?

gregl316

iTrader: (1)

You left me to many options. First off which manifold? 2bbl or 4bbl. Just tell me which one you would buy. There is only one 2bbl but it cost a lot. Is that the best? I'll buy it if it is. The 4bbl has a ton of options.

I have money set aside so that isn't the issue.

gregl316

iTrader: (1)

Here's the manifold and adaptor I think I want.

http://www.summitracing.com/parts/edl-2912
http://www.summitracing.com/parts/trd-2204

This what I came up with after reading another post that the 2bbl flows better in my RPM range.

now the cam.