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Old 07-30-2012, 01:25 AM
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GTA better heads

I have a GTA 1987 Trans am and I will want to add some more power.
This is a TPI system with stock 700r4 trans and aluminum drive shaft.
I dont know what power it has now but it ran 14.35 at the track. I would like to see it in the 13's.
I have heads on it that are from a 305 according to the cast numbers. According to the numbers the engine is a Canadian 5.7. I can get to numbers again if necessary.

I want to upgrade the heads. I was told that Vortec heads are a good option.

I would like to know what options I have for an aluminum set and a cam change to develop streetable 330 hp or so.

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Old 07-30-2012, 04:52 AM
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switching to vortec heads will require u to get a vortec tpi manifold base which is about 475$'s alone then u will need somone to burn a custom chip to correct the tune for the vortec heads and the larger injectors u will need

if u have the tpi 350 it should be an l98 engine if so this engine in good shape should get that car well into the 13's and 12's with some boltons

checkout thirdgen.org/techboard for all the info u could ever want on ur gta
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Old 07-30-2012, 06:20 AM
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There are a lot of budget heads in the 180cc-195cc range, almost any of them can get you 330hp with the right cam and headers. You'll also need tuning work done. Budget about twice what the heads cost for the whole project.
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Old 07-30-2012, 06:43 AM
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look into siamese tubes for the tpi.I dont have experience with this system so ask other members about the increase in power.

what was your MPH when you tested your car?
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Old 07-30-2012, 11:09 AM
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Headers installed

I have headers on it already. I bought the car this way so I dont know which brand or style. I can send pics. I know they are wrapped and the car is lowered so maybe it is not the long headers.
The track speed was 93.59 mph.

And yes I am a member of Thirdgen website. Thanks.
I will be looking for heads for the car now. Can I use Vortec truck heads from 96-2000?
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Old 07-30-2012, 11:26 AM
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Quote:
Originally Posted by TA-Rocks View Post
I have a GTA 1987 Trans am and I will want to add some more power.
This is a TPI system with stock 700r4 trans and aluminum drive shaft.
I dont know what power it has now but it ran 14.35 at the track. I would like to see it in the 13's.
I have heads on it that are from a 305 according to the cast numbers. According to the numbers the engine is a Canadian 5.7. I can get to numbers again if necessary.

I want to upgrade the heads. I was told that Vortec heads are a good option.

I would like to know what options I have for an aluminum set and a cam change to develop streetable 330 hp or so.
Speedway part number 7222200 can be had in straight or angle plugs will use your current intake. Reasonable cost teamed with high power potential and light weight compared to iron. Imported castings but priced like an import instead of import but priced like made in America which is sooo common. In a Car Craft shoot out these puppies honked out 385 horses on a 350. Eight Budget Small Block Chevy Heads Tested - Car Craft Magazine

Flo-Tek Assembled Small Block Chevy Aluminum Heads, Angle Plug - Speedway Motors, America's Oldest Speed Shop

Streetable cam doesn't take much more than 190-210 degrees duration to get to 330 horses. EFI especially if a Speed Density system (MAP) instead of Mass Air Flow (MAF) will take mods to the computer and perhaps injectors going beyond that.

One needs to consider the combustion chamber in total. While modern heads with designs that spin off the Vortec that utilize shapes and spark plug location to generate lots of power compared to old fashion smog era design chambers, it must be remembered that the piston makes the bottom of the combustion chamber.

In that regard the flat top piston offers the best by far configuration for making power. The problem is that with a small chamber head they push the compression to places beyond where the octane ratings of pump gas will go even with aluminum Vortecish chambers. The circular dish piston so loved and used by the factory while reducing compression puts too much distance between most of the piston crown and the squish/quench step of the head. This reduces the squish/quench function making the combustion chamber much more detonation/pre-ignition prone for a given octane of the fuel. The squish/quench feature builds what's called "mechanical octane" into the engine.

The compromise solution is to change to a D shaped dish piston. This puts the dish under the valve pocket while having a flat surface on the piston's far side to close with the matching surface of the head. This will allow you to push the compression of aluminum heads into the range of 9.5 to 10.0 for premium fuel without suffering detonation and pre-ignition or the power robbing spark retardation that occurs automatically with EFI systems.

Bogie
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Old 07-30-2012, 03:08 PM
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Speedway Head

I have decided that my best choice would be the Speedway head that you suggested. I have noticed that they are not a lot different in power from Vortec and will not need a new intake. Is that right on my particular engine?

Now, if I change to this head which Cam would be suitable for the power range and streetability? Which cams would you suggest?
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Old 07-31-2012, 08:42 AM
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Common on the 3rd Gen forum is to get a LT1 'Hot Cam'; assuming you have a roller cam block.

Also, not mentioned in the posts above regarding the Vortec head conversion; according to the guru's at TGO; the Vortec manifold for TPI is a really awful casting in terms of flow. Guys use em, but there's a lot of 'hand work' associated with making it perform on par with the L98 aluminum heads (nice chamber shape and ~58cc's). By today's standards, the L98 is a fossil; however for a budget build on a lot of fronts, they're not a bad head. Thge L98 Aluminum head can go for ridiculous prices due in part to the 'Vette Owners Tax'. With the glut of Chinese cast aluminum cores machined here in the states, there are better deals to be had for the 350.
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Old 08-01-2012, 10:00 AM
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Well, you should be able to get into 13's with that car with just some bolt ons. I ran a 13.5x@99.x in my '87 Formula 350 (essentially the same car) with an SLP cold air intake and SLP cat back (and careful tuning).

heads/cam- well most aftermarket aluminum heads will get you pretty close, assuming that you have the intake and exhaust work to feed/exhaust them. The stock intake should work with some cleanup, but the exhaust basically sucks. Headers and a good cat back will get you more than heads without them.
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Old 08-01-2012, 10:14 AM
How fast is fast enough?
 
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The flowtek heads won't be a bad match at all. I'd look into a single pattern cam with about 215 duration, a relatively narrow lsa (like 108 nothing too extreme) and as much lift as you can find (.500"+). Id also consider larger tpi runners down the road but DO NOT SIAMESE them unless you want to sacrifice low end for top end.

Properly port matching everything can help a lot, but it needs to be done properly.

If its well built and tuned, along with a mild converter you should be in low 12's.

Take your time on assembly and tuning and you'll easily surpass your 330hp goal.
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