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Old 12-05-2013, 08:28 PM
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Pontiac power!

hey there guys, I have a 1974 pontiac ventura custom. it's all of the GTO minus the shaker hood. Anyways I'm looking for some mods to do to bump the power. 300 pounds of torque is great stock but I want more horsepower, kinda give it a bit of a kick in the pants if you know what I meant.
To be straight can anyone recommend a cam, intake, and any other work to be done? it's bone stock except a holley 650 4 barell on top. i'm looking for 300-325 hp to the engine. I've heard great things about lunati cams but not sure where to start with them.
Thank you in advance!

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Old 12-05-2013, 10:42 PM
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Originally Posted by rebel101150 View Post
I've heard great things about lunati cams but not sure where to start with them.
Start with the actual static compression ratio of the motor.
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Old 12-06-2013, 08:05 AM
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Start with the actual static compression ratio of the motor.
it's a 7:6:1 compression engine. kind of awful I know.
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Old 12-06-2013, 12:53 PM
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That is low compression, but how it came with the 350, which I assume you have rather than the 307 offered that year. BTW, there are slight differences between the Ventura and GTO, suspension and chassis wise, for instance the Ventura has a 111 inch wheel base, the GTO 115 inches, and the body length follows suit.

Do you have a reason to keep the 350? Pontiac doesn't have the same dimensional issues Chevy has, i.e. big block, small block, they consider all motors big blocks, even up to the 455, they are all physically the same dimensions. This is Wikipedia data which I assume is accurate.

Have you considered dropping in a 389, 400 or 455?

All that said, you should have 200 factory HP, it's easy to make another 100+ in Pontiac motors. I've built and raced three different street '65 GTO's over the years, cam, exhaust and minor head work made big power for me. There are several good hard core Pontiac guys here who can steer you in the right direction.
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Old 12-06-2013, 01:13 PM
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Your motor lacks sufficient static compression ratio to support any cam over stock specifications.
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Old 12-06-2013, 03:31 PM
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You've got #46 heads.... 96cc? or 89? The GTO got the 89 cc head. TBH i have never heard of a ventura custom. either way you have a very low CR.

you need more compression. Then worry about a "bigger" cam or any other performance goodies for that matter. aftermarket connecting rods would be preferred as well. I've heard of 500+ hp Pontiac 350s but you do have to worry about valve clearances and less-than-optimal flow with the smaller bore.

So there may be a couple of options, most expensive at the top (maybe)
Option 1)
Newer aluminum heads and new pistons and aim for some more compression.
New con rods and crank, balance it all, maybe bore/hone cylinders
new cam and lifter set matched to the higher compression

option 2)
Find some 6x-4 or maybe small chamber 4x heads, *** have them rebuilt if they need it, maybe mill them to a smaller combustion chamber if they can handle it. They will likely need work as they will probably have some miles on them. The 6x-4 and 4x from a 400 have a larger 2.11 intake valve and are both common enough castings. I have no idea about stock flow numbers of the 46 heads esp on a 350 bore.

New con rods and pistons, turn or polish the stock crank, balance it all
New cam and lifter set to better match whatever CR you come up with.

option 3)
shave your existing heads. You're still stuck with the smaller intake valve though.
bore the block 30 over, aftermarket pistons, stock con rods, turn/polish stock crank
you *may* be able to go slightly more on cam duration, but probably not by much. it may depend more on compression height. I've not researched "off the shelf" pontiac 350 pistons so i'm not sure what's out there.

You'd need to get down to around 60-65ccs combustion chamber size (depending on gasket volume and whatever piston compression heights and deck height you end up working with) to get to around 9.5 to 10:1 SCR. The smallest stock pontiac head combustion chamber I can recall is 89ccs. Then again I forget a lot. That's why I'm pushing aftermarket heads... you can get 65cc aftermarket heads. For stockers, that's an awful lot of milling, or go with domed pistons which have their drawbacks too. I think the stock compression height on the 350 piston is 1.7 inches.

All in all it may be worth it to find a 400, it would cost roughly the same to build and have more potential for horsepower right from the start (plus you could probably make that 400 a 455 and be in an even better position.)

Last edited by 68NovaSS; 12-06-2013 at 06:15 PM. Reason: Parts for sale
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Old 12-06-2013, 05:01 PM
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Get some heads that are 72 CC and you will be at 9.0 to one.You could run a comp cams XE256 or a 262 with that much compression.
If you run the stock converter and a tall gear stay with the smaller choice of cams.
Keep in mind to use heads with the smaller choice in valves, typically 1.96 intake and 1.66 exhaust as they come very close the cylinder wall at the top of the cylinder. If you use the 2.11 in 1.77 combo they will be close and it may actually cause a loss in power due to valve shrouding.
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Old 12-06-2013, 06:43 PM
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Just a note to 68NovaSS, the 1974 GTO and Ventura are on the X-body platform (i.e. the Nova), and not the A-body platform like the 1973 GTO/Ventura. The 1974 GTO is a one year only orphan.

No wheelbase differences between the X-body GTO and the X-body Ventura. Ventura Custom, and Sprint were also available, and the 350 Pontiac V-8 was standard in the '74 GTO(200 hp 4-barrel version) and optional on the Ventura.
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Old 12-06-2013, 08:55 PM
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Best bang for the $$$ is a swap to a 400 or 455 engine. The 350 is OK (sorta) but will never run on the street as good as with either of these. You may think the swap will cost more than fixing up the 350- but in the end thats false economy. Price per foot pound is less w/a swaop.
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Old 12-07-2013, 05:33 PM
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well honestly guys I love the input and appreciate it but a swap is not an option right now. It's cheaper for me to build the engine up than order an engine and swap it in. Guys are hoarding pontiac parts out here and its difficult to find much engine wise besides the 350. I was questing why it had a bit more oomph off the line if you will, well it has a decent edlebrock intake and it does have the same duals on it as the GTO from that year. i've found some heads on ebay that would be 72cc or so and that looks like a great option although i'm unsure how much power it would add.
A chevy swap has crossed my mind as I could build a chevy 350 up in my sleep but it seems kind of taboo and if i'm not mistaken there would be an issue with the bellhousing mating up to the chevy engine.
I mean only looking to bump 100 horses really cant be THAT hard in the pontiac block.
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Old 12-08-2013, 06:52 PM
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eh keep it pontiac... which heads did you find on ebay?
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