# Getting More HP



## nanagoat (Sep 4, 2011)

I have a 67 GTO with a 69 YD engine. The set up has the 46 heads .... a 9794234 intake which was used for all 4bbl set ups in 69 and a Rochester Quadrajet. The 46 heads were rated at 290 HP, and I was wondering what additional HP do you think I pick up having the 4bbl? What ways do you think I could spruce that up? Also, for resale how do you think this set up at would effect my value?


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## Instg8ter (Sep 28, 2010)

the 46 heads have the small valves so a set of 72cc large valve heads would make it breathe better along with a set of ram air manifolds or headers and the 290HP is probably more in the 320 range as they were under rated.


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## Chris Holabaugh (Jan 18, 2009)

You have to remenber that a engine is just an air pump. So getting more hp is mostly about getting more air to move through the engine and you can do that in many ways. It just how much you want to spend. The other way is just reducing friction.


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## BearGFR (Aug 25, 2008)

"How much" questions are always difficult because there are so many variables that go into it. Since you already have the non-original engine, you're not going to affect the value of the car much no matter what you decide to do to the motor so don't worry about that aspect of it. 

Both Instg8ter and Chris are dead on --- the more air you can move through the motor, the more torque you can get out of it. Traditional avenues consist of things like better exhaust, better intake, better heads, "more" cam, etc.

Bear


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## geeteeohguy (Feb 2, 2008)

Also, be advised that pretty much any 70-72cc Ponitac performance iron head will require 100 octane fuel to run if you are using stock flat top pistons....


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## nanagoat (Sep 4, 2011)

Thanks guys. I wish that when I purchased the car I did a little more homework. What got me wondering about the engine in the first place was that it didn't seem to have the same ' put me back in the seat' get up and go as the GOT I had back in the seventies. It has a 9794234 intake, which from what I can find is that it was designed for a 69 Ram Air III...if that is so, I consider that a plus. Would an easy bolt on upgrade be to get a more efficient intake? Any suggestions? The car is a really clean convertible with a 4 speed and 3.55 posi rear.


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## geeteeohguy (Feb 2, 2008)

My suggestion would be to leave the Pontiac intake and Quadrajet on the car and maybe do a compression test to roughly figure your compression ratio. The #46 heads are big car heads, and about 84-87cc, if I remember. Not an issue. I think a cam change would help you out immensely...like an 068 type grind. I have small valve heads on my '67 GTO ragtop with an automatic and a TH400, and even with the 2.56 rear gear, it runs really hard. But I have a decent cam.


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## Instg8ter (Sep 28, 2010)

By the way great pics Nana, we were at the Autorama over the weekend and they had a pinup girl contest on the lower level with all the ratrods. My 19 year old daughter (who has claimed the Tempest as hers) was so bummed she did not know about it so she could enter.


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## Thumpin455 (Feb 17, 2010)

46 heads could be 350 heads too, and that means small valves. The good thing about them is they can be ported and larger valves installed, and they will flow as good as any 72cc 2.11" intake 1.77" exhaust valve head that has been ported, but with chambers that will run on pump gas even with a 455. They should have screw in studs already, so no need to change that, just send em off to be ported with new valves, and then go with a bit larger cam, like a Summit 2802 or similar size cam.


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## lars (Sep 28, 2004)

I travel all over the country doing tuning on Corvettes and Musclecars (check "Tuning for Beer" or "Lars Grimsrud" on Google). The biggest immediate improvement you can do to your car is to simply do a good setup on the ignition curve and the carb - we've dyno documented improvements ranging from 15 to 70 horsepower just by doing a precision setup on these cars. Do the following:

1. Pull your distributor. Shim out the shaft endplay, install the missing advance limit bushing, and then install the distributor with a 2500-rpm full-advance curve for 36 degrees total timing. Make sure you have an appropriately-matched vacuum advance control unit.

2. Pull the Q-Jet and set it up right.

3. E-Mail me for my "How to set your Timing" and the "Q-Jet Tuning Paper." The timing paper has all the info on setting up a good timing spec on your car. Use the section of the Q-Jet paper titled "Quickie Performance Setup" to get a great performance tune on the carb. With these tuning changes, your car will really come alive with the setup you currently have. The tuning methods outlined are almost identical to what Royal Pontiac was doing with the Bobcat GTOs. You can also check out my sticky at the top of this Forum section, outlining the process I just described above.

Lars
[email protected]


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## geeteeohguy (Feb 2, 2008)

Thanks for posting Lars. Been awhile! Excellent advice, and the first place to start, for sure!


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## nanagoat (Sep 4, 2011)

Thanks Instr...I was not at the Autorama. The pictures are of a neighbors daughter. The mother called me a few months back and asked if they could use my car for the photos...they came out nice.


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## nanagoat (Sep 4, 2011)

Thanks Lars and everyone. I will look into the cam first and get the Q-jet in tune. Summers coming and it would be a fun project. .


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