No one would laugh. Most people don't have enough interest to ask. You've already made the big leap. More to come tomorrow. You'll get it and people will help.
Greetings all! New to the board, new to the old GTO
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That’s it Beef
Utube ,and the guys here, will give you the knowledge ,
just take on one thing on there at a time
and you’ll be fine , and your knowledge base
Will expand quickly , lookin good😎 man
They are so awesome, there’s nothin else like this
You sound similar to me! I bought a 2006 GTO brand new back in the day and now have a 1970 GTO convertible! I did a full motor rebuild on mine, 400 block bored/stroked to 461, aluminum heads, cam, Pro Flo 4 multi-port fuel injection... etc. Butler performance provided the engine recipe and parts and it put out 500hp/550tq on the engine dyno. It's just the right amount of power to make driving on the street exciting. I'm also in the process of a 200-4R conversion, that's still in the works. No matter what you do, they are fun cars!
Those are great numbers. Congrats on your car.
I’m really curious as to the current tune of my motor now. These guys got me thinking about the ignition, timing, etc.
I’m gonna have to check that out.
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Working on your car is not difficult if you have some mechanical skills. They are really quite simple once you know the aspects of how to work them.
Many of us here can walk you through it if that is what you want and you can decide what you feel you can tackle and what you want to leave to a shop. It is still a wise idea to know what is going on so you can be on the same page as the shop mechanic you choose and know if you are getting facts or hosed.
Plenty of info on timing if you use the search function on this site. Timing lights are easy enough to use and can be a good tool to add to the tool box. If you do, you want to get what is called a "dial back" timing light which has the ability for adjustments used in timing the engine.
You might consider doing the trans/rear axle as an upgrade rather than to dig into the engine right now. You might want to go with the OD automatic and a set of rear gears like 3.55's which would really get the car moving in the lower gears and have the engine loafing at 70 MPH. The acceleration alone will be as adding more HP without touching the engine.
You were thinking OD trans anyway, and I might tackle that first, along with better gearing. My guess is you may have 3.08's, or even 2.78's as factory gearing? Not sure when the 8.5 rear end was installed, but have read it may have been used on some 1971 cars, but for sure 1972. The 8.5 rear end is about as good as any 12-bolt and can be made to handle a bunch of HP/TQ with a few upgrades. So you might try to see what you have. The 10-bolt 8.2 is not a favorable rear end for bigger HP/TQ and sticky tires.
I've been learning about timing since installing the Pro Flo 4 kit. Luckily it's all computer controlled so making adjustments is VERY easy. I initially had 15 degrees of initial timing and 10 degrees of vacuum advance. I increased my initial timing to 20 degrees which made it much more responsive and got rid of the stumble from a dead stop, but with 20 initial and 10 vacuum advance, it started missing during part throttle acceleration. I lowered the vacuum advance to 5 and it seems to have solved that issue. It's certainly a learning experience, just know that the more initial timing you have the less vacuum advance you can run.
So you suggest swapping out the trans entirely?
As for to rear, I know the car does not have a posi rear end. That needs to be addressed.
How can I tell the type of rear (8.5, 12 bolt, etc)? Is it stamped on the diff cover?
Counting the bolts will tell you if it's a 10 or 12. As far as 8.2 or 8.5 there are many references with pictures if you Google. However, if your car has been worked on/modified/restored previously it can be hard to tell if it's a 8.2 or 8.5 because afaik most cases/covers are interchangeable and could be mixes/matched when doing a restoration.
Agreed. Jim has been helping me through my tuning and to wring out the previous owners neglect. Last night I welded up the exhaust and took it for a test drive.
In a weakened state of tune (crummy wires, valves need adjusting, carb not jetted) with a mild 400; While cruising at 50mph, I nailed it and the tires (new BFG radials) almost broke free when it down shifted. Then it tore off and the TH400 chirpped hard when it shifted again.
Meanwhile... Two days ago, the car didn't even downshift at all, because the switch wasn't set right. Persistence is everything here.
See that right there is something else I wanted to address.
The car doesn’t seem to down shift properly.
If I was doing 50 and nail it... no down shift.
It accelerates, but that more a matter of the large torque production.
I gotta see what’s up with that, or if it’s in my head being this is my first fence with a 3 speed car from the 1970’s.
I really need to go though this car. It starts great, cruises, etc.
however, it has been sitting in a garage for about 10 years with maybe a couple weekend outings a year. I have a feeling it’s way out of tune. Granted it has no catalytic converters and has a looney cam (overlap) but it smells rich at idle. I think I’m wasting a lot of fuel.
I almost don’t know where to begin. I guess at the ignition/spark system as previously mentioned, right?
1971 GTO resto mod. Modified 428 HO, 4 sp (built by midwest muncie) Dana 60, 3.55 rear
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Welcome to the forum! Lots of knowledgeable folks on here.. Already some good and sage advice.. Bottom line, it's your car so build the motor or swap it as you see fit. (although I am one of those guys that cringes when an LS swap is mentioned). Yeah, an old school motor is far different than todays variety, but you can do so many different builds with an old school motor. That's half the fun!
As Pontiac Jim said, you have to match your parts up.. But before hand, you have to have a clear direction of how you plan on driving your car and what RPM ranges you plan to operate in. Case in point- While long tube headers have been around for decades and are usually one of the first upgrades to be made, you don't start to see the benefits of them until getting into the 5,000+ RPM range. If you don't plan on being in that RPM range on a frequent basis, then maybe the factory performance exhaust manifolds pared with larger diameter exhaust piping is the better way to go, or "shorty" headers.
Deciding how you will drive will determine your path forward. Remember, doing one change or upgrade affects other components.
As for the original motor, the 71 400 was rated at 300 HP at the flywheel. The original heads were casting #96 and gave only about 8.2:1 static compression ratio. 1971 was the first year of "hard seated" heads due to the feds new rules. While I am not sure what the term "correction cam" means, the original was the Pontiac "P" cam. There are a few good web sites dedicated to Pontiac performance. One of my "go-to" sites is www.wallaceracing.com they have a page full of calculators that come in handy when planning and building your motor/drive train.
Welcome aboard and don't hesitate to start a thread of questions as your journey progresses!
As Pontiac Jim said, you have to match your parts up.. But before hand, you have to have a clear direction of how you plan on driving your car and what RPM ranges you plan to operate in. Case in point- While long tube headers have been around for decades and are usually one of the first upgrades to be made, you don't start to see the benefits of them until getting into the 5,000+ RPM range. If you don't plan on being in that RPM range on a frequent basis, then maybe the factory performance exhaust manifolds pared with larger diameter exhaust piping is the better way to go, or "shorty" headers.
Deciding how you will drive will determine your path forward. Remember, doing one change or upgrade affects other components.
As for the original motor, the 71 400 was rated at 300 HP at the flywheel. The original heads were casting #96 and gave only about 8.2:1 static compression ratio. 1971 was the first year of "hard seated" heads due to the feds new rules. While I am not sure what the term "correction cam" means, the original was the Pontiac "P" cam. There are a few good web sites dedicated to Pontiac performance. One of my "go-to" sites is www.wallaceracing.com they have a page full of calculators that come in handy when planning and building your motor/drive train.
Welcome aboard and don't hesitate to start a thread of questions as your journey progresses!
Thank you very much.
I’m really liking this board very much, you guys are great. And yes, some great advice. I didn’t even think to check the spark/ignition and timing. I’m used to that being computer controlled.
I need to check that, along with the shifting.
Tough part is my tach doesn’t work, so I can’t see where my rom’s are at, and this motor sounds so different from an LS I don’t think I can guesstimate accurately.
As for the heads, they have been worked on. See below...
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Why not? You were planning on upgrading at some point in the future, right? Just make sure it has the Pontiac/Chevy bolt patterns so if you go LS you can use it. You will have to adapt the shifter, but I recall there is a kit for that if you search for it online.
Do a search on the site up in the search box for 8.5 rear end. Plenty input on these and how to ID them from the 8.2 rear. They appear similar until you know what to look for.
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Where are you located in south Florida ?
Wellington.
Palm beach county.
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