Corvetteoz

Just after people opinions on what to do to my stock 350 chev in my 72 that will give me the most HP for the least money?

Engine is the factory original engine which matches the car. So don't want to buy a crate engine, just some simple mods to increase HP.

Engine is as stock as they get. Rebuilt in 99 and has done about 8000 miles since that time. Still has the original Quadrajet, intake manifold, rams horn exhaust manifolds. I'm sure its a stock cam, everything is stock.

Would like to keep the engine as original as possible too however I realise it may not be possible depending on how much power gain I want. If this is about 200HP as a stock engine, somewhere around 350-400 would be nice.

Redhook98

Your not going to keep it too original and get 350-400 HP. If you want simple and least amount of money, put headers, new exhaust, tweek the timing and ignition advance and see what you have from there. Next step is new intake, heads and cam. Intake, heads and cam will cost ya though. ($2k or more for parts alone to do it right).

Corvetteoz

Happy to go down the road of stroker and obviously cam. Happy to change intake, carby and exhaust manifolds to increase power as I can keep those bits to put back to original.

REELAV8R

If it rebuilt just 8000 miles ago you may be able to get to your goals with just heads,cam and headers.
Kind of depends on what pistons you got in there. Cast pistons won't like more than about 350 HP for a long life. If they are nice hyper or forged flat tops that are within .025 of the top of the cylinder or less then you got the basis for a good 400+ HP.

General rule of thumb for heads is to double the intake flow to estimate the HP potential.
Cast iron or aluminum is the choice. Recent tech is in the aluminum heads. Still plenty of cast iron options that will get you to 350 HP and a set of vortecs can get you to 400+.

Headers, I like long tube headers to increase torque. Any header will likely flow better than stock ram horns though.

True dual exhaust. I think 72 still had this though.

Intake choices are pretty limited due to hood height. An Edelbrock performer dual plane is a popular choice and will fit under the hood. I use the 2101 and got to 406 HP with it. Just get rid of the boat anchor intake if it's the stock cast iron version and you plan on changing heads.

Look Cliff ruggles up on amazon. He has a book that can improve your stock carb significantly if you're a DYI type. Otherwise Lars here on the forum is a q-jet expert and very good at what he does. The carb can and will make a significant difference in the performance of any engine if tuned properly.

Corvetteoz

Thanks for your advice.

I would say the pistons are cast as everything external was kept original when the engine was rebuilt. Dual exhaust was replaced with standard dual exhaust only a few years ago, before the car was bought and shipped over here to Australia.

What can I get done to my existing cast heads that will greatly improve HP to about 350? Any idea what flow I should be targeting? Bear in mind too that this car only gets driven on weekends.

Could you please put a link up for these long tube headers so I know exactly what type you mean? I will likely get the exhaust replaced when I get the headers installed.

I do have the standard boat anchor intake so your suggestion for a Edelbrock Performer is a good choice, used one of those in the past.

I am a DIY type however have never pulled down a 4 barrel carby before. I might be able to find someone here in Melbourne who can work wonders with a quaddy. My understanding is that guys that can properly tune and work on quaddys these days are few and far between, but I may be able to find someone.

Corvetteoz

Anyone else have any advice?

REELAV8R

Porting could be done to improve flow. If you don't do it yourself though the cost would quickly exceed just buying some vortecs.

These are long tube headers.
https://www.summitracing.com/parts/h...model/corvette
There are also mid length headers, shorties and block huggers. Many different qualities and brands in each type.
Just search summit for your year make and model and look for headers. I would go with 1 5/8" primaries for a stock to nearly stock set up.

Not much invested in just buying the book. A good rebuild kit is $100. I had not rebuilt a Q-jet either before the one on my 77. If you got some drills and other basic tools you can do basic rebuild. To take advantage of the performance enhancements will require a good understanding of what you are doing. You can really mess up a carb if you don't understand the relationship between various circuits in the carb. With Cliff's book and some past experience with carbs I was able to pull it off. Up to you if you want to try it or not.

Do search for timing and jetting or tuning threads here. You can get the engine to perk up quite a bit through some tuning other than the stock tuning.

Matt81

Keep n mind this gent is in Australia, so shipping anything - heads, intake, headers, etc is going to cost big moolah. As mentioned above, a good solid tune will really wake up your engine. I just went thru my timing settings to about 34 degrees advanced (likely up it again to 36 next time I'm in there) and it made a massive difference on the spunk in the car. Night and day difference. Next, tune the idle mixture screws for the highest vacuum settings.

If you do a quick search in the Tech section for my posting on ignition settings, I link in a couple of great sites. You can get there as well by searching a post titled "Info on Timing". Great info on BarryK site that he links to in that post. Great reading and you should learn a lot - I certainly did.

Best part - cost is zero. Although I did get an advance spring kit for $10 to change my advance curve slightly. You should be able to get that at any local auto parts store.

Corvetteoz

Done an estimate of postage to Australia for those long tube headers in the link. They want $200 for postage alone and then the $212 for the purchase. $412 U.S is quite expensive which would turn out to be around $600AU.

Have bought parts before from other sellers in the U.S before who charge much better postage rates so I might try them.

Any suggestions on what I can do to my existing heads to get more HP out of them?

REELAV8R

I'm going to throw this out there just as a look see. If you like, then give it a shot if not then leave it alone.
I have only ported three engines at this point. I used this book.

https://www.amazon.com/David-Vizards.../dp/1934709646

On two of these engines I have no before and after results to compare, so it is really unknown as to weather I improved things or not. My AFR's was not really porting per se' at all. I just removed surface roughness and polished exhaust runners and combustion chambers.
However I do have an 85 Toyota Corolla that I purchased and it lost the head gasket about 3000 miles into my ownership. While I had the head off I decided to port the intake runners to remove obvious obstructions to flow. Barely touched the exhaust runners at all. Did nothing to the combustion chambers.
I gained 2 MPG and now it can climb rolling hills without engaging the secondary on the carb. So it appears that some benefit was had.

On your 882 heads they could certainly be unshrouded, the combustion chamber could be polished as could the exhaust runners.
The intake runners could be opened slightly (careful not to hit water jackets) and the bowls could be worked to perform better these leave unpolished. Maybe even textured. Look that up and see what guys have been doing.
Use the book to guide you. It can be down loaded from amazon, you don't have to buy it in paper form. I prefer paper still vs digital myself.
I bought some really cheap bits on the internet, don't remember where but were in the less than $30 range, us dollars. They worked just fine. If I remember right I even got one for $8.
Just depends on how adventurous you are. I would recommend getting some junk heads first to practice. To me it was a LOT of work to do porting. More so on cast iron. But it was an interesting learning experience and nothing bad happened in the process.

I did several searches on the internet regarding porting. There seems to be more misinformation out there vs good information. The porters are NOT going to give up their secrets. David Vizard doesn't even give up secrets. But it is a good guide as to how to proceed.

You may even decide to just port the stock manifolds since getting headers may be cost prohibitive.

Haggisbash

Hi Corvette Oz. Greetings to the West Island. My suggestion would be to join the local Corvette club where I'm sure you will find someone who has already travelled down the path you are looking at. You already have a lot of aftermarket options for parts available there that with careful buying won't cost more $$ than importing stuff. FWIW I am contemplating the same for the engine in my '70 but as it is not the original I don't have to worry about modding it at all.
My suggestion would be either get a bolt on kit from one of the vendors (heads, cam lifters etc something like the Edelbrock E street setup to keep $$ down)
Or get some advice on a Head and roller cam setup that will suit your needs, this will be more $$ but will deliver a better overall package. I believe that if the engine is in good shape there is no reason other than easier access that this conversion couldn't be done with the engine in the car ( that is what I am contemplating doing as have no gear or head room to pull the motor).
By all means get the timing sorted, there is plenty of info on the forum or available from Lars Grimsrud about this. If you come across a Haynes manual don't use their smog timing figures.
I fitted a Performer EPS dual plane intake in place to the Torker single plane manifold the car came with. This significantly improved low end power but I would not expect such a marked improvement going from the factory dual plane to an aftermarket one JMPO.
As far as carbs go I can't comment on the Quad as my car came with a Holley that was actually older than the car! Eventually i swapped this out for a Quickfuel BDS1957 Drivability improved a bit but WOT seemed about the same.
There are lots of supporters for the Quad on the forum and an equal number of horror stories of supposedly rebuilt carbs that were absolute POS. So choose very carefully if you are getting someone to rebuild it or school yourself well before you try to tackle it yourself.
rgds from the South Island

Shark Racer

None of the GM dealers in Australia can hook you up w/ a crate engine? The best way to keep an original engine original and modify your car for more power is to bag the original motor. Seriously.

Some of the mods you're describing, like porting the stock heads, are really just throwing away money. You could port the ever-loving hell out of the smogger heads and end up with something that flows about as well as an off the shelf part which will cost ~$750 US and be crack-happy and worth no more than you started with.

Without touching the inside, headers, dual exhaust which you already have and a proper calibration of ignition and carburetion will get you some pretty decent gains with an L-48.

After that, a matched combination of heads, cam and intake is what I'd recommend. Honestly, if you have an alternator and an AC compressor, it will be really hard to tell if you swapped out the stock heads for aftermarket, particularly if you paint them factory colors. Also, it's super easy to get these engines to 350HP with good heads and a cam.

shenango

My friend purchased a 1980 C3 about 2 months ago and did a basic tune up, clean and polish then started enjoying his prize. Last week he and his wife met my wife and me for an EOY vette run and lunch. A very enjoyable 60 mile jaunt through the mountains of Western Pennsylvania. To get to the meat of my story, he asked me about rebuilding his Qjet and how to get more out of his engine. I asked him 3 questions that started him thinking about what he wanted to do. Are you going to race your Vette (no)? Can you go fast enough to get a speeding ticket now (yes)? And can you spin the tires on dry pavement now (yes)? My advice to you would be to rebuild your Qjet, put 3.56 gears in the differential and have a ball.
Now I will ask you the same questions plus. How much time do you want to spent in your garage versus how much time do you want to drive your prize.
Jerry

emccomas

I remember talking to Zora Duntov about this very issue about 1991 (at Cypress Gardens NCRS meet).

When I asked him the best way to increase horsepower, he said (in the so familar Belgian accent "Decrease friction".

As the conversation went on, he acknowledged that an engine is just an air pump, and anything you can do to increase the efficiency of an air pump is a good thing.

He also agreed that one of the most restrictive things on Corvette engines is the exhaust manifolds. He also stated that the low rise intakes that were used on the C3 cars were also an issue.

So, for quick and easy horsepower increases:

1. Headers (move air out faster)
2. Better intake manifold (move air in faster)
3. Adjust timing (burn more efficiently)

in that order.

These changes might get you 30 ish net horsepower. You are not going to get much more than that without some internal engine changes, or forced induction.

Good luck with it.

Corvetteoz

Excellent advice guys. A change of the outlet and inlet manifolds would be a very good start. I might even get the carby rebuilt and tuned first to see what improvement that brings.

My existing ram horns exhaust manifolds are playing up anyway. The left hand side one sprung a leak not so long ago so I got it fixed at the exhaust shop. After 4 or 5 months it is leaking again on the same side. I'm guessing the exhaust manifold itself is warped. Might as well put something decent on that not only gives me more HP but is more reliable also.

riverracer au

for carby rebuild, short of sending to Lars in the US, you could try Hume Performance in NSW.
they have a website detailing their services.
couple of blokes in my local club have used them and are happy with the results.
they also re-graph dissys.

Corvetteoz

Thanks mate.

Didnt really want to be sending anything interstate tbh. I have a guy here not far away who I know has his own Corvette, although not sure what type. He has his own shop and I he has been recommended on the net before. I might go and talk to him.

Pop Chevy

I would suggest headers, intake/carb, cam w appropriate tuning. Really will wake it up and fairly simple. I would steer you towards a Holley carb.

Corvetteoz

Anyone heard of an Offenhauser Port o sonic intake? Would one of these be better than an Edelbrock Performer?

I found someone local who is selling some long tube headers off of a 327 Corvette. Would these fit my 350 small block which has AC? Would be helpful to know what I need to look for when I go to view them.

Another option is a set of these headers. Not long tube but still got to be better than the stock ram horns that I have. I can land these for about $350 Aust. Will these fit a stock 72 with AC?

http://www.ebay.com.au/itm/Patriot-E...4AAOSwn7JYFIbx

sparky77

Best bang for the buck would be to get a crate engine in the HP range you want than put you're stock engine away and if you ever sell you're vette you can give the new owner the stock engine.