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Time to upgrade my l-48

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Old 09-16-2018, 11:20 AM
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nick0187
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Default Time to upgrade my l-48

Even though my stock 1975 l-48 is already soooo fast, I'd like to be able to beat a Kia Rio at some point. I am on a budget as most of us are, but would like to get more out of my engine. After doing some research, I know I can't afford aluminum heads, so I'm thinking about going for used vortec heads. I believe I will need a vortec intake and a drop-down air cleaner as well. I know very little about engine building, just from what I've read in the forums and online at other sources. I'm not trying to get 350hp out of the engine, maybe 250 so it's more enjoyable to drive. There is already a set of true dual exhaust, I had the carb rebuilt by lars last year, and I will upgrade the distributer according to lars' paper this winter.

My question is what should I look for when getting a used set or vortec heads? Is there anything special I will need to look for? I found a set of 062 vortec heads and intake with 5000 miles on them from a crate engine for $650, is that a good deal? Should I just keep the stock cam? I'm looking for more low-mid range power for street driving..

I know this subject has been covered a bit, but any advice is appreciated, I'd love to learn more from your experiences and expertise!
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Old 09-16-2018, 11:36 AM
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cuisinartvette
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That would wake it up..yes a small cam would really help too. You may have to pull a plug wire off for those Kias
These run into a lift issue & have the guide boss turned down. , need to make sure they arent cracked. With 5k mi they are probably fine
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Old 09-16-2018, 11:40 AM
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Guide boss turned down, no clue what that means..lol
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Old 09-16-2018, 12:02 PM
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H-m-m-m-m. Getting mixed messages here.

You say your budget does not allow for new aluminum heads. You also are eye-balling some used heads for $650. These will most likely need a minor overhaul that could reach into hundred$ more.

Brand new aluminum ProMaxx heads, complete, valves, springs, retainers, stem seals, guide plates shipped to your door: around $690.
But, and there's always a but. You will need longer pushrods $100 and you will need ARP headbolt set $130.

Something else to keep in mind with buying any used heavy car parts is the return shipping in the event there is something wrong with them. Would cost a small fortune to return. Ask seller for some type of warranty.

Let us review:
Used: heads $650+ (any parts / labor)
New: heads $900
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Old 09-16-2018, 12:11 PM
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The valve guide must be machined down on a stock Vortec head to accommodate lift above .450. Comp make a specific tool for this and it can be done on a standard drill press.
Although now you have to buy a dedicated intake manifold. But the beauty of the Vortec head is its high torque capability. The ports are small and flow well......GM did a great job on these for a truck head. Note also that you will need self aligning rockers and centerbolt valve covers to round this off.........
I would hold out for a set of real Aftermarket heads..........spend money now on some long tube headers, an RPM style high rise intake (they will fit with mods on a 73-79 hood) and do the Lars paper on your distributor........it will need some cam but you will be pleasantly surprised. A cam from this point and new valve springs would really wake it up. I like the old school Magnum grinds because they make good power, sound good and break-in easy with their lazy lobes........A 268H Magnum is a great old school cam.
Then.....once you build the cash box up.......swap out the heads for some Dart/AFR/Brodix and it will pick up about 60-70 from there or better.........

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Old 09-16-2018, 12:12 PM
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Those Vortecs are limited in the valve lift or in laymans terms: high lift cam. After a certain point of lift the valvespring retainer will actually strike the valveguides, not cool, not pretty. So a trick is to remove some of the material to lower the valveguide, hence higher lift cam.
So you have to ask yourself if you want to get involved with that machining process or not.

These Vortecs heads today are this century's style of the last century's Camel Hump heads. Everybody wanted them. Had to have them to go fast. But as new buyers are finding out, they are limited in valvelift, so some expensive machine work is in order. And some buyers are shocked that they can no longer use their favorite intake manifold due to the different bolt pattern.

Last edited by HeadsU.P.; 09-16-2018 at 12:14 PM.
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Old 09-16-2018, 12:50 PM
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If you are looking to save money, why not just buy a good set of new cast iron modern heads and call it a day? Forget the Vortecs.........
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Old 09-17-2018, 04:50 PM
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Thanks for some good info, I’m still learning a lot about how to tackle this project. I don’t think i can afford to drop 1000 on the motor right now, and if it would even be worth dumping a bunch of money into or getting a new engine. I was looking for some cheaper options to have fun in the mean time before i can drop that kind of money into it. New heads might be out of the budget for now based on the good points you guys brought up. I’d hate to get a set of used heads for cheap but have to dump a bunch of money right back into them
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Old 09-18-2018, 07:05 PM
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If all you want is 250hp then get some rebuilt 1986 C4 '128' heads for about $300. Bolt right up and with the 58cc chambers they will add 2 points of compression ratio over your current heads making the engine very lively until about 4300 rpm when the cam cannot supply more airflow. Add some 1.6 rockers to get about 15 more hp out of that L48 .390/.410 lump stick.

The 128 heads don't flow worth a darn but they add compression and loose 50 lbs over your current heads. Change the intake manifold to a 1980 style aluminum to drop another 17 lbs, change to an aftermarket mini starter to drop another 7 lbs. Change to C4 exhaust manifolds to drop another 14 lb. Aluminum water pump takes off 5 lbs.

Fix the timing to 32'ish total and all together you can add 20-30 hp, 150 ft lbs torque and remove nearly 100 lbs weight from your '75 for about $500-600 depending on how well you shop.

That is the recipe I used. While both HP and Torque in a package is optimal, if you have to pick one go for torque in a street driven car.

Last edited by Dynra Rockets; Yesterday at 06:36 AM.
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