Jd21476

I just pulled my valve covers off my car to see which heads it has. The Chevy 350 thats in it makes almost no HP and its embarrassing. I realized now that the heads I have, GM 462624, are terrible heads and have a 76cc chamber. I dont know what cam I am running or anything else other than the car has a '78 Chevy 350 and the Muncie 4 speed. If I change the heads will I get more power or am I wasting money without doign a complete rebuild?

drwet

If the short block is in good shape, you can certainly upgrade the heads, but you need to do a little research and planning. Just throwing parts at it isn't likely to work. You need to determine what your compression ratio will be with the new heads, and select a camshaft to work with them. If you have the factory Quadrajet your carb and intake are adequate if they are in good shape. On the exhaust side headers and dual exhaust would be a bonus but at the very minimum if you have the factory catalytic convertor you should consider upgrading to a more modern free flowing unit.

Shark Racer

You'll likely make more power if you go with something reasonably sized for the application.

As always, building an engine depends on your goals. If this is a stepping stone to a complete build, purchasing something that works well with your current configuration likely will be sub-optimal in a complete build. Most of the 70's motors are fairly low compression and you won't get much back from a head swap. A rebuild, with different pistons and some decking can get you to a much better compression ratio that you build the rest of the engine around.

Since pulling the heads gets you most of the way to changing the cam, you should get a nice new cam to match the heads you pick. You could also get an intake.

I can't see you getting much over 9:1, maybe 9.5:1 if you go with a 64cc or less head.

If you're truly about doing a budget build, Vortecs will be a big lift for the price, but there's some gotchas and you'll hit their power potential quickly. Also, they're iron so you won't have the weight advantages of an aluminum head, which will additionally have a much higher power ceiling.

Eric P

Go with the TFS 175 with 60cc combustion chamber , obviously add a cam , intake and headers will add more power but this is a good starting point that will bump up compression to 9.5 to boot
Trick Flow® DHC™ 175 Cylinder Heads for Small Block Chevrolet TFS-30210007 - TrickFlow.com

Jebbysan

Do you have a 2.5" exhaust and long tube headers? Do this first and then set the timing correctly per Lars papers (E-Mail him for a copy). You will need the exhaust to support changes to the engine.
Yes heads are weak on these cars.....any aftermarket piece is better but you need to combine the head swap with a camshaft that will allow the heads to work....then a good intake on top of that.
Google up "Goodwrench 350 buildup" and read the different chapters and what they did.....you will get a good idea of how to attack it.

Jebby

Jd21476

I guess I should add that the motor has the Edelbrock 1406 carb (600CFM), Edelbrock Performer EPS intake and headers (not sure of brand) and I just recently put on the Allens chambered exhaust so it does not have catalytic converters or anything. I dont know what cam it has. Im going to pull the plugs and run a complression check to see if all is well internally.

drwet

It sounds to me like heads and cam are your next step.

Jd21476

I just pulled my plugs and did a compression check. I am 149-152 psi on all cylinders. Is that good? I think so right

Jebbysan

Yes....for a late 70’s 350, that is good.

Jebby

Cmurray79

thats pretty damn good. In my opionion and from what i’ve heard, if the numbers vary any more than 10% between cylinders, youll need a rebuild soon. Anything 5-10% i’d be weary of putting heads on or any major change.

Pale Roader

I was VERY close to pulling the trigger on a 76 L82 in the summer... and so i did a lot ov reading on these underrated powerplants.

I was surprised to learn that the pistons sit just a hair under the deck, and are flattop with valve reliefs. That got me to thinking... Someone here linked me to some 59cc (very small) Ebay aluminum heads... 205cc (i always buy for future builds) runners, CNC chambers. They were dirt cheap. So i figured buying those, then factoring a few hundred for corrections and valvetrain upgrades (necessary on Chinese heads) i'd still be well under a pair ov new AFR's. That'll hike that compression well over 10:1, where i like to be with aluminum (think it was closer to 11?). Find the thinnest composite gasket around and cinch it all down and i might even get some quench out ov the ol' dinosaur. Pistons are what .025"ish down the hole? Add a .020ish gasket and its actually a decent squish. Thats very important. I'd prefer .035"or less, but we're not building an engine here...

To that i'd add a used single plane, something modern with flow/angles to match those heads. Both would go to a guy i know, a world-famous Pontiac engine builder with a full flowbench and shop. He'd flow those heads, and match all the ***** up for a bit more coin. Once i had the flow specs i'd get a custom solid cam (cant afford a roller), or even scrounge around for a used roller... this is SB Chevy... you'd probably find them in bloody pawnshops.... I'd imagine the cam will be fairly big, and will perfectly match those heads. I'd jam a flowed (i'll flow it myself) Holley 750 vac secondary on top, and a stub stack and no filter. Roller rockers are easy enough to find used too... though i never did check to see if those particular heads needed something oddball. That would net me a pretty savage little 350, on a bone-stock shortblock.

That was my plan anyways. But once i started adding up even all this used *****, i'm well over a couple grand... and at that point i might as well just save a bit more and go with the modern V8 swap i have intended down the line.

If you have an L82, and that is actually a serious exhaust already (most aren't), then this might be something to chew on... Ov course, if you dont have the L82 then this plan wont work nearly as well.

augiedoggy

^^ That was me who found the 59cc heads on ebay, Ive done some reading on them. They are the procomp castings and while they have improved over the years they are not as good as the other dart knock off castings that some of the name brands are rebranding and are using that are available as generic and kmj, assualt, speedway, AT racing heads on ebay which have some decent flow numbers for budget heads.. but dont come in chambers smaller than 64 that I know of. there are these as well but they are a bit on the small side and are cast iron. https://www.ebay.com/itm/EngineQuest...AAAOSwov5fCJIW

I dont know if it was asked yet but is this a forged L82 with flat tops or the cast L48 with dished pistons? it kinda makes all the difference here on what size head would be recommended?

If it is an L82 ... These AFR enforcers are decent... https://www.ebay.com/itm/IN-STOCK-AF...Cclp%3A2334524

Its very likely the these are the same import castings as AFR uses just not checked over and loaded by AFR... https://www.ebay.com/itm/Renegade-Ba...kAAOSw2QZdRLcU Ive found these as cheap as $190 a piece without hardware.. I would not buy them complete with valves since it would be safer to have better valves and springs put in them. there are a lot of guys in the thirdgen.org forum using these with good reviews and results. I could be wrong but I believe cuisinartvette runs a pair of these as well.

cv67

tfs 175 or afr 180s, Isky 270 meg cam will wake it right up
Headers,intake even better. Will be night and day, sound good with great st manners.

Jd21476

Thats what I was looking for. Thank you

drwet

I have had both TFS and AFR heads over the years and the AFR's are much better. In fairness, the TFS's were among the first heads they produced and I had all sorts of problems from substandard springs to bad seals and lousy guides. I'm pretty sure they have improved since then. If they haven't they probably would not still be in business. The AFR's are still in my car and have been awesome so far. FWIW

Jd21476

The AFRs look to be almost twice the price too

Pale Roader

You get what you pay for. Those Ebay heads i spoke ov are dirt cheap, but i include the (likely considerable) cost ov 'fixing' them in the total cost. They'd like end up closer to the AFR's in price. AFR's are worth the money. If you're on the fence about the budget, look for some used ones. I've seen four different sets come up within driving distance ov me in three months time.

Jd21476

I looked at Summit for prices but I cant tell if thats for one or both heads

lionelhutz

Edelbrock E-Tec are under rated heads that often get ignored when discussing decent heads even though they shouldn't be. They require a Vortec style intake.

augiedoggy

Again... if you have an L48 your options are limited for performance to 58-59cc 305 type heads unless you go with a lower compression ratio and 64cc heads and give up some power. You really should find out which engine you have. If you do have the L82 yoh can't even use anything smaller than 64cc with pump gas so its important.. And again, according to the machinists over at the third gen forum, the AFR budget enforcers are the same castings as the chinese eBay heads just assembled by AFR.. You can have them assembled for few hundred less if your really trying to squeeze every penny.. There a bunch of reviews and even you tube videos on these castings as they are very popular.
Bolting the higher end cnced AFR heads on to a cast dish pistons L48 engine is kinda like putting lipstick on a pig. You'll likely not get to see the potential of them over much cheaper heads in that setup. the 58cc trick flow heads would be a better option to increase compression and power on an L48. Then Again even the procomps would be an improvement over the 76cc smog heads you have. Espcially if they are the L48 smaller valve version.