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Old 03-12-2012, 01:15 PM
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Heads

Hey was wondering if I could put 65 cc heads that came off of a 85 camaro z28 onto my 84 corvette which are 75 cc. Is it worth doing. Would I notice any differences?

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Old 03-12-2012, 03:26 PM
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Quote:
Originally Posted by allansmith859
Hey was wondering if I could put 65 cc heads that came off of a 85 camaro z28 onto my 84 corvette which are 75 cc. Is it worth doing. Would I notice any differences?
Exactly which heads by casting number are your refering to?

The 1985 Z28 should have L98 aluminum castings with the casting number 12556463. The first test is are aluminum or not. These heads have a 58cc chamber but use a really thick gasket give or take about .053 inch so the real size of the chamber is no where as small as the advertised 58 ccs would lead you to believe.

That said from similar conversions I've done and am familiar with that have been dyno tested, it typically the L98 head is good for upward of 10 or so horses with no other component changes.

The latter statement runs you into the fact that compression and cam timing walk together. Increasing compression without a corresponding increase in cam timing does not make a big power difference. Increasing cam timing without a corresponding increase in compression can make a large power difference but not nearly so large as when both are increased.

The 12556463 casting makes a couple different part numbers which vary by the angle the center pair of intake bolts make with the intake mating surface of the head. One version is the older 90 degree and the other is the newer 72 degree. Unless you are willing to get into an intake change or messing around to get angle changes on these center pair of 2 bolts, you need to know which heads your getting as your 84 'vette will use the 90 degree angled bolts on the head's intake surface.

These old SMOG engines really hurt for a better crown design on the piston either flat top or D dish, more cam action at the valve (getting 200 or more degrees measured from .050 lift with .450 inch lift is a big improvement), a better combustion chamber in the head (the L98 is a half step in that direction and the Vortec or Fastburn the rest of the way), and certainly more compression quickly makes a 350-400 horse motor with decent street habits out of a 350.

Bogie
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Old 03-12-2012, 10:52 PM
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The heads off my z 28 305 are 14014416

The heads off my 84 corvette 350 are 3998920
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Old 03-12-2012, 11:30 PM
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Old 03-13-2012, 05:22 PM
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What exactly is the process to port heads? Is there a certain tool used? Im asking cause if I can do it I will instead of sending them off. Im sure I have the tools to do it unless its a certain machine used.
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Old 03-14-2012, 05:43 PM
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Quote:
Originally Posted by allansmith859
The heads off my z 28 305 are 14014416

The heads off my 84 corvette 350 are 3998920
the 416 head isn't worth the effort and cost, the compression needs to track with the cam, unless you're running a hotter cam against the low compression 920 heads, there's little to be gained in power and potent-ally a lot of detonation problems especially if this is an automatic with a high ratio rear end.

In terms of cost versus performance the 416's need to have the larger 350 valves put in them and they need to be ported. But the basic problem with the combustion chamber remains where the 416 has the spark plug as isolated to the far side of the bore as does the 920 head, but the smaller 58 ish cc chamber will run the compression way up against the 'vette's circular dish piston. These two things run into a situation where the burn on a 4 inch bore takes too much time making the engine detonation prone this combined with the lack of squish/quench due to the deep distance between too much of the piston crown surface and that of the squish/quench step of the head does not create enough mixture turbulence nor heat sinking. Ideal the squish/quench clearance at TDC is about .040 to no more than .060 inch with a surface area of about 1/3 that of the bore area. Without a piston change to a flat top or more likely a D dish, this just can't get as good as it needs to be. This is a more manageable problem with a manual gear box and/or steeper rear gears at these give the engine a better choice of leverages against the car's resistance to movement.

Porting 416s with big valves was a common thing a generation ago when there weren't so many reasonably priced better options. We had a guy start a thread here a couple weeks ago where he had his old smog heads "professionally" ported with big valves installed for a couple grand bucks, then had a port crack dumping coolant into the engine. The porter blamed on his driving style. My experience in making thick port sections thinner says that he got it too thin and a few normal operation heat cycles opened a crack. This is a lot more common than you might think. For 2000 buckaroos, you can buy one hell of a set of aftermarket heads with all the trick shapes cast and machined in. Much the same can be said for doing a set of 416s yourself. Casting is an imprecise process; for equal amounts of material removed from the same place on two different heads one can get you a leak and the other not. Without the expense of sonic testing every inch of the ports there is no way to know how much material thickness is there.

Bogie
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Old 06-17-2012, 06:46 PM
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F-Bird 88, I posted this topic a while ago and I ended up putting different heads on my vette. Just some I had layin around just to get it going. Anyway Tomoro I am taking these 416 heads to the machine shop and telling them that I want the bigger valves I had on the vette to go in the 416 heads like you were saying. I am also gonna take your advise and port and polish them myself to safe money. This is my first pair of heads I have ever taken to the shop. So pretty much I need to tell him to make the seats bigger for the other valves. also to mill the heads. But how much should I get them milled down. Will they know that or is it a certain preference to what I want my compression. Also is there anything else I should get done to the heads while there at the shop for better HP. Keep in mind This is going on a 350 in a 79 el camino, 4 speed manual, 3.73 gear ratio with a 420 lift cam. Hope you get this before I have to leave.

Thanks man really appreciate the advice.
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Old 06-17-2012, 07:34 PM
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Quote:
Originally Posted by oldbogie
Exactly which heads by casting number are your refering to?

The 1985 Z28 should have L98 aluminum castings with the casting number 12556463. The first test is are aluminum or not. These heads have a 58cc chamber but use a really thick gasket give or take about .053 inch so the real size of the chamber is no where as small as the advertised 58 ccs would lead you to believe.
'85 Z28's never had 350's in them and never had aluminum L98 heads. They came with 305's either with a 4bbl or with TPI. The Z28 didn't get a 350 until '87 and it received iron heads. L98 aluminum heads were for 'Vette's only.

Quote:
Originally Posted by oldbogie
That said from similar conversions I've done and am familiar with that have been dyno tested, it typically the L98 head is good for upward of 10 or so horses with no other component changes.

The latter statement runs you into the fact that compression and cam timing walk together. Increasing compression without a corresponding increase in cam timing does not make a big power difference. Increasing cam timing without a corresponding increase in compression can make a large power difference but not nearly so large as when both are increased.

The 12556463 casting makes a couple different part numbers which vary by the angle the center pair of intake bolts make with the intake mating surface of the head. One version is the older 90 degree and the other is the newer 72 degree. Unless you are willing to get into an intake change or messing around to get angle changes on these center pair of 2 bolts, you need to know which heads your getting as your 84 'vette will use the 90 degree angled bolts on the head's intake surface.

These old SMOG engines really hurt for a better crown design on the piston either flat top or D dish, more cam action at the valve (getting 200 or more degrees measured from .050 lift with .450 inch lift is a big improvement), a better combustion chamber in the head (the L98 is a half step in that direction and the Vortec or Fastburn the rest of the way), and certainly more compression quickly makes a 350-400 horse motor with decent street habits out of a 350.

Bogie
The OP should have a cross-fire 350 engine (if it's original) with iron heads. He wants to put 305 heads onto it, but they will have PUNY valves due to the much smaller bore of a 305. He'd be better off running a smaller head gasket to try to get the compression up, which by itself won't do much of anything as you stated.
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Old 06-17-2012, 07:43 PM
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Didnt really get that last post but The 416 heads came off of a 305 z 28 engine. I want to put the valves off of the vette heads on the 416 heads. The vette has nothing to do with what I am doing except for the valves that came off of it. I am wanting the 416 heads to go on a 350 that I recently built and put in the el camino. I am going to port the heads myself and was wanting to know if there was anything else I could have the machine shop do to the 416 heads to give me More HP.

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Old 06-17-2012, 09:23 PM
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What a recipe for a total disaster. A guy who's never ported a head in his life, he's going to do it on a total boat anchor of a head, and then put them on a 350. OP, save yourself the time and effort and save up for a decent set of 350 heads for your 350. Vortecs, Performer RPMS, Dart Iron Eagles. You need a flow bench so you can measure each port as you do it so it measures the same as the other ports. Do you have a flow bench? Doubltful. So many smarter ways to make a 350 run than devoting all the time and bother to massively rework a dog of a head to maybe make 410 hp when you can set bolt a set of modern 350 heads on and make well above that number in your sleep.
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Old 06-17-2012, 09:39 PM
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Dont get what your sayin a boat anchor for. I got three pairs of 350 heads and three pairs of 305 heads here and the 416 heads that came off that 305 are rated way better than any of my 350 heads and are considerably light weight if thats what you mean. Ive only heard one person say something bad about the 416 heads well make that two now. And also did you ever think this wasn a race car at all and my goal that I would be happy with is between 350 to 450 HP. Thats why I choose these heads with the cam Im putting in it. These are around 57 cc chamber and I can get that down more and putting 2.02 and 1.60 valves in def will help out. I can get good compression out of these. Im not looking for the baddest race engine to build for this car. Thats not MY GOAL. Just something I can spend a little cash on and put on. If Im gonna spend money on new heads Im going all out and buyin everything not just heads. Can someone just answer the question and not hassle me about it.
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Old 06-18-2012, 05:33 AM
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1.21 giga-watts???!!!!
 
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Take the bad with the good, kid. You will be miles further ahead putting modern 350 heads on your 350. You admitted you don't know how to port, you even asked what tools you need. Those 305 heads shroud the valves, you have to be aware of possible piston to head interference, and you are putting time and money into a head with a combustion chamber that was designed 30 years ago. Some people can handle the truth when its told to them and others can't and say they're being hassled. So which are you?
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Old 06-18-2012, 06:08 AM
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Oh I appreciate any advice. I dont want to buy any heads. I want to use something I got at the house. Hell I ended up putting a pair of 305 heads on my 84 vette and turned out good. Guess your sayin if Im gonna do this I should use one of the pair of 350 heads I got. All Im lookin for is AT LEAST a 50 HP gain which I know I can get more than that but Im just sayin I want to add a little get and go to the car. Plus if it doesnt cost that much then Ill have the guy port them for me. Thought it would make more sense to use a 57 cc over a 75 cc
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Old 06-18-2012, 06:57 AM
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For the kind of port work you're looking to do, you'd spend $700 easy and you would still be stuck with old design chambers. Take the $700 and go to swap meets or E-bay and look for deals on good heads. 416 305 heads are not good heads. When money is tight, the budget is small, that's when you have to be smart and not throw good money after bad. Wait until you can afford better 350 heads. There is ONE guy on here, maybe two, that tout these 305 heads on 350 engines. That should tell you something. BUT, its your money, your engine, your car.
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Old 06-19-2012, 05:38 PM
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Thanks for the input.
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