I was wondering exactly how much difference there was between a set of '73 heads and say a set of '68 heads. More specifically, would it be possible to surface a set of '73 heads and turn them into '68 heads? How much would have to be removed? I have heard if you take off more than about .015-.020 off the heads that you will have to do the same to the intake ports. Just curious. Thanks!

 

Two different combustion chambers, so it's apples to oranges.

 

totally different castings. By the time you shaved enough off of them to make the chamber volume the same as the '68 heads....your intake would not bolt up.

 

ok thanks guys

 

What are you trying to do? There's a lot more difference than combustion chambers. D3 are pedestal rockers while D0 and earlier are stud mount. Exhaust ports are a little different too. D3VE heads can be ported to support around 700 HP while early heads can do around 750 HP.

 

I am building a 460 using a set of c-8 heads. I was porting the exhaust side and broke into the water jacket. I haven't had any luck finding a replacement yet. I also have a set of d3ve heads, but I have already bought pistons and had the block bored to match, so if I use the d3 heads my compression is going to be too low.

 

Too low for what? What pistons did you get? What is the intented use? Cam? Gears? Weight? Without details no one can tell you anything worth listening to.

 

As I said, the compression ratio would be too low if I were to use the d3 heads. I ordered the pistons and had the block bored and honed to match those pistons. The pistons I am using are (I think) federal moguls from an early 90s 460. They have a big oblong recess right in the middle of them. Anyways, I decided to use these pistons because I calculated the compression ratio using these pistons and the 68 heads, which are 75 cc combustion chambers. This put my compression right at 9.4 to 1. As for cam, gears, etc, that all is going to have to wait, but the cam is going to be no more than about .550 lift and no less than .500

 

When choosing a cam isn't not lift that matters so much as duration.

 

Ok, so what kind of duration should I go for?

 

Have you thought about just buying a set of after market heads. By the time you referbish an old set of heads with valves, guides, valve springs, retainers, locks guide plates, valve job, port job you will have a lot of money in them.

One serious down fall to the d3's id the non adjustable rocker arms. when running bigger cams you need the adjustablity.

Cadunkle is trying to help you plan out a motor and you need info to help us help you. like what you intend to do with the motor and what you are putting it in. Myself always start with the cam and plan out from there because the cam is the heart and lots of things depend on the cam choice like CR, valve springs, gears, stall converter, weight of car.

 

Like JW mentioned a lot of engine aspects rely on the camshaft's characteristics. Be sure your camshaft is designed to be used with the target compression ratio you intend to use. Here is a list, in order, to help in choosing your camshaft...
~ Look at the lobe family you want to use. Check the opening and closing ramps along with your lobe durations as well.
~ Look at the intake lobe durations more closely for your decision
~ Look at the exhaust lobe durations more closely for your decision
~ Look at the lobe seperation angle. (The wider your lobe seperation, the larger your piston to valve clearance tends to be, the tighter your lobe seperation, you become closer to the pistons. This specification is not entirely as important as deciding your desired lobe duration, so don't give yourself a headache over this one. Also, the wider you go the less overlap there is, the tighter you go the more overlap you have.)

In a recent racing newsletter I had received, Don Terrill had this list of questions when deciding a camshaft's characteristics for an application.

Last but not least, you need to know what your tire size is. Your vehicle may not be a racing vehicle, but that has no meaning when choosing the correct camshaft. You want the best choice possible for street or track.

The D3s will be fine. Just condition the combustion chamber surfaces with some slight grinding to remove sharp edges etc. Buff the chambers too if you like so you can get some reflection action to retain heat in the chamber for power production. For any quick and cheap effective head modifications, I would suggest touching base with Scotty J a.k.a. "The mad porter". He is on this forum, but I suggest emailing him through his website. I doubt you will need to touch the intake port as they are pretty adequate. Its the exhaust ports that need the attention.

State what you want to do with this engine, and we will help out as much as we can.

 

Ok. Thanks for the help. First of all, the motor is going in a 1979 F-250. The truck weighs 5,500 lbs and is currently on 33 inch tall tires. All drivetrain is stock. Dana 60 rear, Dana 44 front, 3.50 gears in axles will be changed in the future to 4.10:1, np205 transfer case, t-18 4-speed manual tranny. If the motor has too much power and I start breaking things, it will just give me an excuse to improve the drivetrain. I would really like to see at least 425 horsepower. The truck is purely a play truck, I dont care about gas mileage however I do not want to go too extreme with the cam. Ok, so far I have the block (short deck height '68 429 block) bored out .020",the mains line honed. The stock 460 crank has been turned .010/.010. I have my pistons pressed onto my reconditioned rods, will be using ARP bolts. I have the heads (one 1968 casting and one 1969 casting, both 75cc combustion chambers, both have screw in studs for the rockers, not the pedestal type heads like the d3s) ported on both the intake and the exhaust. The intake side I just barely cleaned up; virtually untouched. The exhaust has the thermactor port humps ground off and a small amount of bowl work has been done, just enough so gasses will flow smoothly. Will be using ARP rocker studs as well. Rocker arms have not been bought, but have been looking and have found a set called Scorpions, made in USA. They are aluminum. Anyone see any problems using them? They are the stock 1.73 ratio. Pushrods will be a set of comp cams hardened pushrods, using comp cams guideplates. One question I have is what diameter should I get? I believe I saw them offered in either 3/8 or 5/16 I think. Pros and cons of both? And cam wise, I would like to just buy one of the "k-kits" that comp cams has. That way I get the cam, seals, locks, retainers, matching springs, etc so I don't have to worry about it. Will have a compression ratio very close to 9.4:1. RPMs will never exceed 5,000. I will also be using a set of long tube headers, not sure the diameter of tubing. Intake manifold is a performer, and I have a performer 600 cfm carb like new. I realize that it is borderline too small, so I may eventually go to something bigger. Mechanical fuel pump, mechanical fan (aftermarket light weight though). Any other info needed, just ask. Thanks for all the help. I really appreciate it.

 

I have a similar build as yours in a slightly heavier truck ('86 Supercab) and am running a Comp XE4x4 262/270 with ported D3VE heads, Performer intake, 750 DP Holley 1.75" into 3" long tubes into 2.5" exhaust. I'm running about 9.7:1 compression. This cam is working fairly well for me. It leaves a bit to be desired in top end power (I used to run a Lunati 61602, but that didn 't even get started 'till 3000 RPM). Overall I'm satisfied with the Comp 262/270 in my 6000 lbs 3.55:1 geared Supercab, it pulls much better down low than my old Luanti did which really halps when pulling my 4500 lbs trailer.

If you don't pull anythign with this truck you may want to step up slightly from the cam I run. If I didn't tow, or possibly had 4.10:1 gears I'd have been fine with the 61602.

This is what I'm using... COMP Cams CL34-235-4 - COMP Cams Xtreme Energy 4x4 Cam and Lifter Kits - Overview - SummitRacing.com

A mild cam like this or the Luanti will put you in the 400-ish HP range with a larger carb, though your intake may be a slight bottleneck. Depends on waht you value more, low end torque or higher RPM HP, and how you use the truck. More details on intended use would help to narrow down a selection. From what I see so far look at cams in the 262/268 to 270/280 duration range. Too much more and your bottom end may suffer too much from your lower compression.