More CID or Head Flow?
 

Hey all,

I am going back and forth on taking my .040 400 to 435 with a 4” crank or just going with the 408 and spending money on ported heads.
The car is a 67 LeMans that will be street and highway only with an OD and 3.55 gears. I have 670 non ported heads that need everything and I have a line on some 670s that are ported and ready to go with no flow numbers unfortunately.
For this street only application, is the additional cubes a benefit over the ported heads or vice versa?

If your 400 is choked more CI will be choked more.Heads plus CI would be my choice.Joe Sherman always told me HP is in the heads.Tom

Is a 400 choked with stocked 670 and a better cam than stock? I wish I had the budget for both…

Then IMO start with better heads,you can put the arm in it latter.Tom

Add cubic inches now, get your bottom end built right from the start.

Heads can come later, easy swap later on if you decide to.

Adding a crank later on down the road makes little sense in my opinion.

I will never again dump a lot of money into iron heads. At least for me, it's impossible to find a machine shop that will rebuild and port a set of iron heads properly. I ended up with over half the cost of aluminum heads in these 670s. Not to mention it took 9 months to have them ported and rebuilt. After a local shop screwed them up, I had to source my own valves/springs/retainers/locks, drive 2.5 hours each way to Charlotte NC to bring my heads to Marty Warden for finish work and porting. The results are awesome, but it's still a 260CFM iron head. For not much more, I could have had 290CFM aluminum.

So if I had to do it over, I'd go straight to aluminum. So for your build, go with a set of 72cc aluminum heads and whatever piston will give you 10.5 compression with whatever stroke you end up with.

UNLESS.... You're building the bottom end now, go with the 4" stroke crank. Find a set of 80-84CC iron heads to use until you can afford the 72CC aluminum. That's what I did. I built a 434 with a 10CC dished piston. My 80CC 670s give 9.75 compression until I graduate to 72cc aluminum. Then the compression goes to 10.5 and I make more power everywhere.

Not knowing flow numbers on ported heads is like taking out a loan without knowing the interest rate!
You could end up with less performance then a stock head might provide.

Your beat up 670 heads fully rebuilt should make you an easy 380 hp and with a OD trans and 3.55 gears it will not disappoint you.

Sink your funds into building a solid strong block of 400 cid and later on down the road you can always slap better flowing heads on it in a afternoon.

Age old question..how much power do you want and how much do you want to spend? Is your current shortblock healthy?

More CID. I would chose iron heads again because i would do the valve job, seals, and porting.

Reliance on shop for new Valve guides, and the iron ping could draw the decision to aluminum heads.

3.55 rear gear, fairly heavy car, OD on top of that. I would go for the extra cubes and the torque that goes with it. As Steve mentioned, a set of "ported" 670 cylinder heads could mean anything from a loss of 40 HP, to a gain of 80 or so HP. That is a pure guess without flow sheets and a good idea about the person or shop that did the work. "Just making iron shiny doesn't gain you anything." A quote from Joe Mondello, one of the best. RIP.

I'll agree with that. Not having flow numbers is a big deal. Steve25 and I spoke several times on the phone when I was roughing in the 670s by hand. What I learned is, you just dont make the port bigger. You have to shape it a certain way to guide the airflow through the port. For the exhaust, you raise the roof of the port, as the pressurized air tends to follow the outer surfaces as it makes the turns. The gut reaction is to lower the floor of the exhausts to gain port size, and that's the wrong approach. So thats the sort of thing you need to look for in ported heads without numbers. Does the port shape look correct? Has the pushrod bulge been cut back properly? Are the bowls blended properly? Are the ports symmetrical, is there enough meat to seal off, is the finished surface correct, etc.

For street, go with the extra cubes for more torque and more fun stoplight to stoplight. If you posted in the race section, I'd say better heads for more peak horsepower.

buying ported heads without flow numbers is a little like buying a used car with a broken odometer. you might come out ahead, but only if you take a REALLY close look before you pull the trigger.

I'd go with the stroker over porting factory heads. First, the stroker is not just cid, it's also longer stroke so more torque per cid. Also, as said, then you could always add aluminum heads later. Then you'll have a really nice street motor. And even with the factory heads, it may be enough to keep you smiling. Plus as many others have said too, spending money on factory heads is not worth it unless you're doing a strict restoration or have special heads like factory round ports.

I know Pete McCarthy used to saw the 670s were some of the best flowing D ports. The ones I flowed were some of the worse!

When I swapped a 400 short block under my RAIV heads HO intake and massaged 73 SD Qjet with the same 288/296 UD cam it was dog with the same 3.42 gears and convertor!

More inches AND more head flow:)

Why just 4" crank? Go 4.25" if youre changing the bottom end, would be way ahead on power/tq vs the 4" for about the same price, then can decide if you want/need alum heads down the road.

I helped a friend recently build a 400/467 with 4.25 crank, he used stock 6x-8 heads due to budget and he already had them, crower 60919 cam & stock unported 1972 iron intake & qjet... made 426 hp with no tuning or other mods & lots of tq. His plan was a good stroker bottom end that he could upgrade the heads if wanted more power down the road.

my last wife and i had a similar disagreement... i wanted more head, she wanted more inches. We went our separate ways and both got what we wanted!

That's pretty funny

jinkies i8! 😮

Did anyone get the e-heads without stroking and was satisfied with the street results? Same question for porting iron.

Wow, this took a turn I wasn’t expecting. Lol

So I’ve always liked the 4” 4” bore/stroke approach and I am hung up on stock performance, in this case 1967. I should’ve just bought a 428 block to build. Again this is a cruiser/highway driver so I think the square bore is the best of both worlds.