Don Terrill’s Speed-Talk

Just FYI, I haven't built an engine since 84 (383) so take it easy on me!
So I have 66SS with 406 with 700r4 and 411s & 750 holley, 1.6 roller rockers (many owners)
So not knowing anything about the motor other than it ran ok but missing power I removed the double hump heads (54cc) to find out it has dish pistons 40cc (did the plexiglass across the top and a syringe to both). So my question is if I throw a set of Dart iron eagle 49cc 215s on it and get it to 9.5/1 will it still run decent? Just not sure about those pistons? (no money to replace them!)

Put 5.7" rods in it and cut a .135 thou off the piston tops, been done for years.

Are you sure the old, "double-hump", heads were 54 cc's? (Maybe 64 cc's instead??)...

Even the old 283 Power-Pack heads are like 58 to 60 cc's.

BUT my pair of 305HO, -601 heads cc'd at 53 and 55 cc's. The 1.84"/1.50" valve heads here.

Personally I wished when I built my 406 that I had went with 5.7 rod flat-top pistons, shim head gaskets and whatever 2.02"/1.60" valve cc chambered heads that I would have needed to use to get it right at 9.5 to 1 CR.

Please post back and tell us what you end up with.

Thanks,

pdq67

Put 5.7" rods in it and cut a .135 thou off the piston tops, been done for years.

Yep, did this in the 80's and stuck the 400 in my 78 Gran Prix. Was fun busting the Camaro's Mustang's and Monte Carlo H.O.'s with the sleeper. Plush velor seats and all.....

Buying rods and cutting pistons negates the reason the OP doesn't wanna throw money at it.

Assuming a 4.166 head gasket and deck height of 9.025 and a real 40cc below the deck then the math nets you at 9.5ish CR.
It'll work just fine.

IF you have to buy heads to get this done than I'd spend money on the offshore heads like NGK or Patriot and other that make copies of the older dart stuff.

changing pistons should be cheaper than changing heads by my estimation

Another fly in the ointment on using the 49cc Darts is they are only available with angled plugs...most common street headers won't fit angle plug heads.

New "claimer" pistons and rings, longer 5.7" rods, and straight plug 200cc 64cc chamber import Dart clone aluminum heads runs in the range of just $100 or so more expensive than just the Dart heads alone....even better yet if the Darts were going to force you into a different set of headers. If the bores are good enough for a hone and go, this is the most bang for the buck solution.

Plus you can sell those ancient Hump heads to some fool who still thinks they are the be all, end all to SBC performance.

Good catch on the angled plugs, just had my headers plated! The sad thing about it, the cylinder walls look perfect there is no ridge and still see the cross hatch cut after the 30 over. Those heads, I was going to get them at a good price so I was hoping for under a 1000 I'd have heads, cam, lifters and new timing chain. The old combo calculated out to 8.01/1! (lol) Well my cousin said I can borrow one of those heads and do mock up!

Thanks!

Yeah NO.
Them 49cc heads use off set intake rockers and they are a 21 degree head. Dart angled milled the shit out of a larger chamber head then flat milled to get to 49cc. Valve pocket issues If I remember right they are a 60/40 valve spacing with the intake moved .150 over for the larger port volume.
It still goes on from there but you get the idea its not a cheap way to go.

I would ask what the deck height of the block is now and if its using 400 rods or 5.7 rods??

The issue is the old heads have far too small of port to work with the 1000 times faster piston speed in the 400. It can't suck air fast enough and it stalls in the port making for a big power loss. The 441 heads that came on them had a better port then them old dbl bumps did.
You can get an iron head that's 200 cc with standard rocker layout so you can reuse the rockers you got along with a .035 total deck so get the right thickness head gaskets to suit like a cometic put a bit more stick in it with a tighter LSA and your 400 will be much happier

Thanks for the input!!!

update:
-Scrapped off the carbon on one of the pistons and found : 400NP .040 (looks like 40 over Federal Mogul cast) was hoping for forged!
-As for the heads, I can't beat the 500 bucks for the heads, so I figure i'll paint up a set of standard headers to allow angled plugs
-Cam: looking at COMP Cams SK12-246-3 Xtreme Energy 230/236 Hydraulic Flat (amazon)
-torque converter; looking at a 2200 and stall and I'm thinking a internal lock up would be smart since I drive to a lot of car shows??
-planning on matching ports between head and intake, found a good link using Dykem and hispot blue

Do you see think the lifters and timing chain that comes with that Comp Cam is good enough? (amazon)
Thanks

Looks pretty matched up to me. I would run the rpm air gap intake. Might run mid 12's. Maybe faster . It will eat tires that is for sure.

400NP are for stock short 400 rods 5.565"
pistons probably set about 0.045" below a stock deck; that's a lot.
and have a relatively large dish; probably about 25cc
https://www.drivcat.com/overlays/part-d ... brandId=SP

most budget-minded 400 gaskets are relatively thick 0.039" - 0.051"
far fewer choices than a 4" bore 350