70/71/72 402

Tim

Well Known Member
Supporting Member 4
Starter on this one is on the passenger side with the same mount as my 348. The timing is a chain. Not that it matters I’m changing the cam, distributor etc anyway. Pretty sure though it’s normal rotation.
 

Tooth

Well Known Member
Supporting Member 1
Wristpin was looking for a set of Oval port heads and I sold him a set of 781s I check them for cracks and magna flux them and made him a deal of the century. I would suggest calling or checking with Skip white Performance. You cannot redo a set a cast iron as a heads as cheap as you can buy these loaded oval or rectangle port high-performance with raised exhaust runners. I have checked and they guarantee them and they build them to suit with installed heights and spring pressures for the cam that you have or spec I’ve seen three sets on motors that have been built around here and they’ve all been good quality. If I ever decide to build another big block I will be ordering a set myself. Even though I have several sets of cast-iron heads large oval port on the shelf I cannot rebuild them and put the parts in them any cheaper than I can buy the aluminum complete replacements. I’ve checked! Tim, if you want a set of open chamber high-performance oval port cast-iron heads I have several sets. If you’re interested let me know and I’ll tell you what I’ve got. I can give you the date codes and all the specs. I’m sure it’ll be a good deal for you too. :good 6F2C1CF4-FFA8-4B49-BBE1-C17205D1870B.jpeg 91E299FC-6508-4180-8142-4DA58D68EE72.jpeg
 

Tim

Well Known Member
Supporting Member 4
Wristpin was looking for a set of Oval port heads and I sold him a set of 781s I check them for cracks and magna flux them and made him a deal of the century. I would suggest calling or checking with Skip white Performance. You cannot redo a set a cast iron as a heads as cheap as you can buy these loaded oval or rectangle port high-performance with raised exhaust runners. I have checked and they guarantee them and they build them to suit with installed heights and spring pressures for the cam that you have or spec I’ve seen three sets on motors that have been built around here and they’ve all been good quality. If I ever decide to build another big block I will be ordering a set myself. Even though I have several sets of cast-iron heads large oval port on the shelf I cannot rebuild them and put the parts in them any cheaper than I can buy the aluminum complete replacements. I’ve checked! Tim, if you want a set of open chamber high-performance oval port cast-iron heads I have several sets. If you’re interested let me know and I’ll tell you what I’ve got. I can give you the date codes and all the specs. I’m sure it’ll be a good deal for you too. :good View attachment 88574 View attachment 88575
Thanks Tooth, I’d love to have a set of 781’s but the shipping would be brutal. I know a guy a couple of hours from here that has a couple of sets. I’m going to do some homework and see if a new set makes more sense. Need to pick a Cam first.
 

Don Jacks

Well Seasoned Member
Supporting Member 3
You need to decide what you want the engine to do first.A power band such as the 380 ,just more of it would make a good street truck engine I would think. If you do decide on aluminum heads then a minimum of 10 to one will be needed.
 

Tooth

Well Known Member
Supporting Member 1
I have investigated several 496 builds, And the engine builder seem to like the large oval port heads. 10.5 to 1 compression for better throttle response and reaction on the street. Sometimes large rectangle port heads on the street will cause a lag and kill the bottom end. But as you know rectangle port heads have better flow at the top end and more mile an hour. Some people like the large oval ports on the street so it doesn’t kill the tires off the line. I guess it all depends on if you’re driving it as a cruise or on the street or if you’re racing it. Oval port heads tend to be a lot cheaper. And the more available. But I’m not talking about those peanut port truck heads. 781s are very popular because they have large open chamber oval port runners and factory hardened exhaust seats. People used to throw those things away looking for the rectangle port 990 heads. Now a set of 990 has run about 11 or 1200 bucks ready to go. You can buy aluminum heads from SkipWhitePerformance.com Oval or rectangle port For the same money ready to burn a tire! That’s gen lV parts... go to skips website and look up the 300 cc oval port head for the 496 they are just a little over $1000 and they are completely done by them to your specs. You cannot buy an old set of cast-iron heads put the bigger valves in them put the hardened seats in them and all the components for $1000. They do have raised exhaust runners so when you buy a headbolt kit there will be eight bolts that need to be 3/4 of an inch longer than the factory ones. Been there and done that. And it takes about two weeks to get them. Very nice looking head! Most rectangle port Chevrolet heads are 320 cc untouched. So there’s only a difference of about 20 cc’s but a little more low end and throttle response...
 
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Tim

Well Known Member
Supporting Member 4
You need to decide what you want the engine to do first.A power band such as the 380 ,just more of it would make a good street truck engine I would think. If you do decide on aluminum heads then a minimum of 10 to one will be needed.
Yes Same idea as what I just did for the 380 Don but a lot more of it. I’m thinking 550hp is realistic on a budget with this block. I’m not racing it but off the line everybody likes tire smoke! I’ve read a lot and although I’m on James’ page I think the large oval are the more practical. Easier to get and like Tooth said just as easy to buy complete new ones If I wanted. I liked doing what I did with the 817 heads and ported them myself and I can get a set of 781’s for $200. Other than changing pistons to accomodate bigger valves and compression the bottom end parts should be good. The cam, springs would have to match what I want out of it for performance but that part I don’t know. intake I’d do a single 4 barrel.
 

Tim

Well Known Member
Supporting Member 4
I'd totally agree about he large oval port heads .550 on a budget is realistic,500 is a lot more streetable.,reliable,less maintainence.

Still have homework to do, there’s a lot to pick from. Unlike the W there’s a lot I currently have that I’ll reuse. Cam/piston/spring package will all be new. I’ll shoot for the 500-550 range. I see kits from Comp that give you cam, timing, springs retainers etc....what am I looking for lift and duration? Does it need to be bored unless it needs it to clean it up?
 

Don Jacks

Well Seasoned Member
Supporting Member 3
If the bores are straight[no or very minimal taper] and round then there's no NEED to bore those cylinders.How much will the truck weigh,what are you planning for a transmission?
 

Tim

Well Known Member
Supporting Member 4
Truck will weigh as much as the impala, about 4K plus I think. It’s a 1950 3100
I’ll get the block to Armstrong’s and get it squared checked and cleaned. Just didn’t know if it needed more displacement to get that HP. I won’t buy anything until I know the block is ok,
Transmission I’ll do the same as the car with a 700R4.
 

Don Jacks

Well Seasoned Member
Supporting Member 3
OK give me a little time and I'll work out some sims and come up with a couple of suggestions for you.I haven't done a big block in decades and it was a race piece. You don't need more displacement,but it never hurts either.Displacement will have to come from stroking and it's almost as cheap to build a 496 as it is a 468 and like the 380 the extra torque will be noticable.
 
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Don Jacks

Well Seasoned Member
Supporting Member 3
Going with a 10.5 compression,a Performer RPM intake,an 850 carb[or Holley Sniper] 454 with 2 inch headers on a 454 I found a Lunati pn 20110712 and a Comp pn 11-432-8.Both are hyd.rollers.I like the Lunati a little better because I know what it'll do in a 474 W engine.A 10.25 474 with Walla heads,a McQuillian intake and 2 Fast throttle bodies,1 7/8 headers and this cam made 558 hp at 5500 and 613 ft.lbs. at 4100.A stock stroke 10.5 -1 454 with large oval port heads with 2.25 in.1.88 valves should put you at about 525 hp right around 6,000 with a nice flat torque curve peaking at around 535 at 4000.The Comp cam would be pretty close to the same.Food for thought.
 

Tim

Well Known Member
Supporting Member 4
That’s awesome Don!! No I know what to look for. I’ll see what comp has for a kit with springs etc... the intake will be what I put on the 380 but BBC version. Carb I know where there is one. Once block is known for clean up I’ll get the proper pistons. Likely KB icons like I did for the 380.
 

Tooth

Well Known Member
Supporting Member 1
Erson same parts same specs much cheaper than comp, my 468 has copies of cam lifters etc and was 400.00 cheaper. Cam, lifters, springs, retainers, locks,push,rods 800.00...
 

Tim

Well Known Member
Supporting Member 4
I’m assuming Tooth Erson is as good as comp? Although I had new lifters on the 380 build and 10 mins in 2 of them stuck down. They still haven’t come back up.
 
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