Well why not go best of both worlds with the head. Go with the pressed in stud head and have it converted to screw in studs?

 

Good call, I forgot about that. I'll have to ask him how much that would cost to have done. I figure the head is going to be the most expensive part of this project, so I might as well do it right.

 

Six hundred for porting is pretty cheap. An experienced hand can do a lot in a short period of time. How much does the shop charge for labor? At $75/hr you're getting eight hours of porting.

 

I thought ALL 240/300 rods were forged.

I also prefer studs vs pedestal rockers, especially the ones with pushrod guide slots.

P&P can easily take 12 hours. Including flow testing I would say $600 seems reasonable.

 

They very well may be forged. I was just going from what I'd heard. If they're forged, cool.

The more I think about it, you guys are right on the pedestal rockers being preferred. I'll check on getting screw in studs.

What recommendations on rocker arms?


Also, good to know that the $600 sounds like a good deal. Definitely not cheap, but I've been waiting to rebuild this engine for a good 8 years now, and I want it done right.

 

Make sure you get ARP studs (sbc), or similar quality. Shop ordered my original studs and they sheared (3). Think about roller rockers and 3/8 vs 7/16. You can use 7/16 with a set of bbc rockers and they bolt up perfectly. I thought you were getting larger valves? Is that still in the plan? Oh, don't you guys think that with a nice porting he'd be better off with higher flowing exhaust?

 

I'd definitely go with ARP. I was also thinking about the 3/8" vs 7/16". It doesn't seem like much, but that's quite a bit more material.

3/8" = 0.11 sq. in.
7/16" = 0.15 sq. in.

That's 36% more material.

I thought about roller rockers, but doesn't that require a different valve cover? Also, weren't you saying that they don't really offer much of a benefit on an engine that doesn't see extreme RPMs?

But yeah, I'm thinking larger valves. Thoughts on what size I should go with?

For the exhaust, I'd like to stick with the EFI manifolds, but I'll more than likely have my walker pipe rebuilt for a better, more balanced, Y-pipe.

 

Stay with 3/8". I did. Use the sbc arp studs. If you ever need to use a 7/16" stud, you can simply use a combo. stud, 3/8 into the head, 7/16 up. Oh, and be sure to use thread sealer on them. They hit the water passage. The 3/8" work great.

My engine building experience and knowledge is very limited, but roller rockers seem more of an ego thing, for bragging, than for actual benefit. Usually you have to have a taller v.cover, or modify the oem. I do, however, like to use one r.r. when setting up the engine, as a guide to show me the geometry of the v.train. With a simple witness test I can see how the valve stem is hitting the rocker, if there is side thrust, and that is handy when a head/block has been milled. It tells me whether or not I need a longer/shorter p.rod. Once the adjustment is made, I go with oem rockers (they have zero needle bearings that can fail). Of course some will argue they cause less drag on the engine. (for $100 you can get a nice set of used bbc r.rockers at the auto swapmeet.)

I would be curious to have you calculate the diff. between an oem intake valve and a 1.94, which seems to be the most common mod size. I mean the diff. in air mass moved by one and the other. It would be interesting to know when taking mpg into consideration. I believe making the jump to larger valves could compromise your mpg a bit.

I believe I see one possible flaw in your engine logic. You want more power. You are considering porting, cam, to go with mod. intake and carb and ign. All those mods allow/help the engine to breathe, but yet you're going to install efi's that are designed for an engine that produces how many hp, flows much less. Don't get me wrong, I would love to bolt on exh. manifolds for the reliability and less heat, but it seems they would be hindering flow.

Afterthought: I did not have the stud bosses milled as many on the forum recommend. I have miles of room using both a bbc r.rocker, Comp gold, and the oem rockers. And a bit of info for anyone looking for good info regarding r.rockers for the 300. Big block Chevy r.rockers work. And, the Chevy 409 bb used 3/8" studs. I know. I used them. Comp still, last time I checked, makes them.

 

I'm using the area formula for a circle. Area = (diameter / 2) ^ 2 * PI

Aftermarket:
1.94" = 2.96 sq. in.

Stock:
1.78" = 2.49 sq. in.

It's about a 19% increase in area (minus some for the stem in the center).

I'm not totally sold on the larger valves, but I think it would be a cool idea. I don't want them to kill my mpg though. I don't mind a little ping, but if we're talking a major drop, then it's not worth it to me. I drive my Bronco a lot.

I understand your reasoning on the exhaust. My thought is where would it end? Headers aren't cheap, and they'd require me to have my exhaust redone up front (I know, I'm thinking of doing that anyway). But if I'm adding headers, I should probably seek out an open plenum C series intake since the DP is mostly for stock to mildly modified engines and is somewhat restrictive. And if I get a C series, I should probably get a 500 - 600cfm carb... I feel I need to draw the line somewhere.

I'm not wanting an all out performer. 200hp would make me happy. I also want to keep my reliability and durability, and not burn too big of a hole in my pocket.


I wish Clifford's valve cover wasn't so expensive. I don't really feel like shelling out the cash for one so that I can use roller rockers that may or may not benefit anything. I don't have any means of welding two valve covers together to make a taller one, so I'd probably have to pay someone to do that.

 

So, could we say you'd be using 19% more fuel? Or, at least, that there is 19% more air that needs to be mixed with gas vapor?

When my engine was new I took it on a 500+ mile trip, about 175 miles of 65mph on the freeway each way, 50 thru foothills each way, and the rest street driving. I filled the 38 g. tank when I left, and topped off when I returned so I could accurately check the mpg. I got 15 mpg, with a 4400 lb pickup, 3.31 gears, with a c6 auto. I have the 1.94/1.60 valves. That was with an autolite 4100, 465 cfm.

The efi engine was 145 hp.

You are grappling with what every engine builder struggles with: Where to draw the line. Good luck.

 

I don't know if it means it'd be using 19% more fuel, or if there's 19% more available. Does that mean I don't have to open the throttle as much for the same amount of power?

For instance, if it takes 60hp to move my vehicle forward down the interstate, if I have regular sized valves, I have to have my throttle open 25%. If I have larger valves, does that mean I only have to have it open 20% for the same amount of cruising power? Would that effectively mean I don't use any more gas until I stomp on it?

15mpg with a C6 is really nothing to complain about.
My truck is 4500 (just had it weighed last week when I took in some steel), comparable aerodynamics, 3.00 rear, with a manual trans (no OD). I'm sure it'd be moderately similar. Granted, I have 32" A/T tires, but I'm still getting 16 as it sits right now.

I'm betting that I'm already making more than 145hp.

And yeah, my wife and I are budgeting it out and trying to be reasonable with where to draw that line. Either way, I don't think we'll be unhappy.

 

I've built quite a few engines, though only 1 1/2 Ford big sixes (the prepped parts and finished head to #2 have been wrapped in plastic and buried in a corner for years and years). I build any of my car/truck engines for low-mid-range street power and fuel efficiency. Some years back, the advisor I follow most, David Vizard, said that when building for fuel economy, you particularly want a good exhaust side, which at the head calls for, frequently, a somewhat over-sized exhaust valve only, and a little higher lift on both valves, with a stock or near-stock cam, so that's how I've been doing it. But heads from different engines have different particulars, and Frenchtown Flyer would be my Big Six advisor on whether to use just an oversize exhaust valve, both valves oversize, or neither oversize and only go with a little extra lift (again, building for street torque and mpg)(and again talking a complete rebuild). How about this, Flyer? (Let's specify that we're either using the 240 head or the EFI head, and not the smog head, and that we've done a very moderate port-and-bowl blending).

Extra compression particularly helps an engine built for my purpose. When talking compression, guys usually refer to static compression numbers, but that is a little misleading. You have to watch it because when you free up the intake and exhaust sides, you get better cylinder-filling, thus more dynamic compression, even if you have made no change to the static compression ratio. (Squish also bears on this, but hasn't been a recent part of this discussion yet, so I'll pass).

Bronco, this discussion has gone so long, I forget whether YOU are using a C-6, but if you are, do you know about "rollerizing" it? Check a company called Level 10. Their rolling element thrust bearing is said to "significantly" reduce friction . . . .

 

Back when I was porting a 300 head the advice I got was, "You're feeding six 50 cubic inch cylinders through ports and valves that are undersized for for a 302 V8. Opening up the ports too much should be the least of your worries."

Consider the Ford 400. Not exactly known as a top end engine. It came with 2.05/1.65" valves. To the extent it suffered from any lack of "low end" power or economy that was more a factor of low compression/deck height and retarded cam timing. The same thing that plagues a 300 albeit with a far more restrictive head.

I would not hesitate to have bigger valves installed.

 

I agree with Baron. Bigger valves will not hurt and maybe help.
But with one caveat.

If you are going to be using the late model EFI head, and you want to keep its 'fast burn' qualities for more efficiency then do not use much more intake lift, and keep the clearance of the intake valve to the combustion chamber mask as stock, which I think is around 1.75mm - certainly do not open it up past 3mm. That is because the EFI chamber / valve positioning is designed to get the incoming charge to "squirt across" the top of the chamber and generate micro-turbulence which promotes faster flame travel and more complete combustion. If you lift the valve significantly past this mask then you stop generating swirl /turbulence and are just wholesale filling the cylinder with a rather languid, slow moving charge not conducive to burning rapidly. That would require adding ignition timing and thus contributing to pumping losses.

My personal approach is to use a 240 head when all-out horsepower is required, as in a racing situation, and use an EFI head if you want to extract the most amount of energy from every molecule of fuel, as in building an engine to get the best fuel economy.

 

Makes sense on the bigger valves. That's the way I think I'll be going.

The head I'm going to be using is a regular carb'd head. I believe it was the one off of the parts engine, so it's around a '78 or so.

I asked him about screw in studs this morning and he recommended it immediately. He has a flat fee of $125 to do it, and has the ARP studs already there. He also showed me a set of heads that he'd put screw-in studs in just yesterday. Looked like good work.

My crank is back and looked great. I didn't realize the pictures sucked until after I left, but they're all I got.





He now has the head and is measuring the exact cc of each chamber.


Seattle Smitty, I have a manual trans NP-435.