My heads are cracked, help me select new cylinder heads
 

I put ~80 hours into porting my D8OE cylinder heads. I was goign to JB weld the intake ports but at least one of the exhaust ports is cracked. The exhaust port gets hotter than the intake port so I am scrapping these cylinder heads.

I want the widest torque curve. This is going in my '66 Bronco. I am not sure on the tire size yet but I expect ~38".

-'79 351W block .040" over, decked, copper .020" head gasgets
-Schneider Racing 262/270, 208/214 @ .050", 110 LSA .448"/.470" valve lift with 1.6:1 rockers.
-Intake manafold- undecided. I am leaning toward getting a Proffessional Products intake or a 5.8L GT40 intake.
-7.5L ECU and harness, smog stuff removed, 7.5L 24 lb/hr fuel injectors, Moates Quarterhorse
-Hedman long tube headers, not sure on primary tune diameter but understand that the primary tubes should be larger than the exhaust valve diameter. 1.6" exhaust valve to a 1-3/4" primary tube?
-Cylinder heads, I am leaning toward 180cc Dart Iron Eagle. Will the 1.94" intake valve make a better torque curve than the 2.02" intake valve assuming all valve shrouding has been eliminated?

That's a shame about your heads.1 3/4 primary tubes are too much for that cam.Try 1 5/8 as your goal is to speed up the exhaust gases exiting the chamber/port.I would go with 2 02 valves with the 351.I'm assuming that is a flat tappet cam.The duration is good but if you could get more lift you'll be way ahead.I'm not sure how it will affect EFI(I run carbs on my trucks)performance,but since you're turning 38 in tires,you'll need lots of bottom end torque.I'm sure you're gearing for those tires as well.I run a 5.8 with Performer RPM 2.02 with a "477 "493 lift 210 218 .050 111 LS Comp Cams 4x4 grind,Stealth intake ,Holley 670,shory 1 5/8 in a 5600 lbs van with 35in tires 4:11 gears and it has enough torque to get up steep mountains at part throttle here in BC.I'm sure others will join in with component ideas to help with your combo.

So when valve shrouding has been eliminated, the larger intake valve gives up no torque to the smaller intake valve?

How much valve lift would be ideal for my application? I am getting some nice rocker arms but I am not sure which yet. I an get my camshaft exchanged one time for the high lift option and a wider lobe separation for my EFI. I currently have a 110 LSA and want a 114 LSA.

1.7 rockers with the cam you have would produce 0.478/0.500" lift at the valve which is more like it, and I don't know that the 110LSA would be a problem if you're gonna tune it anyway.

Can I have too much valve lift?

I can get my camshaft re-ground or exchanged from .448"/.470" to .492"/.496" valve lift with 1.6:1 rockers.

Schneider cams said that any more violent a profile than my hydraulic flat tappet can tolerate would be fine with a solid flat tappet or solid/hydraulic roller camshaft. However, I would only gain as much as 5 ft/lbs of torque at the peak horsepower end of my torque curve.

How much rocker ratio can I have? I wouldn't go any less than 1.7:1. I guess it comes back to how much valve lift I want and how it affects the life of my valve seats. With my old cylinder heads I was stuck with soft valve seats and maybe 30,000 miles between valve jobs. I would like to get 50,000 miles between valve jobs.

Big Vann just told me that I should have 2.02" intake valves.
-So all valve shrouding removed, do larger intake valves reduce low end torque over smaller ones?

I am getting Moates Quarterhorse and Binary Editor so my EFI should tolerate my engine. Would a 112 or 114 LSA make a better torque curve with the camsahaft slightly retarted?

http://s1082.photobucket.com/albums/...cpZZ2QQtppZZ16

:D D8OE heads ? Really ? :-wink

A cam with the specs of the stock Ford F4TE roller would be perfect for what you're doing. 256/266 advertised duration, but running it with 1.7 rockers changes the lift (by .030 over 1.6's) to .445/.473. This cam has a 116 LSA. You don't need huge flowing heads for what you're doing. I'd either get a set of iron GT40's (not the P heads) or take a set of E7TE's and open the exhaust sides to match the gasket and remove the thermactor bumps from the port roofs. Nothing fancy here with changing the timing either, just run it straight up with the stock O.E roller chain and gears. Essentially just building a Lightning 351 motor.

I know, that was not a practical venture. Apparently no body is using those cylinder heads. I am going to cut them up and check out the ports from the inside. I will probably post the pictures.

Now about this Lightning GT40 build you have prescribed, what will that do to my mid range torque?

Are the GT 40 cylinder heads going to make more low end torque than 185 cc cylinder heads?

RHS - Which intake runner volume should I choose?


Determining the Correct Intake Port Volume for Your Engine - Super Chevy Magazine

How should I interpret these guidelines in the links? In the second one, the 383 sacraficed some low end torque for more torque in the better part of the torque curve. The 230cc cylinder head made less peak horsepower than the 215cc cylinder head and much less torque everywhere than any other cylinder head. I think the 200 cc cylinder head made the best overall torque curve on the 383.

I have a Dirty Dog torque converter that will stall 1,500 rpm in normal driving and 2,200-2,500 up under high load. I don't know the appropriate terms. I am going by what Dirty Dog told me. The 2,200 to 2,500 depends on my engine.

The shame is that he wasted 80 hrs of work and now he has to go buy some good heads!

Yes.. if it exceeds what the valvetrain can handle or is beyond the point where the heads stop increasing airflow. These Dart and RHS heads flow well up to 0.600" lift while stock Ford heads(E7TE and GT40) give up at 0.500" lift.


If it were mine I'd just use it with 1.7 rockers, I disagree with baddad I think the F4TE cam is too small in both duration and lift for a deep breathing 5.8, the cam you have will make more TQ and HP.


There is no valve shrowding on those Dart heads, I have a set and I'd love to be able to tell you how well they work but that motor hasn't been built yet.

No.. less valve overlap which is lower LSA produces more TQ so you want to use a cam with as little as possible, the reason EFI cams always have 114LSA is to provide a smooth idle but if you can live with a cam that produces a little more of a lumpy idle(;) like that's a problem) then you're all set.

"The shame is that he wasted 80 hrs of work and now he has to go buy some good heads! "

I did not think that D8OEs were worth anything so I decided to use them as sacraficial cylinder heads, the first ones I ever ported. I am out $100 in machining for cutting the seats for larger valves but I don't really care. I tried to make cheap cylinder heads work and they didn't. Now I am serious about getting good cylinder heads.

He's putting a 351W in a 66 Bronco, he doesn't need deep breathing heads, nor a cam to match. Chances are (based on his focus on torque) he's going to spend most of his time below 3000 rpms, where all that capacity is wasted. If he really wants maximum torque, he should stroke it.

I agree that displacement makes torque but I wanted to better understand camshaft and cylinder combinations. I already overhauled my short block and had it apart two times. I would love to build a 434W but this time around I overhauled a running 351W while improving breathing. I actually enjoyed the torque of the engine. I have been reading lots of engine builds and trying to decipher the build's effects on the torque curve.

I have seen trad-offs in torque such as more low end torque in the superficial end of the torque curve or outside the better part of the torque curve, vs. the same engine with more torque in the better part of the torque curve with a small sacrafice in low end torque in the superficial part of the torque curve, outside of the better part of the torque curve. That is what a loose torque converter is for.

What are appropriate camshaft and cylinder head combinations? I would like to compare 180cc and 200 cc on a 351W.

I wouldn't expect a 190 @ .050" camshaft to be ideal here but would a 230 @ .050" kill my torque curve? Would a 210 or 220 @ .050" build more torque and/or a wider torque curve?

In the 383 build article, the 180 cylinder head made the most low end torque while the 215 made the most horsepower and only sacraficed a small amount of low end torque. The 230 head killed the torque curve and made less horsepower than the 215. The 200 was reasoned to make the best torque curve but it was close between the 200 and 215 cc cylinder heads.

Here is where I am critical. I don't want to narrow my torque curve or sacrafice mid-range torque for a superficial amount of low end or top end gain.

This statement doesn't make sense. :-huh

"Quote:Baddad457
Originally Posted by Conanski

No.. less valve overlap which is lower LSA,

This statement doesn't make sense."


Yes, I second this statement. I don't second guess Conanski. He is the most reliable source on the internet but I was confused by this statement.

I would think that 108 degrees of lobe separation angle would have more valve overlap and less vacuum at idle while 114 degrees of lobe separation angle would have less valve overlap and more vacuum at idle.

Lets clarify this with Proffessor before moving on with our discussion. :-drink