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Cylinder head selection
So I've got my heads off of my car right now and what started as a simple repair job has exploded into a "since I've got them off anyway..." situation. I want some advice as to what direction to take this thing.
My combo is 400 .030 over, cam 223/231 @.050 .465/.488 stock cast bottom end with crappy 411NP pistons (like 14cc valve reliefs and way down in the hole, they are awful). Edelbrock Performer intake with a 750 holley and small tube headers, th400 tranny with a 3000 stall converter and 3.23's in the rear. The old heads were stock #16 d-ports. I wasn't particularly happy with the power (ran 15.35 on my best run ever) I'd like to pick cylinder heads to match the rest of the car. Was looking at either ported D-ports, e-heads or kauffman heads. My budget is relatively flexible but I don't want to spend $700 for an extra 5 horses, either. Sorry for the long post, but I've read a bit on the subject and still can't tell what's the best route. Any thoughts, comments, ideas or suggestions from anyone are welcome and appreciated, thanks. |
A motor with specs like yours, if it had 9.2 compression and if you heads currently are the big valve screw rocker stud #16 should make a easy 350 hp.
Rebuilt RAIII motors with far less cam lift and breathing thru stock late model exhaust manifolds have been dyno tested at 360 HP. Its your rear gears that are killing your et. If you want to keep your 3.23 gears I would suggest to get your current heads ported to flow 240 cfm@28 on the intake side and bring the exh side up to 180 cfm. If you are willing to go up to 3.55 gears or a little better, than stepping up to the bigger port volume and better flowing D port type heads from KRE or Edelbrock would be the way to go. Don`t forget that the greater power of better heads and stiffer gears will make traction and good 60 ft ETs a bigger problem! What was your 60 time on that 15.35 run? If you are into changing your heavy dished pistons outyou can at the same time go for much lighter and stronger rods. with this change the motor will rev a bunch faster which will acount for a far better ET, but you will have to also get the motor rebalanced. |
2.437 60 ft. went through at 92 mph. I'm not changing out those pistons until the motor needs an overhaul, but the gears could be a project for next year. So you don't think I'd get much more out of aluminum heads than ported iron, then?
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It might pay for you first to get the car as is dyno tuned, as stock 69 350 HO birds with a 4 speed have run mid 13s with a far better 60 ft time that yours!
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Which 16 D ports do you have? The `70 small valve, press in stud, or the `68 2.11 valve and screw in stud?
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Thanks for the response, Steve. I suspect that the 60 ft is largely a result of the gear and tires, it was practically impossible to get a clean launch.
I've got the heads off now, and whatever I do to the car after it's back together I want to make the right head selection now so that I don't have to take them off again any time soon. Has anyone tried the new d-port e-heads? They look interesting. |
The '68 16's
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I don`t think the heads are causing the mid 15 sec time slip. Even stock. Seems like with that cam, that car should be at least 2 sec. faster. Maybe the pistons are mostly the hard parts problem. But I think tuning is the real problem. How fast you want to go?
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By the way, what car are you running? How heavy?
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It's a '69 firebird, it is 3750 pounds with driver. I had it running perfectly on the street (until I started breaking valve springs but that's another story), though admittedly I'm kinda winging it on the tune. Ideally, I'll be running mid 13's or better.
I certainly haven't heard good things about those pistons, but I can't imagine that they'd hurt me very much. What do you think? |
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If you really wanna leave the shortblock "as-is" for now,here is how I'd approach this.
First thing first if you do opt to go the aftermarket head route,you'll for sure need to use the Kauffman D port heads and not the Edelbrock D port heads,and I'll explain why. The E-D heads have the valve CL moved ever so slightly and that often poses a problem with "old school" pistons like you have with the valve reliefs in the "stock" location,now if you were using a more modern piston with the revised valve relief pockets,then you could use either head,but for now,the KRE D's are the best aftermarket head option with your current pistons. Now that point is cleared up,the next order of business would be to choose the best head CC's,for your 400 cid combo. That also affects the head gasket choices too in a way. With the current piston situation you obviously have a few issues to try and deal with on this front. So with the 74cc KRE D's and a standard head gasket and your poor deck clearance you'd be at like 9.2:1 or so (+/- like .25 CR),which for an aluminum head combo is pretty low no doubt. A .027" thick cometic HG could bump that up like .25 point of CR to maybe 9.5:1 or so,but that's just mostly just amounts putting a band-aid on the real problem. So my choice would be to opt for the 65cc KRE D's,along with using those .027" thick cometic head gaskets,as that combination of parts would both move the piston closer to the head for better overall quench (albeit down in the hole some) as well as reducing the chamber CC's to where the extra valve relief CC's become more or less a non-issue. That would get you to like 10.30:1 CR,not @ all unheard of a CR for aluminum heads,matter of fact some would say that's an ideal CR for that sorta thing. Then all you would need to do is pick out the porting level for those heads,here I'd likely just get the 260 cfm "entry level" ports for now,as that port level will still be a decent jump up from what you got now,and then later on they can be ported even further when you do end up going thru the shortblock. Now I know what some are thinking,whats gonna happen when you rebuild later on and use some better pistons and maybe zero deck this thing,are'nt the 65cc chambers gonna be too small then? Well they dont have to be,at least not so long as one is commited to keeping the stock 400 3.75" stroke that is,as the pistons I'd use for the next incarnation of this combo would be the #KB891 .040" over 14cc Icon dished forgings (which just so happens to be pretty close to the current valve relief cc's). Then all you gotta do when you zero deck the next version is go back to using a .040" head gasket and the CR will be like 10.5:1. And when you do eventually get around to doing the bottom end rebuild someday,I'd maybe bump the porting level up to the 290 cfm ports at that point as well. So that's ^^^^ how I'd approach the whole aftermarket head option. Next thing I'd wanna change would be the cam,for the time being I'd for sure opt for the Crower #60310 solid cam with some coolface lifters and not look back,the KRE D heads will already have good springs to run that sorta cam,so that part of the swap would be a no brainer to me. And I'd swap that performer intake for a TII with that sorta combo seeing that it's using a Holley 750 cfm carb and such. In the right car with proper tuning and decent traction,a combo like that should easily be a low 12 second combo,possibly even high 11's. HP should be like 425 to 450 hp pretty easily. And I'd leave the current gears & converter be for now too,they'll work just fine with this sorta combo. JM2¢ Bret P. |
Thanks everyone, I appreciate the advice. Due to the issues with the pistons, I've decided to just have my 16s fixed and save the aftermarket heads for later with a different shortblock some time.
Not anything against the KRE heads, I just get the feeling this bottom end is a bigger deal than I thought. I think I'd prefer to buy them once and get them ported and such at that time rather than have to mail them back later. |
So,tell us just what's wrong with the #16 iron heads?
Odds are if those heads need any significant amount of work done to them,you'll end up with at least half of what a set of the aluminum heads cost into those iron heads (likely more than half),and then where are you at,pretty much back to square one right where you were before. If those #16 heads still have stock vavles in them,that right there is a serious risk by itself,as it's not @ all unheard of to see the "high mileage" OE 2 pc. valves "pop the heads off" of them when aftermarket valve springs come into the picture. So right there your looking at new valves,guides likely,valve springs,along with the corresponding machine work,and often that's just the tip of that iceberg. Just dont say you were'nt warned that the cost for a basic "re-work" of some OE iron heads can end up being quite a bit more expensive than one originally thought it would be. IMO the bottom end is only a "big deal" if you make it out to be such at this point in time. Dont get me wrong here,I dont care for those "low end" pistons anymore than anyone else here does,but there are ways to deal with those sorta issues if you absolutely have to. And you would only hafta send the KRE-D heads back later if you wanted them ported further,honestly you would'nt really need to do that if you found that you were infact prefectly happy with what you get from them @ the 260 cfm port level. At the very minimum,if you opt to put it back together with the #16 iron heads,I'd be sure to use the .027" thick cometics head gaskets,now understand that they aint low budget head gaskets,but that's about the only way you can help that poor deck height issue besides doing some machine work to the shortblock. In the end,the choice is yours,think about this long and hard,and be sure to get estimates and prices upfront and compare such between all the various options you're considering,as these days it's easy to be pennywise and pound foolish. Nobody I know likes spending money twice for the same thing. FWIW Bret P. |
I broke a couple of valve springs on the #16 heads, exhaust a few months ago and intake #7 most recently. When I put the cam in I was dumb and didn't have the machine work done to accommodate the extra lift, and apparently the valve guide and retainer were hitting or something.
I dropped them off at the machine shop today before I read your post, I'll get an estimate once they have them apart. One of the intake valves had a little chip in it; might have happened when the spring broke and it took the lifter and pushrod with it too. You've certainly convinced me to at least use the fancy head gasket no matter what route I go. I'm a little concerned about how long it will take to procure a set of the KRE heads, I've been calling since last week and haven't had them answer the phone yet. |
Is it possible that the valve train issues were cause me to run slow at the track?
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69 Birdboy,
Bret has offered you some very wise options, give them plenty of consideration. He has boat loads of experience and is only looking out for your best interest. Tim john--- |
I talked to kauffman last week and they were going out of town, thay may be why you cant gat ahold of them. I am doing something similar to my 400. I have a 67 bird with a 400 WITH 6X heads. I found a set of kauffman heads on the PY classifieds that were new in the boxes but pre owned for a few hundred less than new ones, I am having them ported by a local head porter. I didnt know about the cometic gaskets though. I may opt for a pair of those! I think the rise in compression and flow will make a bigger difference than the pistons, you should try and find a set of the kauffman d ports.
Chris |
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I don't have the time at the moment to catch up with what's been said... but fwiw, I had a lot of work done to a set of 6X heads. in the end, for another ~$500-600, I coulda had a set of KRE aluminum d-ports. and alot more power potential.
so, imo if you're going to have a lot of port work done to a set of iron heads, might as well just go ahead and opt for the aluminum heads. I know I will next time. |
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