Hot Rod Forum banner

ARG! Help me settle an argument with my dad

5K views 47 replies 18 participants last post by  jimfulco 
#1 · (Edited)
Alright so I'm building up my 355 again, improving on the spots that were weak last build.

So the subject of heads comes up, currently I have a pair of #993 smoggers on there from back in 1973.

I want to put some new heads on there, in my other thread all the heads I'm looking at are aluminum. I was previously looking at vortec heads until I found out you need to buy vortec intakes for them, and those are more expensive with less selection (afaik).

Anyway, he's real firm on NOT running any aluminum heads on our 355 because they will warp because cool water is not introduced in the back of the head like it is in the front of the head. So the heads will warp and be screwed is basically what he's saying. He's from the old school, very pro Iron. Thinks aluminum heads are for race cars only, or very high end street cars not driven very often.

Me on the other hand, I don't want to keep these stupid smogger heads cause I want to make power with this build. I know aluminum heads won't warp unless they get real hot, they're just not going to warp whenever they feel like it. He says we don't need aluminum heads because they are "racing heads" and this is a street car ('68 malibu).

I know there are a lot of hot rodders out there running aluminum heads on the street with no problem. I also know that aluminum heads will take more compression than iron heads without pinging, and I'm going to be running at least 10:1. This is really frustrating because I want to buy the heads and use them but he doesn't and he's still supplying a lot of the funding for this car, but I'm buying the engine parts.

All the aluminum heads I've looked at are perfect, small chamber, large intake runners, large valves ready to bolt on.

The other heads like the DART Iron eagles require porting and crap and they aren't that good. I can just buy these aluminum heads and they're ready to go. If I spend a couple hundred less on iron heads then I gotta make that up by having the work done...

So, am I right or wrong? I'm going to work on getting my dad to see these points. He's not unreasonable and once he sees this hopefully he'll go for these. Are aluminum heads reliable on the street?
 
See less See more
#3 ·
Tell your dad that just about any new car nowadays has aluminum heads and they have had them for many years. You need aluminum heads if you are going to run any kind of higher compression. Aluminum heads do not warp for no reason. All of GM's performance parts crate engines come with aluminum heads and there are thousands of them in street rods with no problems.

Vince
 
#4 ·
Jmark said:
But what about the cooling issue since the early blocks don't pass water across the back of the intake like the new ones do. Is this a legit issue?

Inquiring minds would like to know.

Mark

The L98 TPI engines had aluminum heads and didn't have a coolant crossover at the rear of the intake.
 
#5 ·
Jmark said:
But what about the cooling issue since the early blocks don't pass water across the back of the intake like the new ones do. Is this a legit issue?

Inquiring minds would like to know.

Mark
In endurance racing where a high HP engine is running under heavy load for an extended time this can still be a problem. Some engine builders for these applications route coolant directly to the head and back of the block to help even out the head temps from front to back. I don't think a mild street engine would see these problems as long as the cooling system was adequate.


As far as convincing your dad goes, do you think saying " a bunch of anonymous guys on the internet said it would be fine" is going to change his mind? I think it boils down to if he's paying the bills, he picks the parts. If you're paying for the engine, you pick the parts. You could tell him that if the aluminum heads warp and get destroyed you'll pay for the iron replacements too. That would be putting your money where your mouth is which would be hard for a reasonable man to argue with...Good luck!



The first pic is the cooling line to the head between the center two exhaust ports and the 2nd is of the line to the back of the block. Both are fed straight from the water pump to keep cool water flowing to all areas of the head.
 

Attachments

#6 ·
Ask him why so many vehicles come from the factory with aluminum heads and iron blocks? Times have changed, aluminum heads are pretty much for the masses now. I'm planning on a set of AFR 195s for my 406 project, no hesitation at all to running aluminum heads in a street application.

As far a not passing water to the back of the block... There are ways around that. If there's room you can drill and tap (pipe tap) the back of the intake where the rear outlets are on the head and connect them to the water crossover near the thermostat housing. Some intakes even come with this provision already available. Using AN fittings and some stainless braided line you can make it look good and you'll get some additional water flow through the rear of the engine.

Look closely at these AFR intakes and you'll see what I'm talking about.
http://www.airflowresearch.com/sbc_manifold.php
It looks like the Edelbrock RPM Air-Gap intakes have similar features as well.
 
#7 ·
Blazin, would you happen to know temperature differences between standard manifold and the ones drilled for rear crossover like the AFRs?
I know street performance/factory vehicles have been running forever without the rear cross but it just seems like a good idea to have the rear crossover.
And how does that work? Do you route the tubes front to rear OR rear to rear. I am assuming its as easy as just running some 5/8s hose across the back.
 
#10 ·
Coolant pass overs on the manifold do absolutely nothing if they go from rear to rear which is why they stopped putting the rear manifold water passage in manifolds years ago. The water take off points on the AFR and other manifolds are intended to route coolant to the front of the manifold under the thermostat (on the engine, not radiator side). The reason you've rarely seen anyone use these is that without bringing additional coolant to those areas you've accomplished nothing.

If you look at high HP circle track and road racing cars where the rules allow cooling system mods you'll see lines running from the back of the manifold to the front but you'll also find the additional coolant lines from the water pump to the head and block as shown in the pics of my RR car above. They work together to get "cool" coolant to each part of the head. If you just add the manifold lines all you've done is starved the center of the head for coolant. Think about how coolant flows in a SBC and you'll see why.

These mods also help an engine running on the edge avoid detonation. Engines don't detonate in all cylinders at once, they start to detonate in the cylinders that get hottest. On a SBC with stock cooling this is usually the center two cylinders where the two exhaust valves sit next to each other. That's why that is one of the areas that gets coolant sent directly to it. With the way coolant is sent through the block the rear cylinders only receive coolant that has already passed through the entire block, picking up heat along the way. That is why coolant is directed there. Companies that provide mechanical water pumps for endurance applications offer pumps with coolant taps on the outlets right before the coolant enters the block to allow for plumbing "fresh" coolant to these areas.

http://www.stewartcomponents.net/Me...PROD&Product_Code=42203&Category_Code=ChevyS4

Coolant temps in endurance engines can vary as much as 40 degrees front to back but with these mods and some tuning of the outlet sizes to each area you can bring them to within a few degrees of each other. This can let you run more compression and timing without sending one or two "hot" cylinders into detonation.
 

Attachments

#11 ·
SlowGTA, how about running a coolant inlet to one side of the intake rear and running an outlet to the heater core on the other side? Or would you bringing cooler water into the rear of the head than is exiting the front? At the very least, it would seem to increase circulation... Right?
 
#12 ·
You will have NO problems running an aluminum head on any engine that has an adequate cooling system. The heads must be straight (the block as well) and properly torqued. Re-torquing would help, but isn't mandatory with good head gaskets. If it is an older block without the additional cooling hole in the lower middle of the deck, you can drill it out to help cool the head and block castings between the center two cylinders.

tom
 
#13 ·
Blazin72 said:
SlowGTA, how about running a coolant inlet to one side of the intake rear and running an outlet to the heater core on the other side? Or would you bringing cooler water into the rear of the head than is exiting the front? At the very least, it would seem to increase circulation... Right?
that's what I am wondering because that's what I was thinking of doing when you were mentioning this.


My current setup 355 7.7:1 270H 4 core rad clutch flex fan and an edelbrock chrome hi flo pump only saw a high of 190ºF. It was usually around 170-180ºF so the cooling system was more than adequate for that motor. Then again there wasn't much of a motor there :embarrass

I would think the same setup would cool a 10:1 355 with aluminum heads pretty well. The temps would be higher no doubt, maybe 200-210ºF max? maybe less but definitely not more.
 
#14 ·
"how about running a coolant inlet to one side of the intake rear and running an outlet to the heater core on the other side?"

I see where you're going but this wouldn't get you there, Except at the water pump and the front intake manifold passage where the thermostat lives the two sides of a SBC are completely separated as far as coolant is concerned. If you plumbed it like you mentioned, if I understand what your saying, you would have additional "fresh" coolant flowing through the head with the inlet and would seriously starve the side with the outlet to the heater core. On that side the coolant would flow from the pump through the block and through the rear of the head and then exit to the heater core, leaving very little coolant flowing through the center of the head. That is the same problem caused by just using the intake manifold water outlets on the AFR manifolds without providing additional coolant.

In a stock SBC all coolant enters the block from the water pump and flows towards the rear with small amounts flowing through the holes in the head gasket to the head, the rest flows through the entire block before entering the head at the rear of the engine. It then all flows through the head towards the thermostat. There are a few problems caused by this:
1. The hottest part of the engine, the center two cylinders in the exhaust valve area only receive coolant that has already been heated by the block for the stuff that comes up through the head gasket passage and by the block and rear of the head for the rest of the coolant.
2. The coolant ports in the head can only be so big because of the space available in the head. This means that the coolant passages are the same size front to back even though, in a stock set up, the front has to flow more coolant than the rear. Remember all coolant must flow through the front of the head to get to the thermostat and ultimately back to the radiator.

With the modifications we are sending "fresh" coolant to all areas of the head. the front gets it from the block through the normal passage as it's right at the water pumps outlet. The center from the line from the pump to the head right below the exhaust ports, and the rear from the line to the back of the block or head depending on the setup. Only then will adding the auxiliary return lines do you any good as the coolant flow that they would have taken away from the stock system is being added by the external lines.

Chevy addressed these same issues by going to reverse flow cooling with the LT1. they sent the coolant to the head, where it's needed most then to the block, which does need some cooling in street and endurance engines. This also helped even out the temps throughout the engine.
 
#15 ·
Alright so people in this thread have been saying you won't need to run all those extra lines on a mild street engine.

Well then, what defines an engine that necessitates those extra cooling lines? Where is the line for which a normally cooled engine with no modifications would need to be modified to keep the heads from warping?

What pushes it over that line? Compression ratio? inadequate cooling?

What's defined as a "mild" street motor?
 
#16 ·
The only aluminum heads I have hands on experience with are AFR and Chevy SB2s and I haven't seen a set warp yet. The AFRs have been on plenty of street engines and no problems. I can't speak for any of the others, as I haven't used them.

A properly configured stock cooling system with keep up with with most all street cars. It's not HP that dictates when mods like this are needed it usage. A road race car will often be run under full load at varying engine speeds for 40+ minutes. Not many drag race or street car are ever run this hard. Make sure the radiator you use is up to the task of cooling the engine and use a quality water pump and you'll be fine.
 
#17 ·
SlowGTA, thanks for the info.

Malibu73, I think even with iron heads you'd be fine, as long as your radiator is in good shape. I put a small supercharger on my 9.7:1 350 and run about 5 psi of boost and I saw no significant increase in engine temperatures using a basically stock cooling system, under any conditions. I use a dual 12" electric fan setup and no mechanical fan. The fans are set to come on at 205 deg and shut off at 190. Engine runs 180 on the highawy on a "normal" day and usually 185-190 if it's warmer than 90, but those days aren't too common around here. Yes my Blazer has a somewehat larger radiator from the factory than a lot of cars do and I only went to a 4 core when I decided my 3 core wasn't repairing.

If you're running a fan clutch then I'd suggest dumping the flex fan. Before I had electric fans I used a 17" rigid six blade fan with a thermal fan clutch and it was very effective.
 
#18 ·
Blazin72 said:
SlowGTA, thanks for the info.

Malibu73, I think even with iron heads you'd be fine, as long as your radiator is in good shape. I put a small supercharger on my 9.7:1 350 and run about 5 psi of boost and I saw no significant increase in engine temperatures using a basically stock cooling system, under any conditions. I use a dual 12" electric fan setup and no mechanical fan. The fans are set to come on at 205 deg and shut off at 190. Engine runs 180 on the highawy on a "normal" day and usually 185-190 if it's warmer than 90, but those days aren't too common around here. Yes my Blazer has a somewehat larger radiator from the factory than a lot of cars do and I only went to a 4 core when I decided my 3 core wasn't repairing.

If you're running a fan clutch then I'd suggest dumping the flex fan. Before I had electric fans I used a 17" rigid six blade fan with a thermal fan clutch and it was very effective.
Ok so it looks like my 4-core radiator will be fine, we've got the hi flow edelbrock waterpump with replaceable innards, if it breaks you don't replace the pump just the impellor or whatever's in there.

As for the fan, I've never heard this or that on them, mainly just that the flex fan is the better of the two because it flattens at higher RPM.

Is there much difference between a rigid fan and a flex?
 
#19 ·
Since I have a 4 wheel drive truck I originally went with the rigid fan/thermal clutch because of the potential for higher RPM operation and low vehicle speed (like when crawling around in 4 low). If I had a flex fan on there the fan wouldn't pull any air when the cooling system needs it most, with a rigid fan and the proper clutch I still had positive airflow when I needed it.
 
#20 ·
Blazin72 said:
Since I have a 4 wheel drive truck I originally went with the rigid fan/thermal clutch because of the potential for higher RPM operation and low vehicle speed (like when crawling around in 4 low). If I had a flex fan on there the fan wouldn't pull any air when the cooling system needs it most, with a rigid fan and the proper clutch I still had positive airflow when I needed it.
So then a flex fan probably wouldn't be much worse or better in a street car application. Unless you were sitting there doing a burnout for 15 minutes :thumbup:
 
#21 ·
arg!

Look up a back issue of Car Craft. They did a fan test of approx. 15 different mechanical fans and those flex fans that are supposed to flatten out at higher rpms were some of the biggest horsepower losers i'd ever seen--as much as 40 hp lost to these turkeys. We hang them on the wall in my shop like snowflake decorations and tell everyone to throw theirs away. The best as far as least hp lost?-- the factory thermally regulated clutch fan, only aroud a 8-12 Hp loss. Only thing that drew less power was an electric fan. Just goes to show that some "high performance" parts are not what they appear to be. :mwink: :D


As an after thought--this test was done on a 496hp smallblock chevy.
 
#22 ·
one other thing that someone may have said is the fact that if you race it, eventually it will break. ma ybe something else will give way and it will cause total carnage. aluminum is easily repaired, cast iron is not. later down the road you may decide to invest in a srtoker motor or may want to go a little faster. if this is the road you decide to travel, just remember portwork will more than likely in your future. some port work may need a little welding in certain spots or the heads can be modified to build something exotic. after all is said and done you have a good investment in your heads. again cast iron has its drawbacks. plus an aluminum head can run a little more compression that c.i. if the cooling system isnt rigged and functions to the best of its ability then the heads wont warp. everything on an engine can warp if you let let get to that point.
 
#23 ·
I guess I'm not going to argue for aluminum over iron, they both have their place. But your dad's memory is mostly but not completely, of the "good ol' days" when aluminum casting technology wasn't as good as today and warpage as well as porosity leading to leakage thru the casting was common. These issues have pretty much been overcome in the last decade to 15 years. Also gasketing has improved, head gaskets in particular were always a problem requiring regular re-torquing of fasteners or warpage and leakage would result. The new gaskets are graphite impregnated composite materials sandwiched with stainless steel having stainless fire bands on the cylinder edge. These have pretty much eliminated the need to re-torque and the problems of not doing so with old design gaskets. On the intake manifold to head side of things the new silicon impregnated synthetic material gaskets have also eliminated re-torquing and leakage. These new gaskets allow for the different expansion/contraction rates of aluminum and iron by being designed to resolve the stress as differential strains inside the gasket, where older stiff gaskets would internally fail and allow the strain on torqued bolts to relax (engineer speak for the bolts came loose) which lead to leakage and warpage.

There are three big advantages to aluminum heads, first is they take about 50 pounds off the typical V8. Second, they allow considerable improvement in compression ratio because of their faster heat transfer rate. This is a big advantage with a long duration cam as it allows enough compression, especially with unleaded fuel, to recover the bottom end torque typically lost with a long winded cam. Lastly, aluminum heads can be repaired if parts disintegrate and get rammed into them.

Cast iron has the primary advantage of being less expensive largely because you can run the valves and the valve stems directly against the raw material without having to machine the head for hard seat inserts and pressed-in valve guides. It's stiffer than aluminum so it increases the beaming strength of the engine, however, beam strength added by the heads doesn't appear to be of any advantage with contemporary block design (long way around to say blocks are strong enough). The big disadvantages are 1) weight; 2) the slower heat transfer rate reduces the compression that can be used for any given octane fuel which drives back on cam timing as you cannot compress the mixture as much, therefore, lost bottom end torque with a long cam can't be as easily recovered; 3) lastly it isn't very repairable, when a valve gets loose or a piston blows it's crown, or worse, cast iron heads become a throw-away items.

Vortecs come in three flavors the old ones do require a specific intake which adds to their cost and they don't take a lot of cam without substantial rework. However, the slightly more expensive two new versions take most any intake your heart desires and accept a lot more cam before requiring major surgery. The Dart and World equivalents, contrary to your thoughts, are ready to go and like the Vortec have the Ricardo fast burn chambers like most contemporary heads. They don't need to be ported, there's just plenty of meat there if that's what you want or need to do.

For aluminum there's also wide selection of modern heads using the Ricardo chamber and great ports, the Edlebrock Performer being a very good choice for the street and GMPP Fast Burns are another. There's many choices here just GOOGLE aluminum heads and step back from the screen.

Basically for a street engine head selection, what you want is the most flow using the smallest ports and valves. Especially with an automatic with high final gearing and a tight converter. This is a place where you have to be careful, it's very easy to over cam and over head an engine and end up with less performance where you want in the cruise speed range. If you're racing or you've got stiff final gears and a manual gear box then you can go for 190 cc or bigger ports and cam timing over 225 degrees at .050 lift. But for a daily driver, such an engine quickly gets old.

Bogie
 
#24 ·
oldbogie said:
I guess I'm not going to argue for aluminum over iron, they both have their place. But your dad's memory is mostly but not completely, of the "good ol' days" when aluminum casting technology wasn't as good as today and warpage as well as porosity leading to leakage thru the casting was common. These issues have pretty much been overcome in the last decade to 15 years. Also gasketing has improved, head gaskets in particular were always a problem requiring regular re-torquing of fasteners or warpage and leakage would result. The new gaskets are graphite impregnated composite materials sandwiched with stainless steel having stainless fire bands on the cylinder edge. These have pretty much eliminated the need to re-torque and the problems of not doing so with old design gaskets. On the intake manifold to head side of things the new silicon impregnated synthetic material gaskets have also eliminated re-torquing and leakage. These new gaskets allow for the different expansion/contraction rates of aluminum and iron by being designed to resolve the stress as differential strains inside the gasket, where older stiff gaskets would internally fail and allow the strain on torqued bolts to relax (engineer speak for the bolts came loose) which lead to leakage and warpage.

There are three big advantages to aluminum heads, first is they take about 50 pounds off the typical V8. Second, they allow considerable improvement in compression ratio because of their faster heat transfer rate. This is a big advantage with a long duration cam as it allows enough compression, especially with unleaded fuel, to recover the bottom end torque typically lost with a long winded cam. Lastly, aluminum heads can be repaired if parts disintegrate and get rammed into them.

Cast iron has the primary advantage of being less expensive largely because you can run the valves and the valve stems directly against the raw material without having to machine the head for hard seat inserts and pressed-in valve guides. It's stiffer than aluminum so it increases the beaming strength of the engine, however, beam strength added by the heads doesn't appear to be of any advantage with contemporary block design (long way around to say blocks are strong enough). The big disadvantages are 1) weight; 2) the slower heat transfer rate reduces the compression that can be used for any given octane fuel which drives back on cam timing as you cannot compress the mixture as much, therefore, lost bottom end torque with a long cam can't be as easily recovered; 3) lastly it isn't very repairable, when a valve gets loose or a piston blows it's crown, or worse, cast iron heads become a throw-away items.

Vortecs come in three flavors the old ones do require a specific intake which adds to their cost and they don't take a lot of cam without substantial rework. However, the slightly more expensive two new versions take most any intake your heart desires and accept a lot more cam before requiring major surgery. The Dart and World equivalents, contrary to your thoughts, are ready to go and like the Vortec have the Ricardo fast burn chambers like most contemporary heads. They don't need to be ported, there's just plenty of meat there if that's what you want or need to do.

For aluminum there's also wide selection of modern heads using the Ricardo chamber and great ports, the Edlebrock Performer being a very good choice for the street and GMPP Fast Burns are another. There's many choices here just GOOGLE aluminum heads and step back from the screen.

Basically for a street engine head selection, what you want is the most flow using the smallest ports and valves. Especially with an automatic with high final gearing and a tight converter. This is a place where you have to be careful, it's very easy to over cam and over head an engine and end up with less performance where you want in the cruise speed range. If you're racing or you've got stiff final gears and a manual gear box then you can go for 190 cc or bigger ports and cam timing over 225 degrees at .050 lift. But for a daily driver, such an engine quickly gets old.

Bogie
Now that's a reply :thumbup:

I've been talking to my dad and showing him things and I think I'll be able to get some aluminum heads after all :) I've also decided to build a 383 stroker, I added up the cost differences and there's almost no reason not to go to one, it's so cheap.

That said I've got a pretty nice little combo going, I'll probably just make another thread to show you guys where I'm at.
 
#25 ·
if dad is against alum heads (my dad would say no to alum heads if he was building a motor, course I'm way to old for him to foot my builds) but don't not go with vortecs cause a $150 to $200 intake (a intake might have to be used for that price ). a set of good runable salvage yard 062 vortecs for $175 or $200 plus $200 at machine shop for work for high lift cam & springs = $375 or $400 plus a intake. so $600 total and you can 10.1cr on pump gas w/vortecs. the vortecs are worth the new intake manifold to me. I've got my vortec heads & intake setup together a little at a time (my motors not ready yet) and the cost don't bother me for the end result.






Mustangsaly

---------------------------------------------------------------------------------------------------------------------------------
Some people are like a Slinky. Virtually worthless, yet bring a smile to your face when you push them down a flight of stairs.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top