Would an lt1 intake and a hot cam be a good setup on an otherwise stock moter? Would it rev up to 6000 like the intake was designed for or do the heads need help?

 

You would need to change to stiffer valve springs for that camshaft.

Stock iron TPI heads with a LT1 intake and Hotcam making power at 6000 rpm? I doubt it.

 

You will gain more from porting or better heads than adding airflow ahead of, and after the heads with a restriction in the middle. You would see a gain, but it would be selling the potential of the intake/cam short.

 

Be sure to email or PM John Millican. He does the conversions and can tell you lots of good information about their performance.

Even with stock heads you will probably move your peak HP RPM up.

 

im planning on this .. i currently have a 355TPI with an LT1 cam.

i bought an LT4 HOT cam, and have an LT1 intake. im planning on using 1.5RR which i currently have on the car, and having my L98 iron heads ported out to 2.02intake (already have 1.60ext) and having bowl work and runners polished.. or i might just get some trick flow 23* heads. not sure yet. for springs im just going to use LT4 springs.. because with 1.5rr the lift shouldnt be greater that .501 ? i think with 1.6rr its .525 for both..

i think this should easily pull to 6k, why would it not?

 

To get the iron heads flowing enough, you are going to spend about $1000-$1200 and then you are still running old cast iron heads. Get aluminum aftermarket to gain the full potential of the cam and intake. The prices will be about the same as a new set of heads.

 

1000-2000 on bowl work and polishing?? who's doing that job? Boyd Coddington???

ive been quoted 600$ tops for that, by a company that strictly rebuilds heads. old iron? arent they the same design as the aluminum ones, without the exhaust cross over?

yeah i wouldnt spend 1000 on just head work..

if i buy new heads, i will get aluminum.. but im just wondering why i've heard people say that aluminum heads will flow better than iron?

the way i see it, (and correct me if im wrong) ALL THING BEING EQUAL, is that you take both L98 heads(iron and aluminum).. they both have the same design(aluminum being 58cc and no heat X over) if you were to equally port them, equally polish them, and have equal size valves.. why would aluminum flow more? i can see the compression ratio being different, and heat dissipation.

maybe im missing something.. im not a head expert.

 

You are correct. Flow is flow. Also, aluminum heads need smaller chambers for higher compression to make the same power that equivalant iron heads need to make the same power. Iron heads actually have the advantage of retaining heat. Heat loss translates to power loss. If you had identical aluminum and iron heads with the same exact combustion chamber and ports, the iron head would make more power. Aluminum heads usually bump compression up to keep cylinder temps higher. Now talking factory iron to aftermarket aluminum, the aftermarket heads are way better, and are designed to outflow anything the factory made. Make that same aftermarket head in iron, and it would make even more power, at the expense of increasing the HP/weight ratio and difficulty machining/manufacturing. For the Hotcam and 1.5 rocker combo, porting will be your best bet IMO. I can have two heads cut for bigger valves, new valves hardware, 3 angle job, hot tank mag'd, etc for under $400. Porting takes about 8-10 hours per head and costs the price of some carbide bits, a grinder, and porting rolls. Have your machinist flowcheck them before/after to see exactly what you get, read up on doing it, and have at it yourself. Just my $.02

 

ZZsmpch

that was so far, the best explaination i have heard to date, reguarding this issue.. thanks for taking the time to explain that in detail.

what i think i will do is have my current iron heads worked on. after all is less than the cost of new heads.. BUT the more important part is that this car is used about 3-4 times a week, and not a drag or race car. so this will suit my purposes.

thanks guys,

 

Bowl work and polishing isn't going to net you much at all, you would need to spend some real cash and get them worked really well.


Let's take a look at the heads...

L98 Iron 083 cast
163cc (RPM Range idle - 4500)
Intake
Lift_______CFM
0.097..........52
0.194..........101
0.291..........145
0.388..........167
0.485..........179
0.582..........185

Exhaust
Lift_______CFM
0.075..........35
0.150..........62
0.225..........87
0.300..........105
0.375..........106
0.450..........106


L98 Aluminum
173cc (RPM Range idle - 5000)
Intake
Lift_______CFM
0.050..........29
0.100..........56
0.200..........120
0.300..........160
0.400..........186
0.500..........196
0.600..........199

Exhuast
Lift_______CFM
0.050..........27
0.100..........49
0.200..........96
0.300..........123
0.400..........140
0.500..........155
0.600..........159


AFR Aluminum
180cc (RPM Range idle - 5500)


Let's take a look at the camshaft....
LT1 HotCam
218* in 228* ex @ .050 .525 lift in & ex with 1.6 rockers 112* lobe sep
(RPM Range 1500-5500)


ZZsmpch, you seem to be slighty intelligent when it comes to heads, but you left some stuff out. The aluminum heads will be a smaller compression chamber to raise the compression. You can get a hotter chamber and still deversify heat to keep the engine temps down. The alumnum L98 is a 10.1 compression where as the iron L98 is 9:1, but would he need to change anything else for the higher compression? No, he would not.

The aluminum L98 heads made an average of 25hp over the stock iron heads, while the AFR was averaging 75hp over the stock iron heads.

KiLLJ0Y, the best thing to do is either save some funds up and get some nice heads, or go a different route than the TPI and HotCam. Don't waste money on the iron and then still spend the cash on the aftermarket ones.

 

True, but iron and aluminum L98's aren't identical either. The smaller chamber is needed to raise the compression (higher compression results in more power), but still runs at the same temp as the iron head at a lower temp. My point is that if the heads were identical, but different material, the aluminum head would be at a disadvantage because it would dissipate more heat from the chamber where you want the heat. Port shape and volume determine flow, not material. You can't compare the Al and Fe L98's because they are different (yes, the Al L98 will make more power)

Don't discount factory iron heads as junk based on just flow numbers and marketing hype. They have their place just like everything else. it all depends on what his goals and needs are. There is always a better head out there, a bigger cam, a better intake, etc. It comes down to the compromise of cost, use of the car, durability, and reliability. When is enough enough? That's something everyone needs to determine for themselves. It comes down to your preference, realistic use of the car, and personal desire. Over 20 years ago I was willing to put up with nasty cam profiles, lowered fuel mileage, constant maintenance, and broken parts in my big block powered daily driver. I'm not into that any more so both of my daily drivers are pretty mild now. I rarely spin them up to 5500 rpm, so I won't build them for high end power at the expense of low end torque when it spends 95% of it's time spinning 1800 RPM or less. They certainly don't "need" AFR's. My Chevelle on the other hand, That is getting AFR's more cam, etc. It's just for fun though.

Anyhow, I guess I'm just getting old. I also agree, he shouldn't spend the money upgrading his heads only to replace them later on. The smart thing to do is to plan your whole combo, from intake to rear gears, save your money, and buy the parts as you can. A well thought out plan will lead to success. No plan will lead you in circles and empty your wallet. Now that's about $.05 worth.

 

http://chevyhiperformance.com/techar...58/index2.html

Just something to keep in mind. I'm not going to say its a perfect test, but its about as close as you could do. I'd like to see the flow#'s on each head, but they should be close.

My thoughts on it is that maybe the loss of heat isn't as great as we've been led to beleive, I mean, I'd like to compare the heat loss out the radiator of an aluminum headed engine to an iron headed one. I don't think its going to be much of a difference if any. IF there was a huge difference, everyone with aluminum heads would be spending more money on their coolant systems, and clearly thats not the case. IMO whats letting you use the extra .5 to 1 point of compression in pump gass motor is the ability of aluminum to distribute the heat better, stopping hot spots from forming. I'm by no means an expert, but it makes sense to me.

EDIT: whoops, heres the link to the main page of the article, not the dyno sheets.

http://chevyhiperformance.com/techar...858/index.html

 

just so you know.. the HOT CAM and TPI are not going together.. its the HOT CAM + LT1 intake.. hence this thread.

my heads have already been cut for 1.60 exhaust and runners have been cleaned up alot.. its the larger intake valve and bowl work that i need, plus finish the runners off.

that, for me, will yeild what i want.

yeah aftermarket, there are countless heads and combo's to consider. im just making do with the parts i currently have or can afford. so far i have the HOT CAM, LT1 intake + rails and AFPR,

i need LT4 springs and heads to be worked. plus reprogramming.

thanks guys

 

My mistake, I meant the LT1 intake when I replied. That's why I was saying get a nice set of heads, because these can't flow enough up top. I just didn't want to you spend cash and then spend some cash later.

Either way, enjoy the performance upgrade. When you are looking for aftermarkets get the 195cc for that and the LT4 cam, I think you will really like it.

 

you know i was thinking about using Vortec heads.. but having them redrilled for 87+ style intakes..

anyone done this?