Vintage Mustang Forums banner
  • Hey everyone! Enter your ride HERE to be a part JUNE's Ride of the Month Challenge!
  • May's Ride of the Month contest ended with a tie! Go to this thread to vote on the winner! VOTE HERE
1 - 20 of 23 Posts

·
Registered
Joined
·
1,036 Posts
Discussion Starter · #1 ·
Hi there; I'm starting to do the ground work to build a stroker motor for a '70 Fastback. I plan on using a forged crank, with H-beam rods, Aluminum heads, w/ 60-64cc chambers, and 12-14 cc dished pistons. It's been many years since Ive been current with todays technologies. So here it goes....... What are the pros & cons of Stainless Steel Vs. T-7 Aluminum, Roller Rockers? Also, Which type of piston is better, Forged or Hyper? This motor will be primarily used on the Street, and Highway., So longevity, and reliability is most desired! Your input will be greatly appreciated!

Happy holidays!
 

·
Moderator
Joined
·
7,124 Posts
Steel is stronger than aluminum. Aluminum is lighter than steel. Unless you are running some humongous spring rate I'd recommend aluminum.

On your pistons, hypereutectic pistons are cast aluminum made from an alloy that contains extra silicon. This silicon comes out of solution as the cast piston cools in the mold, and froms hard nodules along the aluminums grain boundaries, increasing the pistons wear resistance and toughness. Forged pistons are made from a solid chunk of aluminum alloy that is work hardened in a forging press, making a much more dense and even stronger piston. Forged pistons are the best in terms of strength, but they are heavier than hypereutectic pistons and expand more with heat. This means forged pistons need to have a greater bore clearance, that can lead to piston slap, particularly on a cold engine. Forged pistons are also much more expensive.

Unless you are going to use a power adder (turbo, supercharger, or big shot of nitrous) hypereutectics would be the way to go.

Good Luck!

Phil
 

·
Registered
Joined
·
5,552 Posts
Not so on the aluminum. Comp cams pro magnums are made of steel which are lighter than aluminum and can be rebuildable. That info came directly from comp cams when I contacted them 1 months ago about this very question.

H pistons are fine, but from what you are listing to place on a "mainly street" engine, forged IMHO would be better. Specifically, you list performance upgrades like heads, rockers, and I'm guessing cam upgrade won't be fair behind.

If you have any questions about engine builds, contact adperformance and they build, sell, and are extremely helpful with engine questions.

Give comp cams a call about your questions on roller rockers and hear it from them.

You want another unbias answer, check out the owner of the last link. He will answer and talk to him about your questions. Great car guy. He has been around for 40 years building and racing all kinds of stuff.

Links:
http://www.adperformance.com/
http://www.compcams.com/DefaultWide.asp
http://www.jomarperformance.com/
 

·
Registered
Joined
·
4,234 Posts
I dont see any need for forged pistons if the motor is for a street car, unless you are nearing the 500 hp mark, which is tough with a street car w/ no power adder. Hyper's should be just fine for the street.
 

·
Registered
Joined
·
663 Posts
with that said I don't see a need for a forged crank. That is way overkill and would recommend you look for a nodular iron crank. You would save a fair amount of money to put torward something else. Perhaps towards a nice set of heads.
 

·
Registered
Joined
·
4,171 Posts
Ditto on the Comp ProMagnum rockers .

 

·
Registered
Joined
·
12,311 Posts
I'm grateful 5.0's came with forged, as if i feel the need for some nitrous or some other adder, you're already good to go.
 

·
Registered
Joined
·
749 Posts
Is there such thing as a stainless steel comp pro-magnum rocker?

All I see listed is chromoly steel.....no stainless.

I can see a chromoly rocker being lighter than the alum....but not a stainless rocker.
 

·
Registered
Joined
·
1,036 Posts
Discussion Starter · #9 ·
Wow, Thanks for all of your input! I believe I'm leaning towards the SS rockers now. I think I can compromise on the weight vs. the durability. Now I'll just have to decide who's to buy. Crane, Crower,Comp HT Rollers, and the Comp Pro Magnums all look basically the same to me. Their claiming them to be rebuildable, with caged bearings. and the rolling weight to be lighter, but I'm not certain how much of that is crucial, because of the forces at work. I would like to build this motor to accommodate a "Power Adder" at a later date. Anyways, I just wanted to say Thanks again, and have a Happy Holiday.

Best Regards, J.R.
 

·
Registered
Joined
·
6,630 Posts
Why would you want stainless over chromo? Keep the water out of your engine and you should be in great shape ;)
 

·
Registered
Joined
·
6,630 Posts
Steels have a level of stress when, if not exceeded, generally suffer no fatigue. Aluminum, on the other hand, always fatigues. This means, in theory, that a steel part could last almost forever, whereas an aluminum one cannot.

In a roller rocker this might be a materials factor to consider.
 

·
Registered
Joined
·
1,036 Posts
Discussion Starter · #13 ·
Is there a mechanical advantage of using Chromoly Vs. 15-5 PH Stainless?

I do like the looks of "Comp Pro Magnums", and they're almost half the cost of "Comp's" Stainless version.

J.R.
 

·
Registered
Joined
·
749 Posts
WHen would you *ever* need a stainless rocker?

Stainless provides no additional strength at 200deg F compared to a std. carbon steel. IMO 'stainless' rockers are just a sale gimmick for people that think stainless is better.

If the chromeoly ones are lighter (i'd like to see actual proof of that one) then go with them...otherwise get the alum.
 

·
Registered
Joined
·
1,036 Posts
Discussion Starter · #18 ·
Correct me here if I'm wrong, But I believe that the 15-5 PH is harder than steel,because of the 15% Chromium, & the 5% Nickle content. This Alloy is known for it's reduced deflection,strength, and is less affected by the heat range. (better Thermo-dynamics) I believe these rockers will outlast the rest of the motor, or at least be very durable. But if I were to run Aluminums, I'd certainly consider the Gold ones.

Great lookin car ya got!
Happy Holidays, J.R.
 

·
Registered
Joined
·
5,552 Posts
No offense, but when did I ever say anything about stainless. Remember Comp cams specifically stateds to me that I should o with pro mag's. This is from them:




BRAND NEW IN THE BOX COMP CAMS PRO MAGNUM ROCKER ARMS FOR FORD 289/302/351W ENGINES. 1.6 RATIO 7/16 ROCKER STUD.

The strength of steel, the light weight of aluminum.

Before Comp Cams introduced the revolutionary Pro Magnum RockerArms there were only two alternatives in competition rocker arms: Stainless Steel for strength and reliability or Aluminum for light weight and low cost. With the Pro Magnum Rockers you get the best of both worlds. Pro Magnum Rockers are made of 8650 chromemoly steel. This material is some three times stronger than 7075-T6 aluminum which is used for most aluminum rocker arms.
Comp Cams engineers used advanced computer technology (including Finite Element Analysis) to refine the Pro Magnum Rocker. Strength was added where it was needed and reduced mass in low stress areas. The result: Pro Magnum Rocker Arms have less weight (5%) at the valve than most aluminum rockers. This means more RPM and valve train stability.
The unique design of the Pro Magnum Rocker enables Comp Cams to use a larger trunion with more needle bearings. This spreads the load more evenly and the rocker will last longer. Other features include an integral pushrod seat that insures accuracy and saves weight, a unique rocker design also provides plenty of clearance for most high performance valve springs.


ROCKER ARM FEATURES:
# Rebuildable!
# Light Weight
# Strong 8620 Chromemoly Steel
# 5% Less Weight At Valve Than Most Aluminum Rockers
# Large Trunnion & More Needle Bearings To Spread The Load
# Integral Pushrod Seat
# Plenty Of Clearance For Most High Performance Valve Springs
# Lifetime Guarantee
# Applications Include Serious Street, Bracket Racing, Super Classes, & Circle Track Racing
 

·
Registered
Joined
·
1,036 Posts
Discussion Starter · #20 ·
Whoa-Whoa-Whoa, If you got the Idea that I thought you said anything different than what you wrote? I assure you that's not the case. In my first thread, I asked for the pro's and cons of Alum. vs. S.S. I stated that I was doing my homework for a future project, and longevity, & reliability were Key! I later wrote that I was leaning toward steel! And that I liked the look of the "Pro Magnums" and that they maybe more cost effective than "Comp Cams" S.S. version the "Hi-Tech" beings they sell for $375 - $450 a set, depending on where you get them. I'm not sure, whether I would notice any differences in my intended use, so it is likely, I will end up purchasing the "Pro-Magnums". I really appreciate the advice I've received, and now I actually understand what these "Hypereutectic" pistons are all about. Like I said, I'm trying to come up to speed on all these changes that have occured, while I was off raising a kid! Now that he's in college, it's time for dad to play! Once again, Thanks to all of you, and have a Very Merry Christmas!

Best Regards, J.R.
 
1 - 20 of 23 Posts
Top