Thread: 72 402 Truck Motor Performance, Any Ideas?

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I have a 72 2wd blazer with a stock rebuilt 402 that I am wanting to get a little more powere out of. Here is what I am thinking. I bought a edelbrock pro flo, looking to buy a set of 98cc closed chamber heads, going to get a cam, bought a set of headders and 2.5' stainless dual exhaust. I going to get a 2500 stall and I bought a set of 3:73's and locker. How do you think this combo will perform? What kind of horsepower do you think I will achieve?
Thanks

it will work try a small hyd roller cam gm #12551622 thru www.competitionproducts.com this will work good hp 430? tq 500 with 9.6 cr

That should give you a boost for sure. Pat, do you think he will be at 9.6 c/r just because of the heads? Im thinking no...but the combo will still work pretty good for what it is. John

with the small cc and the 402 piston yes if has the 350hp pistons and o deck it will be that

Originally Posted by pat mccarthy

with the small cc and the 402 piston yes if has the 350hp pistons and o deck it will be that

Operating Range: 1600-5800 RPM
Duration Advertised: 270° Intake / 286° Exhaust
Duration @ .050'' Lift: 226° Intake / 236° Exhaust
Valve Lift w/1.7 Rockers: .544'' Intake / .547'' Exhaust
Lobe Separation Angle: 112°
That is what comp cams told me to run.


Operating Range 1500-6500 RPM
Duration Advertised 300° Intake/306° Exhaust
Duration @ .050'' 240° Intake/246° Exhaust
Lift @ Valve .560'' Intake/.573'' Exhaust
Lift @ Cam .330'' Intake/.337'' Exhaust
Lobe Separation Angle 112°
Intake Centerline 110°
Intake Timing @ .050" Open 10° BTDC
Close 50° ABDC
Exhaust Timing @ .050" Open 57° BBDC
Close 9° ATDC
That is what edelbrock told me. Which one will give me the roughest idel and performance? How does the gm cam compare with them? I appreciate the replys.

I probably shouldn't say this, but I'm going to anyway.....

Son, you may not hear from Pat again. Your question about roughest idle nails you as a poser because you're concerned with impressing the geeks at the drive-in with a ratty idle. Pat gave you his best shot, a cam with a very wide power band, reasonable duration for the static compression ratio so that the intake closing point matches up, long lobe separation angle for high manifold vacuum to operate accessories, excellent carb signal and reasonable valve lift for long spring life and easy operation on the rest of the valvetrain. He further estimated 500 ft./lbs. of torque from the motor. Horsepower will be unimportant in moving that big hulk of a Blazer. Pat knows what he's doing with big block Chevys, but I don't think he's too tolerant of youngsters yankin' his chain.

I probably shouldn't say this, but I'm going to anyway.....

I love it!!

Yes, the rough idle. You can have that too, but then your blazer will be a slug, and wont be able to get out of it's own way. What would you rather have? Everyone wants the best of both worlds...and you cant do it. Everything is a compromise.

thanks techinspector1 and 1johnnyO your are both right and did a better job then me telling him so i will not add to it .you both get a A+ from me

Originally Posted by pat mccarthy

thanks techinspector1 and 1johnnyO your are both right and did a better job then me telling him so i will not add to it .you both get a A+ from me

I was just asking advice. If I knew all this I wouldn't ask. I thought that was the reason for the question? You guys might not like my ride anyways. the cams mentioned above will supply 10 to 13 lbs vaccum, is that not enough. Sorry to be so young and stupid.
kade 010.jpgkade.jpg

"I was just asking advice."
I know, and that's why I almost didn't post. I know you don't know what you're doing. All of us guys have lived through the nasty cam period of our lives. We've put up with the stalling in traffic and not enough vacuum to operate accessories and clunking going into gear and lack of low end torque and being just generally a pain in the ass to drive, just so we could amaze the geeks who don't know any better.

"You guys might not like my ride anyways."
Your ride is gorgeous.

"is that not enough."
No.

do not be to hard on yourself .when you get older there will be plenty of people that will do that for you

Originally Posted by techinspector1

I probably shouldn't say this, but I'm going to anyway.....

Son, you may not hear from Pat again. Your question about roughest idle nails you as a poser because you're concerned with impressing the geeks at the drive-in with a ratty idle. Pat gave you his best shot, a cam with a very wide power band, reasonable duration for the static compression ratio so that the intake closing point matches up, long lobe separation angle for high manifold vacuum to operate accessories, excellent carb signal and reasonable valve lift for long spring life and easy operation on the rest of the valvetrain. He further estimated 500 ft./lbs. of torque from the motor. Horsepower will be unimportant in moving that big hulk of a Blazer. Pat knows what he's doing with big block Chevys, but I don't think he's too tolerant of youngsters yankin' his chain.

You know I am young 26 years old, but if I remember every big block my old man has ever built had a hell of a cam in it and would just about shake the fenders off. They would also run like a raped ape, the last big block he had in a 66 nova with the 871 blower and twin 850's had the ''rough idle'' and the largest mickey thompson tires on back of it that you could put. That cam in that car didn't seem to stop it from spinning both back tires running 55mph down the road when he got on it. Now I know that he had a blower and aluminum heads and didn't need alot of vaccum for this application. Next motor was a ls1 and my brother has a ls1 and both of them have a large cam that is very noticeable for a fuel injestion car and they run like a bat out of hell also. I am not doing this for drag racing but to just pep the motor up a little bit. I will for sure want to show off at the car shows with my rough sounding big block, I think it is cool and do a lot of other people. I guess it is just preference. Sorry for trying to learn a little something!! I guess you might also ask if your old man knows so much about big blocks why are you here asking questions, well I like do things on my own without the help of my old man ( don't like seeming like a youngster that doesn't know a lot about motors and cams). Thanks for the help.

Originally Posted by pat mccarthy

do not be to hard on yourself .when you get older there will be plenty of people that will do that for you

You seem to know you stuff and I appreciate the info and cam suggestion. I may go that route. Thanks for your time.

Originally Posted by pat mccarthy

it will work try a small hyd roller cam gm #12551622 thru www.competitionproducts.com this will work good hp 430? tq 500 with 9.6 cr

Couldn't find that cam on there.
Thanks, Kade

Kade, you seem like a nice young man and I'm sorry I gave you a bit of a hard time.

Just to further your education, a very narrow Lobe Separation Angle (LSA), also called Lobe Displacement Angle (LDA) will give you the rough idle you're looking for, although a cam ground in this manner will peak early and have a very short field of power. 104 degrees is absolutely nasty with very little vacuum (won't operate power brakes), 106 is fairly nasty with little vacuum, 108 and 110 are lopey with low vacuum, 112 is fairly smooth (with decent vacuum) and 114-116 would be a factory (grandma goes to the grocery) kind of a cam that would get you 22 inches of mercury easily.

The cam that Pat suggested is 224 degrees @0.050, 0.483" lift and ground on 115.5 degree lobe centers for a smooth idle and outstanding vacuum. I'm sure he has run this cam before and that's why he recommended it because he knew it would do the best job for you.

You say your father ran a blower, yeah, well, a blower will cover up a multitude of sins in the choice of parts. It's a little more difficult when you're running naturally aspirated.

You may have to call those guys to inquire about the cam.

Again young man, my apologies.