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Old 10-15-2008, 06:48 AM
How fast is fast enough?
 
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CHP 467hp 355ci build

I just got my copy of CHP and there was a "budget build" for 467hp. It ran about $3900 but that was including machine work and some "parts on hand."

The thing that interested me the most about it is that they used a cam with more duration than even I would have chosen and a lot of people on here think that I go crazy with duration. I was wondering if anyone had some ideas as to hwo they could increase the power of this combo without drastically changing it, loosing streetability, or increasing the cost.

my ideas would be to run a set of ported Vortec or Bowtie Vortec heads with an AirGap RPM intake instead of the old Vic Jr. they used. the AG RPM has been shown to hold its own with the single planes and I think it would really improve streetability- Also the heads they used seem a bit too big for this power level. Vortecs ahve been shown to live up past the 500 HP level and their smaller ports would again help with drive-ability. Lastly, as stated the cam had a little too much duration for my tastes, since it was a "custom cam" I would have gone with something with about 5 degrees less duration @.050" on both the intake and the exhaust- Again combos like that have been done and have made slightly more power so I think over all the tq and hp would pick up, idle speed would drop, and milage may move up to the 8 MPG range .

I like the approach of a basic budget build with a 7,000 RPM max though, it gets people out of the same "flat top 4VR, 268 cam, RPM intake, 750 holley with vacuum sec." builds.

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Old 10-15-2008, 07:10 AM
How fast is fast enough?
 
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upon further reading I found that it was a "bracket engine"... I still say put it on the street.

Also, from my calculations they are not at the 10.5:1 compression, its actually more like a hair under 10:1- which with that cam could run on 87 octane.
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Old 10-15-2008, 07:28 AM
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?????

I dunno any of the motor or build particulars... I don't have CHP.

I dunno what you consider wild duration either, with nothing to start a comparision from.
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Old 10-15-2008, 09:50 AM
How fast is fast enough?
 
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ok, its a 355 with Speed Pro 4vr forged pistons, a 1969 vic Jr. intake, a 255/263 cam, MoTown 220 heads, ported and polished, Eagle SIR 5.7" rods, a DZ Z/28 carb, and 1.5:1 roller rockers that were 30 years old.

The chamber size is listed at 62 cc's, but the also list 10.5:1 compression- which doesn't add up.
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Old 10-15-2008, 08:11 PM
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Quote:
Originally Posted by ap72
ok, its a 355 with Speed Pro 4vr forged pistons, a 1969 vic Jr. intake, a 255/263 cam, MoTown 220 heads, ported and polished, Eagle SIR 5.7" rods, a DZ Z/28 carb, and 1.5:1 roller rockers that were 30 years old.

The chamber size is listed at 62 cc's, but the also list 10.5:1 compression- which doesn't add up.
the 10.5:1 cr "adds up" when the motor has a 0 deck clearance at tdc.
Don't think there was a Victor Jr. manifold in 1969.
Torker, Trantula, Scorpion were the Edelbrock single plane manifolds of the day.

Haveing built simular motors I can go along with the power results.
The 200+cc Dart/WP heads tend to want a big cam to make this power.
If you pick a cam for this motor based on your subjective taste in cams
you will come up way short on power with this combo.
The motor wants what it wants for a cam, not what you want.

Needs a 3500 stall minimum 4000-4500 stall better and a healthy rear gear ratio. This motor likes to rev. You want to gear it to go thru the traps at 6800-7200 rpm for best results. I use a simular Isky solid cam in this 355 Dart head combo. Actually made more power.
good at 10.5:1 way better at 13.5:1 cr and race gas.
The low compression ratio version likes the cam advanced in the motor for best overall torque power band 99/100 in C/L
I also built a 12.5:1 $$$cheapy version$$$$ of this using fully ported big valve 305 heads and a Holley strip dominator that made impressive power considering the low budget heads. lot of fun for a buck... 12.5:1 is a bit much for pump gas thou...
It does have a very rough racey idle, but when set up properly in the car, it "drives" well for a race motor. Just don't be shy on the converter or gearing.
Needs a vacuum resevior for the PB's. Idles rough but steady at 950 rpm.

You sort of need to read between the lines a bit when looking at these magazine engine build ups.

Last edited by F-BIRD'88; 10-15-2008 at 09:07 PM.
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Old 10-16-2008, 06:38 AM
How fast is fast enough?
 
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[QUOTE=F-BIRD'88]the 10.5:1 cr "adds up" when the motor has a 0 deck clearance at tdc.
Don't think there was a Victor Jr. manifold in 1969.


Haveing built simular motors I can go along with the power results.
The 200+cc Dart/WP heads tend to want a big cam to make this power.
If you pick a cam for this motor based on your subjective taste in cams
you will come up way short on power with this combo.
The motor wants what it wants for a cam, not what you want.

QUOTE]

Its labeld as a 1969 Vic Jr in the mag, and it does look different than today's Vic Jr, the compression "adds up" to 9.7 at best when you figure in a .030" overbore, 5cc valve reliefs in the pistons, zero deck, .040" compressed gasket, and 62 cc chambers- in all actaullity its probably lower since they polished up the chambers and cut larger valve reliefs into the pistons.

Secondly, *** does "The motor wants what it wants for a cam, not what you want." mean? Did you snuggle up with the enigne last night and have it wisper in your ear that it wants excessive duration? Sure it needs a healthy amount of lift, but there are solid cams with less duration and more lift that you can buy right off the shelf using 1.5:1 rockers- if they would have used 1.6 or 1.7 rockers they would have even more lift with less duration. From what that engine told me that's exactly what she's been craving.
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Old 10-16-2008, 01:01 PM
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[QUOTE=ap72]
Quote:
Originally Posted by F-BIRD'88
the 10.5:1 cr "adds up" when the motor has a 0 deck clearance at tdc.
Don't think there was a Victor Jr. manifold in 1969.


Haveing built simular motors I can go along with the power results.
The 200+cc Dart/WP heads tend to want a big cam to make this power.
If you pick a cam for this motor based on your subjective taste in cams
you will come up way short on power with this combo.
The motor wants what it wants for a cam, not what you want.

QUOTE]

Its labeld as a 1969 Vic Jr in the mag, and it does look different than today's Vic Jr, the compression "adds up" to 9.7 at best when you figure in a .030" overbore, 5cc valve reliefs in the pistons, zero deck, .040" compressed gasket, and 62 cc chambers- in all actaullity its probably lower since they polished up the chambers and cut larger valve reliefs into the pistons.

Secondly, *** does "The motor wants what it wants for a cam, not what you want." mean? Did you snuggle up with the enigne last night and have it wisper in your ear that it wants excessive duration? Sure it needs a healthy amount of lift, but there are solid cams with less duration and more lift that you can buy right off the shelf using 1.5:1 rockers- if they would have used 1.6 or 1.7 rockers they would have even more lift with less duration. From what that engine told me that's exactly what she's been craving.
1. you'd best check your math and calc method again.
The cr based on your supplyed specs would be 10.579:1

2.
Don't know if your motor talks to you but...I find this info thru actual testing. A friend of mine after testing a box of all different cams of every discription in just such a motor on a dyno, came up with a very simular near identical Isky solid as the best cam for this motor. Many cams with more lift made less power in this motor. All the cams with less duration including rollers tested in this motor, made less power.
The best power was made with 1.5:1 rockers.
Again, if you want to build a powerfull motor you cannot spec the cam by what you think the motor wants for a cam. The cam is a part of the whole system in a running engine. When you run such a cam in this motor you get very average power and loose overall torque. Give it the cam it wants that allows the induction and exhaust sytem to work in sync and the power comes up. Go much beyond that point and power goes down and torque goes way down.
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Old 10-16-2008, 01:46 PM
How fast is fast enough?
 
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bore stroke swept vol head vol gasket th gask vol comp
4.03 3.48 44.38939415 67 0.04 0.510222921 9.652357394

disp 355.1151532


I checked and rechecked and it still comes out to a hair under 9.7, the 67 cc's for the head chamber volume are the result of 5 cc's in the piston and 62 in the chamber. I didn't account for the space above the top ring land- which would lower it even further, though only slightly.

As for the cam bit... You're just silly! Its quite alright though, I understand where you're coming from and I don't hold it against you.
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Old 10-16-2008, 02:02 PM
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If you're reading a magazine to get your recommendations, then you'll be just as disappointed as the numbers on their dyno. They want to wow you with big HP numbers. They don't care about power under the curve, nor do that care about streetable torque or stall speed. A bracket motor is designed to run for 20 seconds at a time, idle at 2000 rpms, and operate in a very narrow power band.

Of course they stretch the cam choice... that's their JOB. Advertisers don't pay for ads in the magazine if the article headlines read, "Build Adequate Street Torque with Ample Vacuum and MPG for your street truck."

Listen... stop using forum anonymity to scream at us. You're young, you're obviously a great bench racer, but you keep posting just to try and tear down our experience.

Build the engine how you want, but until then either listen to our advice or shut up. Don't just randomly post with your big wisdom, build the damn engine and prove us wrong.
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Old 10-16-2008, 02:13 PM
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Quote:
Originally Posted by ap72
bore stroke swept vol head vol gasket th gask vol comp
4.03 3.48 44.38939415 67 0.04 0.510222921 9.652357394

disp 355.1151532


I checked and rechecked and it still comes out to a hair under 9.7, the 67 cc's for the head chamber volume are the result of 5 cc's in the piston and 62 in the chamber. I didn't account for the space above the top ring land- which would lower it even further, though only slightly.

As for the cam bit... You're just silly! Its quite alright though, I understand where you're coming from and I don't hold it against you.
Your math formula for engine compression ratio is incorrect
The correct formula is:

don't for get the "1+" part of the formula as people often do.
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Old 10-16-2008, 02:28 PM
How fast is fast enough?
 
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I know why you add the one, but it oversimplifies the chamber's dynamic volume. It should be less than one.
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Old 10-16-2008, 02:37 PM
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Build Adequate Street Torque with Ample Vacuum and MPG for your street truck!

Yeah, likely headline in a CHP rag.

Like the "Cam swap nets 90 HP on small block!" So I flipped to the page, they built a nicely rounded 355 with aftermarket heads etc and a 929 stocker type camshaft. Replace it with a Lunati camshaft and voila - 90 HP more!

Lunati may have been advertiser of the month, I dunno. The next month was Moser.
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Old 10-16-2008, 02:44 PM
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Quote:
Originally Posted by ap72
I know why you add the one, but it oversimplifies the chamber's dynamic volume. It should be less than one.
There is nothing "dynamic" about this. Its purely a static compression ratio formula.
Now whois getting silly?

You seem to not have a problem with bending and twisting physics
and logic and mathmatics to suit your own theories. (or to just try to appear to be right or intelligent.)

Give it up.

For your convenience while you're learning to calculate engine compression ratio (by hand or with a calculator) here is a online engine calc page that when you enter the required inputs, does the math for you and gives the correct answer.
Try it.
http://www.wheelspin.net/calc/calc2.html
No need to reinvent the wheel here today.
Have a nice day.

Last edited by F-BIRD'88; 10-16-2008 at 02:57 PM.
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Old 10-16-2008, 03:57 PM
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I get 10.63:1 cr with a zero deck (doing it by hand).

727cc= 355 cid cylinder
62cc= head volume
5cc= piston
8.5cc = gasket
0cc= piston below deck

(727cc + 62 + 5 + 8.5 +0)/(62 + 5 + 8.5 +0)= (727 +75.5)/75.5 = 10.63
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Old 10-17-2008, 06:39 AM
How fast is fast enough?
 
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Quote:
Originally Posted by F-BIRD'88
There is nothing "dynamic" about this. Its purely a static compression ratio formula.
Now whois getting silly?

You seem to not have a problem with bending and twisting physics
and logic and mathmatics to suit your own theories. (or to just try to appear to be right or intelligent.)

Give it up.

For your convenience while you're learning to calculate engine compression ratio (by hand or with a calculator) here is a online engine calc page that when you enter the required inputs, does the math for you and gives the correct answer.
Try it.
http://www.wheelspin.net/calc/calc2.html
No need to reinvent the wheel here today.
Have a nice day.
You're right, the calc for static compression is the same regardless- I was the one over thinking it. I'll admit when I'm wrong and I was blatently wrong when it comes to this calc.

I still feel a cam with slightly less duration with the same or greater lift would win more races, and while it may give up a peak hp or two it would have a lot more area under the curve. A great cam for this budget build would have been the "#8 cam" which you can buy from most budget circle track suppliers for about $65 It has a hair less lift, but the money saved could be put into a set of higher ratio rockers.

Int. Duration @ .050": 248
Exh. Duration @ .050": 252
Int. Lift: 530
Exh. Lift: 542
Lobe Separation: 106
Adv Int Duration: 278
Adv Exh Duration: 282
Valve Lash: .018-.018

If that is too small for you they also have another one that is a hair bigger, the #6 cam-

Int. Duration @ .050": 252
Exh. Duration @ .050": 256
Int. Lift: 542
Exh. Lift: 552
Lobe Separation: 102
Adv Int Duration: 282
Adv Exh Duration: 286
Valve Lash: .016-.016


Also, keep in mind that these cams are NOTHING FANCY, they're budget off the shelf cams which perform better and cost less. Another contention of mine on this build is the SIR rods- many people have had bad expierences with these- I think off the shelf GM PM rods would have been a better choice- rebuild ones with ARP bolts would be even better and cost less.

So in total, run a set of ported Vortecs, 1.6 rockers, the #6/#8 cam, and rebuilt PM rods. You'd save about $400 and make more torque with equal hp.

I'm not saying this is the only way to do something, but I do think its a better way for less money.
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