Cam choice and build choice Pontiac 400 or 461? low budget! - Hot Rod Forum : Hotrodders Bulletin Board
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Old 09-21-2014, 06:49 AM
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Question Cam choice and build choice Pontiac 400 or 461? low budget!

Hi Everyone,

First post here. I am building this on a budget, selling old engine parts & wheels to buy the basic offering from eagle with the I beam rods and cast crank.

So the car is a 68 Firebird
350 with a 4v intake and Qjet,
XE256 cam
TH350 with the smaller converter from the original ST300 a
8.5 10 bolt posi 3.42 rear end.
Dog at the track runs out of steam in 3rd before the traps and does 15.5 @87 mph. This has to change!!!

So here I am contemplating a build. I already have a 988 400 block and and -5 cc flat top cast pistons at mys disposal. I also have a 557 block with a summit 2801, 6X-8 heads with gasket matched performer intake.

What I want to do is build a 461 using the Summit 2801 cam and 988 block. Is this a decent cam for this combo? It seems pretty good to me, but need your thoughts

Another option is to stay 400, and get a cam that will work with the 400 at 9 to 1 CR (XE268?). The shop says they can get me there or a little higher with zero decking and milling the heads.

Thanks!

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Old 09-21-2014, 09:54 AM
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contact user named "poncho"
That cam you chose is small,especially for a larger engine. continue shopping your area for a suitable stroker kit and please find a few extra dimes and buy a roller cam. A hydraulic roller cam will brighten up the engines performance all through the rpm range,excellent buy for your application. hope poncho jumps in and gives you a tried and true "combination" soon
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Old 09-21-2014, 10:20 AM
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Here are the specs, I run this through Desktop Dyno and it looks fine. Both engines will be between 9 and 9.5 I don't see where this cam seems too small. The 461 runs out of breath at 5k, but on the 400 it seems to go into 6000 rpm barely losing any power with that cam.

The 461 actually seems to always run out of breath up top no matter what cam I throw at it. I guess the stock 6X heads are the limiting factor there.

Basic Operating RPM Range:1,800-5,000
Duration at 050 inch Lift:214 int./224 exh.
Advertised Duration:288 int./298 exh.
Valve Lift with Factory Rocker Arm Ratio:0.444 int./0.466 exh.
Lobe Separation (degrees):112
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Old 09-21-2014, 10:32 AM
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if thats what you want then use that cam,,,,
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Old 09-21-2014, 12:57 PM
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The 57 block is a poor choice for a stroker. Weak main webbing is to blame.
The 988 will work.
Use the Eagle stuff you talked about
Zero deck the block
use the 5cc eyebrow flat tops
.041 compressed head gasket
84 CC chambers/aluminum heads
4.180 bore 4.25 stroke
a nice tight 10.52 to 1 compression
Run a summit 2802
IVCA at 83 degrees
Dynamic CR is at 7.11 to 1
Very pump gas friendly
the 114 LSA moves the power band up .
I would rather a cam with the same advertised and .050 specs with a 112 LSA.
But what do I know ..........
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Old 09-21-2014, 01:00 PM
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Quote:
Originally Posted by Kyle68 View Post
What I want to do is build a 461 using the Summit 2801 cam and 988 block. Is this a decent cam for this combo? It seems pretty good to me, but need your thoughts
That cam will want 8.75:1 to 10.0:1 static compression ratio. Build the motor to that and it will make power from ~1800 to 5000/5400.

Quote:
Originally Posted by Kyle68 View Post
Another option is to stay 400, and get a cam that will work with the 400 at 9 to 1 CR (XE268?). The shop says they can get me there or a little higher with zero decking and milling the heads.
The XE268 cam closes the intake valve at 38 degrees ABDC @0.050" tappet lift and will work best at 9.5:1 to 9.8:1 static compression ratio. If you want to build the motor at 9.0:1 SCR, use a cam that closes the intake valve at around 28-30 degrees ABDC @0.050" tappet lift such as the XE250H.

Last edited by techinspector1; 09-21-2014 at 01:22 PM.
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Old 09-21-2014, 01:12 PM
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This would also work well with stock Iron heads.Providing you install screw in studs and make the valve train adjustable.Using 1.6 rockers would be an option
http://www.summitracing.com/parts/hr...w/make/pontiac
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Old 09-21-2014, 01:14 PM
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Thanks for your replies guys.

Latech I like your proposed set-up but I have no money for aluminum heads right now. What I listed is what I have. I can either break the bank on a stroker kit or maybe go hyd roller on the 400, but the top end's gotta be the 6X-8s and the Performer or 1968 OEM 4 barrel intake.

SO techinspector1 the 2801 is a good choice for the 461?
9.5 to 9.8 CR seems beyond the limits of the 6X heads so I guess the Xe268 isn't the one for the 400.

Open to Other cam suggestions!
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Old 09-21-2014, 01:24 PM
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Quote:
Originally Posted by Kyle68 View Post
Open to Other cam suggestions!
See my edited post.
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Old 09-21-2014, 01:36 PM
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XE series is for low compression motors.
With 101 CC chambers....that's what you'll have
Get some 6X-4 s (94 cc ) mill them .010
That will bring your static to 8.3. With an XE 262 your dynamic will be at 7. to 1. Still pump gas friendly and ponies on a budget
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