Login    Forum    Search    FAQ

Board index » Racing Forum » Engine & Cylinder Head Tech




Post new topic Reply to topic  [ 3 posts ] 
Author Message
 Post subject: cam upgrade
 Post Posted: Mon Jan 07, 2013 6:12 pm 
Offline
User avatar

Joined: Wed Apr 19, 2006 4:11 pm
Posts: 2749
Location: Shepherdsville, KY
I ran out of funds when I built the new bullet last year and decided to use the old cam over. Now I am ready to order a better cam for it and I am looking for opinions. I ended up with a 436 ci SBF with D3 Yates heads. It seems to run it's best shifting around 7800 and I have been going through the traps at about 7600 in the 1/4. It's a 4.165" bore and 4" stroke with 14.5 CR. Here's the flow #s on the heads. This was before Tim (machinist) fixed some problems with them. He said what he did should have improved the numbers about 5 across the board but we didn't check them when he finished. I run a single plane intake with one of those junky 1050 2-circuit dominators.
Code:
LIFT      CFM      CFM
@28"     INTAKE   EXHAUST

200      131      103
300      222      155
400      294      194
500      338      221
600      359      239
700      376      252
800      387      261
900      397      269


Here's the specs on the current cam. This is based on a 1.7 rocker arm ratio and I have 1.8 on it so the gross lift at the valve is .756 instead of .714. I also have it in at 106* instead of the 104 the card calls for.
Code:
Part #35-000-9
Grind number 316-5\330-1 R8
Serial # Z 6089

                               Intake    Exhaust
Valve Adjustment               .024     .026
Gross Valve Lift               .714     .714
Duration @ .020 Tappet Lift     316      330

                                 Open      Close
Valve Timing @ .050      INT   37 BTDC   65 ABDC
                         EXH   78 BBDC   34 ATDC

These specs are for cam installed at 104 intake center line

                     Intake      Exhaust
Duration @ .050         282      292
Lobe lift             .4200    .4200
Lobe seperation            108


Tim called CompCams for a new grind and they recommended leaving the exhaust like it is and raising the intake lobe lift to .460 with a little more aggressive ramp and changing the separation to 110*. He said they estimated the change to be worth 25-30 HP.

_________________
Chuck Woloch

Chuck's Automotive
Full line Computech dealer
chucksautomotive@yahoo.com
Image


Top 
 Profile  
 
 Post subject: Re: cam upgrade
 Post Posted: Tue Jan 08, 2013 11:01 pm 
Offline
Moderator
User avatar

Joined: Tue Apr 18, 2006 3:20 pm
Posts: 1457
Location: Missouri
I'd give the ex more duration along with the other changes Comp recommended... more intake lift and wider LSA.
Intake lift is usually good if your springs are good. Bigger engines usually want wider LSA I'd probably pick 112.

I doubt you'll see anything like 30hp from a cam change, but Comp wants to sell cams so they'll say it will like everybody else.

JMO
Rick


Top 
 Profile  
 
 Post subject: Re: cam upgrade
 Post Posted: Wed Jan 09, 2013 10:54 pm 
Offline
User avatar

Joined: Wed Apr 19, 2006 4:11 pm
Posts: 2749
Location: Shepherdsville, KY
rick360 wrote:
I'd give the ex more duration along with the other changes Comp recommended... more intake lift and wider LSA.
Intake lift is usually good if your springs are good. Bigger engines usually want wider LSA I'd probably pick 112.

I doubt you'll see anything like 30hp from a cam change, but Comp wants to sell cams so they'll say it will like everybody else.

JMO
Rick


Thanks Rick. How much more exh duration would you recommend? I'm good on the springs and Comp said this cam will only reduce my piston to valve clearance .006-.010 and I should be good there too. I think you posted in a different thread that you liked Comp because they give you more info on the cam profile than anyone else but I wonder about their recommendations. The cam I have in it now is the one I ran in my 370 with c3 heads. When I talked to them when I was building the 436 last year the tech guy told me the old cam should work well in the new engine. He said the grind was actually better suited for a bigger engine. So now I wonder why they recommended this one for the 370? This is a really old grind and I figured there had to be something better now. I forgot to mention in my 1st post that I want to try to keep the maintenance down on this so I don't want a cam that's going to be too hard on the valve train.

So how much of a gain would you realistically expect?

_________________
Chuck Woloch

Chuck's Automotive
Full line Computech dealer
chucksautomotive@yahoo.com
Image


Top 
 Profile  
 
Display posts from previous:  Sort by  
 
Post new topic Reply to topic  [ 3 posts ] 

Board index » Racing Forum » Engine & Cylinder Head Tech


Who is online

Users browsing this forum: No registered users and 4 guests

 
 

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
cron