440 Cam Timing Question

Posted By: bobs66440

440 Cam Timing Question - 01/29/12 01:16 AM

As some of you know I'm building this 440 with Stealth heads and a Summit 6401 cam. We degreed the cam today and here's what we got.

Exh open 2 deg retarded
Exh close. 4 deg advanced

Int open 2 deg retarded
Int close 1 deg retarded

These are departures from spec. The crank sprocket has keyway options for 4 degree advance or retard. Are these differences worth worrying about for street car that will likely never see more than 4500 rpm?

I entered the differences into my desktop dyne and there was no more than a 5hp difference either way.

Thanks!

Posted By: 383man

Re: 440 Cam Timing Question - 01/29/12 06:19 AM

Where did the intake centerline come out. Was it advanced or retarded or on spec ? Ron

Posted By: Cab_Burge

Re: 440 Cam Timing Question - 01/29/12 07:38 AM

Quote:

As some of you know I'm building this 440 with Stealth heads and a Summit 6401 cam. We degreed the cam today and here's what we got.

Exh open 2 deg retarded
Exh close. 4 deg advanced

Int open 2 deg retarded
Int close 1 deg retarded

These are departures from spec. The crank sprocket has keyway options for 4 degree advance or retard. Are these differences worth worrying about for street car that will likely never see more than 4500 rpm?

I entered the differences into my desktop dyne and there was no more than a 5hp difference either way.

Thanks!

Explain retarded in relation to Top Dead Center on both valve events please

What is the duration (at .050 lift), lift and lobe seperation on that camshaft?

Posted By: bobs66440

Re: 440 Cam Timing Question - 01/29/12 03:43 PM

Quote:

Where did the intake centerline come out. Was it advanced or retarded or on spec ? Ron

Here is the cam card, what it's supposed to be...

I went out and double checked everything. This is what I got...

Int open - 1* BTDC = 2* retarded
Int close - 41* ABDC = ON SPEC

Exh open - 54* BBDC = 2* retarded
Exh close - 2* BTDC = 4* advanced

Lobe centerline - Int 109* ATDC = ON SPEC
Lobe centerline - Exh 120* BTDC = 1* advanced

Thanks!

Posted By: bobs66440

Re: 440 Cam Timing Question - 01/29/12 04:05 PM

And just to confuse things, the cam card posted on the Summit site has a different spec for the "intake open" event than the card that came with the cam. One is 3* BTDC and the other is -3.

I'm not sure which one is correct...

Posted By: Dodgem

Re: 440 Cam Timing Question - 01/29/12 06:10 PM

How is your dial indicator set up off the lifter? variations in angle and such can affect @ .050. I like to do .050 and .100 before and after max lift /2 to get a good read on Intake max lift (intake centerline)

You are using a solid lifter I take it??

You indicating right off the lifter? indicator in pushrod in lifter (I have a short push rod made up for this! Or off the valve retainer?

Posted By: BSB67

Re: 440 Cam Timing Question - 01/29/12 06:49 PM

First, you've measured the intake at 222 degrees duration and the exhaust at 232 verses Summit having them at 224 and 234. Could be your measurements, or it could be the cam. I would not get too worked up about it.

Second, their "-2 BTDC" on the card is not 2 ATDC, it is simply 2 BTDC. I don't know why they would write it this way.

Therefore, both openings are a couple degrees retarded, and the closings are per the timing card.

The cam is ground with a 114 degree LSA, with a recommended 109 installed intake centerline (ICL) As you have it, it's installed at 110 degrees. You can leave as is.

Posted By: bobs66440

Re: 440 Cam Timing Question - 01/29/12 08:37 PM

Quote:

Second, their "-2 BTDC" on the card is not 2 ATDC, it is simply 2 BTDC. I don't know why they would write it this way

Do you think that applies to the difference in the 3 degree/-3 degree discrepancy in the two cards also?