BugPak 4061-10 weirdness

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E4ODnut
Posts: 38
Joined: Sat Aug 31, 2013 3:36 pm

BugPak 4061-10 weirdness

Post by E4ODnut »

To make a long story short, my son and I are trying to identify a mystery cam installed in a DP 1600. What started it all is that this is a fresh rebuild on the engine and we can't seem to get it to idle properly with a 34 PICT-3. At ~900 RPM it has a severe lope and we can't get the AFR below ~17:1. After ~1500 or so it smooths out and runs reasonably well at ~12.5:1 AFR. We've tried several carbs and they all do the same thing. We've experimented with timing with no success so we thought we'd better check out the cam. We are told it is from BugPak but there are no marks on it to prove it. I was able to get the specs on this forum, I think from dougydee. They are as follows:

At 0.050" lobe lift, IO = 14 BTDC, IC = 40 ABDC, EO = 50 BBDC, EC = 4 ATDC, Dur = 234 degrees, max lobe lift = .338", Lobe separation angle = 108 degrees.

When we degree it we get the following:
At 0.050" lobe lift, IO = 10 BTDC, IC = 45 ABDC, EO = 45 BBDC, EC = 10 ATDC, Int Dur = 235 degrees, Exh Dur = 235 degrees, Intake max lobe lift = .337"
Exhaust max lobe lift = .337", Intake lobe centre line 105 degrees, Exhaust lobe centre line = 110 degrees, Lobe separation angle = 107.5 degrees, 107.5 - 105 = 2.5 degrees advanced.

So it looks like this is a 4061-10, but now the mystery is that the opening and closing numbers suggest that the cam is retarded by ~ 5 degrees, but the indexing marks on the crank and cam gears align. Any possible explanation for this?
Robert
2001 Dodge 2500, 4x4, extended cab, long box, 8.0L V10, NV4500 5 spd manual, Custom EFI
Ol'fogasaurus
Posts: 17881
Joined: Mon Nov 13, 2006 10:17 pm

Re: BugPak 4061-10 weirdness

Post by Ol'fogasaurus »

http://www.lowbugget.com/bugpack_cams.html

Maybe this will help. Playing with cam shafts can be a pain in the poo-poo.

In my buggy, being run on the sand, I run a high lift short duration reground cam shaft which is for low end power/torque. There are other types of grinds (lift) and/or duration for different engine power. Getting them adjusted properly can also a problem especially if they are not marked correctly.

Lee
E4ODnut
Posts: 38
Joined: Sat Aug 31, 2013 3:36 pm

Re: BugPak 4061-10 weirdness

Post by E4ODnut »

Hi Lee,
Thanks for the link but it's really not enough information. I've been giving this a lot of thought and done some numbers. Everything points to the cam being retarded one tooth, which would mean that the indexing mark is on the wrong tooth. Long shot, but we are running out of ideas. We are going to advance it one tooth and do the whole degreeing process again. I'll post the results.
Robert
2001 Dodge 2500, 4x4, extended cab, long box, 8.0L V10, NV4500 5 spd manual, Custom EFI
E4ODnut
Posts: 38
Joined: Sat Aug 31, 2013 3:36 pm

Re: BugPak 4061-10 weirdness

Post by E4ODnut »

Update:
Nope, that's not the problem. There are 50 teeth on the cam gear, so each tooth represents 7.2 degrees. I expected by advancing the cam 1 tooth everything would be offset 7.2 degrees. Not so. Comparing to the numbers I should see they were all advanced ~ 13 degrees. This requires more thought and some more careful measuring.
Robert
2001 Dodge 2500, 4x4, extended cab, long box, 8.0L V10, NV4500 5 spd manual, Custom EFI
Ol'fogasaurus
Posts: 17881
Joined: Mon Nov 13, 2006 10:17 pm

Re: BugPak 4061-10 weirdness

Post by Ol'fogasaurus »

https://www.bing.com/search?q=cam+gear+ ... 43b0cca6b5

For what it is worth, this talks about cam gear advancing or retarding the cam shaft.

It could have happened that you got the wrong cam gear as I know that has happened to people I knew years ago.

Again... for what it is worth.

Lee
Bruce.m
Posts: 931
Joined: Sun Aug 11, 2013 1:44 pm

Re: BugPak 4061-10 weirdness

Post by Bruce.m »

Cam tolerances can vary by a degree or 2. Potentially that is an outlier & didn’t get caught in QC.
E4ODnut
Posts: 38
Joined: Sat Aug 31, 2013 3:36 pm

Re: BugPak 4061-10 weirdness

Post by E4ODnut »

Update:
I'm getting stupider as I get older. 7.2 degrees on the cam is 14.4 degrees on the crank. Allowing for measuring errors the numbers I get advancing (or retarding) one tooth make sense. Speaking of measuring, errors our initial measurements were done on the pushrods. The pushrods work at a slight angle to the lifters. This may explain some of the odd numbers. We are going to do it all over again measuring on the lifters. I suspect that they will be very close to the published numbers. If it all works, we still have the problem of getting it to idle with the 30 PICT-3. I'll pose that question in another thread.
Robert
2001 Dodge 2500, 4x4, extended cab, long box, 8.0L V10, NV4500 5 spd manual, Custom EFI
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