302 Thumpr Cam Won't Idle

73azbronco · Nov 11, 2018

pennyduke said:
I will ask Comp about advancing the Cam. I never really understood what that does for a engine. Here are some pictures of my Intake.

Advancing a camshaft means you install it one tooth earlier than lined up on the timing gear. Advancing lowers the torque band but does slightly reduce top end HP. Retarding increases HP at high rpm but reduces torq at low rpm.

pennyduke · Nov 12, 2018

Advancing the Cam is tempting, I really don't want to find out what happens over 65 mph anyway. I've always installed Cams with no advance. This one is already in so maybe I will try it on my 351W build in the future. Thanks for the explanation DirtDonk and 73.

pcf_mark · Nov 12, 2018

Good luck and make sure it fires up and run it between 2000-3000 rpms to give the cam a decent break in for 20 minutes.

(Comp cams already have 4 degree advanced ground into the profile I read once)

pennyduke · Nov 25, 2018

Success!!! I broke the Cam in by using the 10 10 10 method suggested by Comp Cams. I really like that method because you get 2 10 minute cool downs to check everything over.
after that I let it cool down for 30 minutes. Started it back up and set the idle to 700rpm then set the timing to 15 degrees with the vacuum advanced plugged. That was where I got the most steady and highest Vacuum at 19. When I put it in drive I'm at 510 rpm. Does all this sound right? It sure sounds good and the motor runs much smoother.

Thanks for all the help everyone. I will update after a test drive tomorrow.

73azbronco · Nov 25, 2018

19 is great vacuum, good to hear success.

pcf_mark · Nov 25, 2018

Excellent work! Night and day difference in idle quality I bet!

pennyduke · Nov 26, 2018

Yes it does make a big difference. At one point I had the idle down to 600. That Thumper Cam was a bad idea. I'll never do that for the first time again.

I'm gonna change the oil and do some fine tuning then take it for a test drive today if I have time. Thanks again

tirewater · Nov 26, 2018

pennyduke said:
Yes it does make a big difference. At one point I had the idle down to 600. That Thumper Cam was a bad idea. I'll never do that for the first time again.

I'm gonna change the oil and do some fine tuning then take it for a test drive today if I have time. Thanks again

Yes, please let us know about the power. Also, when you'll upgrade your 3 speed transmission.

pennyduke · Nov 27, 2018

My C4 was just rebuilt. It shifts almost perfect. I would like a Overdrive Transmission one day because I have 3.50 gears. tirewater what would you suggest for a replacement?

tirewater · Nov 27, 2018

Other than rebuilding my own C4, I don't have any experience with transmissions. I still have the stock 3.50 gears as well. I don't do a lot of freeway driving, so it hasn't been an issue.

As great as the C4 is suppose to be, I still very much appreciate modern automatic transmissions.

pennyduke said:
My C4 was just rebuilt. It shifts almost perfect. I would like a Overdrive Transmission one day because I have 3.50 gears. tirewater what would you suggest for a replacement?

pcf_mark · Nov 27, 2018

I used a C4 with stock wheels / tires. Now I used a 4R70W with 31" tires. Sure the overdrive is not very useful until 50 mph but the gear spread is so much nicer in the lower gears and the torque converter is perfect for my mild 5.0.

pennyduke · Nov 30, 2018

UPDATE: The first test drive went very well. I did some half throttle pulls from a dead stop and a few while rolling about 25 mph. Seems like this Cam is the perfect fit for my Bronco. It has plenty of low end torque and idles very smooth. I do have some gas smell at idle but I have not played with the idle mixture screws yet. I wanted to thank you all again for your time and patience with me. Time for a CRUISE!!! Happy Holidays

pcf_mark · Nov 30, 2018

That is great news!

You might get a gas smell from an overly rich idle mix screws but you can also get it from too much timing advance fyi.

pennyduke · Nov 30, 2018

Yea, I think I have too much timing. Gonna try to fine tune it tomorrow.

302 Thumpr Cam Won't Idle

73azbronco

Bronco Guru

pennyduke

Sr. Member

pcf_mark

Bronco Guru

pennyduke

Sr. Member

73azbronco

Bronco Guru

pcf_mark

Bronco Guru

pennyduke

Sr. Member

tirewater

Sr. Member

pennyduke

Sr. Member

tirewater

Sr. Member

pcf_mark

Bronco Guru

pennyduke

Sr. Member

pcf_mark

Bronco Guru

pennyduke

Sr. Member

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