V8 thumping under hood

wbcamaro6 · 08-23-2022, 08:12 PM

Hello all, I mostly feel this with Dodge Challenger 392s but in general do bigger engine cause almost like a heavy idle surge? The best way to describe is if I start my vehicle and let it idle it’s noticeable thump under the under like the motor is moving. I felt this in many used performance vehicles but I just want to know is this the norm of owning a performance V8

taylorforschool@gmail.com · 08-23-2022, 08:48 PM

I would say when the engine is warming up.. it’s normal

But I’m no mechanic so most would say upload a clip of what you exactly mean.

SSDan · 08-23-2022, 08:59 PM

Well the term “ it has a big thumping V8 under the hood” certainly applies to our cars. A humming sewing machine Honda 4 cylinder it is not.

That said when at idle the engine should not be noticeably rocking around. If so then you may have a misfire. A under hood video would help.

JamesNoBrakes · 08-23-2022, 10:10 PM

A little cam-lope, but put the best fuel you can in it, 93 octane. Barring that, 91 and octane booster, not the snake-oil stuff that comes in tiny little bottles. Royal Purple unleaded works for me. There is a big difference between octane "points" and "numbers" BTW.

2004YZFR1 · 08-24-2022, 12:15 AM

Quote:

Originally Posted by JamesNoBrakes

A little cam-lope, but put the best fuel you can in it, 93 octane. Barring that, 91 and octane booster, not the snake-oil stuff that comes in tiny little bottles. Royal Purple unleaded works for me. There is a big difference between octane "points" and "numbers" BTW.

The Royal Purple uses MMT in it also. The owners manual says not to use anything with MMT. Have you used this on your 1LE for a few years?

95 imp · 08-24-2022, 07:59 AM

Quote:

Originally Posted by 2004YZFR1

The Royal Purple uses MMT in it also. The owners manual says not to use anything with MMT. Have you used this on your 1LE for a few years?

It's safe in low quantities. I think VP say no more the 2.2 oz in 10 gallons for pollution controlled motors.

Crushin_LT1 · 08-24-2022, 09:22 AM

My impression on the MMT issue was it was all about emissions / cats, not particularly going to hurt your engine.

ctrlz · 08-24-2022, 01:06 PM

Quote:

Originally Posted by wbcamaro6

I start my vehicle and let it idle it’s noticeable thump under the under like the motor is moving.

Uhh, my V8 does not do this. Smooth idle, initially about 1100 then drops to 600 after about 60 seconds, as intended.

In addition to the noise/thump, what are you seeing on your tachometer?

cthulhucaller · 08-25-2022, 09:33 PM

Motor vibrating the car? Yes. Motor moving around and thumping because its bouncing on the mounts? No.

JamesNoBrakes · 08-25-2022, 10:41 PM

Quote:

Originally Posted by 2004YZFR1

The Royal Purple uses MMT in it also. The owners manual says not to use anything with MMT. Have you used this on your 1LE for a few years?

They have two versions.

I'm fairly sure that's what I'm using, without MMT. I am careful to not use the MMT or leaded.

ctrlz · 08-26-2022, 10:28 AM

Quote:

Originally Posted by cthulhucaller

Motor vibrating the car? Yes. Motor moving around and thumping because its bouncing on the mounts? No.

yep, a cam lope is, to me, very different than a thumping sound. Maybe a video would help.
OP is in Louisiana and posted this in August. I really only sense any bit of erratic idle during winter cold starts. Otherwise, this thing kicks off pretty smooth and goes to high idle then drops rpms over a minute or two.

08-23-2022, 08:12 PM	#1
wbcamaro6 Drives: Chevy Camaro Join Date: Apr 2022 Location: louisiana Posts: 36	V8 thumping under hood Hello all, I mostly feel this with Dodge Challenger 392s but in general do bigger engine cause almost like a heavy idle surge? The best way to describe is if I start my vehicle and let it idle it’s noticeable thump under the under like the motor is moving. I felt this in many used performance vehicles but I just want to know is this the norm of owning a performance V8 __________________ 04

08-23-2022, 08:48 PM	#2
taylorforschool@gmail.com PKG4U Drives: 2018 ZL1 Join Date: May 2021 Location: Huntsville AL Posts: 631 View My Garage	I would say when the engine is warming up.. it’s normal But I’m no mechanic so most would say upload a clip of what you exactly mean. __________________ 2020 Camaro LT1. Bought 10/2020 \| GM PERF. CAI \| GM Muffler Delete (Performance Exhaust 4” tips). \| SOLD 1/2022\| 2018 ZL1 Summit White \| Bought 1/2022 \| PDR, Recaros, Carbon Dash, WeaponX Hx System, Apex SM-10 in ZLE fitment w/PS4S Mods after Warranty “Imma keep it stock”

08-23-2022, 08:59 PM	#3
SSDan Drives: 2016 1SS 6MT NPP Join Date: Feb 2010 Location: Lake Murray, SC Posts: 2,245 View My Garage	Well the term “ it has a big thumping V8 under the hood” certainly applies to our cars. A humming sewing machine Honda 4 cylinder it is not. That said when at idle the engine should not be noticeably rocking around. If so then you may have a misfire. A under hood video would help. __________________ 2016 Camaro 1SS Hyper Blue 6MT NPP 2010 Camaro 2SS Cam/Headers/CAI/3.91 gears 476 rwhp/440 rwtq (sold)

08-23-2022, 10:10 PM	#4
JamesNoBrakes Drives: 2SS 1LE Join Date: Oct 2011 Location: AK Posts: 2,301	A little cam-lope, but put the best fuel you can in it, 93 octane. Barring that, 91 and octane booster, not the snake-oil stuff that comes in tiny little bottles. Royal Purple unleaded works for me. There is a big difference between octane "points" and "numbers" BTW. __________________ Everything happens for a reason, except when it doesn't, but even then, you can, in hindsight, fabricate a reason that satisfies your belief system. 2018 2SS 1LE 2023 Colorado ZR2 2022 Stinger GT-line AWD

08-24-2022, 09:22 AM	#7
Crushin_LT1 Drives: 2021 LT1 6spd Join Date: Nov 2020 Location: Arlington, VA Posts: 767	My impression on the MMT issue was it was all about emissions / cats, not particularly going to hurt your engine. __________________ Current: 2021 LT1 Camaro, 6spd, Crush, Corsa NPP, GMPP CAI, Soler Performance Throttle controller Previous: 1997 V6 Camaro, 5spd, Black

08-25-2022, 09:33 PM	#9
cthulhucaller Drives: 2022 1SS Team Joe and Becky Join Date: Apr 2021 Location: Georgia Posts: 188	Motor vibrating the car? Yes. Motor moving around and thumping because its bouncing on the mounts? No.

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