New cam is TOO LOUD!!!

[Tim_K]

Ok, here's the problem. The new cam I put in makes my car too loud.
BEFORE THE CAM: 1979 Aspen R/T, # match 360-4. 7.58 compression (cc'd to get the exact numbers), reground "340" cam with 268/276 duration, 210 at .050", and .410" lift (micrometered several times). Stock heads, '72 360 iron exhaust manifolds, 2-1/4" pipes, and Flowmaster #42551 3 (right?) chamber mufflers. 1973 TQ 6322S and LD-340 intake. 727 lockup trans with stock 2000 stall converter, 3.90 Sure Grip in the 8-1/4" axle. Ran 15.2 @89 in the 1/4 mile. Nice sounding flowmasters. Best times came while shifting at 4900-5000 rpm.

AFTER THE CAM CHANGE: All I did was port the 051 casting 1.88" / 1.60" valve heads to flow 215/160 at 28" with stock seats (tested), add thin head gaskets to boost compression to 7.70, add 340 replacement springs with dampers, and a Comp Cams Xtreme Energy 274 cam. 274 / 286 duration at .006, 230 / 236 at 50, and .488 / .491 lift.

The engine idles rough, and I'm sure there's a lot of carb tuning to be done, but that's another story. I'm sure the stock manifolds are choking it down big time, because the first day back at the dragstrip it ran 15.5's at 89. Best times came while shifting at 4900-5000 rpm again. (?!?!?!)

The real problem here is that my beautiful Flowmaster sound is gone. Mostly. It's loud at idle, and at 1500-3500 rpm at part to mid throttle, it sounds like a Shivvy with worn out glasspacks. This thing barks LOUD, which I do NOT like! If I step on the gas fairly hard, and wind it past 3500, I can hear the Flowmaster sound somewhat, but nothing like it used to be. What will my headers (Hedman Hedders from Summit) do to the sound when I bolt them on soon? Are Flowmaster #42551's 2 chamber or 3? I thought they were 3, but now I'm not sure. Waiting for answers soon. Thanks.

[The-Challenger]

well in my opion the cam is too big for your compression but that is my opion.
on my 340 the exhaust was louder with the manifolds than with my new tti headers.
i have a cross over pipe in the system . 2-1/2 in pipes and dual flow tech after burners. with the manifolds there was a bad resonance at about 45 to 55 mph that is gone now and i like the sound and can hear the radio.

[amoparguy]

I agree with the Challenger...with those cam specs you should have at least 1 point higher compression ratio. A long duration cam will have more overlap which will bleed off cylinder pressure @ low rpm's. You might be better off going with a shorter duraton cam to keep cylinder pressures higher (more torque & horsepower)

[Darn Dart]

I agree, you need more compression. Mill the heads about .050 and use a thin(.020) head gasket. You are also gona need more stall speed with that cam. I run the 268 Comp X-treme cam and it too has a fairly rough idle, and loud. I run a 3500 TCI converter and it works great.

[Tim_K]

Thanks for the responses so far, but only one had addressed my problem so far - why all the noise, and how to get my Flowmaster sound back.

I agree, the cam is too big for the compression. I cc'd the heads, and they're all between 76-78 cc's stock. Taking into the account the thin head gasket, and volume below the deck (28 cc's with stock 360 dished pistons!), if I cut the heads 0.060", that would only get me to 8.5 compression. So a piston change is needed here. I was going to get a 268 Xtreme Energy cam, but changed my mind at the last minute. No $ to change cams again, at least not before spring 2002. I'm building a new non-lockup 727, but a decent converter is a few hundred bucks more than I can spend right now. It'll happen, though. I don't want to raise compression any higher than what 87 octane can handle. Mileage is poor, (11 mpg before the cam change) so the least I can do is be able to use cheap gas to make up for it.

So back to the big question - what to do about the exhaust? Add a crossover pipe? Something else?

[djswwg]

Tim_K; your question was ansered by several of the guys-you changed the breathing characteristics of the engine which changes the power it makes at any given rpm, which of course changes the exhaust note. The remedies are also there-more compression, a higher stall converter, and YES, DEFINETELY, a balance pipe in the system.........................djs

[6pakman]

i'v said it many times on this website and i'll say it again, when doin a engine mod OR rebuilding an engine, its alot of work AND alot of money. spend it right and do your homework first. nothing worse than doin all that work and get poor results.

[Billydelrio]

A lean mixture can cause a loud exhaust noise as compared to a slightly richer one. I experinced this with my Dart running open exhaust. The larger cam (weaker signal) may have your low rpm mixture too lean.

Billy

[ehostler]

A set of Rhoads or Crane High Intesity lifters will help you out, until you decide to change the cam. The fast bleed of those lifters will restore your idle. They will also allow you to get away with the current converter. As the RPMs increase, the lifters will pump up and give you the advantages of the larger cam.

The Rhoads are a little more noisy (sounds like a solid lifter valve train).

[TT440]

These guys have hit it.
The cam is too big for the compression. You may need gears and a looser converter to get the times back. Milling the heads for 8.5 would be beneficial.
Check your tune (carb and timing). It will change the exhaust note.
Headers and a balance tube would really wake it up and quiet it down. The tone will be much more mellow and loose that raspy glasspack sound.

[shawnronan]

Just a side note on Rhoads type lifters, they bleed down fast which creates extra valve lash therefore less duration at low end. This will increase low end torque, Unfortunately it also beats the HELL out of your valve train and can cause premature failure!!! I saw a perfectly good 440 sixpack drop a valve and destroy itself because of Rhoads lifters! P.S. I run a solid valvetrain in my 440 and it is not loud at all.

[Tim_K]

I thought about the lean mixture thing also. I had the TQ's metering rods set at stock height, 1-1/2 turns up from all the way down. When the engine was idling, if I put my hand over the carb to cover the primaries, it would slow down and quit. I tried raising the rods to 2-1/2 turns without seeing much change. I tried stall testing it yesterday on a paved hill. With the 3.90 gears and the brakes held on, it will spin the tires at 2000 rpm.

I'n going to put on the headers, then will add a balance tube and see how that goes.

When I initially set up the carb, I took the original 10 degrees advance all the way to 20. This plus mechanical plus vacuum advance equals 64 degrees. Didn't ping or kick against the starter. After 2 runs at the dragstrip, I turned the timing down to 13 degrees to see what would happen. No change.

[ehostler]

I ran the Rhoads for two years, on an engine that the prior owner had cammed up. During that two years, I put over 24,000 miles on the car (it was my daily driver). I kept in touch with the guy that I sold it to, for about 5 years. He never had any problems either.

The Crane High Intensity lifters are a little more smooth than the Rhoads, as they don't bleed down as fast. They may help the valve train survive longer than the Rhoads.

[bk340dust]

Tim that number is a 3 chamber Flowmaster. Headers will probably only make it louder but a H-pipe does help. I agree the cam has made it louder. I run Dynomax ultraflows but if you want quiet go with the super turbos. They probably flow as well as the flowmasters.

[PRO]

2 possible explanations for the LOUD exhaust,1st you were runnung a reground 340 cam,that means it had a smaller than stock base circle,adding the edelbrock cam with stock base circle will produce WAY TOO much lifter preload,probably .100 or so more than stock(.030-.060),this will keep the valves from fully seating and will let compression escape into the exhaust making it loud,what you really would notice is the exhaust note sounds WEIRD,2nd this cam should pull to 56-5800 rpms regardless of compression,it may need to be degreed,it acts like its advanced 4-6*,also check the basics, look for steady manifold vaccum,equal cranking compression and not less than 100 psi,also check your plugs for proper mixture,hope this helps........PRO.......

[moparking]

The ex. valve is opening much earlier on the new cam.The cyl. pressure is higher at the new opening point,and the "pop"out of the ex. will be louder.

[Karl43]

I think that shawnronan is mistaken about Rhoades Lifters. I ran them on my 318 for over 18 years and put over 170,000 miles and did not beat up my valvetrain. I rounded the lobes on a cam with over 200,000 miles on it - not bad. I just rebuilt it with another set of lifters. I researched them for 4 - 5 years before using them. I use them religioulsy now. Think about it - when they bleed down they slow down the valve - not speed it up. This should reduce the wear and tear on the seats. Be sure to use hardened seats on the exhaust without leaded gas. I have also heard that the Rhoades lifters work better than the Cranes.

Rhoades lifters bleed about .025" lift and 15° duration out of your cam. This will make it seem smaller to the engine at idle. By 3500 RPM you have the full lift and duration of your cam. If you are going to put in new lifters, think about a smaller cam - it is not that much more since you need new lifters for a new cam anyway. I recommend the 268/272 .450/.455 lift cam. It can save you changing the pistons and compression hassle. The .484/284 is too big.

I have two 68 Cudas. One everyday highway cruiser and one weekend toy. One 318 with 9.2:1 compression and a 260/268 .430/.455 cam and 2.02 intakes. One 340 - S with 10.5:1 compression .484/284 cam and they both have the same exhaust system and stock 340 intake manifolds. The 340-S has the good exhaust manifolds where the 318 has the stock 318 manifolds. Dual stainless steel with an H-pipe and Dynomax mufflers. I was surprised how much louder the 340 - S was than the other. It goes to show that the compression and cam influence the sound at the tailpipe greatly.

An H-pipe might quiet yours down a little. It adds more throttle response and top end also. A smaller cam with Rhoades lifters might be the easiest way to get this back to where you want it

[Tim_K]

Thanks for the new responses. A couple things I just remembered to mention:

The spec card for this cam (XTreme Energy 274) says the exhaust valve opens 77 degrees BBDC.

When I centerlined the cam, it came out to 107 with the stock keys. Comp suggested 106, and that the cam was ground 4 degrees advanced. I left it at 107.

When I've started up new cams in the past, like the reground 340 cam that was in this car before, the lifters will click pretty good for a couple minutes until they get oil in them. This new set of lifters with this cam didn't do that. I don't remember hearing any clicking at all. When I was putting oil on the outside of the lifters during assembly, I pushed a drop of oil towards the hole in the side of each lifter, but didn't try to force it in. Just gave it a second or 2 to drain in. I don't believe all the Comp Cam BS about how I HAD to buy THEIR springs and lifters. Got them for a much better price at the auto parts store. A company in Tennessee called Johnson Tappets makes 80% of the lifters on the market, and that's what these are.

I don't know what kind of base circle this cam has, but nothing in the instructions said anything about watching the lifter height or pushrod length or anything.

I had a 0.039" head gasket set in this engine before, but changed to a 0.025" set upon reassembly to boost compression.

I checked a spark plug (#1) and it was clean, but it only had 100 miles on it since the engine was reassembled.

Yesterday, I got the headers put on. A set of Hedman Hedders #78050 from Summit. A friend helped me, and they went in pretty easily. Not one clearance ding was needed anywhere on the headers. I did have to hammer the inner fender on the R side where #8 tube passes it because of a big unneccessary bulge around the upper A arm mount. Other than that, no problem. I was even able to leave the 2 studs in the head on the drivers side. Had to switch to the shorter oil filter. Next up is to connect the pipes, then add a balance tube and see what's what.

Since the new cam needed to be shifted at the same low rpm (4900-5000) for best 1/4 mile time, I think the exhaust manifolds were the restriction. I hope so anyway. Since the headers were pretty well scratched up when I got them, Summit said to Scotch-brite them and repaint with barbecue grill paint. I got a can of 1200 degree paint, which looks like flat black primer. We'll see what happens.

I'm not changing mufflers. I want my Flowmaster sound.

[dewme5]

cam... when you reground it, you changed alot of the charasticts. the overlap and such are going to play alot with the sound. running a low compression is going to kill some power.. everything needs to be matched well. this costs money but if you dont do it, its going to not end up what you want for a very long time! probably long after you have given up on your project.

compare your overlaps. I had 74 degrees on my old cam, and 43 on my new one. the 74 sounded much better idle was nice and rumbly with out being LOUD. but,, as you come into it.. they would really scream.. 4000 rpm in the neighbor hood would not have been appreciated.

[Tim_K]

The problem is pretty much solved now. I finished connecting the headers to the pipes, and it now sounds much better. It has the tink tink tink sound you get with a header / flowmaster combination, which is what I wanted . Idling through town is fun again. Can't wait to pull up next to some high school kids in a jap car at a stoplight now! I ran it up on some straighaways several times for testing, and at not quite full throttle it can pull well to 5500 rpm and maybe a little more. Since I blocked the heat crossover in the heads, it'll stumble at higher rpms unless it's fully warmed up, but that shouldn't be a problem. Next job is to make a balance tube for the pipes. If it is an easy way to get a couple more horsepower I'll do it.