do racy camshafts affect engine braking?

[65TerrorCuda]

Has anyone gone to a big cam and seen engine braking change? By big cam I mean significantly bigger than stock.
Thank you

By engine braking I mean how much the engine slows the car down, for instance, when you downshift and are off the gas. Thank you Maxxicek and Tom for clarifying. I think their explanation is better than mine though.

 

[doug 371]

Power brakes, yes

 

[Professor Fate]

I guess we'll need your definition of "engine braking"...

 

[Maxxicek]

I guess we'll need your definition of "engine braking"...

He's probably talking about letting your foot off the gas and having the engine decelerate the car instead of the brakes. Does a bigger cam change the rate of deceleration from a stock cam.

 

[Professor Fate]

He's probably talking about letting your foot off the gas and having the engine decelerate the car instead of the brakes. Does a bigger cam change the rate of deceleration from a stock cam.

That is also what I consider "engine braking"... but there seems to be a sidetrack into power booster effectiveness... so just want to clarify before the thread goes off the rails.

 

[RustyRatRod]

No it does not.

 

[fishmens67]

I guess we'll need your definition of "engine braking"...

Engine braking to me is a compression scratch when dropping into low gear.

 

[65TerrorCuda]

I guess we'll need your definition of "engine braking"...

Compression braking is maybe what I should've said.

Maxxicek nailed it.

 

[Captainkirk]

Yes. I had a pretty long duration (lumpy) cam in my 340 and the power brakes were definitely affected. JMHO

 

[PROSTOCKTOM]

I don't think he's talking about vacuum. I think he's talking more of the mechanical action of letting off the gas and the engine pulls down.

In that case a larger duration cam with more over lap will keep the valves open longer, thus probably decreasing the mechanical engine braking from the compression cycle.

Or at least it sounds good to me.

Tom

 

[Bewy]

I think [ a bigger cam ] it will have some affect, but it might be every slight & hard for the butt-meter to pick up. When you lift off, the engine wants to go back to idle. With a bigger cam that means a higher idle rpm.

 

[AJ/FormS]

Here is my experience;
Since 1999, my 367, 4-speed Barracuda has had these three cams;
248/248/108 DC 292/508
223/230/110 Hughes HE2430AL
230/237/110 Hughes HE3038AL
The Scr has varied from 11.3 to 10.95
The CCP has varied from 185 to near 200.
I have run 3 Holleys; a 600VS, a 750VS, a 750DP, and
a Big Thermoquad, and an AVS 5XX off a 340 car
Variously, these combos have regularly run gears from 3.23s to 4.30s and several others on occasion.
The Transfer slot exposure underneath the Primaries has always been from square to a little bit taller than square, and the Idle-Timing has always been 12>14 degrees.

Engine-braking/compression-braking has never been an issue, and I cannot point to any iteration as being significantly different.

Nor has my vacuum brake-booster had an issue at any time other than at first start in the morning, when it takes a couple of blips on the throttle to charge the booster. By the time I have backed out of the carport and pointed the nose towards the street, she is ready to go. I never even think about it.
My F-body booster will haul the car down from hi-way speed to a stop, with the engine off and the trans in neutral, at least once, with full assist.

FYI
On the back, I have 295/50-15s, and 10x2 drums. I gutted my Proportioning valve and the back now gets the same hydraulic pressure as the front. The back now does a lotta work, and I wear out shoes back there between 2 and 3 times as often as front pads.
Car stops dang nice.

If anything, the thing that will increase/decrease compression braking, will be the amount of throttle opening. This will have a far greater effect than the cam.
This is something that YOU the tuner can change.

 

[Murray]

It will effect it if it requires a faster idle speed.

 

[Charrlie_S]

I think [ a bigger cam ] it will have some affect, but it might be every slight & hard for the butt-meter to pick up. When you lift off, the engine wants to go back to idle. With a bigger cam that means a higher idle rpm.

I agree. If you did some accurate measurements, I think you would see a differance. However in real world driving, I don't think you would be able to tell. Just a WAG on my part.

 

[340six]

Here is my experience;
Since 1999, my 367, 4-speed Barracuda has had these three cams;
248/248/108 DC 292/508
223/230/110 Hughes HE2430AL
230/237/110 Hughes HE3038AL
The Scr has varied from 11.3 to 10.95
The CCP has varied from 185 to near 200.
I have run 3 Holleys; a 600VS, a 750VS, a 750DP, and
a Big Thermoquad, and an AVS 5XX off a 340 car
Variously, these combos have regularly run gears from 3.23s to 4.30s and several others on occasion. 78-83
The Transfer slot exposure underneath the Primaries has always been from square to a little bit taller than square, and the Idle-Timing has always been 12>14 degrees.

Engine-braking/compression-braking has never been an issue, and I cannot point to any iteration as being significantly different.

Nor has my vacuum brake-booster had an issue at any time other than at first start in the morning, when it takes a couple of blips on the throttle to charge the booster. By the time I have backed out of the carport and pointed the nose towards the street, she is ready to go. I never even think about it.
My F-body booster will haul the car down from hi-way speed to a stop, with the engine off and the trans in neutral, at least once, with full assist.

FYI
On the back, I have 295/50-15s, and 10x2 drums. I gutted my Proportioning valve and the back now gets the same hydraulic pressure as the front. The back now does a lotta work, and I wear out shoes back there between 2 and 3 times as often as front pads.
Car stops dang nice.

If anything, the thing that will increase/decrease compression braking, will be the amount of throttle opening. This will have a far greater effect than the cam.
This is something that YOU the tuner can change.

If the 223/230/110 Hughes is HE2430AL is the cam that has .504/.515 lift ? Then I ran the same cam in a stock bore 340six but mine was made by Engle as that was who was grinning them back then. And my machinist was a Engle dealer he picked it. I think i had way to much compression for it but it ran fine with 1.6 ratio .(538/.549 )
EDIT) Engle said it was supposed to be installed 4* advanced.
We degreed the cam and was right at 3-4* so no adjust was needed.

As far as engine brake.
Gear ratio in the rear was a definite engine brake change. 276 vs 430 was different

 

[AJ/FormS]

I ran that 223* cam at about 200psi with alloy heads on 87E10, FULL-TIME, with Power-Timing of 34*@3400, and no detonation was ever detected, in 4 or 5 years.
and Yes, I run the 1.6s as well.
and yes the 4.30s were different from 4.10s, as were 3.91's and so on. But in my case, a 5% gearchange, was not significant enough to notice. Therefore I carefully chose the phraseology;
"I cannot point to any iteration as being significantly different." ......... as part of "my experience".

Had I gone from 2.76s to 4.30s, yes, the compression-braking would have been significant . But who does that, lol.

Ok well the truth be told, I geared that 223* cam up one day with overdrive, such that the final drive presented as a 1.97, for 65=1650 rpm.
This was in preparation for a 10 hour trip down to Shakopee Minnesota, to attend the 2004 CarCraft Nats.
South of the Canadian border, on the Interstate, traffic was booting along sometimes over 85mph.
I settled in at 75=1850.. By the time we got there, that fabulous 223* cam had pulled off 32mpgs with a prepared carb, and distributor.
On the way back, we tailed a Corvette for a few hours, who might have been going speeds up to 120, lol;
so, no more 32mpgs on the way back. We didn't care, the car was doing what it was built to do.
I loved that cam, and it would still be in my 367, had it not dropped lobes in late 2004. But I missed the top-end charge of the 292Purple, so I installed the next size bigger from the same manufacturer. Just one size, and I knew right away the mistake I had made. So for the last twenty years, I've been waiting for this 230 cam to die, so I can swap it out.