cam duration for a 454 tow rig

[dave brode]

Hello All,

Assuming a late 70s flat top 454 with a little CR increase to 8.5 -1 maybe 9-1, via either small chamber 366 heads or '96 up vortec truck heads. I have studied the subject here and elsewhere. I can post or send a pile of links if anyone would like. I gather that .050" duration in the 212 to 218 range works well. Opinions vary on LSA, from 106 to 114. Imo, potential exists for the tight LSA to do better, but the engine might be more finicky for exhaust tuning with a tighter LSA. Some feel that a single pattern cam is better for power in tow rpm range.

My main question is how much more of a gas hog would such a rig be with .050" duration in the mid 22Xs range? Esp if one does not lug the thing. I've always kept rpm in the 2500-3500 range when towing.
thanks for any input.
Dave

[HDBD]

Is the motor carbureted?

[dave brode]

Is the motor carbureted?

To be clear, I recently bought an all stock TBI454 2wd '88 C3500. It's a nice old truck, but what a dog. For the sake of not getting into duration/idle/overlap vs efi issues, let's say it is not efi. I do realize that getting above 2teens at .050", even with wide LSA with tbi would be a bad thing.

Let's make topic duration/overlap vs economy on a carb'd 454 towing 5000-8000.lbs. I suppose that I'm suffering from hotrodder more is better. I just can't help think of how much better a 9-1 454 would run with duration in the mid 220s vs 210s. I would not want to give up 2+ mpg though.
Thanks.
Dave

[RevTheory]

I'm thinking somewhere around 220* at .050, give or take a few, single pattern on a 107 LSA would make quite a tow rig. I don't have a clue how mileage may vary with other LSAs.

[DaveMcLain]

I just did one with 205 205 on 108 flat tappet hydraulic using the Torque Master lobes from Demos' Cams and it works very well in a low compression 454 as a tow rig. Too much duration will make the EGT get very high.

[RevTheory]

I've done the single-pattern deal a few times and even reverse-split and, depending on the heads, although the peak hp may not have been where it could have with a little more exhaust split, the lower end and mid-range torque and throttle response was always better than what I'd expected.

I've also increased the valve lash on the exhaust side of an already single-pattern cam and cleaned up the idle and low-speed manners with no noticeable down side on an engine that didn't see North of 5,500 rpm.

[bigjoe1]

Many tears ago I did some testing on 454 trucks used for towing race cars.. When it came to cam selection, I found an Isky cam that worked very well-- It was the 264 Mega cam- It made much more mid range power than the stock cam ( 3000 RPM ) and was much better when pulling a trailer up hills and so forth-This cam is 214 -214 on 108.


JOE SHERMAN RACING

[CamKing]

My main question is how much more of a gas hog would such a rig be with .050" duration in the mid 22Xs range? Esp if one does not lug the thing. I've always kept rpm in the 2500-3500 range when towing.

If you normally cruise in the 2,500-3,500rpm range, you would lose less then 2mpg going to something like this.
224/224 @.050"
.561"/.561" Valve Lift
111 LSA

[dave brode]

Thank you Gents.

[dave brode]

for the sake of future searching, here are related threads;

viewtopic.php?f=1&t=28801&hilit=366+truck
viewtopic.php?f=1&t=19453&hilit=towing+cam&start=15
viewtopic.php?f=1&t=19135&hilit=towing+cam
viewtopic.php?f=1&t=29585&p=347085&hili ... ck#p347085

[HDBD]

In my 94 dually I ran a crane 2020. It seemed stock, very mild , but got 2 more mpg than stock, and had better midrange torque. Great for towing. Today I think I would look for a mild hyd. roller.