I am pulling the 351W out of my 82 Bronco to rebuild. It is mostly stock except a holley $ barrel, hei distributor instead of the eec3, and hooker headers and true duals. MI would like to increase performance a little and have the choppy idle with a new cam. I am looking at a melling state 2 cam with the following specs. My question is if it will make enough vacuum for the brake booster, hvac, etc. Any experience with this or advice will be appreciated greatly.. Thanks

• Cam Type: Hydraulic Flat Tappet
• Range (RPM): 3000 rpm
• Intake Advertised Duration (Deg): 300 Degree
• Exhaust Advertised Duration (Deg): 306 Degree
• Lifter Type: Hydraulic
• Cam Lift Intake (In): 0.31 Inch
• Cam Code: Class 2
• Exhaust Duration At 0.050 Inch Lift (Deg): 234 Degree
• Exhaust Lobe Center (Deg): 117 Degree
• Exhaust Valve Lift With OE Rocker Arm Ratio (In): 0.832 Inch
• Exhaust Valve Lift (mm): 21.132mm
• Idle Quality: Fair
• Intake Duration At 0.050 Inch Lift (Deg): 224 Degree
• Intake Lobe Center (Deg): 107 Degree
• Intake Lift With OE Rocker Arm Ratio (In): 0.496 Inch
• Intake Valve Lift (In): 0.497 Inch
• Intake Valve Lift (mm): 12.623mm
• Intake Valve Lift With OE Rocker Arm Ratio (In): 0.795 Inch
• Material: Cast Iron
• Valve Lift With OE Rocker Arm Ratio (In): 0.496 Intake, 0.520 Exhaust
• Exhaust Valve Lift (In): 0.52 Inch
• Lobe Separation Angle (Deg): 112 Degree

 

Nobody have an opinion??

 

A choppy idle means lousy vacuum at idle. Can't get around that. You may want to research converting to electric vacuum pump to help it out. There were various cars and trucks through the years that had electric vacuum pumps that can be used for this. You could also convert to hydro boost which uses hydraulic pressure from the power steering pump to boost the brakes.

 

It has too much duration at .050

Keep it below 220 degrees at .050 for streetabiliity.

 

Way way WAY too much cam for a motor with slightly over 8:1 compression, use something like the Comp cams 35-238-3.

 

Your 351w in stock form is about 8.5 to 1 STATIC compression. Maybe a bit lower. To run a big cam you need higher compression to support it if you want any kind of performance. If you run that cam in your engine, assuming it's stock compression, your dynamic (running) compression will be anemic. Previous poster recommended that xe262 which is As large as I would consider going. Personally IMHO the xe256h or similar would give the best performance although I believe the durability of the Comp Xe line is questionable.

 

Hmmm I think its too much cam for a street engine.

Cam I am looking at which is a street cam is 216*/224* @ 0.050" lift compared to yours of 224*/234* @ 0.050"

The LSA is where its at for vacuum at idle. Wide LSA cams 112* - 116* have higher vacuum while narrow LSA cams 102* - 108* have lower vacuum.

In theory you should generate enough vacuum at idle for street use with a 112* LSA, the 107* centerline will give you a snappier throttle response from the reading I have done.

But I am think the 224*/234* @ 0.050" duration is just too much for a street engine.











Did a little math real quick. The cam I have picked out for my application is 278*/286* advertised duration with 112* lsa which comes out to 58* overlap. Yours of 300*/306* @ 112* lsa comes out to 79* overlap.

Chart I saw shows 79* overlap is advised for bracket/oval track racing. Mine of 58* overlap falls on the low side of Hot Street Performance. I personally don't agree with that opinion considering Crane lists this cam I picked outf or myself as "Good low-end torque and HP. Good Idle. Daily driver with economy. Towing and Off-road performance. Compression 8.75 to 10.0." But yours on the other hand I think it will be too much to have enough vacuum for power brakes or your vacuum blend doors. Me I don't have that problem as my truck is dealer AC so no vacuum blend doors the heat plenum is controlled via cable. Only vacuum I need is for my brake booster and hopefully this cam I picked out for myself will net me around 14" of vacuum otherwise I need to rethink my plans. yours I don't think would have but around 10" of vacuum at best.

 

I feel certain my truck was a dealer or factory a/c, but everything I’ve read and the EVTM show vacuum for the hvac. I appreciate the info on the cam; I’m learning. Thanks

 

Think we all are still learning on something. This is the smallest hyd roller truck cam that crane offers for a 302 HO so its what I am forced to go with. I don't like the thought of 58* overlap when I read online from places like hotrod talking about 20* overlap to get 18" of vacuum. All I know is I am trusting the description on Crane`s product page showing "Daily driver" for my cam I selected and DD2000 that is showing 14.67 psi on intake pressure. I hope it will be more or less around 15 to 16 inches but I doubt it will be that much but I hope its 14" as I do have power brakes and don't want to lose how effective my brakes are which I am always afraid it might.

Only other option for me is to go with a smaller cam such as their powermax but even then its only one step smaller. Sad thing is there is no way to figure vacuum based off cam. valve overlap plays a part in vacuum, so does duration, so does carb size, so does exhaust system, etc. Too many variables. All I know is I will be extremely pissed off if I don't have 14-15 inches of vacuum cause I put fitech on a customers truck was a 350 sbc with a beating cam had 8" at idle and at 1,000 rpm it was almost 15" of vacuum. This cam is supposed to be very very mild compared to that so I hope it makes more vacuum than that.

On yours being a 351w, your larger displacement might help your vacuum out I have seen it reference a few times that displacement has an effect on vacuum as well when it comes to how big of a cam you can run.

 

What does "Range (RPM): 3000 rpm" mean? is that the idle RPM or the max RPM for the cam or what?

Some other things not posted besides the vacuum or lack of:
If the idle RPM or the start work RPM is to high you will also need a higher stall converter if using and auto.
Some times off the shelf converter will work and other times it will not and you need to have a custom one made.
To have a custom one made they need a lot of information like HP/TQ, RPM range, weight of car truck, gearing, tire size just to name a few. Change any of them will change the stall needed.

Valve lift: With that lift will the valve clear the top of the pistons? Even with stock pistons any time you go changing valve lift you need to check this.
Even if they say "yes it will clear" if you put it together and try and fire it up and wipe out valves or pistons who is going to pay for it? YOU!

Just more you have to think about.
Dave ----

 

Yep that's why I myself will be putting a piece of clay on cylinder #1 and torque the head down. Was thinking of doing it without the head gasket and just adding the compressed thickness to the clearance I get in the clay. I know the photos shown on the short block I personally am looking at shows four valve reliefs cut in and I should have no problem with 1.90"/1.60" valves on the AFR heads but I personally want to double check it since the roller cam I am looking at from crane is 0.520"/0.542" lift.

Hate to do all this work and time waiting on sourcing the parts only to grenade it from not taking the time to double check it.

 

When I was looking for a cam for my AMC 360 and wanted the most lift with out machine work Summit gave me one.
I did not trust what they said and used the clay with out the head gasket.
I figured if I had clearance with out gasket I would be more than good with the gasket.
Dave - - - -