Factory hydraulic roller LA cam advice

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JakenBake805

JakenBake805

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Lompoc CA
I am in the process of building my first engine and could use some help on cam selection.

Build specs:
1969 Dart
1989 factory hydraulic roller LA 360
Speed pro 4.03" pistons (H116CP 30) - zero decked
Summit CP calculator shows ~ 9.5:1 CR
308 heads with stock valves (1.6 & 1.88)
Edelbrock performer intake
Dougs headers
650CFM holley (willing to upgrade)
8.25 rear end with 3.23 gears (willing to change)
904 Trans w/ 2500 stall

This is car is for meant for ripping around town on the weekends, not a daily driver and not for the strip.

Im now looking at cams and am considering the Comp XR280HR-10 but have a few questions about this cam:
  • This cam is listed as a "Retro-fit Hydraulic Roller" however I would be using this is a factory roller block with factory roller lifters. Will this cam drop into my application or do I need to be looking at a different style of camshaft?
  • The lift on the XR280HR is advertised as .541/.537 but from what I have read that is more than the stock 308 heads can handle. Can this amount of lift be achieved on the 308 heads easily with some head work? If so what will need to be done to the heads?
  • I know I will need new valve springs with the upgraded cam but will I be required to upgrade rocker arms or are the stock ones fine for my application?
  • If I am way off on this cam please feel free to suggest something else!

I appreciate any input you guys have!
Thanks a lot!
 
Couple of thoughts, that cam will want more gear than 3.23 but it will work. The lift is too much for a stock 308 head because of retainer to guide clearance but any competent machine shop can handle that. You can also buy a tool and do it at home. You “can” use factory rockers but being non adjustable you better be damn good at measuring pushrod length to get the preload set correctly. Better idea is to use aftermarket adjustable roller rockers. You can use your factory roller lifters without issue, just disassemble and clean them. Last thought, if this is your first engine build learn to degree the cam now and it will save you on every engine you build from here on out. Do not assemble it until the cam is right! Good luck and let us know how it goes.
 
go get a performer rpm or rpm air gap.....i would not use the performer for such a build, you can also consider a single plane.

Michael
 
considering it's just a stoplight eliminator, i figure that you'd be looking at something that's not gonna get full wrung out all the time. so keeping the "small" performer and those 308's might be just fine and dandy.

i'd go with more gear out back for sure.

personally, i'd probably err toward a little more conservative on the cam. XS268S10

but if you were changing the manifold and carb i'd probably say the howards 710525-10 would be a pretty stout piece. i think you have the compression and stall for it, but you would definitely want something like 3.91's out back.

just my 02
 
I would double check your compression figure. I built one similar with same piston and zero deck height a few years ago and it came in at 10.5.
 
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Agree, keep the Performer. Rpm range of the Performer is listed as idle to 5500. Rpm range of the RPM is 1500-6500. Also, one step smaller cam than listed.
 
Your looking at a cam on a LSA of 106 for maximum torque.
 
If you have the ability and tools, open the performer 318/360 port window up and blend it back in the runners. Run a 1" open spacer and you will get REALLY close to an RPM/AG intake performance wise.
 
Agree with post #8. If you want a smoother idle, reduce duration, do NOT widen the LSA. Last custom roller cam I had done by Comp was the same price as a shelf grind.
 
Thanks for all of the advice everyone!
Sounds like I should definitely plan to add some rear gear - I will likely go with 3.91's
RustyRatRod said:
I would double check your compression figure. I built one similar with same piston and zero deck height a few years ago and it came in at 10.5.
Click to expand...
Thanks! I was using 74cc for my cylinder head volume but after doing some more research it looks like the 308 heads range but are closer to 65cc so that would bump up my CR to 10.5:1.
rumblefish360 said:
Your looking at a cam on a LSA of 106 for maximum torque.
Click to expand...
Ok, Thanks for the suggestion.
crackedback said:
If you have the ability and tools, open the performer 318/360 port window up and blend it back in the runners. Run a 1" open spacer and you will get REALLY close to an RPM/AG intake performance wise.
Click to expand...
I currently have a 1" spacer and am happy to try to open up the performer to flow better before I spend the coin on a different manifold.

Just to confirm: The "retrofit" style cams work in the factory hydraulic roller engines even though it is not a retrofit application?

Any input on what a reasonable price for the head work to run a cam with larger lift on the stock 308 heads would be? My local machinist said it could be $1k + which surprised me. I was trying to keep the build under a reasonable budget but the project is quickly spiraling :rolleyes:

Thanks again for the support and help!
 
JakenBake805 said:
Any input on what a reasonable price for the head work to run a cam with larger lift on the stock 308 heads would be? My local machinist said it could be $1k + which surprised me. I was trying to keep the build under a reasonable budget but the project is quickly spiraling :rolleyes:
Click to expand...
question: was that price just for machining the spring seats or more of a price that covered rebuilding the heads and the associated machine work?

for the one it seems like a reasonable number, for the other it sounds like a i don't want to do that price.
 
JakenBake805 said:
This is car is for meant for ripping around town on the weekends, not a daily driver and not for the strip.
Click to expand...
For a this application, you want to be in the powerband from say 20 to 40 mph, am I right?
If your power peak is at 5300rpm, and it rolls off the cam at 5600, then 5600 can be 40 mph.
To get there with 27" tires, will require a Roadgear of 10.12@10% TC slip. With a regular torqueflite the ratios are 2.45-1.45-1.00
So then 10.12/2.45=4.13rear gears, rounds down to 4.10s and you use First gear.. 20mph will be ~half that, or ~2800, depending on TC slip.

To the OP;
Now: I'm gonna tell you a secret; the biggest street tire
that you can fit under a 69Dart with factory tubs is a 255........ and with 4.10s, any good 360 will spin those 255s all the way to the top of first gear.
So my 2 cents is this; for a first timer, I would stick to a modest cam in the 218 to 223*@.050 range, on a 106/107LSA, and adjust the Scr to a number that brings the cylinder pressure low enough to not get into detonation on best gas.
Course if you did that, you would no longer need the 4.10s........ cuz these cams will power peak 400 and 600 rpm lower than your contemplated 280 cam; and the cylinder pressure should be higher......
Either of these cams will make your high-pressure 360, plenty powerful enough, to be a 255 fryer all the same, even without the 4.10 gears.
>If it was me, and I needed a convertor, I would get at least, a 2800. But if it was me, I'd get a solid flat-tappet cam of about ONE size bigger than [email protected]
>I didn't talk about lift because for this application, it hardly matters.
>Headers are a must if you want to take advantage of the overlap cycle, that a 106LSA cam will generate..
>If you want the idle of a big cam, without the big cam penalty, get a small Whiplash/Mutha, depending on which one has the lift that your heads can handle.
<Once you start going to/over 6000rpm regularly, you gotta do some oiling mods, so your rod-bearings will live. You might as well do them now, cuz keeping the tach under 6000 when the tires are screaming can be a bit of a chore. Therefore
>If no oiling mods are done I suggest to install a rev-limiter.
> if it was my car, and I had to buy a carb, I'd put a 750DP on there cuz I put that on everything with a 2800TC. If you already have a 4bbl not a 750DP, then just stick anything on there that you already own, cuz again; for this application it won't matter much.
> Here's another secret;
Guys build 400hp 360s that can trap the quarter at 110 mph or better.......... and they need that power to push these old bricks thru the air. Wind resistance begins being a thing, beginning at 1mph, but doesn't add up to much until the speed creeps up past 30/40 mph. Just stick your arm out the window and see.
Your street-rocket never/rarely sees over 65 mph, am I right? .
The power to overcome wind resistance varies by double-double with each doubling of speed. So Doubling the speed, going from 14 to 28 Requires FOUR times the power. From 28 to 56, requires another FOUR times the power. From 56 to 112 is again Four times the power. So you can see that the power is rapidly swapping from going faster, to pushing air.
To get a sense of this; if your body-style requires a typical 30 hp to cruise at 56 mph, it will take 120hp to cruise at 112mph. From 400 hp, this only leaves 280 to continue accelerating with.
In other words;
my 2 cents is this:
why build a 112 mph motor that never/rarely exceeds 65?
 
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Skip all that and pay attention to the amount of overlap the cam has and work within the duration @050 parameters.

Working with your displacement and valve size sets up your LSA.
Lift the valve as much as possible to take advantage of the cylinder heads flow capabilities.

Pay attention to the amount of collector added onto the header as this is a huge gain in low end torque.

Let’er rip potato chip!
 
Jaken,
Keep in mind that many 'power adders' are what I call 'torque shifters'.
Your original parts list is well thought out & on the money for your needs. Any dope can fit the largest carb, the largest intake, the biggest cam, the biggest XYZ...& end up with a dog. It takes smarts to select parts that will work in harmony to produce the desired result.
Two 'torque shifters': big duration cam & open carb spacers on dual plane intakes. Big cams shift the low end tq to the upper end; same with carb spacers but probably by a smaller amount.
The parts you nominated should work well with your 3.23 & c'ter to provide a nice balanced combo.
 
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Pretty sure both Comp an Lunati offer LA roller cams with .485 .513 and .517 lift specs.
 
AJ/FormS said:
For a this application, you want to be in the powerband from say 20 to 40 mph, am I right?
If your power peak is at 5300rpm, and it rolls off the cam at 5600, then 5600 can be 40 mph.
To get there with 27" tires, will require a Roadgear of 10.12@10% TC slip. With a regular torqueflite the ratios are 2.45-1.45-1.00
So then 10.12/2.45=4.13rear gears, rounds down to 4.10s and you use First gear.. 20mph will be ~half that, or ~2800, depending on TC slip.

To the OP;
Now: I'm gonna tell you a secret; the biggest street tire
that you can fit under a 69Dart with factory tubs is a 255........ and with 4.10s, any good 360 will spin those 255s all the way to the top of first gear.
So my 2 cents is this; for a first timer, I would stick to a modest cam in the 218 to 223*@.050 range, on a 106/107LSA, and adjust the Scr to a number that brings the cylinder pressure low enough to not get into detonation on best gas.
Course if you did that, you would no longer need the 4.10s........ cuz these cams will power peak 400 and 600 rpm lower than your contemplated 280 cam; and the cylinder pressure should be higher......
Either of these cams will make your high-pressure 360, plenty powerful enough, to be a 255 fryer all the same, even without the 4.10 gears.
>If it was me, and I needed a convertor, I would get at least, a 2800. But if it was me, I'd get a solid flat-tappet cam of about ONE size bigger than [email protected]
>I didn't talk about lift because for this application, it hardly matters.
>Headers are a must if you want to take advantage of the overlap cycle, that a 106LSA cam will generate..
>If you want the idle of a big cam, without the big cam penalty, get a small Whiplash/Mutha, depending on which one has the lift that your heads can handle.
<Once you start going to/over 6000rpm regularly, you gotta do some oiling mods, so your rod-bearings will live. You might as well do them now, cuz keeping the tach under 6000 when the tires are screaming can be a bit of a chore. Therefore
>If no oiling mods are done I suggest to install a rev-limiter.
> if it was my car, and I had to buy a carb, I'd put a 750DP on there cuz I put that on everything with a 2800TC. If you already have a 4bbl not a 750DP, then just stick anything on there that you already own, cuz again; for this application it won't matter much.
> Here's another secret;
Guys build 400hp 360s that can trap the quarter at 110 mph or better.......... and they need that power to push these old bricks thru the air. Wind resistance begins being a thing, beginning at 1mph, but doesn't add up to much until the speed creeps up past 30/40 mph. Just stick your arm out the window and see.
Your street-rocket never/rarely sees over 65 mph, am I right? .
The power to overcome wind resistance varies by double-double with each doubling of speed. So Doubling the speed, going from 14 to 28 Requires FOUR times the power. From 28 to 56, requires another FOUR times the power. From 56 to 112 is again Four times the power. So you can see that the power is rapidly swapping from going faster, to pushing air.
To get a sense of this; if your body-style requires a typical 30 hp to cruise at 56 mph, it will take 120hp to cruise at 112mph. From 400 hp, this only leaves 280 to continue accelerating with.
In other words;
my 2 cents is this:
why build a 112 mph motor that never/rarely exceeds 65?
Click to expand...

Post like this remind me of exactly how bad at math I am and how little I know about hot rodding.
 
JakenBake805 said:
I am in the process of building my first engine and could use some help on cam selection.

Build specs:
1969 Dart
1989 factory hydraulic roller LA 360
Speed pro 4.03" pistons (H116CP 30) - zero decked
Summit CP calculator shows ~ 9.5:1 CR
308 heads with stock valves (1.6 & 1.88)
Edelbrock performer intake
Dougs headers
650CFM holley (willing to upgrade)
8.25 rear end with 3.23 gears (willing to change)
904 Trans w/ 2500 stall

This is car is for meant for ripping around town on the weekends, not a daily driver and not for the strip.

Im now looking at cams and am considering the Comp XR280HR-10 but have a few questions about this cam:
  • This cam is listed as a "Retro-fit Hydraulic Roller" however I would be using this is a factory roller block with factory roller lifters. Will this cam drop into my application or do I need to be looking at a different style of camshaft?
  • The lift on the XR280HR is advertised as .541/.537 but from what I have read that is more than the stock 308 heads can handle. Can this amount of lift be achieved on the 308 heads easily with some head work? If so what will need to be done to the heads?
  • I know I will need new valve springs with the upgraded cam but will I be required to upgrade rocker arms or are the stock ones fine for my application?
  • If I am way off on this cam please feel free to suggest something else!

I appreciate any input you guys have!
Thanks a lot!
Click to expand...
Find a machine shop in your area that can install liners or one piece guides for 11/32 valves. Use the 5.011/5.025 long 1.94/1.60 valves and have a good 4 or 5 angle serdi cut valve job done.
$200 guides
$150-175 valves n retainers/locks
$250 valve job/surface
$25 seals
So let's say 700.00 after tax...could be 900 idk...every shops diff. Ours does that minus the serdi and parts 'stone vj' instead. 400.00

You can spend a grand on speedmaster and have a better flowing head
 
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