dyno test- Alum head Big car motor

Jim, would you happen to have the cam card for the 'stock' cam you put in this engine? I'd like to make a comparison between it and the OEM replica cam from Federal Mogul.

Even subtle differences on these cams can make a difference in IVC points and detonation resistance.

Did you use the stock timing gear set? I ask because the OEM replica cams (at least the ones I've looked at) are asymmetric in lobe design, and are intended to work 'dot to dot' with 0* advance on the cam install. The OEM timing gear sets are 0*/0*; the advance/retard settings @.050 and .006 are built into the asymmetric lobes.

These cams are more complex than first glance would suggest.


Thanks.

 

This cam is the factory 70 SF cam.. not a duplicate, the actual one that came in a 70 Motor from Buick.

So there is no cam card per se.

From the build records..

Here were the valve events, as installed

.050 duration/events

200/225 Duration

Intake opens -17*
intake closes 37*
Exhaust opens 49.5
Exhaust Closes -4.5

.006 Duration/events

293/340 Duration

intake opens 29.5
Intake closes 83.5
Exhaust opens 107
Exhaust closes 53

LCS is 117

Degreed to 117 ILC

Lift .388/.423 with 1.55 rockers.

 

Thank you, Jim.

For a comparison, here's the Federal Mogul (Speed Pro) OEM variant. Notice the similarities as well as the differences, particularly IVC @.006 (91* vs 83.5* on the other one, despite less duration) and how it would affect DCR, as well as higher exhaust lift.

Cam card:




I plugged the valve timing events into a calculator at Wallace to get the following specs:

@.006

[FONT=&quot] Intake Duration is 282.00 degrees. [/FONT]
[FONT=&quot]Exhaust Duration is 328.00 degrees.[/FONT]
[FONT=&quot]Installed Intake Centerline is 130.00 degrees ATDC.[/FONT]
[FONT=&quot]Installed Exhaust Centerline is 111.00 degrees BTDC.[/FONT]
[FONT=&quot]LSA is 120.5 degrees[/FONT]
[FONT=&quot]Overlap is 64.00 degrees.[/FONT]

@.050

[FONT=&quot] Intake Duration is 194.00 degrees. [/FONT]
[FONT=&quot]Exhaust Duration is 225.00 degrees.[/FONT]
[FONT=&quot]Installed Intake Centerline is 115.00 degrees ATDC.[/FONT]
[FONT=&quot]Installed Exhaust Centerline is 119.50 degrees BTDC.[/FONT]
[FONT=&quot]LSA is 117.3 degrees[/FONT]
[FONT=&quot]Overlap is -25.00 degrees.
[/FONT]
If my math is correct, it sits 2.3* advanced @.050, but 9.5* retarded @.006 with a wider LSA @.006 than at .050, showing asymmetric lobe shape which opens faster on the opening side of the ramp while closing slower on the closing side of the ramp.

It's curious as to why the engineers would incorporate such a shape into the lobes this way, don't you think?

Thoughts?

 

Hey Jim would it have been beneficial to put a roller cam and sp1 intake on it? Getting the hp more around the 550 range while keeping the torque curve in the low to mid range? I was finally convinced to go with a roller cam and TA heads for my land yacht 455. My goal is to make 600hp while keeping a fairly good low to mid range torque curve (10 to 15 mpg would be nice to :beers2. For my 70 Electra the best way to go (imho)

TA Stage 1 heads with good porting (valve sizes yet to be determined)
TA roller rockers (probably going with 1.65)
Wiseco reverse dome forged pistons and stock reconditioned rods
TA hydraulic roller cam (unsure of cam grind at this time)
TA SP1 ported intake
TA shorty headers (I would go with stage 2 heads, but TA only makes shortys for Sg1 heads for 69-70 big cars)
Holly 4150 870 CFM carb (and maybe a super sucker 1 inch spacer if I have clearance)
double roller timing chain
stock HEI distributor

That should get me close to my goals and give me one hell of a runner. I do plan to upgrade the transmission later on with a 700R4, but for the meantime will have to stick with the TH400.

 

Not at all uncommon for asymmetric lobes to be slower on the close ramp. This aids in valvetrain stability, noise elimination, and long term physical wear. All important factors to OEM's.


JW

 

Jay,

Roller cam yes

I would certainly want mid 3 series gears and a converter in that car, should you choose to go with a single plain intake.

JW

 

I concur; in addition, some more observations that can be derived from the replica specs:

1) While the aforementioned aspects communicated by you would indeed be important to OEM's, this 'replica' camshaft isn't necessarily affiliated with GM or Buick per se (from a modern, longevity viewpoint congenial to reputation and/or warranties), but rather a modified and improved variant for use with modern fuels and better understanding of how the older engines function from a 'stock' point of view and its relevant and associated characteristics.

2) Quicker opening and slower closing events also keep the valves open longer within the target lift zone, helping them to 'act' larger than they are, with less emphasis on 'overshooting' the lift as often seen on symmetric lobe designs (not saying this is 'better', just another way of procuring a positive effect within certain parameters).

3) With such a late IVC, the engine would require much less octane at low load/RPMs, but as RPMs climbed (and load increased), VE and cylinder fill would overcome this making the engine need a higher octane as RPMs/load increased.

4) A type of 'EGR' effect would be observed at lower RPMs and low loads (cruising) potentially increasing fuel economy, when considering the dynamics of the valve events.

5) Room for improvement is a reality, using similar design philosophy for higher performance applications.

Thoughts?

 

how close do you think your getting to the limit of them stock rods?

 

I don't believe rod durability is an issue, if you have a good set already done with bolts and resizing use them.. if not, do yourself a favor and use one of the available drop in replacement rods.. well worth the extra expense, and no worries about someone doing the rods incorrectly.

 

I think you're thinking Pontiac with their cast rods. Buick rods are good for at least 600hp resized with ARP bolts.

 

Hey, nice to see this thread still pop up from time to time!

After a few rainy days forcast for this week, said engine ahould come out on the street again.

 

I dont know how well done my rods were, but one of them sure came undone, broke near the piston and did a nice job . Im now against stock rods unless its a near stock motor. Or a crash up derby motor.

 

Gary F.
You cant have variable octane fuel . BUT you can have variable valve timing, Which OEM s have been doing for quite some time now.