Comp Hi-Tech .420 lobes

[n2oracer]

What are your thoughts on this series of lobes. Do they make good power? Spring life?

This is in a 6800rpm BBC bracket motor.

[bigjoe1]

I have used those lobes many times.. They are mild and are easy on everything, There are other lobes that will make more power, but they are pretty good overall- I use them in street racer type engines mostly


JOE SHERMAN RACING

[n2oracer]

How much spring for a 2.25 steel valve turning 6800 rpm?

[Bob Hollinshead]

3/8 stem valve?

[n2oracer]

Ferrea 11/32". I don't remember the part #, seems like they were the 6000 series valves.

[n2oracer]

The rockers will be 1.8 Int & 1.7 Ex .

[n2oracer]

What are your thoughts on this lobe series with 1.8 rockers?

[Adger Smith]

They usually work very well with a little more RR ... good stable lobes. In the past I used them in a lot of Marine applications. very easy on parts and won't tear up expensive valve jobs. You might make a little more power with a more aggressive lobe, but it won't last as long. .440 lobes are good, too! Look at these; 11-703, 11-704 W 1.8 on In , 11-702 W 1.6 on in
All are mild and will make good Tq and HP.

[n2oracer]

Thanks for the info Adger. I was looking at 01-712-9. What do you think about that one? Need more duration?

[Adger Smith]

That is a good TQ grind. more duration and lift??? It All depends on your actual static compression ratio & your TQ converter's actual stall speed. It's a balancing act to balance the combination. I think I would go with something just a little bigger on duration if you have the Static compression. It won't make the power @ 6800 if you don't give it fill time. On these small lobes I do like the 1.8 RR at least on the intake. Knowing your actual combination would help make an informed selection, but your question was just on the .420 lobes. ;~)

[n2oracer]

454 11.75:1
990 heads w/ 2.25 valves
1.8 Int. / 1.7 Ex. rockers
Manley #221424 springs
Single plane & 950cfm 4150
2" headers
6800 RPM max (cast crank & stock rods)

3300#
Glide w/ BTE 8" C100+ ~5000 RPM
4.86
29.5 x 10.5 slicks

1/8 mile only
Previous engine crossed @ ~6600 RPM
Made est. 625 HP

[Adger Smith]

ditch the other two numbers...11-704 or 11-715 the 11-715 w - 1.8 intake might be the best for your compression ratio. The 11-704 might work well with the 5,000 stall move the Tq curve up. With cast iron heads I would run the one with the longer duration ex. I would ditch the 950 carb and go with an 830 or 850. Check the venturi size on your carb. I bet it is one of those with a 750 body and 850 base plate that is just "Rated" @ 950 and is really not there. Sales pitch sells those carbs or people wanting throttle response and to be able to "say" I have a big carb.. Good luck.

[n2oracer]

Carb is a C & S Specialties. Not sure about venturii size, but it has a 1-3/4 baseplate. It belongs to a friend, so I don't know much about it.

[Adger Smith]

Might be a big one, check it out!