You have about 20 degrees to much cam duration for your build and gearing.
The stock low seat and open pressure springs with that much lift and ramp speed will likely have valve float well before you get close to peak HP let alone redline with that cam. You will be lucky to not wipe a lobe if you rev it very high. Valve float will take out a cam quick. You broke it in with lightweight springs. You will have to change the springs before you drive it or rev it much.

 

Nothing personal but you have mismatched parts. Always use the manufacturer's recommended springs with a new cam. You need more gear, a stall converter, new heads, etc. to make all of this work in unison. It will probably be low on vacuum and hard to drive on the street. If your going racing it'll be great with the new combination of parts. You may be the victim of the "bigger is better syndrome". We have all been there. Good luck with your project however you decide to go with it.

 

New heads and likely your smaller cam is probably a much better setup. What are the specs of the smaller cam ?

Too bad you only have the slightly too small and the slightly too large holleys !
Better throttle response and alittle mileage with the baby carb, but better upper midrange and hp with the other.
If you have an 870 holley - it is a vacuum secondary carb ? A 750 vac would be perfect.

 

Rear gears would help once you get the springs to match the cam. Honestly heads would be the way to go. If it's got an auto transmission you'll need to match the stall converter to the cam. Bare minimum would be springs and converter though.

 

Do you have the casting numbers on the heads?

 

If your smaller cam is in the 262-270 advertised duration range, you should be back in the ballpark; especially if you get a nice set of cylinder heads and fresh valve springs to match the smaller cam. 64-65cc chambers, 2.02/1.60 valves too.

272 adv duration is the most I would go with 3.07 gears and stock stall converter. Before my conversion, I ran a Crane Energizer 272H10 grind with my 3.07's and a tired TH350C and the car sprinted off the line easily. Back around 2002, I stepped up to the 3.55 gears and 700R4 trans at the same time and retained the Crane cam... the car even more easily smoked the tires off the line.

Now, having stepped the cam kit up to retro roller, the total package is VERY strong on the street with the 270/276 duration of my roller conversion.... I have 1.52 Ultra Pro Magnum roller rockers so I trust the .502/.509 lift numbers (before, I had Summit stamped 1.5's of questionable lift). I went conservative on my roller conversion so I would not lose any of the snappy performance off the line (no changes to timing or carburetor). I was looking more for the roller benefits of eliminating lobe wear issues and the improved lift and low-midrange performance improvements.

One final thought, have your mechanic record and share the timing numbers (idle, 1500 and 2500). I run about 12 degrees of base timing (ie. 12 degrees BTDC) at idle and am at 36 degrees total timing at 2500rpm. If you are not getting 36 degrees total by 2500rpm, you are leaving power on the table. My Accel Performance Replacement distributor has an adjustable vacuum can. I had a tuner lay that timing curve down and it has not changed since around 1999. Lars built and tuned my carb and the whole pkg is VERY lively. I drive on street only.

 

Thanks for all the feedback from everyone. It is a mish mosh of mismatched parts...and I knew better, but thought I could get away with it, but numbers never lie.

Here is what the new cam specs are:

cam lift valve
int exh int exh
.281 .296 .422 .444

sae duration .050 duration

int exh int exh
278 288 204 214

Plan on new converter and the 870 carb was supposed to be a 750 until I looked at the numbers, but it was free. Maybe someone has a trade locally. It already has headers so that's good. he did time it out at 12 degrees and total 36. It just spits at you when you rev it. The cam is probably flat so that's good I have a cam kit already for it. Lord knows where I got all these cam kits. I don't even remember buying them. I also have a new identical Comp cam like the one in the motor now. Strange.

I will keep you guys posted. Gonna pull the cam and heads this week or next. We are "expecting" snow here in Austin so everyone is going crazy about having to drive in it. lol

Thanks again.

 

I don't have the numbers yet. I will.

 

Your 204/214 duration at .050" is a better measurement than the SAE/Advertised Duration. Looks like a good match to your diff/trans. Glad to hear you are getting sufficient ignition advance.

When you say it spits at you, do you mean the carb spits fuel when you rev it? That does not sound normal but if lobe(s) wiped, that would explain it.

Sounds like you may have it sorted out soon with the head/cam swap.

 

I guess spit isn't the right word. When you manually push the throttle it bogs down for an instant and then straightens back up. I get the gut feeling it has a bad lobe. I shall see.

Thanks

 

that bog is likely in the carburetor, maybe too lean. you may need a bigger squirter.