Hello Oldsmobile Nuts, I'm just finishing putting my engine back together and was looking for some expertise. I'll lay out my build specs and then propose my questions. Thanks in advance for any help. General driver with some racing.

70 Olds Cutlass Supreme, 455, Turbo 400/2200 RPM stall, Chev 12 bolt posi-currently 3.08 gears( want to try them and see how it does, I have a set of 3.42 gear also)

-455 block, bored 0.030, decked 0.020, line bored
-Stock Rods
-'N' cast nodular crank, 0.010
-Probe SRS Pistons, almost '0' deck height
-Ga heads machined to 77cc chambers with 2.0 Intake/1.68 Exhaust valves(Machine shop screwed up and it was suspposed to be 2.07/1.70)
-Factory 'X' & 'Z' exhaust manifolds-wanted to stay away from leaking headers but have exhaust dumps for racing
-Edelbrock Performer RPM Air Gap Intake Manifold
- Comp Cams "Big Muthr Thumpr" cam#42-602-5, 0.512 intake lift/0.497 exhaust lift, 294' intake/312' exhaust duration,lobe separation 107', 2500 to 6400 RPM Range(based on a small block)
-comp magnum pushrods,5/16 dia X 9.800" lenght
-comp fully adjustable roller tip rockers
-comp #995-16 dual valve springs
-comp #3113KT adjustable timing set
-MSD 'Ready to Run' distributor with MDS 6AL with Rev Control
- No carb as of yet

*Questions*
-What postion should I put the crank timing gear at ? "0" or 4' advanced?
-What should I set the distributor timing advance bushing to and recommended intial timing and total timing?
-What Carb. is recommended? Brand and CFM?

*Just a Note* I live in the Rocky Mountains of B.C. Canada so no where near sea level.

Thanks Again

 

If it were mine I would start with the cam straight up, timing at 12 deg. initial, all in by 3000 rpm = 36 deg. Use the vacuum advance also, hook it up after getting your mechanical advance numbers dialed in. I would use a Quadrajet, either 750 or 800 whatever you can find in good shape, jetted and metering rods for your altitude of course.

 

I agree with Run to rund. I found that you can find good big block Chev quadrajets in this CFM range with an electric choke for ease of choke set up. If you are using the Comp push rods you might invest in a better set to start as they can be a weak link. Would be nice to have the bigger valves.

 

Sorry but I disagree with both. That cam is designed to be put it where they say, on a 102 intake centerline. Straight up would be a 107 intake centerline. You'd probably actually have to retard it in order to achieve that. I hate that term "straight up". It's very commonly misused. You need to degree it.

And to run a Qjet on the RPM you'll need an adaptor as those will only accept a square bore carb.
Quick Fuels are my favorite, great carbs and excellent tech help as well.

How high are you? I hope real high cuz your combo is yielding a compression ratio of 11.5:1. Unless you're way up there and going to run race gas, that's steep with iron heads.

Best of luck in your build.

 

Thanks Guys. I plan to degree the cam that why I bought the adjustable timing set. Was just wondering in the crank gear as it it also adjustable for the 3 positions. I have advanced it on SB Chevys with bigger cams and it worked great but in my SB Olds I swapped it back and forth and didn't seem to find much difference. Just wondering if I should leave it at the stock setting and just adjust the cam gear to get the 102'.
Ya my compression is high and with my Old comp 268 cam I had pinging issues so that why I went with the Thumpr cam to lower my cylinder pressures a bit so I could at least run premium.
Thanks Again

 

That cam is designed to keep cylinder pressure high, it'll work but that particular grind wouldn't have been my first choice. The whole principle of the Thump'rs is to have a bunch of overlap but grind it with an early intake closing so that you retain cylinder pressure. What you're hearing is actually the combustion process and you won't hear that that well without ample cylinder pressure.
And your 2200 converter will be marginal with that cam. It states it needs a 2800 stall, and those are normally conservative estimates.

 

Hmm. This cam is what was recommended by the comp tech. Line. I guess I'm going to try it as its already in and wife will shoot me if I get another one. Any tips on how to make it work better? Race fuel here I come.

 

As far as the 2800 stall it asks for. Tech line also told be that is based on the small block as the cam will fit in either SB or BB. They have to list the specs based on the small block or it would be miss leading in the discription. They said with the stroke if the BB it will lower the RPM band down close to the 2200 RPM range. This I have experience before as a Crane cam I had in my old SB was 3000 and up and I put it in my Dads 455 and it runs great with power right around the 2000-2200 range,also has no lope like it did in my SB. Hoping this will work for me but??

 

My main concern is did your machinist check the open clearance on the valve guide? I have heard from numerous people that the factory heads will only take about .500 lift, when I installed my cam (.513 or .523 lift, cant remember) I checked out my height clearance and I had to machine down the valve guides on my head, otherwise the spring retainer and valve guide were gonna smash the seal and destroy it!

 

I have already checked the valve guide clearance and it was ok but I machined it down a bit to be on the safe side. The machine shop was useless, they installed the wrong size of valves that I had asked for and even forgot to grind the exhaust valves and seats. Long storey.

 

Is a stock Q-Jet run up to 800 CFM? BB Olds? Or? Thought they couldn't get much performance out of them?
Thanks

 

"How high are you?"



What have you been smokin' boy?

"Oh, Mustangs, Camaros, Hondas..."

 

Really?
I did a cam for my buddy's 455 Olds in a 78 T/A, 232/244 @.050 on a 108. He had a 2200 stall and it didn't work well at all. Went to a 3000 and its a different car.

 

So what would you set the crank gear at? -4', 0, +4'? Is that what changes the cam centre line? Pardon my #'s on 102', I was going to degree it to make sure it matches the lobe separation angle of 107'. Is this correct? Just want to get the best out of what I already have. Thanks Again for all the help.

 

The way they list it, isn't it misleading for people that have big blocks?

 

Most Q-jets are 750 CFM but there are some performance 800 CFM Q-jets out there. They can be modified to get performance out of them.

 

Thanks

 

Just what t

 

Just what the tech guy told me and just from my previous experience the rough idle and power band changes when going from SB to BB. So it sounded like the comp cams tech was correct but I'll find out this spring. Need the snow to melt faster so I can try it out.

 

Start it at 0, then check it and go from there.
You'll want to see 19 degrees before tdc on your degree wheel at .050 tappet lift for it to be on a 102 intake centerline. I wouldn't worry about the 107 lobe sep being correct. I think you have them mixed up anyway.

 

You're correct. But I would have asked him if he's installed this exact cam in a 455, or if he can reference someone who has.
I have that similar one in that 455 T/A build. In fact it's a bit milder with 10.0:1 at sea level. It needed more than a 2200 stall.

Jmo.

 

Ok Thanks a lot for the help guys.