I just picked up a 403 from QS442, .030 with arias -3cc forged pistons, the bottom end is done and all together. Currently has 4a's on it, but I bought a set of big valve E's with the crossover filled to go with it with a performer RPM port matched to the heads. I'm looking to run them at around 77-80 cc (depending how far I find the piston in the hole) for right around 10:1.
It's going in a driver g body cutlass, stick car, with 4.10's (may go 4.30's)

My question is, I'm looking at the lunati 60805 cam (http://www.lunatipower.com/Product.aspx?id=2351&gid=287) and was wondering if this is where I should be looking to go for cam. Obviously I don't want to be leaving power on the table, but I do honestly want some overlap and a nice lopey idle in addition to being able to run pump gas with no issue. Like I said, it is mostly a street car driver.
Additionally, what springs do you guys suggest for this cam, or any cam for that matter in the .550" lift range? I do have a stud mount adjustable setup on the heads, and I'm gonna pick up 1.6 ratio adjustable rockers.

And lastly, what kind of et's do you think I'm gonna be able to turn with this setup?

Thanks,
Martin.

 

Good lord the world is coming to a end.LOL At last a performance build for the street and maybe some track time. Posted in the correct forum.No disrespect but i think cutlassefi can help you on a cam choice. On Rop i noticed you posted. DR Dan may be a good sound board for a 403.JMO

 

How high are you going to spin it?

 

Not expecting to spin it past 6000 ever, but I plan to shift at 5000-5500, to keep it together. Its not girdled as of yet, undecided if I'm going to or not but I'm leaning towards not.

 

Don't buy the Chinesium girdle...

http://www.ebay.com/itm/151173321106...84.m1555.l2649

but a proper USA made unit would be nice insurance.

 

Figured if I was gonna go girdled, I'd go to J&S machine most likely.

 

Personally, I would do it a little differently. Less gear, less rpm, 403s like to rev fast as it is. You basically have big block cubes in a SBO platform, build it to make massive torque and keep the shift point in the low 5,xxx range. 375 HP and 425 ft/lbs will put you in the high 12s with a good tune, it will be more reliable and street-friendly. I do not think the girdle would be required. IMHO.

 

Well the girdle is on the way already. Spoke to Jim @ J&S and he suggested a 5 main halo. I don't mind doing the girdle anyway to help strengthen the block, it can't hurt, especially since those bb heads should let it rev. And to make a long story short, the bottom end needed some touch up machine work anyway.

The gearing has a lot more to do with the .5 overdrive of my t56, with my 3.42's it isn't really usable below 70. I'm doing the 4.10's to make overdrive useful.

 

Even the .67 od of the 2004r is almost too much for 3.42 gearing. I am going 3.90 when my 350/2004R gets swapped into my A body. I am also thinking of the 5 main girdle, machined caps, 2.07 intake in place of 2", polishing chambers, Cutlassefi custom cam and block machining next spring as the challenger will be paid off. I will not go more than 9.5 to 1 with iron heads, I want some manners and not a pinging mess like my current 350. Big torque should be no problem from a 424 403 based stroker.

 

You will find it difficult to get a combo that maximizes power and can use that low OD. From here,
http://www.superchevy.com/how-to/148...-transmission/

"Other than making one fit in a strange chassis along with the hydraulic clutch setup, the one drawback to the T56 is its Bonneville-gear overdrive ratios, but there are two schools of thought on this. Dropping 600-800 rpm with a normal overdrive transmission is usually a great improvement, but making a hi-po powerplant lope along at 1,500 rpm, frequently well below where it starts making power, is another matter entirely.As a result, Sixth gear was all but useless unless you live in Montana or drive the Autobahn on a regular basis. It also takes some serious horsepower to be able to push that steep of a ratio"

The following will probably get me creamed, but it is just my personal opinion. Engines that rev fast "waste" HP. The higher gearing you can use (lower numerically) the more efficient your car will be. If you run this car with a 3.42 gear and no OD and build the engine to have a broad torque curve it will run a better ET than a car with a "peaky" engine and a ton of gear, both rear and trans. A TH 350 is easy and inexpensive to build, converters are cheaper, less hassle and just as fast. the 373/2004R is a good combo as well, but the 200 costs more to build. I am really not familiar with manual transmissions, not sure what your options are in that case. JMHO.

 

Captjim just what was your fastest car? I seen your post about rev fast wasted hp your personal opinion so i thought i would ask. The op has enough parts to get 12 seconds pass maybe high 12's. This would still be a street able combo. It is a stick car. 373,390, 410 are good enough gears. I think 410 for over drive should work fine. JMO

 

Fastest Oldsmobile was 12.78 @ 103 in a 355 powered G-body wagon, 9 to 1 cr, driven to the track and back.
http://www.dragtimes.com/Oldsmobile-...lip-10876.html

Fastest car was a 68 Dart with a 440, mid 11s, bracket car. Not sure what any of that has to do with this thread, though. If you can read, you will see that I stated in my first response that a high 12 was easily attainable, even without all the gear.

As to the "wasted HP" theory, it is easy to defend. Take your car to a chassis dyno, make a pull in 2nd gear, 3rd gear, and OD. Same engine, same car, HP results will be higher with less gear.

 

Jim they were just questions nothing else when i asked about how fast of your cars have been. You know curiosity.Don't know why you throw out the{ if you can read} stuff. As for defend gear results. I am not saying good or bad the op said that is what he want's a 410. Yours was view was a different. I don't think he will ever see over drive in a 1/4 mile With the parts the op is using. JMO OD on a chassis dyno LOL what for?

 

The 403 has some advantages and disadvantages. The advantages are big inches in an SBO platform, large bore, good valve unshrouding. Disadvantages are VERY thin cylinder walls, resulting in ring seal issues, Siamesed cylinders making it prone to detonation and overheating. Not to mention the windowed webs. A low rpm torque monster plays to the advantages while a high revving engine exposes the weaknesses. IMHO.

 

I understand what you are saying about overgearing it. It makes sense, if you keep it where it makes power longer, you go faster. I don't want more and more gear, I really only want enough to get it to make od usable on flat highways. My original plan was for 3.90's but the 4.10's came up new and cheap. A 6th gear swap to something usable sure would be nice though, as the article states is possible.

Also, I'd *like* more than high 12's out of it, but I'll take what I can get.

 

Never heard that before. I think I follow what you are saying there, but not sure if I agree.


NewvsOldconverter_zps07ae45e8.png


Here is an RPM graph from my car. Green line had a much looser converter which made it "rev" faster. Both were 8" converters but the new one (red line) was a bit tight. It was supposed to "multiply torque like crazy". Well, it was slower by .25 seconds.

 

The 6 gear in a t56 is ridiculous, I have 4.10's in my 66 and I almost only use 6th if I'm doing 80 plus otherwise my Rpms are to low, about 1800 at 70.

 

What if someone used a 330 block to start with on the sbo build? How far can it be bored to be safe to get close to the 403? We know it has the better crank to start with.

What are the thoughts on this?

I love reading this technical engine stuff. it has always been my weak area of knowledge.

Larry

 

"What if someone used a 330 block to start with on the sbo build? How far can it be bored to be safe to get close to the 403? We know it has the better crank to start with"

Sounds like a plan. Come pick up my 330. I'll give you a deal!

 

Not even an option. 330 bore is 3.938, 403 bore is 4.351, that would require boring .413". Heck, you would need 4 cuts at .030 just to hit a stock 350 bore, and the 330 block is mo stronger than a 350.

 

That's a great graphic. You can see how the looser converter allows the engine to get up into its power band quicker, which results in it reaching each of the shift points quicker -- and the end of the track quicker. I bet it's even more drivable on the street. What's not to love?