455 performance... what next?

No, not at all.. first off, your never going to see 2800 stall, the car will be accelerating, or the tires spinning long before you get there.. That's a flash stall number, that you would only see if you stabbed it in second gear at 30 mph, or recorded the tach on the drag strip with slicks on.

This converter drives very much like the one you have in your car now, under light throttle.. when you get on it, then you will notice the difference.

Your torque peak is well beyond 2800 rpm, so if anything it's actually a compromise. The converter is built very efficiently, the stall comes from the ability of the engine's power, and the weight of the car vs. the small converters ability to move it. So, unlike bigger diameter converters, there is no need to build inefficient angles into the converter. Those angles are what makes a 12" high stall street converter feel like mush at light throttle.

Not to mention the stall torque ratio on a 12" is typically about 1.2.. so the efficient smaller converter is working harder to multiply your engine torque, than the inefficient big one, even though they may be rated at the same "stall speed".

These thin, small diameter converters have really revolutionized the street/strip market, so much so that the VP stuff is really no longer needed. Many guys have called me looking for a 12" VP converter for their combo, and have changed to one of these converters.. and been very happy with it.



JW

 

How much difference can an x-pipe make if nothin else is changed?

 

I can't understand why you would have detonation issues with that combo. you should be fine on pump gas.

 

Great question.

Not sure how much it would help, but with that single pattern cam in a Buick that likes more ex. duration it should be a noticeable difference with ex. manifolds.

The idea behind the X-pipe is that as the ex. pulses from one side go though the X it creates a draw on the other side and vice a versa. Headers will to a point help draw on the other cylinders as well without an X and even better with one to help get the spent gases out.

But if you're planning on an new ex. system then it doesn't make sense to spend $$ twice unless you're curious and it will be a year or 2 before you get a chance to change the entire system? If so then the closer you can get the X pipe to the manifold exits the better they will work. Which would mean right around the rear of the trans.

Here is a few choices to pick from;

https://www.summitracing.com/search...tch&SortOrder=Ascending&keyword=2.25" X pipes



Derek

 

Thanks Derek, if I'm going to spend $100, I may as well go all the way with full 2.5", xpipe, and decent mufflers. This would likely help the 268 cam now and I'd be set up for future mods with the new exhaust.

As for the torque converter, I may wait a bit for now. Jim makes really good points, just not sure what cam to use with it and how much I want to do this year. Best to do some of this in the fall and winter.

 

If I add this converter, and 5 years later do an engine rebuild, will this converter limit me? What if I go to 400 hp? 500 hp? Basically, what conditions is this converter suited best?

 

The stock manifolds can do lots better than that. My motor with a mild cam (228/237 115 LC) and stock manifolds dyno'd at 468 with headers and 450 with the stockers. Compression was built at 10.5 static. Car runs 12.90s at 107+ on radial T/As.

 

Matt,

Nope, that converter will grow with you.. first off, your never going to break it, and if you do, it's lifetime warranted, so no issue there.

I sell that same combo for stock w/small cam to a 550 HP 470 with the 230ish duration camshaft. As the power goes up, the stall speed automatically increases.. from about 2800ish with a motor like yours, to more like 3200 with a 550 beast..

The key is that the positive feel under light throttle says the same, stall increases because the torque converter is a reactionary device, reacting to engine output vs vehicle weight.

All the stall speeds I quote assume a 3800-4000 lbs gs, with mid 3 series gears.

The only time I would alter that build is if you put a really wild cam in, and needed it to absorb more pulses at idle. Of course if you decide to go drag racing, then the program changes all together, for a much higher stall unit.

 

Matt, I'd go with exhaust first, your going to need that anyway down the road. I used a Pipes stainless system with a X-pipe and there head pipes, it fit very well, I did order it with GTO tailpipes and modified it to fit for N-25 tips . I don't think a X pipe does much for HP but it does help with drone in the car.

Second, 9" or 10" convertor, 3000-3200 stall, it will be fine on the street, we put 30,000 miles on in 15 yrs with a 3000 stall 10" ATI. Shortly after we did the motor a few years back went with a PTC 9" 3500 stall, it was worth about 2 tenths over the ATI. I really like the PTC but would go with Jims convertor if I did it again.........Would love to do a back to back test with Jims conv and PTC.......(hint, hint)

I think it would like more timing if you have good fuel, bet it would pick up with 36-38 total over 3000 rpm..........

Keep a lookout for a good used KB 118, just swap the cam and good single spring till you can afford to build a motor.

 

Not sure what real world HP is but I know for a fact you can make 480hp with all iron motor (ported), 11.0 comp and 91 pump gas on a engine dyno.....It will push a 4100 lbs GS to low 12's on most days and high 11's in really good air...

 

If they are tired stock non Stage 1 springs a shim job can make it feel like it just had a valve job. Cheap performance gain. Stops valve float and the valves seal better with the extra (or restored) pressure. Put air in cylinders and use a pen magnet to grab the locks. Second person helps....

 

(using this quote to make a point, not necessarily to respond to the person posting this)

Stock cams for these large bore, large combustion chamber engines (BBB) without quench gives a very generous valve closing event of 91* for the FM OEM replica, vs the 64* (60* @4*advance) IVC point of the 268 cam, which would create a dynamic air flow pressure too great for pump fuel at higher RPMs with even minuscule overlap/scavenging that manifolds could barely muster.

Putting headers on this engine with that cam would make it detonate apart.

As Derek has said, a cam change is in order here above all else (also my opinion).

This cam is too small for a BBB, and doesn't have the exhaust emphasis it needs.

You won't be able to tune the specs out of that cam to make it functional beyond what you have now.

You'll have to fix this part before working on the rest, since the cam is a fundamentally flawed component for this engine's engineered architecture.

I'll check back here later on when I have more time, but this is my simple, 'first impression' answer.

 

Thanks guys!

So far, for cam selection, I've received the following:
-Kenne Belle 118
-TA 284
-TA 212

thoughts?

 

Year in and year out, the 118 is a great street cam with plenty of the exhaust timing you need. Great sound too!

 

Of course you have detonation problems.
9.2+ compression, a small cam and heat retaining manifolds with a fully fast advance mechanism?
Definitely asking for it.
Aside from the obvious "knock increasers" like hot intake air and water temps, a lesser known factor with the unknown machine work is the seat contact on the exhaust valve and if the machinist left the sharp edges around the chambers when they decked the heads.
Both of those can and do create problems with borderline builds.
Even though a slightly larger cam than stock appears to lower dynamic compression at times (on paper), the extra overlap is intended to pull more atmosphere into the cylinder when that cam does wake up...and if it doesn't or the cam phasing is mis-timed then the hot manifolds contribute heat back into the cylinder.

 

How did you come to believe that this is "correct"?

1. I suspect a few more degrees of advance would add power--provided it doesn't create detonation.
2. Until you know what RPM those figures are at, I'd hate to say that the existing curve does--or does not--contribute to your detonation problem.
3. WHERE'S THE VACUUM ADVANCE?

 

I added some cams to an existing cam list. At what point is it too much cam for my car?

I did a quick color code. Green is it will work. Yellow on the fringe and red likely not. Just some thoughts for discussion.

This really shows how putrid the 268H is for a 455. I've lost a little faith and trust that comp cams would even sell this one.

 

I have a c118 cam that has taken my car from 14 seconds to 11.80's on 91 octane and stock 1970 pistons, along with an old b4b intake and quadrajet! Good heads, tuning and traction did most of the rest.
I had a 2800-3000 vp converter till I reached mid 12"s then switched to a JW 3500 10" converter. Start out with a JW converter.
Without a good converter you will miss out on a lot of fun.
Buy some braces that tie the rear trailing arms together, then proceed with the steps toward your goal. Don't destroy tha car before you begin. Get those braces on!

 

Oh yes, the c118 Kenny Bell cam has a low dcr and should not cause detonation unless there is some other problem. Yet that cam can do 450 hp and probably more with TA heads.

 

Tried to tell you that! LOL

Nice list, The 284 would work good and still have decent gas mileage but if that doesn't matter to you then either 118s would be fun!

The 118 would like a bit more squeeze but your gearing isn't to bad so once the engine starts spinning it will be like turning a switch on once in the power band and then hold on! This one would allow for more upper RPM that you may want so get a rev limiter so you don't go past 6,000 to far. Notice how this one has 18* more duration on the exhaust, this is what will let you get that thing to keep pulling past 4,000!(same with the 284 but not as much, only 7* more)

Not sure if you read all of the BBB engine posts but if in you do the stock class engine build that Vortecpro built made over 500 HP with un-ported heads! It was from the ultra high duration cam it uses, it'll be less in the car if in he has to run manifolds when its in the car though.

Also the 118 will help kill a bit of low end torque so its not so easy to spin the tires from a dead start. But with it being a BBB you won't notice much, its hard to kill to much low end because it is a BBB after all. Especially if and or when you get the Tri-Shield converter to go with that cam! Say goodbye to the 14s and hello to the 12s!(with converter and cam and maybe with 2.5" X system if the cam and converter don't get you there but they should if you can hook)


Derek