89newfun

iTrader: (3)

I do have a 3.42 rear end. Car was a v6 to start life.

89newfun

iTrader: (3)

Yea I have hardly locked converter unless on highway actually

skinny z

I'll contribute here to say that one of the single best improvements I made with respect to 1/4 mile performance was the addition of the higher stall converter.
Even though I run the less the high end TCI Street Fighter, it still made a big difference in both my 60' times and the way it performs on the street.
From my experiences with a few other cars, once you step up to a converter that's custom spec'd (be it Yank, Vigilante, Edge, etc) then the performance goes up another nothch. So much so that we found the big gear split in the 700R4's 1-2 shift is substantially reduced.

86LG4Bird

iTrader: (1)

Bingo! Same thing I concluded years ago. And it's even more glaring when you go back to a tighter converter on the street after being spoiled by that seamless flow of power through medium-to-heavy throttle 1-2 shifts.

FRMULA88

the SLP 3" collector pipe system is a big improvement over the OEM collector pipe
and will give any 2 1/2 true dual systems a run for the money.

I had one for years before switching to a Mufflex 4" collector system which performs as well as a 3" true dual system.

Now I run open headers with collector mufflers.. Removing the full exhaust saved over 100# LOL


A lot of people get hung up on this.. but it's quite simple when you calculate the area of circle... One bigger circle has more area than 2 smaller ones... LOL PI baby ..!

skinny z

RPMs in my friends 81 Monte Carlo now never drop below 5000 (+/-) even though the ratio split from the top of 1st at 6500 rpm says otherwise. Something like 3500 if my math is correct. Part of the reason I shift at 6500 (even though I'm past peak power by 5800) is to drop into the next shift at a better part of the torque curve.
I want a Yank converter.

skinny z

Don't forget to include the CFM of the muffler(s) you have. That's probably the biggest shortcoming of a 3rd gen exhaust. One muffler.
The idea of a set of headers with mufflers attached is the way to go if you have the room. In a lowered car, that's not the case.

89newfun

iTrader: (3)

More of a way of keeping rpms up for smooth powerband, I see. Would it even be worth buying another converter for a 600 rpm difference. Stock 1900 to a aftermarket 2500?

89newfun

iTrader: (3)

Yea I've got the slp bullet, it's like 14 or 16 in long. Assuming the flow would be plenty for my motor


Side note, back to 1.6 rr on exhaust side. Is it always worth doing this for exhaust scavenging purposes?

FRMULA88

it depends on the camshaft, the heads you use, and how much lift you actually need.

A dual pattern cam with more lift ground into the exhaust lobes would not need more RR than the intake.

BUT based on the camshaft you have and the tech data on the Iron Eagle heads your combo would benefit from Higher RR on the exhaust valve. This does does the same thing and a custom ground cam, for less money since you don't; have to remove your cam and buy a new one.

FRMULA88

On my setup I have:

1.7s on the intake for .748 lift intake duration of 268
1.6s on the exhaust for .688 lift exhuast duration of 274

For this application we did the opposite since the cam has 6 degrees of additional duration on the exhaust this promotes scavenging at RPM..
Per the cam mfg. there was benefit to run a bit more lift on the intake
All of which compliments the cylinder heads.

FRMULA88

my "mufflers" fit inside the collectors.

The old SLP "2 on the left" system was big improvement. it was still one muffler but with 3" inlet (for the collector) and twin 2 1/2 outlets for the tailpipes on the left.

compared to the factory single 2 1/2 collector and cross flow muffler this is great upgrade.

Looks like SLP refined their system over the years.

FWIW a true dual is not needed if you install a properly sized collector system.

My Mufflex 4" system fit like glove, ground clearance was never an issue and I ran it on the car from 2000 until 2014.

89newfun

iTrader: (3)

Ok, I will just have to pay attention to what the head flow is when I decide which heads to get. Great info here. I'll prob keep same cam for a while though, so I'll be running numbers with the 480 lift in mind. With 1.7 rr most heads would have to worry about binding on push rods right?

89newfun

iTrader: (3)

I looked into the mufflex systems just thought it was to much for my car and also price was a factor. I do have to persuade and massage the ypipe I have to fit properly against body, since my car is about 1.5 lower than factory. It was custom made at exhaust shop for hooker shorty headers, and I have dynomax headers which are a pain to match a ypipe to. Just takes time, which isn't always the easiest to find. Heh.

FRMULA88

I have 18 degree heads with shaft mount rockers. The pushrods are one length for the intake and another for the exhaust.

we measured once, twice, three times then ordered the correct length needed.

All routine when working with high-lift cams..

FRMULA88

sounds like it will be a fun street car when it is done.

89newfun

iTrader: (3)

Yea I agree with measure til your mad then order. Lol

And I'm hoping its a nice street ride when done. It isn't bad now I guess, just like more. As we all do. Also just picked up a b&m pro ratchet shifter, going to make it look stock. Love the slight and subtle queues. I will be obtaining more of the auto shifter plate than this image, but you get the idea.
Similar to this image:

FRMULA88

I had the B&M shifter for almost 20 years LOL, it looked cool stock but it really is a crappy shifter compared to what I have now.

I changed to a Turbo Action Cheetah Shifter when I replaced the 700 trans with the turbo400 and 'brake. The difference in quality is night & day. !

FRMULA88

looks pretty stock.

FRMULA88

FRMULA88

upload of file failed... nice !

89newfun

iTrader: (3)

Could you see the image?

Stock looking is what I'm going for, lol

FRMULA88

I saw your shifter, I was trying to upload mine.

89newfun

iTrader: (3)

Oh ok. To bad, enjoy seeing others cars.


Side note to picking heads.
Would a 200cc intake head be to large for my bottom, piston setup I currently have. 64cc combustion with the 200cc intake. Found many iron eagles, but they all are the larger 200 cc as opposed to 180cc mentioned earlier.

86LG4Bird

iTrader: (1)

I'd look for closer to 180cc intake ports if you'll be limiting your shift points to 6500 rpm or less.
I run 200's on a 350, but spinning it to 7100 and making over 500 hp.

89newfun

iTrader: (3)

Ok, that's what I was thinking. Figure if I do the 180 heads I could always just do more work to them if I need more flow.
Also what is the difference in the degree on heads, I'm seeing 23degree 18 degree, ect. What's that all about, will they all work for me?
Rpm limit, I currently shift around 5500, think that short shifting? I have no rev limiter from when car was swapped over to current setup. Not sure what the limit would even be at.

Night rider327

iTrader: (13)

23* is std. sbc valve angle. 15, 18, etc degree heads flows MUCH better but they are not a direct replacement. In fact nothing you have now will work with them. They are true race heads and will need pistons to match head, valvetrain to work, etc.

200cc head is too much for you at this point. Stay in the 180-190cc range.

As an example I run a 200cc head on a 355 (brodix IK 200 heads), I shift at 7200/7300 rpm. Car has 10.34:1 compression, 249/252@.050", .570"/.579" lift cam, 9.5" 3500 stall converter, th-400 trans, ford 9" with 3.89 gear

89newfun

iTrader: (3)

O, ok. The degree makes sense now. Thanks
I'm going to continue to look for the 180 190 heads.

When I had the car at dyno guys, they said that my spark plug wires were producing a lot of noise, electrical noise they meant, kept throwing off there system. Anyone heard of this? And also the effects it could make on proper spark production.

FRMULA88

what spark plug wires are you using?
IMHO the best wire are MSD.

the only interference I can think off would disturb their inductive pick-up for the the dyno's tach?

if you have a MSD box, it could throw off their tach at LOW RPM but that is a problem on their end,
not yours. same thing happens with timing lights..

otherwise they can connect to the coil for a clean tach signal or have to rely on your tach for the dyno pull.

89newfun

iTrader: (3)

It's a universal accel set from my 305, they also used same plugs too from 305. Which had blow by and ect.

Street fire msd?
The would connect to the wire and their monitors would jump or shut off, tach would be zero read. Lol. Could that be a sign of poor wires and maybe incomplete ability to produce good spark?
The r45ts good, they work with headers well?

Also with my hei cap/coil combo, how do I adjust how fast spark advance should be introduced. If so with my setup with cam, what should I be set at

skinny z

With the cam you posted at the outset, (Camshaft, Hydraulic Flat Tappet, Advertised Duration 280/280, Lift .480/.480) 5500 RPM would be below your peak HP numbers provided the rest of the combination matches.
Have you done a compression test yet? That'll help going forward with your project, especially if you're contemplating getting new heads.

Regarding your ignition timing. I'm sure someone here will offer suggestions and a possible tutorial on how it's done.
Here's a link to a paper that explains why it's done.

http://classicinlines.com/spark.asp

After you read it (if you choose to) you'll see how it'll be next to impossible for someone to spec a curve for you based on the information you've provided about the engine.
Here's a quick couple of paragraphs that'll give you an idea:

"The biggest factor affecting the required advance curve in the distributor is the camshaft. The longer the duration the lower the cylinder pressure is at lower rpm. When swapping out a stock cam for a bigger cam we find that the advance needs to come on sooner and faster. The next factor to consider when determining what curve is likely to be needed is the compression ratio. When the compression goes up the compression pressure at the end of the compression stroke is higher so the rate at which the advance needs to come on goes down. In other words it works around the other way to the effect a bigger cam has.
Just for the record when a bigger cam is installed in a normally aspirated engine, the compression ratio should be increased to get best results. By having a better match of CR to cam duration the loss of low speed output from a bigger cam is almost negated until cams of over about 280 or so advertised degrees are involved. In other words pairing off compression and a bigger cam means more top end without loss of bottom end. For the amount the compression would be typically raise though, the effect of the bigger cam will still be the principle control factor."

The HEI will have advance springs that can be changed that will affect the rate at which the curve advances. That will have to be combined with an appropriate amount if initial timng to arrive a total amount that the engine wants. What the engine wants for a total is dependent on a number of factors not the least of which is heads that you're using along with the camshaft specs.
Don't forget also that it's important to run a vacuum advance. That too can be custom tailored to suit your needs but any vacuum advance is better than none.

89newfun

iTrader: (3)

Skinny z
I'll definately read that whole link. I havnt done the compression test, just hadn't been able to borrow on yet and get out there to do it. I will attempt this either Sunday or Tues Wednesday of next week, that's my weekend. As soon as I find the average number I'll post it up.

As far as my rpms go I'll have to find my dyno print out and link it in, it doesn't show rpms at what hp or tq was reached. Which I though was a bummer. I'll post that when I'm home after 7pm. That way you guys can chime in on that too.

skinny z

You may be able to get a reasonable guess at your dyno rpms but looking where the HP and TQ curves cross. That'll be 5250 RPM.

Regarding the article, keep in mind there's stuff in there that's not entirely directed at you particular situation such as "bulk burn rates" and the like. But most of it will have a direct impact on how your timing curve will develop. Especially the vacuum advance.

89newfun

iTrader: (3)

Hmm. Ok, you figuring that number from my engine combo? I'll post them tonight, did 3 pulls one with air cleaner.

skinny z

5250 is where ALL HP and TQ curves cross regardless of the engine specs. It's a function the relationship between the two.

89newfun

iTrader: (3)

So I've read the page on timing. Wow, alot of information in there. It definately gave me a better understanding on mech and vac advance. I see now that finding the best information out before trying to mess with the rate at which timing comes in is imperative. So I will try to get more info for you guys. Starting with psi average of compression.

89newfun

iTrader: (3)

While waiting for pressure testing to happen. I have another question I have is, can I run 58-62 cc heads without running into clearance issues with the piston eyebrows using the same cam? Just trying to get compression up without tearing short block down. I prob wont be able to do heads til Aug but then might wait for wintertime deals. But just wanna pick your guys heads on that too. Thanks again

86LG4Bird

iTrader: (1)

Nothing to be concerned about.
I run 23 degree 52cc heads with a 280 cam on 104 ICL, .035 quench clearance, flattops with eyebrows.

89newfun

iTrader: (3)

Oh wow, really. Super high compression I take it? Just another thing I was told that I'd have problems with, I did forget to mention the larger valves, 2.02/1.6. Still no reason to be concerned?

86LG4Bird

iTrader: (1)

Yes, 12:1 CR.
No reason to be concerned with 2.02's/1.6's either.

89newfun

iTrader: (3)

Ok perfect thanks.

skinny z

Nice.
Any idea of your cranking compression? I wouldn't mind doing a reverse calculation on your engine specs to see how accurate my formula is (not my formula actually). It's spot on with my combination. Then again, I'd need your cam specs and a few other details and if you'd rather play your cards close to your chest...

Here's a spread sheet I started to develop.

89newfun

iTrader: (3)

That's seems like good research. I'll add to your info here hopefully by next week and maybe be able to calc my comp ratio, atleast ballpark it compared to the normal cc head gasket deck height type of calc. Since I don't know what's in mine.

86LG4Bird

iTrader: (1)

No secrets. Hopefully the weather warms in a few weeks and I'll be changing plugs, so I can get some cranking numbers then.
In the meantime:
350 ci
4.000"
3.48"
5.7"
12.0:1
280 adv
108 LSA
103 ICL
200m
~50 degF


What does your calculation say for predicted psi?
I run 93 pump for cruising around and at the dragstrip. I mix half 110 octane in it for roadcourse duty where things get pretty warm in a 30 minute session

skinny z

Yours works out to 230 PSI cranking pressure. I suspected it would be high with the cam duration number listed and the SCR posted. The calculator is a little crude as there's no input for ICL. That's makes a huge difference in the observed cranking pressure as well as your DCR.

I'm guessing that's an LT/Gen 2 SBC based engine?

89newfun

iTrader: (3)

So how close was he to actually matching to what your psi is?

skinny z

No cranking numbers available yet.
With 12:1 SCR and a 280 adv cam duration, you know the pressure will be high. North of 200 psi for sure. That said, you have to take into account the advanced position that his cam is installed with a 103 intake centre line. That means the intake valve opens sooner and that effectively reduces the cylinder pressure. The tight LSA also contributes to less pressure as the amount of valve overlap is greater than with a cam that has a wider seperation angle. The compression test values will then be lower still. By how much, my somewhat crude calculator can't predict.
It did however nail down my theoretical vs actual results to within a few percent. I'm guessing that the calculator is based on a more typical off the shelf grind. Your average 350 Gen 1 SBC typiclly gets spec'd a cam with a 110 LSA and a 106 ICL.
I'm curious as to what LGs results will be.

EDIT: It's been brought to my attention that I've got my facts wrong. The intake closing moment in an advanced situation will raise cylinder pressure (as I've alway been aware of). For whatever reason, my logic at the time of posting was backasswards. Sorry for the confusion.
Thanks LG.
Kevin

86LG4Bird

iTrader: (1)

Yes, reverse cooled, 160 tstat, the engine in my ImpalaSS. GM timing algorithms for those LT1/LT4 engines aren't completely unlocked by the tuning programs (I use Tunercat for OBD1 and JET DST for OBD2), but WOT timing in the tables for best power is 29 degrees. Most would acknowledge that to be 33 to 34 deg actual, which is what Datamaster shows on a log (33.5).
Stock tables for that engine, iron head 10.0:1 CR, 87 octane, tiny roller cam, have WOT max at 29.5 deg, which would be 34 actual.

86LG4Bird

iTrader: (1)

Maybe when it cracks above freezing....lol!

89newfun

iTrader: (3)

Yea it's cold here too,

Would that make a difference in numbers, for my own benefit. As to wait or not for my numbers til it's warm er ?