tweaking my 355/polishing a turd

[Barry Burch]

Dave Brode. Bingo on the shorty collectors. Chop off the cheap useless factory collectors
and weld in a pair of cone engineering or headers by ed collectors and shortys will work fine.
If power below peak torque is important kill off the low lift flow.

[rfoll]

I have to wonder about the effects of the extreme rpm drop at shift point. Many here are talking about top end power increases, but a 2600 rpm drop is huge. I think the current cam may be wrong to recover well from 4000 rpm. I think a single plane manifold would hurt recovery as well.

[falcongeorge]

That shouldn't be an impossible task, I had an 82 s10 that i street raced for years with a 355, you say that you want to keep
the shorty headers and imho that's going to be your cork
this is what I would do if it was my truck
engine- if you can afford to go 383 do it if not well
get the compression to 11.1:1, port the Edelbrock heads they work very well fully ported
I'd swap to a solid street roller 242-248 xtreme lobes 108lsa 104ilc
keep that rpm intake but port match it to the heads and add a 1" open spacer its worth 8-10hp upstairs
I would do anything possible to get a set of 1-5/8 long tube headers 3" collector
you will make a lot more power and midrange torque than you ever will with your shorties been there done that there is no comparison !
In a light S10 a 3200 vert is too tight I would honestly recommend a ptc or continental 4200 stall as they will literally drive like stock and they only flash to 4200 under max load
I drive 3500-5000 stalls on the street all the time and I also cruise at 17-1800rpm
run a 4.10 or 4.33 rear gear and sticky tires you should hit 11.5-11.7 @ 114mph from my experience
I have a customer with a 388 60 over tbi block
scat crank, scat prostock 6" rods KB factory performance forged flat tops
11.08:1 compression .034 quench
Custom bullet hydraulic roller cam 228-234 @ .050 .550 lift 110lsa 107ilc
stock gm hydraulic roller lifters, sb pushrods 1.6 rockers
Edelbrock rpm heads 185cc version fully ported by me flows 275cfm in 225ex 193cc intake port 67cc chambers
port matched rpm intake, modified plenum, 750 ultra hp carb
HEI ignition and 1-3/4 long tube dyno headers
made 493hp at 57-5900rpm and 492tq @ 44-4600rpm
added a one inch spacer and made 508hp 503tq
this is a verified dyno sf dyno, standard correction factor
a buick 455 I built just made it to the track and ran 10.82 @ 123mph 3500lbs 76 camero
That one made 527hp 558tq so I feel the dyno is accurate
Anyway sorry for the ramble, I just wanted you to know you can reach your goals without a 1500$ set of heads
even though I like the afr heads a lot
A 150hp shot might be the best way to go considering your happy with the truck as it is

Nothing to be sorry about, lots of good feedback there. I'd definately be a happy camper if I could get 275 cfm out of those heads! Did you by chance measure the CSA on the heads before and after you started porting? Do you have any photos of the finished porting on those heads?
Not enough hood clearance for a 1" spacer on the Perf. Rpm. I will end up track testing the rpm against a Victor Jr on it, with used Victor Jr's all over the place at $100-$150, theres no reason not to. At that point, I will probably cut the divider down an inch on the RPM, and re-test that as well. No spray, for one thing, I am more than a little spooky about spraying hypers.

On the whole converter thing. I have run non-lockup good quality 8" converters on the street before and they have worked very well, but because I have no previous first-hand experience with lock-up converters (or 700R4's) I feel a little lost, am maybe lending more credence to forum gossip than I normally would. One of several conclusions I have drawn form this thread is I at least need to do more research before I make a choice on a converter. I think I am going to start a thread on 700R4 lock-up converters here on the drivetrain forum and see what sort of feed back I get there.

Someone mentioned that El Camino, its impressed me, I have always been pretty dismissive of the RPM heads. I ran across that combo somewhere on the internet while I was trying to search up info on what sort of results guys were getting with ported RPM heads. Theres very little out there, it seems like most guys dont bother with these heads. Honestly, I never would have went out and bought a set of these heads, they were on the truck when I bought it.

[falcongeorge]

Dave Brode. Bingo on the shorty collectors. Chop off the cheap useless factory collectors
and weld in a pair of cone engineering or headers by ed collectors and shortys will work fine.
If power below peak torque is important kill off the low lift flow.

This is worth looking into, for sure. As a general rule, I have seen way more in the way of meaningful change on a time slip by messing with collector changes than I have in messing with the primaries. Good input here.

[BOOT]

Your 1.5 shorties may be a bit small for 6600rpm, still I think 1 5/8 would be as big as I'd go with a smaller stall. I'd try a open spacer before I cut the divider, for example just a small 1/4" would be about the same as cutting it down some. The alum box may not hold up in your heavy truck on the street, well depends how you drive.

[falcongeorge]

I'll make another comment here regarding header primary length. This is more of a "curiousity" thing. I use Engine Analyzer, one thing I have noticed in playing around is that the software will more or less duplicate the power curve between peak torque and peak hp if you combine a smaller primary diameter with a shorter pipe. In other words, the curve for a 1.75x32 primary will more or less overlap the curve for a 1.625x28 primary. Has anyone noticed any trend like this on the dyno, or is this just a software abberation?

[dave brode]

Dave Brode. Bingo on the shorty collectors. Chop off the cheap useless factory collectors
and weld in a pair of cone engineering or headers by ed collectors and shortys will work fine.
If power below peak torque is important kill off the low lift flow.

Barry/All,

I've wondered if another section, 1/8" larger step AND a good collector would be better yet, esp on a 1.5" header. With the header sloped down, there may not be enough room. I've seen collector with a bend on them, but I'm not sure that a bend right after the merge section of the collector would wreak havoc.

falcongeorge's post above makes me question the logic though.

Dave

[falcongeorge]

Dave Brode. Bingo on the shorty collectors. Chop off the cheap useless factory collectors
and weld in a pair of cone engineering or headers by ed collectors and shortys will work fine.
If power below peak torque is important kill off the low lift flow.

Barry/All,

I've wondered if another section, 1/8" larger step AND a good collector would be better yet, esp on a 1.5" header. With the header sloped down, there may not be enough room. I've seen collector with a bend on them, but I'm not sure that a bend right after the merge section of the collector would wreak havoc.

falcongeorge's post above makes me question the logic though.

Dave

Well, hey, like I said, I'm not AT ALL sure that effect isnt just a software thing, I just kind of threw it up there for discussion.(edit: I think I jumped to the wrong conclusion, you were referring to the post re: collector vs primary I guess?) I gotta make a parts run in an hour or so, before I go, I'm going to take a really good look at the truck and really try to suss out if there is space for a better collector and/or adding a step, interesting ideas here. I will also try to find some good internet pics of the 1.625 Sandersons I mentioned earlier and compare that to what I see under the truck. Maybe there is a way I can improve on things without having to go to a header thats going to interfere with ground clearance or turning radius. This is turning into a pretty good thread, lots of good food for thought here.

[falcongeorge]

Ok, heres another thought. Right now, the collector is dumping straight into a fairly long 3" pipe leading right into the mufflers. this was already bugging me a bit, with the huge rpm drop inherent in the 700R4 I was already contemplating that I might be better off with the shorties transitioning into a 2.5 or 2.75 collector extension about 16"-18" long, then into the 3" right around the locaton of the balance tube. This, in conjunction with a better collector shape might be worth track testing. I have to go outside and crawl around under the truck now.

[Barry Burch]

Exhausted has wrote in another post that a shorter primary will need
a smaller collector to hold up the bottom end. And a longer primary will
need a need a bigger collector to top end. My experences exactly.

[falcongeorge]

Exhausted has wrote in another post that a shorter primary will need
a smaller collector to hold up the bottom end. And a longer primary will
need a need a bigger collector to top end. My experences exactly.

My thoughts exactly, thinking a smaller collector extension will have much the same effect as longer primaries. Looked at the truck, the only way to fit a conventional collector on the drivers side would be to heat and bash the sh*t out of the frame. Its REALLY tight in there. Think it would help much if I just put a nice collector on the pass. side??

[cjperformance]

Ok, heres another thought. Right now, the collector is dumping straight into a fairly long 3" pipe leading right into the mufflers. this was already bugging me a bit, with the huge rpm drop inherent in the 700R4 I was already contemplating that I might be better off with the shorties transitioning into a 2.5 or 2.75 collector extension about 16"-18" long, then into the 3" right around the locaton of the balance tube. This, in conjunction with a better collector shape might be worth track testing. I have to go outside and crawl around under the truck now.

This is exactly why i asked about your exhaust setup after the shortys, and you are right on track about using a smaller pipe off of the primary pipes, then stepping up but step up before your balance tube. You will just be using the smaller pipe off of the primaries to keep the gas velocity there in the shift recovery rpm, 2.5" is a bit small for the aprox hp you have but is great for the hp you will be dealing with around shift recovery, because of this the length of the smaller section is not going to be as long as you suggest to work best, I'll suggest half that but it will take track time to perfect. Then step back up to 3". Do you run any pipe after the mufflers?

[falcongeorge]

Ok, heres another thought. Right now, the collector is dumping straight into a fairly long 3" pipe leading right into the mufflers. this was already bugging me a bit, with the huge rpm drop inherent in the 700R4 I was already contemplating that I might be better off with the shorties transitioning into a 2.5 or 2.75 collector extension about 16"-18" long, then into the 3" right around the locaton of the balance tube. This, in conjunction with a better collector shape might be worth track testing. I have to go outside and crawl around under the truck now.

This is exactly why i asked about your exhaust setup after the shortys, and you are right on track about using a smaller pipe off of the primary pipes, then stepping up but step up before your balance tube. You will just be using the smaller pipe off of the primaries to keep the gas velocity there in the shift recovery rpm, 2.5" is a bit small for the aprox hp you have but is great for the hp you will be dealing with around shift recovery, because of this the length of the smaller section is not going to be as long as you suggest to work best, I'll suggest half that but it will take track time to perfect. Then step back up to 3". Do you run any pipe after the mufflers?

yes. right now its 3" all the way through, with about 2' after the mufflers. Sorry CJ, somehow I totally missed the last sentence of your earlier post...

[cjperformance]

If you run it with mufflers on it is also worth messing with pipe length and diameter after the muffler. Im guessing that if you only have 2' after the muffler that it wont have many bends in it? Mufflers of differing internal design can benefit from differing pipe styles behind them. With a large tail pipe of short length and minimal bends i can tell you that It can be worth something to simply step down a pipe size a few inches after the muffler, even if only for a couple inches then back out again. Yes this is to an extent crutching an imperfect size/length system but when its a street/track vehicle not all things can always be perfect!

[falcongeorge]

If you run it with mufflers on it is also worth messing with pipe length and diameter after the muffler. Im guessing that if you only have 2' after the muffler that it wont have many bends in it? Mufflers of differing internal design can benefit from differing pipe styles behind them. With a large tail pipe of short length and minimal bends i can tell you that It can be worth something to simply step down a pipe size a few inches after the muffler, even if only for a couple inches then back out again. Yes this is to an extent crutching an imperfect size/length system but when its a street/track vehicle not all things can always be perfect!

They do bend out to the sides and turn down towards the ground at the ends, but the bends are large radius. Crutching stuff to dovetail with the dictates of reality is a fine art unto itself which is lost on a lot of guys.