caribbean 85

The engine was installed & fired up four days before test day

All times are with borrowed 28x10.5x15 M/T's,

N/A times were :-

(through mufflers)
1st run - 13.987 @ 98.03 (0.688 r/t - 2.042 60ft)

(uncapped cutouts)
2nd run - 13.201 @ 97.61 (1.150 r/t - 1.903 60ft)

3rd run - 13.128 @ 102.50(0.692 r/t - 1.925 60ft)


WITH NOS 100hp jets - no change in "timing"

4th run - 12.908 @ 109.76 (0.972 r/t - 2.110 60ft)

5th run - 12.730 @ 106.38 (0.873 r/t - 1.914 60ft)


WITH NOS 125HP jets - no change in "timing"

6th run - 12.622 @ 110.29 (0.721 r/t - 1.790 60ft)

I probably need to get the timing sorted out - and the 600 edelbrock is probably not the best carb down the strip but it is launching pretty well

I am using all mechanical advance racing HEI from Accel - (never tampered with advance mechanism)and pump gas

I want to get 12's N/A and 11's on the bottle hopefully with no more than 150hp jets - I dont trust going any higher on my pistons

How does it look so far and how can I improve

89gta383

iTrader: (5)

What's with your 60 ft time, did you hook up with the slicks or not?

Play with your jets and timing and see if you improve. Try and swap on sombody's 750 and see if you get any more power also.

IHI

iTrader: (1)

I'd be ditching that Edelbrock for a Holley DP in at least a 750cfm size or a 950HP. I dropped .4 last year switching from a Holley 750 VS to my Holley 830DP. You got the gears, but your 60's seem a little slow for your set-up. And after going back and reading your sig again, I'd say that y pipe single exhaust is'nt helping your cause either, but that's my opinion. Your combo should not need a shot of juice to see 60's in the 1.7 or high 1.6 range. Play with your timing, most the motors we've been tuning at the strip are liking around 40 degrees total timing with no pinging problem or hard starts.

1983Z28

I agree with IHI.

My setup is very similar to what you are running but you should consider going to the 750DP and 1 3/4" full length long tube headers.

Prior to going with the 4" exhaust I was able to run the same time (with open headers) as I am running right now.

1983Z28

I forgot to include my setup:

355 Dart II iron heads 66cc ported and polished 9.5:1 compression, Harland Sharp 1.5:1 roller rockers, KB Hypereutectic pistons, 6" steel rods, Victor Jr, Holley 750 DP, Engle Solid cam .520"I/.536"E 108 LSA, MSD Digital 6, MSD 8461 dist, Hooker Super Comp long tube headers, 4" Mufflex - no cat, Spohn Torque Arm, LCA & Panhard Bar, welded SFC, 350 THM 3000 Stall, B&M Megashifter, Currie 9" 3.70

0-60ft 1.742
1/4 mile 12.747 @ 107.7

AlkyIROC

Stay away from playing with the NOS for a while until you decrease that ET N/A. Timing can make a huge difference with ET. What's the timing set at now? Bump it up 2 degrees on each pass until the ET slows down then move it back to when you had the best ET. 4-6 degrees off what the engine likes can make a huge difference in HP. Advancing it until it pings then backing it off a few degrees is "NOT" the best timing for the engine. The best timing can be a long way from the point of pinging. Once the timing for the engine is determined, it never needs to be adjusted. If you're concerned about timing when using the NOS, buy a timing retart system that's activated when the NOS is used. A 100-150 shot usually doesn't need the timing adjusted.

You may have to play around with the distributor for more than just adjusting the timing. Adjusting the initial timing also increases the total timing. You should be at full advance before 3000 rpm. Bring the rpms up and watch the timing marks. When they stop advancing, you're at full advance and the rpm should be noted. Initial advance is only a base line. If the car doesn't crank over very well because the distributor is too far advanced, you either need to have the distributor recurved or get a start retard. My distributor is locked out at full advance. I don't need a spark curve in a race car. My timing is locked at 36* (BBC don't need a lot of advance) and I have no problems starting the car but I have a starting spark retard just in case.

A 750 or 850DP will really make a big improvement over that tiny 600.

Any sort of drag racing and "pump gas" still means the highest octane you can buy. 91 or 92 should always be used especially when playing with NOS. Pump gas as 87 octane is not considered performance fuel even for a low compression engine. My 454SS truck is only 7.9:1 compression and runs better on 92 octane.

Another thing to check is to make sure the carb's butterflies are opening all the way. Have someone sit in the car and push the gas pedel right to the floor. Look down the carb and check to see where the butterflies are. Many times when a carb is changed, the position of the linkage/cable isn't always the same.

SLP IROC-Z

iTrader: (1)

those slicks are wayyyy to tall man. u should be running 26" tall slicks, 28 is gonna slow down ur car big time.

IHI

iTrader: (1)

Normally I might agree with this, but after running 26" x 9.5" last year and 27" x 11.5" this year-was gonna go 28" x 11.5" but figured that'd be too much for my gearing/hp so I split the difference. To my surprise my 60's dropped into the 1.76-1.79 range with the 3.42 gears, go figure?! If he were running the 4.10's like I misread in his first post the 28" would be perfect for a 1/4mi. car. and by actually running the 3.70's he's only losing out on about 600rpm roughly on the big end. But then all the other things would factor in too I guess for finish line revs, so it could be more/less than 600rpm, but I can't imagine much. He's got bigger issues than tire size affecting his combo and lack luster performance. Respectable, but IMO there should be more in it NA and quite a bit more on the juice once it's properly tuned.

caribbean 85

Just to say that I appreciate the replies - constructive advice is always welcome

IHI, I do have dual - meaning dual- 3in exhaust pipes coming off the headers but the left side is curved in front of the oil pan - so its technically longer - the way the y-pipe was configured and the right side header comes straight back leading to the driveshaft well

they intially terminate into 3in flowtech brand exhaust cutouts - I staggered the cutouts so that they are roughly equal length per side - then the duals merge into one just about at the start of the right rear quarterpanel - into the stock after-cat pipe and then to an aftermaket stock configuration muffler

with the cutouts open I went from 13.9 to 13.201 - so I take the point about the exhaust

I do have 4.10 gears and with the 28in tyres I should have a 3.70 overall ratio - which I hope would keep rpm in a good range

Tyres are loaners so I am stuck - I really want to buy a new pair
do you think I should just stick with 26in or try a 27in - split the difference ?????

I am installing a 650DP tomorrow for testing - I will leave the NOS at home and see how my times improve (thats what I can locate right now)

I have had timing problems because I put on an 8in balancer this time and the pointer had to be modified to fit - so I was told by another camaro forum - to measure the circumference of balancer - divide by 10 and mark that exact distance away from my remarked TDC and that would be 36*

I have done so - and she drag starts but the revs are much more responsive - so I moved distributor back a tad - and it still is sharp on the pickup but starts o.k. - I dont have an advance light but I will have use of one on the track tomorrow

Will keep you posted on improvements, if any

IHI

iTrader: (1)

Good luck today, and the 650DP is gonna definately help, but your still gonna come up short on the big end until you get at least a 750cfm carb. Alot of the small block guys at my track jumped up to the 950HP and are averaging .4 with that simple bolt on. Sounds crazy, but to all those that read magazines and take ALL that **** to heart-DON'T!!!! Take those formulas and shove'em. They might be all right for a general base idea for a starting point, but reading, arthimatic will only go so, far-bolt on's actually changing stuff and tryin it is what makes a difference. Let us know how much your 60' picked up, then if somebody has a biggger carb you can throw on, tell us how many tenths you knock off.

caribbean 85

Well guys - changed the carb to a 650 Holley DP

Got the floats sorted out - till it just seeps out the sight holes

took a few passes on Saturday - all the ET times (naturally aspirated) were down from the Edelbrock 600 - I duplicated the timing and air pressure for the 28in slicks as much as possible

best time was a 13.6 @102.98 mph - worst was 14.2 @ 97.6mph

compared to a best of 13.128 @ 102.50 with the edelbrock 60

in 3rd gear I was straddling 4200- 4900 rpm heading through the traps - but 1st gear and 2nd gear were all strong - 60ft was near 2.00 up to 2.2... -

Tried incremental advance up to very near to my 36* mark - still no improvment in ET or 60ft - so I know its not advance that it needs

Turned out that car was leaning out or detonating badly - I cannot think it was low float levels because it never bogged or backfired -

later in the night - after 4-5 passes - mufflers turned white phosphorus looking and plugs were white - so we called it a night

opened up to recheck jets - 66 primary #31 squirter - 73 secondary # 28 squirter

I felt the plugs/headers meant gas starvation and couldn't find any jets to step up on incrementally so I put in

68 primary/ 84 secondary and# 28 squirters all around for


Sunday testing turned up 13.3@103... mph - with new R43ts plugs gapped 0.35" - plugs were checked after and looked perfect

car had a slight hesitation on the way to the track and a whistling sound from the carb under throttle but on the track no flat spots or hesitation of any kind -

3rd gear top end - car steadied at 5200 rpm up to 5700 rpm through the traps

advanced to my 36*mark - 13.6 - confirming advance is not liked by this engine

All the other passes were 13.4 - plugs maintained a relatively clean new look throughout (using local pump gas - not high octane )

I don't like the big secondary jet compromise but it was desperation so I am presently sourcing some other jets -
the 66/73 combo ran well but the plugs/mufflers & rpm tach show that it was not providing enough fuel

what would you recommend as alternative jetting -

IHI

iTrader: (1)

Well being how your running a Victor Jr. an open plenum, your jetting can be off the wall because it all gets dumped into the same spot. My buddy with the 454 Malibu runs 76 up front and 88 out back. If your running really lean try uping the fronts to a 72 as well and see what happens, some motors like the jets squared, and other like them stagered front/back. But if your were THAT lean, WOW you definately need to go up before your pistons go bye-bye and cause a mess of headaches. The old rule of thumb is only go up 2 jets, but if I'm running really lean, I'll go 4 and see what the plugs look like cause you know how much a PITA jet swaps are, not hard, just a PITA!! I'm still bothered by the low 60' times, and if there is any chance you can get a bigger carb to try do whatever you can to borrow it. It will definately help bring the ET down and mph up a little as the tiny 650cfm is kinda small for your set-up. I'll bet it's got gobs of throttle response though.

caribbean 85

IHI, I am going for race fuel next time out - to see if lean has anything to do with detonation also

I am thinking of going square jetting ( I have tried everything else) 73/74 - but will replace the 84 secondary first at the back with 74 and try staggered 68/74 one day & then 73/74 on the next

Part of my 60ft problem is that I can't get more than 1800 - 2000 rpm foot brake stall out of my 10in competition TCI

So I am launching from low rpm & by the time it hits I am slow out the hole

As soon as I start bringing up the revs, the tyres start a slow spin and push me forward -

Also our track is a small operation with mostly imports - so track bite isn't really laid down consistently at test & tunes - only leaidng up to official meets

The tyres aren't new by any means - but the track needs some better preparation for me to have more accurate times

IHI

iTrader: (1)

I hear ya bout the poor traction on T&T. Our track is the same way, on TT most the cars are street cars so the track would rather save the dynabite for race day instead of wasteing it for a few passes to have it gone when the street tires bring the sand up. What is your overall compression with your pistons/and cc of your heads. If your only running your timing at 36* and are around a 10.0:1 compression, 92 octane should carry it without a problem, but then again the "every motor likes different things" quote pops up again. cause the overlap on the cam might not be as much and the true compression might actually be that instead of allowing some to escape when the piston comes up. I would personally bring the primaries up into the low 70's on jets right away and leave the secondaries @ 84, I don't know if the small fronts are gonna carry it on the top end, and don't be surprised if you can find a bigger carb to try that you have to install jets that are bigger yet than what's in the 650-more air coming in more fuel needed to burn. Last year when I foot braked I could only bring it to a max. of 2200rpm and it would start to push like yours, but then it flashes right away to 3600 when the light turns green. Every person has their preference on launch, in my car I've always preloaded it on the line to the same rpm that would'nt push me through since it always flashes at the same point anyways, other guys have better luck leaving it at an idle, then flashing it when the light turns, so don't think by only getting 1800-2000 when staged is hurting you. Without having much traction it's difficult to say what the convertor truely flashes at since it's probably spinning a little, but for my own intrest have you ever looked at the tach when you leave the line and remembered where the needle was at? This is a "good" estimate of what your stall really is since it will hold that number until the car catches up to that point and the needle will start to show a rise in rpm again. A low stall point will be hurting you if the cars in the 3300-3600lbs range, I personally love my current 3500 (actually flashes at 3600) stall, but would prefer to have a 4500 at a minimun in the future. How old-old are the slicks? and are you doing a okay burnout or a really good burn out? This will have a big effect on traction as well, I try not to do a John Force, but everybody knows I like a hot sticky slick for my personal piece of mind and my motor is'nt nearly what yours is, and I have a wee bit more rubber touching the pavement too. This Fri. is aways away, but please keep me posted with what you did and if any improvements. It really is'nt helping matters with this hot sticky weather we're having, but your motors got lots of potential, just need to get a few of the tuning problems worked out. When you say your gonna try these jets 1 day and these jets the next, try taking the jet assortment you have and some tools to the track and swap them out there-the plugs are gonna look the same after 1 pass or 20, so don't be afraid to swap them. We don't have a high tech Holley bowl to catch the fuel outta the bowls, we just cut a 16oz bottle down enough to fit between the intake and bowl, works like a champ.
On a different note we're currently running a new truck at the track, everything was built around the drivetrain that is ment to be in the 10's how low or high yet we don't know. Last Fri. was the first run of it's new career on a TT night, the first pass was a 11.44 @ 121mph spinning to the 330' mark, then the following 4 passes were consistently slower and the short itmes were a terrible 1.80 leaving off a transbrake with a 4800 pill. Very disappointing, but we redid alot of things Mon. and we'll do a few more things before Fri. night gets here, so be patient as good things don't happen right away.

caribbean 85

Thanks for the support -

you know when the performance is not what you expected it so easy to want to go for the quick fix

I have been playing with all sorts of ideas but I will persevere with the 650 for now

As far as day to day running it has been basically set and go even with the odd jets

I keep thinking I should just up the nitro to 175hp and go for broke for one run and hopefully have an 11 time slip to show my grandkids

Will try all the suggested mods to the carb and see where she goes

Thanks again

Trevor

1983Z28

I would not recommend going to 175HP with the hypereutectic pistons. I don't think they will be able to survive many runs with that much nitrous.

With regards to getting your 60' time improved, try what IHI suggested and leave off of idle (do not pre-load the convertor). Like he says, some vehicles work better with the converter pre-loaded and some work better leaving off of idle. Give this a try.

How are you shifting? Do you manually shift it at a certain RPM or do you leave it in drive and let it shift. What RPM does the shifting occur? I have found that I get my best run when I shift at 6800-7000 RPM for both the 1-2 and the 2-3 shift. If I shift at lower RPM's my run can be as much as 0.3 seconds off.

What is your fuel delivery system setup like? Are you running the stock electric in-tank fuel pump?

Take care,
Mike

AlkyIROC

Sounds like you had a good day of test and tuning but when playing with timing and jets, ignore the ET. You're adjusting things for the best MPH since that's what shows an improvement in HP. Once you have the highest mph, that's the most you're going to get out of the engine. Now you start on driveline and chassis to lower the ET.

Square jetting the carb is the way to go for a strip only car. When you square jet it, you remove and plug the power valves. Go up 8 jet sizes and start from there. My alcohol carb is square jetted and when I ran gas, I square jetted that carb also. There was no power valve in the secondaries so the primary one was removed and plugged and the primary jets were increased to match the secondaries (usually 8 jet sizes). Since the butterflies, metering blocks and everything is all the same, why change things by running different jets? In a street car using a power valve it's nice to have smaller jets in the primary and let the power valve provide the extra fuel when required but in a drag car you want to remove as many variables as possible. If there's no power valve then you know the engine will be getting a constant supply of fuel all the time.

The downside of square jetting is that you need 4 jets of each size when doing a jet change. That means having to buy 2 jet kits. I have a lot of jets in the 64-99 range and they're all too small for the alcohol carb.

caribbean 85

Stephen

I will try upping the primary first like IHI suggested on my way to square jetting - funny you mentioned that because I have access to a number of low to high 80's and up

1983,

I shift at 6500 1-2 and just about 6300 in 2-3 - I am always wary of my 2-3 shift because I have a lag in the time between punching the megashifter and the gear hitting - which does take it up to 7000 ( my msd limit ) before it hits

I am using a Holley Blue pump and #6an braided lines and fittings straight out "top" of stock gas tank with 5/8" copper line into spare wheel well where pump is mounted on spare tire brace

Will keep you posted on the jets changes this weekend

caribbean 85

I have since taken all the tips here and decided to up the primary jets on the 650DP to 74 with the 84 remaining out back

I also forget to mention that the carb was modified before I got it with a 1:1 link linkage arm

Owing to my first gear 3.06 700 r4 + 4.10 rear - stumbling/too high jetting at low rpm issues even with these seeming heavy jets never happens

I took it down to the track but however did not have slicks this weekend and ran on my 16" IROC Z rims with regular radials

could not leave the line without fanning 1st gear but I think the car felt very strong on the top end - got 97 - 98 mph on a 2.0.. 60ft

so i am going to try the slicks later this week and get some real times

will keep you posted

trevor

IHI

iTrader: (1)

Good idea on the slicks, hard to tell for better/worse of your changes when ya go up in a blaze of glory at the line.