Just got back from the dyno and not very impressed... Its a 355 9.5:1 comp., comp cams xfi 224/231 113lsa hydraulic flat tappet and .488 lift with reccomended valve springs, hsr intake, k/n drop ins, stock tb, flow balanced 24 lb injectors, 1:5 rockers, gm cast heads 1.94 and 1.5 valves ported and bowl blended. Not sure on the casting #s, i think they were 880somethings. The shop said they were an old heavy but good flowing head and he was shooting for 240 cfm after the port and blend job. and 1 5/8 headers and microtech maf sensor. It dynoed 242 rwhp and 278 tq. The shop that built the engine was shooting for 375+ at the crank which even figuring a leiniant 25% drivetrain loss is around 280. My brakes are not dragging and my transmission is in ok shape, not the firmest but not slipping. The only thing is they did the dyno tuning with open headers and he said the o2 sensor is not reading 100% without the pipe to hold the heat in but i dont see a loss that large and the tune will be touched up after the exhaust is put on tommorow... What is wrong here or are those heads simply holding me back??? Both shops are pretty reputable and the guy doing the tuning has customers all over the US. There is no smog equipment on the car, no ac, just the alt, water pump, and power steering. The shop the built the engine didnt want to go with the big valve heads saying it would loose throttle response and the hp gain wouldnt be worth it, and I wont lie there it is very crisp and snappy but these dyno numbers seem very low compared to all Ive seen on here...if it makes a difference it was a 305 car but i did change the knock snesor and esc module. Were we shooting to high or do you guys see a problem here??? Any help is much appreciated, thanks....

 

Also the ign system has all been replaced for the hsr swap its an 86 so it has a new small cap dist, new coil, new wires, and new plugs... And not sure on the brand of the dyno but he said most 3rd gen stock 350s put down 160-170 on his dyno...

 

My first question is did you ask what was done in the tune? The mod's you're listing would need some tweaking of both the fuel map and spark map. Rockers are adjusted right, meaning their not too tight?

 

the heads and cam might be holding you back a bit. And how was the tune??

 

Stock L98's put down 160-170 there??? most put down 215-230 depending on the L98. I'd say his dyno reads very very low.

240whp on that dyno may be closer to 280-290 on others. The biggest thing right now is to check how it runs at a track.

Or find another dyno to compare numbers. But the track times wont lie. IF that car traps well over 106 mph, you know its got the power.

Even with open headers, the o2 sensors (wideband sensors for dyno tunning I"m assuming) would read correctly under load. At idle they may read way lean due to fresh air getting in there but at WOT they should read the exhaust well.

If you were to go with a good flowing 2.02 valve head, you would make a bunch more hp and torque overall. The compression is abit low for an aluminum head so if you upgrade to aluminum get a slightly smaller combustion chamber...60-62cc or so.

 

I agree, I'd track test it as dynos are.. dynos.

However, I'd still throw the heads and cam in the scrap pile. I can never understand why anyone would rework old GM junk when you can buy good heads for around $1300, and even kinda stinky chinese heads for under $800 that blow the reworked GM castings out of the water.

You can make over 450hp out of a 9.5:1 355 all day with the right parts.
Building a motor takes the same amount of work with the right parts as it does with the wrong, so better off do it right the first time.

Maybe I'm being harsh on the cam, but I'd be looking at 112lsa on a 108 centerline for an EFI motor, 110lsa for carb. 113-114lsa maybe for a turbo.

-- Joe

 

I dont know what he has done as far as the tuning... changed the chip or prom and did drivabilty and dyno tuning is what the reciept says. I do know he has worked on alot of cars like this and there were 2 others in the parking lot with more mods than me that he tuned. As far as the heads go the shop that did the engine assured me that he would make them flow plenty to support the intake and the cam, and the car needed alot of work and i had already spent enough money on odds and ends that the extra $$s for the aluminum heads was outta the question... and the cam was picked after a discussion with the owner of the engine shop and a rep for comp cams. Also I dont have a racetrack within 2.5 hours off me, so track testing is limited and another dyno is just that far away too... I was just kinda shell shocked by that low of numbers and i thought i had read of people getting way better results with cast heads. or89rrocz if what you said about higher numbers maybe his dyno is just low?.? I thought that was all these cars put out at the flywheel...But you guys definately have more experience and knowledge when it comes to these cars than me so im all ears...

 

Put it this way, I have the dyno printout to prove it. My 91 Z28 with a 30xxx mile L98 (350) with EdelB headers and an airfoil in the throttle body made 232 rwhp and over 300ft lbs before 4000 rpms.

I'd have to look at a few things with your scenario, the accuracy of the dyno and the tune.

 

You could buy a $60 ALDL cable and connect to the ECM and download the PROM / BIN and find out exactly what the "tune" consisted of. You would need access to a laptop computer, an ALDL cable (buy or borrow) and some free software. The DIY PROM board could help you learn what your tune was.

 

I am not sure about the readings, but my lame stock 1986 LB9 puts out about 170 rwhp which seems to agree with what the dyno operator reads.

 

Good idea, he just needs a cable, a laptop, and free Tunerpro to grab the bin file, post up in the DIY and I'm sure people would have comments as to how your modified bin/tune compares to a stock bin/tune file.

 

ALDL wont grab the bin but the datalog can tell what timing you are running. To grab the bin you would need the chip burner/reader assuming the dyno shop used a moates like adapter and typical burnable chips. I dont know any other way to do it.

My L98 with just headers/exhaust put down 200whp with EST wire disconnected! ran 14.0 at 94 on that setup. I adjusted base timing to 8 deg and FORGOT to put EST wire back in. No wonder car felt slower. Popped it back in and went 13.63 at 97mph. Thats a good 230-240whp with STOCK tpi and just exhaust mods.
They were rated at 230 but its well underated. WHP is typically 215-220 for these cars.

Do you have any dyno numbers from any of the other cars there, and their mods to compare? Did the dyno shop feel your numbers were acceptable?

If they were shooting for 375 and assumed 20% loss for 280whp, and didnt get close to that, then that would raise a red flag that something is wrong here. L98's doing 160-170 whp is a red flag already. Dyno may not read correctly. My bolt on L98 ran 12.95 at 103.8 mph with 254whp and 315wtq. MOST days it ran low 13's at 100

Also, do you have a higher stall converter in the trans? Was it locked up on the run or did it stay open? Locked will gain 15-20whp sometimes over open converter.

Considering this shop has done many other cars like this they probably are ok at tuning. MAF cars arent all that hard to do anyway and your setup should be dialed in.

Does the car feel strong? You could by a Gtech meter and do some 1/4 runs to get an idea what it would do. Not totally accurate but can be a good indication.

 

Not true. There is a command sequence in the 1986 up TPI code to dump the bin via the ALDL. The command dumps according to the base address and range given. I am not sure if TunerPro supports it, but I know other packages do. I think I read the newest version of TP supports all the commands so it should dump the bin.

 

Really? Thats VERY Interesting to me, because I was having problems reading a friends current chip tune with my burn programmers. I COULD connect ALDL and did a datalog. If I can get his bin from ALDL that would be awesome because that car runs hard but is pig rich at WOT! He's gonna be happy when I get it leaned out.

 

Moates used to have a MS-DOS ALDL scanner with the command sequence built in. It is probably still downloadable at his site. Could also ask if the latest version of TunerPro has it built in or how to send the command sequence.
If you read the code you can see all the features that GM put in there for debugging. There is also a mode where you can play with AFR / fuel and stuff on the fly via ALDL, BUT you can't save to the PROM of course. It is only good for that session. If you go with the MonteCarSlow module (Moates sells it) you can program and tune on the fly via the ALDL and save to the PROM (really NVSRAM). This only works with the 730/749 ECM and requires a code patch. Last I know it was only in the $8D code, but maybe the $59 guys added it by now.

 

There will still be a problem when you program(write) the chip and try to read back for verification. You may have to program, install in car, read back via ALDL, and then do a file compare with MS-DOS "fc \b bin1.bin bin2.bin"

 

When I open up the datalogging feature I see quick command options and I see it has Mode 1 ALDL Dump request. Not sure what that is. This is the first time I heard you can read the bin thru the ALDL port. Not to get off topic but if the OP can do this, you can see whats in the tune to be sure the car isnt doing something weird. I would think the shop did everything right since they are tuning alot of these cars but you never know.

 

The way I look at it is this: A person spent a lot of money and know what is in the engine so why not know what is in the ECM too. One reason I am not a fan of dyno operators is because they try to mystify the job like they are doing something no one else can. In reality, just poking numbers at a keyboard. I will not say any names, but I do know of instances where a tune was just throwing in a new fuel curve and spark curve that was a generic tune and not for the specific engine.
From memory it is Mode 3 or 4, but it has been a while. A search at DIY PROM should bring it up.

https://www.thirdgen.org/forums/diy-...ig-moates.html

 

like said before a dyno is a dyno. they are tuning tools only and not the final word. with the push of a few buttons they can make it read what they want. i have been on dyno's and had a good friend show me a bunch on one when my old truck was strapped to it. it only showed 450hp at the wheels with a 175 shot of nitrous. and this was in a 5100 pound truck and it ran low 12's. dont believe all dyno's. as a matter of fact i will not believe any of them as final word. i always have and always will use them for a tuning tool only.

 

Every time I think of putting something on a wheel dyno I end up at the track instead. I look at it this way.......it is a night of fun, $20, and 1/2 tank of gas.
Like you said, they are fine for tuning but the numbers don't mean all that much. Just a another number. I can get that info. from the ECM in the vehicle with similar if not better accuracy.

 

The car seems pretty strong to me but I bought it several months ago with a very very tired 305 (several broken rings and warped valve seats) so its pretty tough to compare the two... I wasnt quite as impressed with the pull as i had hoped to be but its not doggy by any means and has no trouble spinning both back tires on dry pavement all the way through first and 2nd if the shifts were firmer. As far as the tranny goes like i said i just bought the car as far as i know its a bone stock 700r4, and i dont know if it was locked up during the tuning... I dont know how much more loss to be expected from a tired tranny either it didnt seem it at first but the more im driving it you can definately notice lazy shifts and whatnot.