[v8hed]

When I have my engine dynoed to break everything in and do some power pulls, I'll be testing a couple of different intake and carb combinations in addition to the usual jet changes, ignition timing tweaks, etc. I'm just wondering... who would normally be responsible for swapping parts out? The customer who's engine it is, or the dyno operator? I had assumed (without really thinking about it) that the swapping of parts and the changing of jets would be done by the dyno operator all as part of the price you pay for a 'dyno day', but now I've thought it through, I'm not so sure.

[sjkonyndyk]

I had mine chassis Dyno'd. We were having a problem with preignition, the operator asked if I had Platinums (OEM PLugs) in it I said yes, he told its 100 an hour if I do it. He handed me the plugs and the tools and cracked a soda, I wrenched it out and he was back on it in 30 minutes.

It depends I'd call and ask. I had 10 pulls on my motor and it costs me 200 bucks with programming (fuel injection).

[cobalt327]

I would expect to do it myself, w/the possible assistance of the operator- but that's definitely not a given.

I also think giving them a call and discussing it will be the best bet, along w/whether or not this is by the hour, by the pull, or exactly how the charges are figured.

I would also request they immediately abort a run if suddenly things take a turn for the worse.

Recently a member was having his engine dynoed and got a printout that showed the HP/TQ peak occurred at the hit of the throttle, then went nose down from there. Turned out he had a broken valve spring. But the dyno op went right on ahead, running it out to 6800 RPM! before the run ended.

This could have EASILY cost him an engine. I suspect the pull was computer controlled to increase the RPM at a given rate until the end of the run, and he just let 'er rip, ignoring the fact that the power dropped the whole pull.

10 pulls for $200 w/pauses to program is a killer deal, IMHO. I hope you can do as well.

[v8hed]

Originally Posted by cobalt327

I would expect to do it myself, w/the possible assistance of the operator- but that's definitely not a given.

I also think giving them a call and discussing it will be the best bet, along w/whether or not this is by the hour, by the pull, or exactly how the charges are figured.

I would also request they immediately abort a run if suddenly things take a turn for the worse.

Recently a member was having his engine dynoed and got a printout that showed the HP/TQ peak occurred at the hit of the throttle, then went nose down from there. Turned out he had a broken valve spring. But the dyno op went right on ahead, running it out to 6800 RPM! before the run ended.

This could have EASILY cost him an engine. I suspect the pull was computer controlled to increase the RPM at a given rate until the end of the run, and he just let 'er rip, ignoring the fact that the power dropped the whole pull.

10 pulls for $200 w/pauses to program is a killer deal, IMHO. I hope you can do as well.

Yea, I'll discuss it with him when I call to book it in.

This guy is a race engine builder with an excellent reputation, so I very much doubt he'd be negligent on the dyno.

What did worry me was that I'm running Comp 987-16 dual springs with a solid FT cam and I said to him I assume he recommends leaving the center spring out for break-in. He said no... install both springs as normal... he's got amazing faith in the Joe Gibbs break-in oil he's using these days. However, everything I've read (and that INCLUDES an article on the Joe Gibbs site) says to remove the center spring during break-in. Kind of a tricky situation because I don't want to upset the guy (who I had assemble the short block and I've turned to a few times for advice) by implying I don't trust his professional judgment (he's built 500+ race motors over the years), but I also don't want to take any unnecessary risks with the cam. Still thinking about how I should handle that one diplomatically.

Oh, the rate is for more-or-less a full day on the dyno and he's quoted around $600-$650 + fuel & oil. Remember, I'm in the UK, so that might sound expensive to you guys.

[cobalt327]

Who's got more to lose in this situation- you or him?

Sure, it might tweak him a touch for you going by your own instincts, but if he's truly a pro, he should understand that there is more than one "right" way.

The only real 'gotcha' I foresee is whether it will cost you either dyno time or dollars to extend the session long enough for you to reinstall the inner springs. But if you have a day's time, it should be up to you, as to how you use that time.

Remember- it's your call. Be firm but polite w/any request, and I can't see it being a big issue. I mean, it's not like you're asking something unheard of, or lame- it's a legit (IMO) request.

[richard stewart 3rd]

Hi
Unless he's using a set of low-ratio break-in rocker arms, I'd take the inners out regardless of what he says. I'm assuming this is mostly a street car. (not a race engine that will be torn down often) Proper break-in is what will give you maximum cam life. Breaking in the cam with both sets of springs on, well the lifter doesn't turn as well & this doesn't allow the lifters to establish rotation and develop a good wear pattern. Proper flat tappet camshaft set-up and break-in are keys to how long a camshaft will last.
Good luck with it,
Rich

[F-BIRD'88]

If someone else does the wrenching for you ,you should expect to pay them for their effort and time.

[4 Jaw Chuck]

Break the engine in outside the dyno, it would be a huge waste of money and time doing this on the dyno. You will need all the time getting other things right and making pulls to get it dialed, thats what you use dyno time for...not break in.

Besides you can break it in anywhere, it doesn't need a trans to drop into the chassis temporarily to hook up the electrical and get it rotating...its only got to run for 20 minutes at 2000rpm to break the cam in and your ready for the dyno. You can use a jack to support it from the back to hold it up in the chassis and using the stock engine mounts hold it down...you don't even need to torque the bolts!

Spend some time to do this part ahead of time and you will thank me, the time you spend on the dyno is invaluable and always seems too short...spending it changing springs to break in a cam is a huge waste of time. I agree do it with just the single springs...just not on the dyno. Besides you will need to change the oil etc.etc.etc.

Bring the motor to the shop just before closing the day before ready to rock and roll with parts you may want to try at the same time. This way you can bolt in on and be pulling in an hour or so drinking coffee and watching the readouts...bring a friend who can wrench and two sets of tools...double check each others work before the next pull...bring extra gaskets for everything including the headers. If your running carbs bring lots of extra parts (at least three power valves!) and if you can an extra carb just in case. Don't forget three sets of plugs (pregapped!) and a couple of rotors/caps, you know how many times I forgot to clip down the cap and trashed a cap and rotor on the dyno after swapping an intake in a rush...you don't want to know!

Lots of ways to skin that cat, be prepared for the day it happens...the last place you want to do menial tasks is on the dyno. I wouldn't assume the operator is going to lift a finger to help you other than hand you tools and point out obvious mistakes...he's there to run the thing and make sure it makes a good solid run without overheating and destroying your investment. Don't forget you will need time in between runs to discuss the results and plan a course of action before the next run, that can take as long as changing the parts to make it happen.

A cooler full of drinks and sandwiches wouldn't hurt either, it should be fun not scary! I used to bring the wife/girlfriend to make runs to the store for food or a local supplier to get whatever necessary, I sent her on three separate occasions for oil...I don't know why but I always forget to bring oil...mental block on that item for some reason.

[SSedan64]

That's some great Info 4Jaw. Definitely not your 1st Dyno Dance.

[v8hed]

Thanks for all the advice

I definitely want to break the cam in on the dyno for a few reasons...

1) The dyno shop also built the short motor (incl. cam install).

2) If anything happens on 1st start (or shortly thereafter), I want it to witnessed by those that built the short block both in terms of onus of responsibility and being in the right place to address any problems and fix them.

3) The shop is extremely experienced and is always rushed-off their feet with engine builds for race teams (can hardly move for engines on stands), so I'm anxious to pick-up as many 'tips of the trade' and words of wisdom as possible while I'm there. As the cam break-in is so critical, I'd rather be surrounded by experts than on my own.

4) AFAIK, the rate I've been quoted is a flat rate where the dyno room is booked-out for the whole day, so 30-mins to 1-hour for breaking in the cam / swapping springs isn't really significant in the big picture.


Taking refreshments is a good idea... including some snacks/soda for the guys there... as well as being friendly, it might make them just that little bit more forward with advice and help

Low ratio rockers is a good point I hadn't considered... I'll ask them about that. My pushrods will be set-up for 1.6 rockers, but I guess 30 mins running with a low ratio set won't hurt anything in terms of the rocker sweep being off for a short while.

Would any professional dyno shop be expected to have the tools to swap springs with the heads on? I'm positive the answer to that must surely be yes... I kinda don't want to ask that in case it insults the guy... bit like asking him if he's got a torque wrench!

[richard stewart 3rd]

Hi,
Just bring your own tools to change the springs & everything else. I myself don't like to loan my tools, so I don't ask other people to do something I wouldn't want to.
Rich

[v8hed]

Originally Posted by richard stewart 3rd

Hi,
Just bring your own tools to change the springs & everything else. I myself don't like to loan my tools, so I don't ask other people to do something I wouldn't want to.
Rich

Don't you need a compressed air source to keep the valve from dropping when changing springs in-situ? Having said that, the Teflon seals I'm running will prob keep the valves up through friction alone.

[richard stewart 3rd]

Yes, air would be a good thing to have, not just for holding the valve, don't you use air tools to? I use them for almost everything, I even have an air compressor(a big US Army one) in my Ford mini bus(E350) for when I'm working out on the road.
Rich

[cobalt327]

I've never enjoyed the luxury of having an engine broken in on a dyno, but I would sure like to.

I'm sure the dyno at a good shop will have a program(s) to cycle the engine through the break in process- you don't just hold the engine at "X" RPM for "X" amount of time- the engine speed has to vary during the process, and the dyno can induce a load for the engine to "work" against as it cycles.

You will want to try a couple different heat ranges of plugs. Start w/a safely cool plug to break in with. Better to be a touch cold than too hot. Then judging by how they look AFA heat range goes, install a fresh set for the pull.

Same thing for the carb jetting. Go w/your best guess, leaning towards the rich side if anything for the break in. Then, make changes as needed for the pull.

There should be someone there well versed in plug reading and you should expect to get advice in this regard as part of the dyno session. You have a real advantage in having this shop well versed in racing engines and dyno'ing/tuning them.

You need not be so hesitant to ask them about things like if they're equipped w/an air line and plug hole fitting to swap out valve springs, etc. If you don't ask, then your only option is to bring everything you need. ASK if there will be someone there who will look at the plugs and give jetting advice, etc. The last thing you want to do is assume ANYTHING.

And it's OK to be new at this, and for them to know it. Say what you don't know, and ask questions. Hell, they didn't come out of the womb w/all the knowledge they have now, either!

[ap72]

If you're running the springs spec'd for that cam I wouldn't sweat running them with the inners for break in, assuming you have good oil and the engine was built well. You'll be wasting time removing them and reinstalling them, and it takes well over an hour, you can spend half the day just doing that.

Remove the valve covers, remove the rocker arms, remove the locks and retainers, replace the springs, reassemble. BTW, you need something to hold the valve stem in place when you change springs, if it slips down at all it makes installing the locks near impossible and placing all 16 retainers back on without bumping the valve and causing it to drop is not likely.

Also, I'd be sure to run your initial lash a hair on the tight side.

What intake manifolds will you be changing to/from? What carbs?