I bought a 76 LT type for my son a few weeks back. It has been rebuilt' but I am not sure what cam, if any, or what bore changes if any. I was thinking it might be time to seek a dyno.

Question is, what do they do at dyno shops? Will they fine tune it and give me a benchmark of where the ignition timing should be set- I mean the engine has been rebuilt by unknown parties, so when it is time to tune it up I need to know what it needs to be set at? What all should they be able to tell me? Are these shops generally user friendly, or are they mostly performance snobs?

Ed

 

[8D] ed the experience you have at the dyno shop will be uniqe to each shop. some may be willing to do necessary mods or adjustments while others may just perform the dyno "pulls" and simply provide the info from them to you and you will have to make necessary adjustments. i suggest you do some shopping by phone first and ask a few shops what they do for thier dyno fees and wheather or not other services are included and or provided for additional fees or not

while simple dyno time can be a tuners ultimate test, i dont think its necessarily the best money and time spent for the weekend rodder who is simply trying to tune or dial in a newly assembled motor. dyno time usually starts in the couple hundred dollar range ( dont get me wrong it is the best and a fun way to go if you dont mind spending the money) but most tuning can be done in your driveway by checking the sparkplugs and listening to and feeling the engine during a series of test drives.

the info you seek that will be provided by the dyno shop will usually be torque and horsepower over the engines rpm range. its then up to you and or those you chose to interpret that info to make necessary changes in the search to pull all the hp and torque out of your combination. the shop will most likely , based on thier experience, be willing to give you some free advice to improve your numbers.

dont think of dyno time as a one time thing ( it can be if you bring the tools necessary and the changes arent too drastic) its establishing a base line and then making changes, can be as simple as a timing change or a different carb or changed jetting, to improve your numbers. remember you then get to do another run or visit to see what differences or improvements your modifications have made.

as a start your timing will depend on your engines specifics but as a good rule for chevy motors around 4-6 deg initial timing with no vacuum to distributor and around 36 deg total by 2500-3000 rpm for mild to moderate motors.

if you have more questions hit us up here or you can pm me kurt

 

Kurt, Thanks for responding. I don't mind doing the work myself. I just though I would be better off if I had a baseline for the necessary subsequent tune-ups. I have purchased a timing tape- Mr Gasket, I think. I bought it a few years ago to run numbers on my wifes 351 cleveland. I have not got around to the planned mods yet though. The bit I found that sounded intimidating was the part where on-line advisors would say: "Just be sure to get it all in by___RPM". I don't understand this term. Since you used a similar term, could you please explain it. My C20 truck has a 350 crate that I put in a couple of years back. No mods and straight forward 4 degree at 600RPM idle. I did put a 600cfm 1406 Edelbrock on it and feel the jets and needles are about right. I am a fairly decent mechanic; but I have not wandered too far from book specs... I'd like to on this camaro. "all in by..."?

Ed

 

ed the distributor has the ability to not only control the amount of timing and where its set at but how fast or soon its increases it relative to engine rpm. most tune ups include a base timing setting and on a stock engine and parts thats all you usually need to worry about, unless the timing isnt advancing at all in which case you will see a lack of power and poor mileage usually from stuck fly weights in the distributor. for modded motors and stock and aftermarket distributors you want to get the most power possible out of the motor without destructive detonation and this is where paying more attention to the timing becomes more critical.

most distributors use vacuum and or mechanical systems to increase timing advance as rpms increase, this has a large effect on the power output of the engine and is every bit as important as air fuel mixture. the mechanical weights in the distributor can be modified or replaced to achieve a timing curve that matches the engines parts and its intended purpose. as a basic rule you want as much timing as possible without causing detonation ( pinging) so being able to tailor your ingnition advance curve thru the rpm range will produce the maximum power.

at the end of this timing curve , maximum advance, you want to see at you primary operating or power producing range. this depends on your engine mods but you want "all your ignition timing in just before this range, ALL IN BY" so with this in mind you can see that with a stock or mildly built engine you will set your dist at around 4 deg BTDC at idle and 36 deg all in by 2500 rpm or so. as this is the range the engine can take advantage of full timing and power production

there are as many variables on this as there are people with opinions, auto or manual trans, stall speed of the torque converter, rpm range the engine was designed to operate in, nitrous. most mods are designed to increase power and in order to do this you must move more air thru the motor this in turn means a higher rpm operating range and thus a different ignition curve will be required. this is where the testing and tuning come in and will only come with experience so get out and play with the timing light, try different settings and see if you can feel and hear the difference and how the engine feels.

avoid DETONATION ( pinging). your 600 cfm carb is the perfect choice kurt