compression test today

[nutxo]

Welp, got a compression tester yesterday, gonns do the test today.

Im almost afraid to see the results.

On the flip side my neighbor just dumped a 307 on the alley, in good shape, Im wondering if its a sign from god to nab the crank and build the holy grail of all small blocks, the chevy long rod 350,..

[nutxo]

just got done, most freakish results ive ever seen

1- 120psi

2-120 psi

3-120 psi

4-122 psi

5-120 psi

6-122 psi

Ive got to admit Ive never seen the inside of an engine so clean, the oil looks like its a brand new engine, clean and clear. The plugs get a little black but i think thats a rich condition. Theres absolutely no smoke EXCEPT when I very first romp on it when i get on the freeway in the morning.(thats very white smoke, and very little) I burn no oil.

In addition to that I have no problems breaking traction even double clutching at 25 mph, serious wheel hopping and rear end banging around.

Did this engine just wear perfectly even or is there another issue that could cause this?

[texasz]

nutxo, off topic a little but since you mentioned it I must know. What is double clutching??? I've heard the term before but never know what it was.

Now on a similar note, my compression readings are 120, 120, 120, 120, 40, 120 (give or take a few, it was done a couple months ago and I don't remember the exact numbers). So except for that one cyl the car seems to have worn evenly much like yours. The low cyl is a ring problem, we poured some thick oil in there and the compression jumped in like with the others or better.

[ZmeFly]

well if you have a 240Z then your compression readings are a bit low. have you adjusted valves and retested. thats something i would do.

also on the white smoke is it thick or thin, if its thin and more grey to me that sounds like unburnt fuel.

id adjust vavles and see if you get a better reading on compression, then maybe advance the cam, also while your in there once your sure everything is good, valve adjust compression, check your timing as well too.

then adjust your carbs and see what results you have when all is right.

[nutxo]

Originally posted by texasz

nutxo, off topic a little but since you mentioned it I must know. What is double clutching??? I've heard the term before but never know what it was.

Now on a similar note, my compression readings are 120, 120, 120, 120, 40, 120 (give or take a few, it was done a couple months ago and I don't remember the exact numbers). So except for that one cyl the car seems to have worn evenly much like yours. The low cyl is a ring problem, we poured some thick oil in there and the compression jumped in like with the others or better.

double clutching

if ya dont wanna just sit and spin yer wheels off the line hit the clutch again, grab traction and bring it up to like 4k -5k and pop it again

[nutxo]

Originally posted by ZmeFly

well if you have a 240Z then your compression readings are a bit low. have you adjusted valves and retested. thats something i would do.

also on the white smoke is it thick or thin, if its thin and more grey to me that sounds like unburnt fuel.

id adjust vavles and see if you get a better reading on compression, then maybe advance the cam, also while your in there once your sure everything is good, valve adjust compression, check your timing as well too.

then adjust your carbs and see what results you have when all is right.

its a 76 280 FI

I did the valves a few weeks ago but i guess i can try it again. the timing thing has been kickin my arse, it doesnt seem to wanna run right in time,.ill try again tomorrow mebbe. thanks for your input.:classic:

[ZmeFly]

well its still a little low, id try advancing the cam might bring it up just a bit.

now that i know its fi, and you cant get it timed right or running to well the next thing i would check for is vacumn leaks. look hard and long and double check and double check again.

they are hard to find, just make sure you go over all your hoses with a fine tooth comb

[texasz]

Mine is a 240Z zmefly. I'm not too concerned though, I'll be replacing the engine with an F54 block (flat top pistons) and N42 head soon.

Double clutching sounds tricky and like something you must practice a lot to get it right. It also sounds very hard on the car, the clutch especially.

[christ0ph]

That's funny, double clutching (to me ) is entirely different. To me, double clutching occurs while shifting ( up or down ). I suppose another name for it would be rev matching. See the way I learned of double clutching, it goes something like this: First you clutch in, then bring it into neutral, clutch out while still in neutral, blip the throttle to match revs, clutch back in, go to your desired gear and let out evenly. This is used when your synchros are pretty much gone, or in the case of big trucks or older cars, that don't have synchros, you must do this in order not to grind every gear. I use it mainly to get smoother shifts. Anybody have a different definition?

[ZmeFly]

explain it any better then that:cheeky:

[Ben]

Double de-clutching is as christoph said: instead of depressing the clutch & changing into the desired gear, you change into neutral, rev to the appropriate point for the next gear and then clutch in, and make the final change.

Rev matching is the next-best thing - clutch in, match revs for the next gear/shift clutch out.

Double de-clutching is used in gearboxes that have no synchros (crash boxes), and is also used with dog-boxes (which have dog-rings instead of synchros). A dog box must be shifted like you want to break it, or you will break it!

Gearboxes with dog-engagement are used in high-power applications where normal synchros would fail.

All the Datsun L-series boxes have full synchros on all forward gears (Porsche or Borg-Warner), so double de-clutching should not be required for smooth shifts.

Gearboxes with Quaife, Hollinger or OS-Giken gearsets fitted are a different matter....