Compression Test

[jonszr1]

does altitude make a difference in the readings ????

[Sgreg]

Originally Posted by jonszr1

does altitude make a difference in the readings ????

Only if you are smoking a funny weed.

[flyin ryan]

Originally Posted by Nick

Interesting comment, Ryan. Mine are as follows (with 70,000 miles on the clock; test done per the '94 service manual):

#1: 220
#2: 220
#3: 215
#4: 210
#5: 215
#6: 210
#7: 215
#8: 215

I'm not so sure the numbers themselves are that important. What is important, at least to my mind, is the consistency between the cylinders. But, Ryan, you would know more than I!

Well...when i build an engine from scratch, i always shoot for between 165-185 pumping comp., if it's a maximum effort combo like Super Stock or Competition Eliminator it will get up to 200ish, but those have around 15:1 static comp. ratio too. it's all about balancing out the comp. ratio & camshaft(s), for me. i'm doing a, call it 'serious', comp. elim. engine right now, 358 cube & will be right on 16.2:1, so guys might think well it's going to have a pump. comp. number that's through the roof but this will also have a cam around .970" lift on the intake & 277º@.050" on the Int. & 295º@.050" duration, lobe seperation is 115.5º also. so what it's going to do is bleed off a bunch off cylinder pressure. now of course what we are talking about here is an engine that's turning over on the starter, what's happening, at 10,200 RPM, on this Comp. engine i'm talking about for instance, is a completly different story for another day. also... if i get close to 200 pumping on a good street deal that's say...1.5 HP per Cube, i'll be looking to put in a slightly, for lack of a long winded explanation, 'larger' camshaft to help bleed off some cylinder pressure. i guess an LT-5 could have that kind of cylinder pressure, it does theoretically have 11:1 Comp. ratio from the factory & the camshaft's are teny-tiny, IMO. if those cylinder pressure numbers are pretty close to what they are supposed to be from the factory, i'd have to say the knock sensor must be working overtime under light 'load', not at 'RPM' but lower RPM grunt situation's. Nick's car with his milage & those numbers must be in range, cylinder pressue is never going to go 'up' once an engine is broken in. Lee's on the other hand, that has some 240 numbers...well that's getting crazy high at that point. i'm assuming all the guys the posted here are cracking/opening the butterflies & have all eight (8) plugs removed when pumping. generally five (5) revolution's is the number, even when NHRA P&G's a competitor for cubic inch, (Pump & Gauge), same thing, five. i always measure one (1) pump, reset, then do five (5). both numbers can mean different things that help me.

[jonszr1]

Originally Posted by Sgreg

Only if you are smoking a funny weed.

hehe, guess i better retest without the additives .jk

[Nick]

Originally Posted by flyin ryan

i'm assuming all the guys the posted here are cracking/opening the butterflies & have all eight (8) plugs removed when pumping. generally five (5) revolution's is the number.

That's exactly what I'm doing, Ryan, except butterflies wide open. Also, the crank sensor is unplugged during the test.

[LGAFF]

I will retry the test this wekend with a warm engine, etc.

[Pete]

My research has found the 4 valve is more efficient then 2 valve motor.

LT5 makes 1.5-1.6hp per inch (550-575chp 350ci) idles (750) and drives like a stocker on punp gas,very well mannered.

Don't get me wrong i'm not saying the LT5 is a better just pointing out they are 2 different beasts,build for different purposes.

I have a question can we build a 358 that can be street driven i.e. (traffic,grocery store,pump gas) idle ok and make 750chp or 650whp?
How much?
You can PM/email me or post here.

Pete

[flyin ryan]

Originally Posted by Pete

My research has found the 4 valve is more efficient then 2 valve motor.

Ya that's no secret for sure, but they aren't more efficient than the Comp. Elim. engine i was using as an example, that's why it will make 2.6 HP per Cube. again...not a street deal at all & again, it was just an example, wasn't intending to directly compare the two 'styles' of engines.

[flyin ryan]

Originally Posted by Pete

I have a question can we build a 358 that can be street driven i.e. (traffic,grocery store,pump gas) idle ok and make 750chp or 650whp?
How much?
You can PM/email me or post here.

Pete

Define your idea of 'idle o.k., LOL. honestly you'd be better of going to something with more cubes for a street deal, IMO. at 358, it would have to see some RPM, then you get into expensive valvetrain pieces. 750 HP is 'A LOT' for a 23º type head deal, i've done it on pump gas, but it's a lot, everything has to really well sorted out. 600 HP is one thing but 750? well that's a completely different animal. don't know if that's what you want to hear or not but i'm not going to B.S. you

[diamond zr1]

put it on the juice like Kevin