When I was in college and couldn't afford that buret package, but was playing with SB Chevys I made my own. Took a rigid piece of plexiglas (big enough to cover the chamber) and drilled a 1/4" hole in it, sealed it to the flat surface of the head with grease and used a syringe to measure the CCs that I added until it filled. Use water mixed with a little alcohol to make if "thinner." I've pulled that setup out and used it in the past few years to identify the dome displacement on ski domes too.
PLEASE respond!!
- Thread starter norcal ex
- Start date
When I was in college and couldn't afford that buret package, but was playing with SB Chevys I made my own. Took a rigid piece of plexiglas (big enough to cover the chamber) and drilled a 1/4" hole in it, sealed it to the flat surface of the head with grease and used a syringe to measure the CCs that I added until it filled. Use water mixed with a little alcohol to make if "thinner." I've pulled that setup out and used it in the past few years to identify the dome displacement on ski domes too.
D-Roc
I forgot!
- Location
- Dirty River Rider
i didn't think you used psi as a way to build a motor, you should be doing like supertune said and do all the math to give you a true compression ratio, that will determine what fuel to run. check it with a compression gauge afterwards as a means to check on your motor to make sure it is still running the same way it was built and when it will need some new rings. if you build a motor on squish and psi and you hit 185psi whose to say the rings won't seat and build more psi after breakin. a cheap gauge will work the same even if it reads 20 psi low. you build your motor and alway check it with the same gauge. as long as it is consistent you now your good.
norcal ex
X-H2
- Location
- San Jose, CA
supertune also said he has 2 snap on gauges.... why don't you go tell him to buy the cheap ones... I love how people always say buy the cheap ********, but their the ones who's ******** is always breaking! I didn't ask for opinions on what gauge... i just wanted to make sure that the threads on the gauge i posted were right.
Also, you said i should use the dome size and squish to "do the math". well You should also use a compression guage to double check everything. this happened to me once where the compression shoul dof been at 190 but it was 215!! my cheap guage read it at 160.... what now?
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D-Roc
I forgot!
- Location
- Dirty River Rider
whoa easy, buy a good gauge, it will be the last one you buy. all i was saying is that it shouldn't be the way your building your motor, because like you said the psi could be way off with a good gauge or a cheap gauge. so yeah now what???? your still getting a wrong psi with an expensive guage as you would have with a cheap one. i was trying to point out that its a tool to check between front and rear cylinder, not a means of setting up a motor. what happens if you have a 11:1 compression ratio that would require say...110 octane but you port it and it gives a psi reading of 170 with a snapon gauge, would you run high octane fuel or pump gas because the gauge is reading 170? i think that is why supertune said to get the good cc'ing tools to figure it all out and not by simply relying on psi numbers.
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crammit442
makin' legs
- Location
- here
Calculated compression ratio doesn't always tell the whole story either. Two engines with identical ratios can require very different octane fuels. You have to decide whether to use four stroke or two stroke method and there are good arguments for both. Both methods can come up with invalid octane numbers. Unless you're gonna be setting up your own motors from scratch(decking,sleeving, domes,etc..) the best bet(IMO) is to understand what's going on in your motor, but to rely the advice of a trusted builder. Some use calculated comp ratios and some use cranking comp. Good cases can be made for either/both.
Charles
Charles
D-Roc
I forgot!
- Location
- Dirty River Rider
i agree, but would an engine builder build a motor to a calculated compression ratio or with a psi reading. i would think he does all his math, R@D, timing and run it. record all the psi readings after assembly, after breakin, through out the season, then if you where to rebuild that setup again or build several ones you use the same gauge to check. one motor could run fine on pump gas with 190 psi and less timing vs another motor with 170 psi with more timing. so many variable. i am sure norcal knows all this and don't doubt his engine building skill. just make it clear to others that a good gauge isn't all that is needed to build a good motor, and by building i mean building, not assembling random stock parts with stock pistons bla bla bla. for me and my current mostly stock motor a cheap guage that reads 20 psi low has been fine for me. i know it is cheap and would never trust it for anything but checking that the motor is still reading the same as it was after i assembled it and the front and rear cylinder are close to the same psi. if i am wrong pleas inform me, i like to learn. (ps norcal....my shiat, doesn't break,.....much, and if it did it wasn't from my cheap canadian tire psi gauge.
IceRocket1286
Site Supporter
- Location
- Metro Detroit
That is the best gauge. Buy it
oxnard111
Creative RE Purchasing
- Location
- so Cali, Ventura/Oxnard area
I just loss a bid snipe on a snap on w/o case. It sold brand new for $95.