A number of VW Trends' advertisers carry a "head cc'ing kit" that includes all the necessary pieces to do this. One of the most important aspects of the compression ratio formula is measuring the volume of the combustion chamber. The higher the compression ratio, the more heat will be generated, which is why, with today's less-than-perfect fuels, most builders of street engines keep the compression down below 9-1/2-to-one, or lower. This compression has a ratio, which can be anywhere from six- or seven-parts-to-one on a stock engine, all the way up to 16- or 17-parts -to-one in race-only engines. Now, as the piston moves up into the cylinder on the upward (compression) stroke, you will be compressing that air/fuel mixture, until the piston has reached Top Dead center (TDC) when the mixture has been compressed as much as possible. This is when the piston has pulled the maximum air/fuel mixture into the cylinder. ![]() Compression begins when the piston is at Bottom Dead Center (BDC) on the downward (intake) stroke. First off, is the cubic centimeters (cc) in the combustion chambers of your heads, and you will need to know the deck height, as well.įirst, let's discuss the compression ratio. In order to set the compression ratio, there are a few things you will need to know. If you are going to be building your own engine, then there is one sometimes overlooked portion of it that is essential in getting the utmost longevity and performance out of the engine, and that is setting the compression ratio. Last edited by vwairheads on Wed 6:40 pm edited 1 time in total Posted: Wed 6:38 pm Post subject: Re: How much can you flycut a stock head?ĭepth of Flycut cc's in combustion chamber Last edited by Art Thraen on Wed 6:38 pm edited 1 time in total the newer GO styel heads the chambers are alot deeper so to achevie the 28cc range you have to go 200 plus. 180 should give you around the 28/30cc range. i wouldent go any deeper than 180 unless its a SOLID CHAMBER after market head like a 041/044 stely head. its when you go to 210 or 220 is when the top fin has to come off. no need to totaly remove the fin at that depth yes the top fin gets thiner but will clear. Usaly if it is a 040 brazilan head you are goin to be taking off 180thou and counter boring for barrel clearense and slighty faceing the top fin. Last edited by Art Thraen on Thu 7:55 am edited 2 times in total Posted: Wed 6:28 pm Post subject: Re: How much can you flycut a stock head? Tell them you want to acheive a CR of xx:1. 150 off of the heads will be a fairly safe bet?ĭon't you have a target CR in mind? If so, measure the heads, deck height, etc. Looks like it was painted with a live chicken,polished with a brick and buffed with a pine cone "If you don't run into the Devil every once in awhile, you must be going in the same direction!"ĭo you have any junk SP heads you can cut apart and see how much metal is there for the removing?īad News Racing 2018 NORRA 1000 3rd in Classīest Day Ever Racing 2022 NORRA 1000 2nd in Class and first All Female team to complete the raceĮveryone is gifted. I've had them cut far enough that a fin had to be removed. It would just be nice to hand him the heads and say "Take _ off of these heads. If the compression is too high (doubtfull on racegas) I'll use copper gaskets to reduce it.ĭoes the amount you can flycut off the heads vary based on the heads? (Stock Dual port castings)Īnd yes, I am gonna CC the heads, deck height etc. ![]() I know I have to CC them for accuracy, but I was wondering how much can actually be trimmed off of a stock head? So, I am gonna bump up the compression as much as I can.īut, the machine shop wants me to tell them how much to cut off the stock heads. The rule book requires a mostly stock motor with any compression and any cam. I am building a Class 11 off road car for this season's SNORE race classes. Posted: Wed 10:23 am Post subject: How much can you flycut a stock head? Quick sort: Show newest posts on top | Show oldest posts on top
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