Hey guys, This question has been talked about before, but I'll post again as I'm trying to understand quench area. Here's the combo: 70 455 block Wesico pistons (22 cc dish & .042 in hole) 72 Stage 1 heads (71 +- cc & untouched cambers) Fel Pro Gasket (.040 thick) T/A 290-08H cam Ok, my question: Is this setup prone to detenation? Should we polish the comb. cambers & piston tops? I'm concerned the quench area is too much even through we're around 9.4:1. Also would like to run 91 octane California junk fuel. Thanks, Wes
too much quench? I don't think that will be a problem in a Buick. You have no quench, or poor at best. You need a maximim of about .050 and preferably 040 between the flat part of the piston and the flat part of the head. You have about 082, so yes, you'll probably be more detonation prone for your compression ratio. You should always polish the chambers to get the most from your combo. Not having calculated your compression ratio, I would suggest decking the block to 0 or 005 in the hole. Steel gaskets should help if you don't deck it, but it's not the best way to get the job done, though often adequate. HTH
As for me, if I were using that thickness head gasket, I'd shoot for the deck of the piston to be .002/.003 down in the bore from the head gasket deck. As far as I am concerned, the piston decks are too far down in the bores.
Guess I should have been clearer.. "I would suggest decking the block to 0 or 005 in the hole" meant so that the piston was 0-.005 down the bore from the deck surface. So I believe that IgnitionMan and I are in agreement within +or- 002" :grin:
Hi Guys, I also totally agree with what has been recommended about decking the block. You can also think of quench as "squish". The closer the piston's flat surfaces are to the heads flat surfaces the more the air/fuel mixture will be "squished" (and the fuel droplets further atomized) into the combustion chamber area toward the spark plug. That decreases the chances of detonation or the mixture "self-igniting" and causing two flame fronts. When those two fronts collide you have detonation or the dreaded "ping" that tears parts up! Polishing the chambers and pistons tops only enhances this to the good!:TU:
Your compression calculation of 9.4 is right on. I had about 10.00 with my original setup. Then I zero-decked the block, polished the piston tops and removed the casting button, polished the combustion chambers and removed/blended the casting point. I used to have to run half racing fuel to avoid detonation. With my redone engine, my compression is now 10.13 to 1. I run only Sunoco Ultra 94 or other 92-93 octane fuel and have no detonation problems at all. Car runs smoother IMO also. I would highly recommend taking the time to do these things. It does take about 1-2 hours per combustion chamber. This was with simple grinding stones, nothing fancy. Then polish with an 80-grit flapper wheel. Phil
Kerry, funny you should mention "squish". Did you have a motorcycle background? I've worked for a few Japanese manufacturers, and found that different auto and motorcycle people were speaking of the same thing, in three different titles. What we refer to as "quench distance" is referd to as: Quench, automotive Squish, motorcycle Ignition gap, Japanese engine designers and mechanics Funny that the Japanese refer to this "gap" or clearance, distance as having to do with ignition. Seems they know, as Ford knew, that this critical dimension is important to getting fuel management at the piston tops correct is vital to getting the engine right. They are referring to both the electronic lightoff of fuel by a spark plug AND the fuel management/flame propagation in, and across the chamber as it gets fired off when they refer to "Ignition Gap". Quench all started in this country way back ion 1929. In 1928, Model A Ford engines had an open chamber design on their 4 cylinder heads, 4.00:1 compression ratio, and extremely sensitive tuning requirements. In 1929, Ford changed the head (nothing else), to give .045 clearance from the piston top to the profile of the head, over 80 percent of the bore diameter, as this engine was a flathead design. They also raised the compression ratio to 6.25:1 in those quench engines, and the tunability and tuning/fuel octane sensitivity left town. Those Ford 1929 and later engines were referred to as "quench design", 1928 and earlier were cqalled "pre-quench". Odd how the importance of quench has been around that long, and blown completely out the window of the last twenty years, by gasket and piston manufacturers that have no old coot engineers like those early guys around anymore.
I want to save my quench heads (pre 75) for the track. If I run the junk 75/76 non quench heads on the street what is the max copmression ratio I could get by with on 94 octane? What I really want to know is what would the max ratio be with 89 octane @ 4000' above sealevel with the non quench heads.
Hey Kerry....... it's been a while. I'm just curious how much is the quench effected on a boost application? Did moving from a .043 to a .56 gasket help or hurt me in your opinion?
Hi Guys, Dave....no I don't have have any motorcyle background at all unless you consider having a few buds that that have street bikes.:grin: As far as "ignition gap"....I've always thought of that as the distance between the electrode and the grounding strap of a spark plug.:grin: Can't say I've ever done too much reading up on the old Model A's or the flatheads but I did enjoy just reading your little history note about them and their designers:TU: WOW :jd: 4.0:1 compression ratio.......what a torque monster that must have been!:grin: _________________________________________________ Kevin.....that's a really hard question to give a totally accurate answer to because many different varibles all play into it...in other words....the complete combination. But for the poorly designed open chamber '75-'76 heads you should at the very least run a flat-top piston as close to zero-deck as possible, preferably at zero deck would be the best for that combination for the reasons shared above. I would also mill those heads to further help things along too. _________________________________________________ Rich.....I agree it has been awhile! As far as "helping or hurting you"....you had to reduce it to reduce your over-all compression ratio for more boost so in that regard..it helped you in the "boosted mode" by allowing more boost pressure. But it will hurt you somewhat in the naturally aspirated mode. While not totally optimized you'll be Ok!:TU: For my still future Procharger effort...I will be using custom JE's that have a reverse-dome (unlike the Speed Pro or TRW that is just a round, open dish) that is a mirror image of my Stage3's combustion chambers (which by the way...will be MUCH larger than the 53cc's out of the box). By doing this I can still run a very tight quench and still lower my compression ratio which will be of dual benefit in that regard!:TU: Hope this helps....
quenstionable quench Hey Wes; I didn't mean to jump your thread, just trying to "propagate" the quench topic. Kerry S; I understand you can run higher compression with the quench style head than with the non quench 75/76 heads. ( I wonder how the BB MOPAR guys get by with their non quench heads [ all but the 1967 440 heads were non quench I believe] they seem to do fine). As far as shaving the 75/76 heads, Dr. Weise or one of you Dr.s said he was aware of a fella who totally shaved the non-quench area down and ran it successfully. I don't plan on doing this. I don't think I can improve the condition enough with a zero deck, flat top pistons, composite gaskets and shaved heads to run very high comp. What I was hoping to do was; leave the piston deep in its origional negative deck, 0.40 or so, run composition gaskets, non shaved, 75/76 heads, 11:1 pistons and end up with around 9.8:1 compression. At 4000' I think I cound get by with 89 octane. I would also use one of the smaller cams (revs up to 4500 to 5000 rpms). This would be a mild engine build for my 76 truck, then I could get rid of the 454. Note: As we all know the 75/76 heads are prone to cracking in the combustion chamber. The cracks I have seen run from the center of the valves into the non-quench area. I think they weakened the head when they went to the non-quench head and removed so much metal.
Nope, Ignition Gap has always referred to the distance between the flat deck of the piston at TDC and the head flat of the gasket face. The J-models didn't call it Ignition Gap, they referred to it as "I-Gap", just shortened up what was written on every engineering blueprint and design schematic. Spark plug gap was referred to as just that "plug gap". Another "gap" they referred to was about electrical parts, magneto sine waves and when the spark should occur, at the top of the positive sine wave of the magneto charging cycle. They called it "Energy Gap" or shortened, "E-Gap". What I was referring to as far as the first quench engine was, it went back as far as just before the 1930's.
Having had a 440 with pistons about .125" down the hole I'll venture to guess they don't get away with as much compression as we do on the same gas. Are you having that hard a time finding some earlier heads? I would say that you are at least taking a gamble that wouldn't cost much to remedy. One of those 6 455's you have must have some decent heads? You're going to hate yourself later if it doesn't work well, and with the 11:1's you won't be able to switch to the earlier heads unless you want to have gobs of compression. The mild cam will only exacerbate the detonation issue.
Pat Kelley is a personal friend of mine. The DCR is his baby all the way, started from suggestions from me to him, years ago. Pat and his son drag race Chevelles and drive them on the street. He is a member of Team Chevelle, and when they have Chevelle get-togethers at a place called Fuddrucker's in Pasadena, Ca., I go along as well. One evening at one of the meetings (the very first one for the Team Chevelle people), Pat was speaking with a few other TC members, open discussion, about cam durations and compression ratios, and I asked what his dynamic compression ratio was. He said, "what's that". I introduced myself, and explained that I used very sophisticated Japanese programming for engine development as an engine design consultant for them, and one of the factors was dynamnic compression ratio (what the cylinder actually had for a comp ratio after factors like cam duration/timing parameters were installed into the equasion), added to a static comp ratio reading. He asked what the DCR was and how to find it, I gave him the very basic stuff needed, and Pat went to work, invented the user-friendly DCR calculator we now have for everybody to use. As I said, it's his baby, all the way. I haven't seen Pat for about 6 months now, but the last Fudd's, we sat and talked about engines and I gave him a few more parameters to add to the DCR. There's a lot more, but I just don't want to overload him with too much info all at once or give all the Japanese info away, as confidentiality issues would undoubtedly arise. Pat is very approachable, will help anybody whom asks, no matter the engine make/type, and is a great guy. And, yes, you do need the DCR, it will help immesurably.
Are DCR requirements the same across all engines or are there unique parameters for specific engine families? I.E., does the the general guideline of "less than 8.2" for 93 octane apply to BBB and not just BBC?
Pat's DCR setup is universal for all engines, not any one specific. I have more to give to him to work into the DCR, but you should use what is there now, don't wait for more input info, what he has works as it is, quite well.
Hi Guys, Dave.....I would like to let it be known that I in no way could even come close to the knowledge you obviously have concerning all the engineering background from all the various sources you've definately compiled over the years! A BIG Thank You for sharing your knowledge with all of us too!:TU: I bookmarked the DCR article and am sure it will take several study sessions to completely digest all that valuable info.:Smarty: Thanks again.....
Well, until you offer your version, let everybody use your program for free, simply because you love cars, we mortals will have to just use Pat's DCR calculator. And, you miss about 30 points from the stuff from Japan I use has. BTW, last three engine engineering exercises I worked on for Honda Racing Corporation Japan, were the RC 201 V, V5 road race engine, the RC 205 V6 and the yet to be implemented six valve per cylinder heads for that same V6. And...your last engine engineering design projects were?
I would think that something like iron vs aluminum heads would have to be taken into account when looking at the raw DCR numbers.
