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View Full Version : Sbc 355 Detonation Or Preignition


jetsprint
07-03-2008, 08:50 PM
Hi guys !, I have sbc 355 with dart 215 platinums & 49cc chambers, flat top pistons, comp cam 268*@ .050" and about .040" quench,825 gold claw and 110 sunoco fuel, the problem I am having is sever compbustion/exhaust temps,(valves sticking in the guides !) the timing is set at 34* with .035 plug gap,
The last run I had I ran the engine rich enough that the plugs were dark brown on the ceramic and the out side of the plug, BUT the ground electode looked like it had been cherry red !!! and there was no spark line on the electode. Replacing valves is no fun after the third time, as is coming in last a the races.

Can anybody add some insite to my problem ???:confused::confused::confused:

want-a-be
07-04-2008, 03:58 AM
what heat range plugs are you running? What intake? Cam? Jets? power valve or not?

Don

WCRE

Awesome Bill
07-04-2008, 01:34 PM
I would need a little information concerning your build. I have seen this many times and its not a hard fix. You have to PM me, I would prefer to give this type of information out in a more private matter. Your combination is way off with just what you have listed on the forum. Your problems prove it. No matter what spark plug you use, it will not help. Let me know!

jetsprint
07-07-2008, 03:32 AM
what heat range plugs are you running? What intake? Cam? Jets? power valve or not?

Don

WCRE
Thanksfor the reply, I am running NGK race copper plugs _9, a super victor with a 2' super sucker, 88 jets square, no power valve, the cam is a comp cam # 12-908-6 ( 300/308* @.005 with 630/630 lift

Hope this helps. thanks again. John..........

lun40119
07-07-2008, 11:13 AM
Sorry to compound this more, Don will have more answers to this. Don, do you think this sounds similar to the turd with the World heads. High egts on the dyno, with alot of exhaust contamination. Have you checked leak down? He has around the same duration at .050 but 10 more at .005.

Jake

jetsprint
07-07-2008, 06:38 PM
Hi Jake, thanks for the reply, I have not checked leak down since the last time the valves got stuck in the guides, at that time it had leakage past the exhaust valves and by the rings small ( total seal top ring gapless) with not many hours on it, I am guessing that it was not fully broken in, static compression is 190#

John........:confused::confused::confused:

lun40119
07-07-2008, 07:12 PM
I am not sure if you are having the same problem that I was having but, I had really high egts, with a set of sportsman heads. It was also way down on power. When I switched to my 215's the problem went away. I sold the sportsmans to my little brother, who did a valve job on them, and now they are fine too. I have the temps listed on a thread here somewhere, and I am at work now and don't have the numbers in front of me. i think like 1500ish rings a bell. Either way, when I purchased the heads, and redynoed, the problem was cured. Im not a pro by any means, I am just sharing my experiance with you. Don is a really big help, if you have questions. I have even talked to him at home, with some questions setting up the valve train on mine. He is more than willing to help. Take care and good luck.

Jake

lun40119
07-07-2008, 07:26 PM
I would need a little information concerning your build. I have seen this many times and its not a hard fix. You have to PM me, I would prefer to give this type of information out in a more private matter. Your combination is way off with just what you have listed on the forum. Your problems prove it. No matter what spark plug you use, it will not help. Let me know!

Why do you want to keep this type of information private. It would be nice to know what you are thinking too. I am not nitpicking Bill, just curious what you are thinking.

take care

Jake

Awesome Bill
07-08-2008, 10:57 AM
Specialty situations require professional information that you usually pay for. Whether you realize it, some of us are professionals and this is our livelyhood. Go ask your doctor or your lawyer for advice free. You won't even get in the door. You will pay for the visit and he will only tell you what you ask for and that won't be so vague you won't be able to make heads or tails of it. General information that you can find anywhere is out there. Procedures, assembly tricks that have been learned and applied and work our tricks of the trade. Go ask Richard or Ken Black for their blueprints on their Pro Stock engines. Years of experience is worth a ton. Break a few more engines and you will agree. A professional is well worth what you pay him or her for. Some stuff you don't give away.

Dart Vader
07-08-2008, 11:44 AM
The forums are for open discussion meant to benefit everyone.

lun40119
07-08-2008, 01:34 PM
Specialty situations require professional information that you usually pay for. Whether you realize it, some of us are professionals and this is our livelyhood. Go ask your doctor or your lawyer for advice free. You won't even get in the door. You will pay for the visit and he will only tell you what you ask for and that won't be so vague you won't be able to make heads or tails of it. General information that you can find anywhere is out there. Procedures, assembly tricks that have been learned and applied and work our tricks of the trade. Go ask Richard or Ken Black for their blueprints on their Pro Stock engines. Years of experience is worth a ton. Break a few more engines and you will agree. A professional is well worth what you pay him or her for. Some stuff you don't give away.

So if I send you a pm will you tell me what you think is the cause of this, or do I have to send you a check???????????????:D I have acknowledged numerous times that you are in fact the professionals, and I am just a guy turning a wrench. I am guessing that you aren't your marketing professional though, you seem to foul alot of cheerio's.


Jake

lun40119
07-08-2008, 04:24 PM
Back to the point though, I would check leak down again, and does it look like there is exhaust in the intake runners?

Jake

jetsprint
07-08-2008, 06:47 PM
Afternoon, at least here in mountain standard time it is, after all the recent failures it showed no discoloration in the intake ports, ( it did last year but the valves were warped) the last time i did a leakdown test it showed no variation (100%) with the guages set at 80psi and 100psi. the only way I could tell if there was leakage was to listen at the headers, carb and valve covers using shop air ( 175psi) static comp is even
John.........

want-a-be
07-08-2008, 09:17 PM
Did you degree in your cam? If so whats it installed at? What kind of timing are you running?

Don

WCRE

want-a-be
07-08-2008, 09:22 PM
Specialty situations require professional information that you usually pay for. Whether you realize it, some of us are professionals and this is our livelyhood. Go ask your doctor or your lawyer for advice free. You won't even get in the door. You will pay for the visit and he will only tell you what you ask for and that won't be so vague you won't be able to make heads or tails of it. General information that you can find anywhere is out there. Procedures, assembly tricks that have been learned and applied and work our tricks of the trade. Go ask Richard or Ken Black for their blueprints on their Pro Stock engines. Years of experience is worth a ton. Break a few more engines and you will agree. A professional is well worth what you pay him or her for. Some stuff you don't give away.


I totally agree with you there Bill. Especially when it come to getting what you pay for. My deal is I like to help people out....even if it means I'm not making money at it. :rolleyes: But...I don't consider myself a professional. :o
Just a good trouble shooter. ;) But I have to have symptoms before I can make any calls.

John feel free to pm me also if you want.

Don

WCRE

BAD67
07-08-2008, 11:53 PM
So let me get this straight for the record,you want us to pay you now for your bull**** opinions???????:D:D

want-a-be
07-09-2008, 05:01 AM
So let me get this straight for the record,you want us to pay you now for your bull**** opinions???????:D:D


LOL Bad...don't be shy ...lets hear your true feelings.:D

Later Bud, Don

Catch ya on msn some time. So you can let me know how the fishing has been. :cool:

Awesome Bill
07-09-2008, 10:31 AM
Not @ all. I just don't put that type of information out there for personal reasons. A private message is much more appropriate and will do much more good than a ton of guess work. I can train a monkey to assemble a short block but diagnosis of a problem like this is what separates the field. Knowing this type of stuff requires a little more thought and expertise and that is not spread around like trash. We have got this under control, and no one is charged for anything. The only opinions that count are the ones he or she decides to use. Problems are when someone really needs help, he or she has to wade threw all the bull**** from people who thats all they got!

Dart Vader
07-09-2008, 11:51 AM
Information delivered via these boards should be kept out of IM as much as possible, for the benefit of all readers who come here looking for answers.

jetsprint
07-09-2008, 01:20 PM
Did you degree in your cam? If so whats it installed at? What kind of timing are you running?

Don

WCRE

Morning Don, yes I did degree the cam, the cam spec card showed 106* and with all things and tolerances I got the cam to 105.5* with a 11" dia wheel, figured my eye site was of .5* Ignition timing has been at 34* total, I am going to drop that to 30-32* at the next race

John.....:D

want-a-be
07-09-2008, 09:11 PM
What carb and jets are you running? Are you running a power valve? If so, what vac is it rated for and what vac are you running at an idle?
I think the 34 should be ok.

Don

jetsprint
07-09-2008, 11:21 PM
What carb and jets are you running? Are you running a power valve? If so, what vac is it rated for and what vac are you running at an idle?
I think the 34 should be ok.

Don

I am running a gold claw 825 w/ 88 square and no power valves, I do not know the vacuum no real good way to check ( no ports) It idles @ 1250 , better @ 1400 rpm, if I leave it at 1250 it will die after a minute

Thanks John........

Awesome Bill
07-12-2008, 11:53 AM
At wide open throttle, the powervalve is not a factor, it has no vaccum with all the throttle blades wide open. As you can see on the video, the rpm is around 5500 on that particular engine. Idle air bleeds only factor in a small percentage of total fuel at wot. It is possible, the gold claw needs a smaller high speed because they usually are lean when you get those carbs. Without dyno testing and getting the fuel curve aka bsfc at wothrottle like you run it, your fuel consumpution could be down and causing lean conditions and you not even know it. But you don't have a dyno and a mass air flow, fuel counter or any way of knowing lbs of fuel per hour so your guessing. Wonder how much money you could of saved verses 1 dyno trip and getting it right with someone who knows how to tune? Pistons, rings, valve jobs etc all cost pretty much more than 1 dyno session. ( we charge $500 for a full day!). Just playing with your head. Any way, I don't think that is the problem, but you could take some air away from the high speed air bleeds, this will richen only the top side up and should bring down the egts. Also, when you retard the timing with race fuel, most times this brings the egts temps way up and well over 1500. This also could be your problem. hope this helps a little.

It is also possible your fuel level is too low and you should have jet extensions in that thing to keep the fuel on the secondaries. This could cause lean rich lean rich, lean rich conditions while weaving threw the course. So there is something else for your little box of thoughts. Jet extensions for sure in the back are a must. I would run the fuel level as far topside as the engine would permit and still maintain good idle qualities.

Also lock your timing out if you have a msd distributor. If you don't have one, weld the distributor so it has no mechanical advance at all and then just set your timing @ 32 and work up from there at a time until you feel your time slip proves no more timing is needed.

We just dyno tested another 632 Pro Magnum engine yesterday, Dart Block, BMF 385 heads, Sniper Jr. intake, Dam Best 2-1/8 billet dominator, 15-1 NOS engine and @ 32 timing the engine had higher than normal egts but still made 1048 hp and 867 torque @ 5800 and 6800 rpm. I bumped the timing 1 and the engine went to 1068 and 888 same rpm and the egts droped 75 and all were under 1250. So not enough timing will cause your fuel to keep the head hot and can cause pre ignition. Detonation is to much compression for the fuel, pre ignition something hot in the chamber could set it off. Reason being, just 1 in timing pulled 75 out and made 21 more hp and 21 lbs of torque. Think about it. Never change the fuel curve because John from DamBest set the lbs of fuel per hour right on his flow bench and told me not to touch it. I told him I wanted enough for 1050 hp and he put it right on the money. Best Carb man I have ever delt with. He actually knows how a carb works and makes one hell of a carb with the billet pieces he sells. Pricey but killer. I never set a float level and only pulled turn out on the base fuel idle to get it to idle perfect. If you look under his patented booster design @ wide open throttle, you can only see a fog of fuel. With slow motion and magnified, not one droplet. These carbs get the best bsfc for hp in the buisness. He is the only carb man out there worth dealing with in my opinion because he has the patent and no one else can use it. Just something else to chew on.

jetsprint
07-14-2008, 08:10 PM
Thanks Bill, as far a the time on the dyno you are right !!! for the cost of the repairs I could have paid for a day on the dyno, but for know we are trying our best, I am going to change the air bleeds, the carb does have jet extensions and the float levels are as high as I can use, because of the angle when launching.

If you saw 5500 in the video you were most likly watching a superboat (methonal injected) they run lower rpm with (larger impellors)with tons of torque, the jet pumps have a max usable rpm of 7000, then they start to cavitate .

Thanks again for all your support !!!

John......

Awesome Bill
07-15-2008, 10:17 AM
I noticed that the rpm would jump to around 6000-6500 maybe 7000 in tight turns and then catch back up. I don't know the classes, but that impeller he has is tight. We used to run the jet boat thing with those killer 455 Olds engines, we still build them occasionally, and they could not make the pumps tight enough for the power we made. They always would get over on the pump and we would have to pull back. Seems like someone should come up with a better design, and I am sure they have.
Keep up with the info, I am very interested in these engines. Torque is what I shoot for in all my engines, that is power!

jetsprint
07-15-2008, 01:13 PM
Morning, yes the new generation of jet pumps are much more efficient in their power transfer and the best units are built in New Zealand specifically for the type of racing we do. The rpm jump you saw was probally the boat hitting some small waves causing the boat to loose contact with the water and was cavitating.

I have made all the changes in line with all the advise received, I will be racing this weekend, y'all cross your fingers for a positive outcome !!

Going Racing..John........

For those who don't know what we are talking about here is the link to the web site for my type of racing

http://www.ussbaracing.com

jetsprint
07-23-2008, 01:42 PM
Morning, well we went racing, and survived. (bad driving) but the motor survived, You were correct in the carb jetting, I changed the air bleeds down by 0.010" and the motor found a new life, timing was about 32* I might drop it some more according to the line on the strap, at the next race I am going to try droping the bleeds another .002 to .003" and see what the plugs look like. I think it still might be lean but it is producing some horsepower now (went so fast i missed a corner)

Thanks y'all for your knowlege and thoughts

John.... I will keep you posted with some final results:D:D:D