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"Detonation problems" rebuild 440-6

Posted By: 6pakdude

"Detonation problems" rebuild 440-6 - 05/05/09 06:17 PM

Rebuild my org 440 this winter.
Now detonates over 4800 RPM?
Any help appreciated to solve this problem.

Engine specs:
KB237 030" block 0 decked
Moly rings, top ring filed to KB spec
906 heads, 2,14" and 1,81", hardened seats, shaved to 84cc.
Fel Pro 8519 PT-1 head gasket 0,029" thick
10:3 comp ratio using KB calculator.
Lunati voodoo 60303 hyd camshaft
Champion plugs RJ12YC
Rocker shaft shimmed for preload
Stock dual point distributor, petronix ignition, total ignition at 2300 RPM
Stock HP exhaust manifolds, with repro mufflers and pipes.
Under 4800 RPM runs strong and great, idle 900 RPM,vacum 15 HG, 16 degree ignition total 36.
Gas unleaded 98 octane (sweden)
Have tried to set ignition down to 10 intial and total 30 without any result.

Carbs stock 1970 auto
Center 64 jets, powervalve 65, shooter 31. fuel/air set with vacum guage
Front stock metering plate 34R-6153-35
Rear stock metering plate 34R-6153-35
Front and rear fuel/air set with blocking outer air bleed holes.
Still detonates over 4800 RPM

Changed metering plates in front carb to 34R-9716B
Have no idea what size it is.
rear carb 34R-5113B size unknown

These metering plates was mounted when car had a mech camshaft, Racer brown. pullig hard to 7000RPM.
So i figure they give more fuel than the stock plates.

Finally checked the spark plugs, they look to white for me, want a more tan/brown color.

So here is my question:
Is my engine running lean above 4800 RPM and cause the detonations.
The voodoo 268 camshaftit should rev to 6200 RPM.
any idea what size jet to use, if thats the problem.

Or do I need to change to a thicker head gasket?
Or change heads, build a Quench engine with the shortblock above.

Want to run the car on the strip this summer.

Long story, hope to get some input on the detonation problems I have.

Thanks Peter
Posted By: Mr.Yuck

Re: "Detonation problems" rebuild 440-6 - 05/05/09 06:35 PM

sure your distrib isn't advancing? is it locked down or welded? Is your vacuum advance hooked up? Is this under load only?
Posted By: ph23vo

Re: "Detonation problems" rebuild 440-6 - 05/05/09 06:49 PM

first see what it takes to make it stop OCTANE wise.. maybe its NOT detonation... ck real engine temp [mech gauge] suspect ign is over advancing ... good luck dan
Posted By: lewtot184

Re: "Detonation problems" rebuild 440-6 - 05/05/09 06:57 PM

my , too much compression, short cam, no quench; sorry, it'll never work.
Posted By: Mr.Yuck

Re: "Detonation problems" rebuild 440-6 - 05/05/09 07:00 PM

Quote:

my , too much compression, short cam, no quench; sorry, it'll never work.



I'm using a 440-6 w/ ported 516 74cc heads (2.14/1.81) and a MP 528 solid. Haven't driven the car yet but so far no problems. I think my compression is a tad higher.
Posted By: GTX MATT

Re: "Detonation problems" rebuild 440-6 - 05/05/09 07:00 PM

Not enough cam for that compression, really high cylinder pressures.
Posted By: GTXKen

Re: "Detonation problems" rebuild 440-6 - 05/05/09 07:03 PM

how big is the exhaust? What kind of mufflers are you running?

I had this issue with my new motor last spring. It fell flat at high RPM and had detonation issues. It turned out my mufflers were too restrictive. When I looked at my mufflers the ends were balloning out like they were going to explode.
Posted By: lewtot184

Re: "Detonation problems" rebuild 440-6 - 05/05/09 07:18 PM

Quote:

Quote:

my , too much compression, short cam, no quench; sorry, it'll never work.



I'm using a 440-6 w/ ported 516 74cc heads (2.14/1.81) and a MP 528 solid. Haven't driven the car yet but so far no problems. I think my compression is a tad higher.

i have two iron head 6-pak engines and both are around 9.3:1 compression with good quench. the short cammed engine makes about 185psi cylinder pressure and has got a little "testy" with 93 octane on occasion. the other engine has a longer solid cam and about 165psi cylinder pressure; its a lot more forgiving with 93 octane. i'm not a believer in 10+:1 compression with iron heads and 93 octane gas, good quench or no quench. just a voice of experience.
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/05/09 07:25 PM

Have run engine with or without vacum hooked up.

Distributor advance is 20 degrees.checked.

Repro mufflers and resonators. 2,5" front pipes and rest 2 1/4".

Last summer drove the car with around 9:0 comp ratio, with a comp 268xe.
No problem with detonation or pinging, same distributor 18 intial 38 total.
stock metering plates front and back.same exhaust.
5600RPM.

I still think the plugs should have more color on them.

Peter
Posted By: JohnRR

Re: "Detonation problems" rebuild 440-6 - 05/05/09 07:29 PM

Two things I see wrong

First the felpro 8519 is not .029 thick , it's .039 , but the compression is still 10.0ish in a 440 with a zero deck piston .

Next is shimming the rocker shafts for preload , did you have ave incorrect rocker tip to valve tip geometry ? If you did then that's fine , if you didn't then you should check it as it sounds like you used the shims to make up for milling the heads which is the WRONG use for rocker shaft shims ...
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/05/09 07:38 PM

yes, you right about the head gasket.should be 0,039"

I used the shims for compensate for decking and millig the heads.What can I do? shorter pushrods or adj rockers?
peter
Posted By: JohnRR

Re: "Detonation problems" rebuild 440-6 - 05/05/09 07:41 PM

Quote:

yes, you right about the head gasket.should be 0,039"

I used the shims for compensate for decking and millig the heads.What can I do? shorter pushrods or adj rockers?
peter



The correct way to make up for the head and deck milling is to get the correct length pushrods , in this case shorter .

But this has little to do with your detonation issue, you'll have to tune it out.

I wonder if your plug choice has an effect since it's one step hotter than stock ?
Posted By: Mr.Yuck

Re: "Detonation problems" rebuild 440-6 - 05/05/09 08:02 PM

I'll guess I'll find out soon, I'm also running J12's. Don't know if it matters but the 2 1/4 pipes are like drinking a thick shake thru a soda straw. I'd unhook the vacuum advance, bump the jets up 2 and back the timing to 35* at 2400 and see if that helps.
Posted By: BSB67

Re: "Detonation problems" rebuild 440-6 - 05/05/09 11:44 PM

Gasoline octane here in the states is determined using the (R+M)/2 method. Not sure how that relates to your fuel octane rating of 98.

Like Lew said, I dont think that our premium fuel (93 octane) would be able to support that small cam at that comression ratio. What is your cranking cylinder pressure, in psi if you would.

A couple of things to look at or try.

First, Usually detonation is observed at lower rpm and higher load and may continue through the upper rpm range. If you only have detonation above 4800 rpm, that can be from a lean condition due to low fuel pressure.

Try spark plugs at least two steps cooler and a 160 degree themostat. Make sure cooling system is good overall.

64s center and 0.089 inch dia. plate restrictions in the outboards will put you close if everything else is unmodified, like the MAB

I think that 6200 rpm is optimistic for that cam
Posted By: JohnRR

Re: "Detonation problems" rebuild 440-6 - 05/06/09 01:05 PM

Quote:

I'll guess I'll find out soon, I'm also running J12's. Don't know if it matters but the 2 1/4 pipes are like drinking a thick shake thru a soda straw. I'd unhook the vacuum advance, bump the jets up 2 and back the timing to 35* at 2400 and see if that helps.



But you have good quench , he doesn't. You might want to find a set of equivalent heat range to JY10's ?
Posted By: Mr.Yuck

Re: "Detonation problems" rebuild 440-6 - 05/06/09 01:10 PM

Quote:

Quote:

I'll guess I'll find out soon, I'm also running J12's. Don't know if it matters but the 2 1/4 pipes are like drinking a thick shake thru a soda straw. I'd unhook the vacuum advance, bump the jets up 2 and back the timing to 35* at 2400 and see if that helps.



But you have good quench , he doesn't. You might want to find a set of equivalent heat range to JY10's ?



John I'm dumb on quench.. I've never worried about it much. I've used 906 heads, 915's, 516's, and the rest on 383's and 440's and never had issues. Most were 9:1ish stock bottom end motors, except for the 11:1 383/915/509 cam motor. Whats makes mine a non-quench problem? the 516's? I mean my slugs are only .020 down (or there abouts)
Posted By: JohnRR

Re: "Detonation problems" rebuild 440-6 - 05/06/09 01:14 PM

Quote:

Quote:

Quote:

I'll guess I'll find out soon, I'm also running J12's. Don't know if it matters but the 2 1/4 pipes are like drinking a thick shake thru a soda straw. I'd unhook the vacuum advance, bump the jets up 2 and back the timing to 35* at 2400 and see if that helps.



But you have good quench , he doesn't. You might want to find a set of equivalent heat range to JY10's ?



John I'm dumb on quench.. I've never worried about it much. I've used 906 heads, 915's, 516's, and the rest on 383's and 440's and never had issues. Most were 9:1ish stock bottom end motors, except for the 11:1 383/915/509 cam motor. Whats makes mine a non-quench problem? the 516's? I mean my slugs are only .020 down (or there abouts)



Yes the 516's , closed chamber , what head gasket did you use ???

I know of guys with 9.0ish compression that just did poorly thought out builds have detonation issues with lower octane fuel and too much timing . I built a good quench distance 440 for a friend with 10.3 compression and 906's that doesn't have any detonation issues with 93 octane and 38* total timing .
Posted By: Mr.Yuck

Re: "Detonation problems" rebuild 440-6 - 05/06/09 01:23 PM

Quote:

Quote:

Quote:

Quote:

I'll guess I'll find out soon, I'm also running J12's. Don't know if it matters but the 2 1/4 pipes are like drinking a thick shake thru a soda straw. I'd unhook the vacuum advance, bump the jets up 2 and back the timing to 35* at 2400 and see if that helps.



But you have good quench , he doesn't. You might want to find a set of equivalent heat range to JY10's ?



John I'm dumb on quench.. I've never worried about it much. I've used 906 heads, 915's, 516's, and the rest on 383's and 440's and never had issues. Most were 9:1ish stock bottom end motors, except for the 11:1 383/915/509 cam motor. Whats makes mine a non-quench problem? the 516's? I mean my slugs are only .020 down (or there abouts)



Yes the 516's , closed chamber , what head gasket did you use ???

I know of guys with 9.0ish compression that just did poorly thought out builds have detonation issues with lower octane fuel and too much timing . I built a good quench distance 440 for a friend with 10.3 compression and 906's that doesn't have any detonation issues with 93 octane and 38* total timing .


I used the standard Fel-Pros from advice by a local Mopar guy. Said if I used the steel shims the compression might be to high for pump gas.
Posted By: JohnRR

Re: "Detonation problems" rebuild 440-6 - 05/06/09 02:53 PM

Quote:


I used the standard Fel-Pros from advice by a local Mopar guy. Said if I used the steel shims the compression might be to high for pump gas.



Well your Quench is not as good as it could be, dare I say not very useful??? , what CC did you end up with on the heads ?
Posted By: Mr.Yuck

Re: "Detonation problems" rebuild 440-6 - 05/06/09 03:07 PM

Quote:

Quote:


I used the standard Fel-Pros from advice by a local Mopar guy. Said if I used the steel shims the compression might be to high for pump gas.



Well your Quench is not as good as it could be, dare I say not very useful??? , what CC did you end up with on the heads ?


74cc.
Posted By: JohnRR

Re: "Detonation problems" rebuild 440-6 - 05/06/09 03:14 PM

Assuming 4.350 bore , stock correct length rods , 7 cc for valve reliefs , .300 down to the top ring , 4.410 bore I get 10.43 ...

Using a steel shim it would have been 10.89 , so I'd have to agree with your local guru a bit on that , but since you might have to mix anyway I would have opted for the higher ratio and good quench , rolled the timing back a little on the street

cross your fingers
Posted By: Mr.Yuck

Re: "Detonation problems" rebuild 440-6 - 05/06/09 03:17 PM

Quote:

Assuming 4.350 bore , stock correct length rods , 7 cc for valve reliefs , .300 down to the top ring , 4.410 bore I get 10.43 ...

Using a steel shim it would have been 10.89 , so I'd have to agree with your local guru a bit on that , but since you might have to mix anyway I would have opted for the higher ratio and good quench , rolled the timing back a little on the street

cross your fingers



I can always put the steels in, I have a set on the shelf. I'm goint to start the timing at 35* and go form there.
Posted By: JohnRR

Re: "Detonation problems" rebuild 440-6 - 05/06/09 03:25 PM

I just said screw it on my 383 stroker build since I was going to have to mix anyway, good quench or not, and upped the compression from 11.4 to 12.5 ...
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/06/09 06:44 PM

Checked the cylinder pressure after work today.
Cold engine 170psi.

Is this to muck for my voodoo cam? If so what head gasket should I use to lower the pressure/comp ratio.

Have located colder plugs here in Stockholm, I gonna buy a set this weekend, Accel 124 should be one colder step then the champion plug.
(I might have the wrong number of the plugs, forgot the note at work.

Peter
Posted By: moper

Re: "Detonation problems" rebuild 440-6 - 05/06/09 06:56 PM

You have a lot of cylinder pressure there, but not too much. You have no quench, but that should not be an issue. You ned to add fuel, as you suspect. You should get the Pro Max metering plates that will use standard jets to adjust the outboard mixtures. I seem to recall that Euro 98 is about the same as our 93. So it's not octane. i think you're lean as you think. So instead of rebuilding the engine, give it the fuel it wants. You should NOT be running that engine until you figure it out. KBs and pinging are NOT GOOD at all. Also, you should be able to go to the purple springs in your outboard vacuum pods after you get some jet in it. What is you timing curve? You should be around 15° initial, and total around 36° with it all in somewhere around 3K.
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/06/09 07:37 PM

Before I asked this question on moparts. I decided to try to shorten the slots in the distributor. before 2x10 degree, now 2x7. used epoxy so it's easy to remove.

So timing and curve of today is inital 16 w vacum, total 30. full timing comes at 2300 RPM.

Havn't run this combo yet, because of rain ,hopefully this weekend.

I drive the car, but not going over 4500 RPM until problem sorted out.

Yes thats my thoughts to, using those billet plates from ProMax, because of the cost I need to know that it solves my problem.

I have long yellow springs in the vac pods.
Thanks peter
Posted By: JohnRR

Re: "Detonation problems" rebuild 440-6 - 05/06/09 08:27 PM

Quote:

You have a lot of cylinder pressure there, but not too much. You have no quench, but that should not be an issue. You ned to add fuel, as you suspect. You should get the Pro Max metering plates that will use standard jets to adjust the outboard mixtures. I seem to recall that Euro 98 is about the same as our 93. So it's not octane. i think you're lean as you think. So instead of rebuilding the engine, give it the fuel it wants. You should NOT be running that engine until you figure it out. KBs and pinging are NOT GOOD at all. Also, you should be able to go to the purple springs in your outboard vacuum pods after you get some jet in it. What is you timing curve? You should be around 15° initial, and total around 36° with it all in somewhere around 3K.



Dave , I have seen KB spec a max of 34* total ???

Edit I just reread your first post , I'm with moper it sounds like you are too lean .
Posted By: JohnRR

Re: "Detonation problems" rebuild 440-6 - 05/06/09 08:30 PM

Quote:


Yes thats my thoughts to, using those billet plates from ProMax, because of the cost I need to know that it solves my problem.


Thanks peter



Peter , the Pro Max plates allow you to use standard holley jets to change jet size to richen or lean out as needed , right now the plates in those outboards just have a drilled hole , you can drill the hole bigger as needed, but it's not easy to undo if you go to big .
Posted By: moper

Re: "Detonation problems" rebuild 440-6 - 05/06/09 09:21 PM

John, the pistons will take whatever the engine can, right up until it pings. With all the variables involved in mass production pistons and a thousand things that could go wrong that are not KB's fault, I think it's one of those "Publish it so we have an out" when something does go wrong that is not thier problem. They can take a little detonation and ping, but on a fresh build... I cringe at audible ping.
Posted By: BSB67

Re: "Detonation problems" rebuild 440-6 - 05/06/09 11:11 PM

Quote:

Cold engine 170psi.

Is this to muck for my voodoo cam?



No. But everything needs to be right.
Posted By: Dodgem

Re: "Detonation problems" rebuild 440-6 - 05/06/09 11:28 PM

It's leaning out for some reason. High RPM ping is lean low rpm is compression / cam / fuel.
My gut feeling is the vacuum carbs are not coming open???
Posted By: dulcich

Re: "Detonation problems" rebuild 440-6 - 05/07/09 12:12 AM

I doubt your problem is detonation, do yourself a favor and figure out what all that racket you hear up top really is. I would suspect that you'll hear the same "detonation" on race gas. Try it.
-dulcich
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/07/09 05:17 AM

Have had a paperclip on the rod to the vacumpod, to see if it opens, it does.

Last year tried the purple spring, it didn't open.

Might thou be a different story this year with more comp and vacum.

Anyone have a recommendation what size jet in front and rear carb to use for my engine.using the Promax plates


Those metering plates I use right now, does anybodt know what size they are. Same for the stock plates.

Accel 124 should be a step colder than the champ12

Peter
Posted By: 1_WILD_RT

Re: "Detonation problems" rebuild 440-6 - 05/07/09 05:46 AM

Quote:


Anyone have a recommendation what size jet in front and rear carb to use for my engine.using the Promax plates


Those metering plates I use right now, does anybodt know what size they are. Same for the stock plates.




Secondary metering plates are identified by the number stamped into them... This chart gives you main jet sizes plus idle jet size & the full holley part numbers...

http://www.junkyardgenius.com/holley/2ndplates.html
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/07/09 06:12 AM

Wild R/T thanks

If I Understand the chart, the stock metering plates 34R-6153-35. means size 35 0,071" jet size ? or

But the plates 34R-9716B
34R-5113B

How do I decode that number.

Or do I have to look for a stamped number on all plates.

peter
Posted By: 1_WILD_RT

Re: "Detonation problems" rebuild 440-6 - 05/07/09 06:24 AM

I looked but couldn't find a good image, the raised number isn't the one you need, the two digit stamped number is the identifying number...
Posted By: 70sixpkrt

Re: "Detonation problems" rebuild 440-6 - 05/07/09 06:25 AM

I got this chart from Promax.

Attached picture 5213442-100_1804.JPG
Posted By: 70sixpkrt

Re: "Detonation problems" rebuild 440-6 - 05/07/09 06:27 AM

The left is Promax chart and the right is out of the Speed Secret Mopar Engine book.

Attached picture 5213445-100_1803.JPG
Posted By: 70sixpkrt

Re: "Detonation problems" rebuild 440-6 - 05/07/09 06:29 AM

Hopefully this comes out clearer.

Attached picture 5213447-100_1805.JPG
Posted By: 70sixpkrt

Re: "Detonation problems" rebuild 440-6 - 05/07/09 06:32 AM

I am using 65 jet in the center and 80s on all 4 corners.
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/07/09 06:38 AM

70sixpkRT thanks

that helps, have to find out the size on the stock plates.

Gonna measure it later today.

have the info when i get in contact with ProMax.
peter
Posted By: 1_WILD_RT

Re: "Detonation problems" rebuild 440-6 - 05/07/09 06:41 AM

Quote:

I am using 65 jet in the center and 80s on all 4 corners.



#80 jets have a .093 orifice...

So if you were to start with a .085 pin drill & creep up from there...
Posted By: 70sixpkrt

Re: "Detonation problems" rebuild 440-6 - 05/07/09 06:48 AM

This is the chart if you are using the Promax metering plate for the center carb.

Attached picture 5213454-100_1806.JPG
Posted By: 70sixpkrt

Re: "Detonation problems" rebuild 440-6 - 05/07/09 06:52 AM

80 jet is a .0890 drill size. I talked to Ben at Promax and he told me to run 80s. I used to have staggered jetting but I was fouling the plugs so I compromised on 80s.
Posted By: 1_WILD_RT

Re: "Detonation problems" rebuild 440-6 - 05/07/09 06:58 AM

Quote:

80 jet is a .0890 drill size. I talked to Ben at Promax and he told me to run 80s. I used to have staggered jetting but I was fouling the plugs so I compromised on 80s.



My chart shows .089 drill as a 79 jet size...Don't ya love specs that don't agree... Either way I'd start just a little small cause it's easier to drill bigger than drill smaller..
Posted By: 70sixpkrt

Re: "Detonation problems" rebuild 440-6 - 05/07/09 07:04 AM

Quote:

My chart shows .089 drill as a 79 jet size... Either way I'd start just a little small cause it's easier to drill bigger than drill smaller..



Thr promax chart shows 79 and 80 jets are .089 drill size. I did not want to drill anything because I knew I would screw up something so that is why I got the Promax plates. I agree. Start off small.
Posted By: 1_WILD_RT

Re: "Detonation problems" rebuild 440-6 - 05/07/09 07:16 AM

My reason for suggesting drilling is because Peter lives in Stockholm Sweden & getting parts might be a challenge, though the parts we're talking about are small & could be shipped reasonably easy... As long as Customs doesn't sideline the box...
Posted By: hemigod426

Re: "Detonation problems" rebuild 440-6 - 05/07/09 07:49 AM

i dont think it detonation issues, what hyd lifters did you put on the voodoo cam? those cam have wierd base circles only there lifters have cups in right spot, for there cams. i think your valves are not closing all the way @ high rpms, wrong lifters or you need adj rockers for your setup. try rockers first
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/07/09 10:51 AM

I bought a kit for the Lunati 60303, with cams, lifter and spring/retainer.

Drilling the metering plate 0.089"(2,26mm).
So found and drill to metering plates gonna be hard.

So front 0,089" jet
back 0,093" jet
Posted By: 70sixpkrt

Re: "Detonation problems" rebuild 440-6 - 05/07/09 02:23 PM

Quote:

So front 0,089" jet
back 0,093" jet


That is what the Speed Secrets book says. That would put you at a 79 or 80 jet in the front and 82 in the rear. You should contact Cab Burge here on the board. He knows alot about six pack stuff and helped me out with my carb problems.
Posted By: GomangoCuda

Re: "Detonation problems" rebuild 440-6 - 05/07/09 03:08 PM

Quote:

Yes thats my thoughts to, using those billet plates from ProMax, because of the cost I need to know that it solves my problem.



QuickFuel plates are much less expensive. http://store.summitracing.com/partdetail...mp;autoview=sku
I have used them successfully on sixpacks.

66 jets in the center and 80's in the outers will get you close enough to rule out jetting being your problem. if you want to fine tune you can try staggering 78 frt, 80 rear or 80 frt, 82 rear. If you need to deviate very much from these numbers then there is something else wrong.

Just out of curiousity which vacuum port did you use in the center carb? The one on the main body or the one on the metering block? It needs to be the one on the main body that angles forward.
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/07/09 07:34 PM

I checked a pic on the engine,no time to work on the car until tomorrow. vacumport on center carb body hooked up to both vacumpods front& rear carb.
from metering block to distributor.

Summit charge $25 for international orders, so a pair is $30 cheaper than ProMax.
peter

I thinking of drilling a pair of plates if I can find the correct size.
Posted By: Mr.Yuck

Re: "Detonation problems" rebuild 440-6 - 05/07/09 10:11 PM

what kind of vacuum are you pulling?
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/08/09 05:57 AM

Hi again
About 15 hg last time checked.
Posted By: Mr.Yuck

Re: "Detonation problems" rebuild 440-6 - 05/08/09 12:38 PM

good vacuum signal. What PV are you running? I'm also wndering if you're outboards are opening fully.
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/08/09 06:06 PM

Removed the fuel bowl for the front carb, the metering plate (34R-9716B) had about 0,0910" drill size, jet 81. So I left it as it was.

Removed the rear carb, the metering plate(34R-5113B) had about 0,0870# drill size, jet 78.

Checked the org plate stamped 35, driver side about 0,0910" drill sze, pass side about 0,0870" drill size.both were the same.

So I took one org 35 plate drilled it 0,0910"
and mounted it in the rear carb. jet size 81.

so all 4 has about 81 jet size now.

Distributor 16 intial total 30 w vacum.

Took the car for a test drive (heavy after work traffic fridays) well I got a couple of chances to try it out.
Going in second at 2000rpm and floored it, could take up to 5400RPM in second, later tried rolling slowly 1 st gear and floor it, 5500rpm, shift manually to second and 5400RPM, to much traffic to try 3 gear.

But at 5500RPM I got that sound I called detonation, perhaps thats the wrong name for the problem.running lean.


So more gas helped bring the RPM up another600-700 RPM.

Thinking of go from 64 to 66 in the center carb, what you thoughts on doing that. maybe to much?
but I think the engine wants more gas to bring up tp 6000RPM
and try without vacum, maybe have 2-4 degree more total timing. No pinging today.

PW 65, outboards open fully

Bought new colder plugs Accel 124, havn't put them in yet.

So its slowly getting there.
Posted By: Classof70Chally

Re: "Detonation problems" rebuild 440-6 - 05/08/09 07:36 PM

Sounds like you are going in the right direction. My combo may have more comp ratio and cam than yours but on my 6 packs I am now at 79 jets on the front, 68's for center and 81's on the rear. I also went from a 6.5 PV to an 8.5 PV which eliminated a hesitation when I mash the gas. My timing is straight mechanical, now set at 12' initial and 36' total all in by about 2,800 rpm. Keep at it and make notes of ALL of your changes so you can go back if need be. I keep a hand drawn 'diagram' of my carb and jet positions and every time I make a jet change I cross out the old number and write in the new one.
Posted By: 70sixpkrt

Re: "Detonation problems" rebuild 440-6 - 05/08/09 08:13 PM

You are going in the right direction. What ignition are you using? I am using the MSD Pro Billet Dist. set at 14* initial timing and 35* total. Stay at it and you will get it. Oh never mind. I see you are using a stock dual point with Petronix. I have heard some people say they have had problems with Petronix.
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/09/09 07:31 AM

Have had no problems with the Pertronix since installed 2004.
Running a stock dated coil (repro) with Pertronix black plug wires.

Have a set of repro dated wires waiting to go on, but have read they are no good

My 70 Challenger R/T is a match # car, try to keep everything as original as possible.
These cars run good when new (after some updating) and they should run as good today.

Did you use Promax Throttle plate on your rear carb, with the jet plates.


Concernig the fuel 98 we have here in SWEDEN, It's what you call 92 in the U.S.A. We have someting sold by Shell called v-power, and it's the same as your 93 premium.
Posted By: 70sixpkrt

Re: "Detonation problems" rebuild 440-6 - 05/09/09 05:09 PM

I am running the Promax jettable plates on the front and rear carbs. Your gas is higher than what I can get here in Calif. The highest octane is 91.
Posted By: 6pakdude

Re: "Detonation problems" rebuild 440-6 - 05/10/09 07:34 AM

I meant the "billet throttle base plate" from Promax. So you can adjust the rear carbs air screws while motor runs .
Posted By: 70sixpkrt

Re: "Detonation problems" rebuild 440-6 - 05/10/09 06:07 PM

Yes, I am using the Promax billet base plate for the rear carb. Easier to adjust the mixture screw but you might have to notch the float bowl alittle. I still have not done this.

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