Small block combo suggestions

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AJ I forgot to mention the ambient temp here is normally in the high 80s wt close to 90% humidity. Heat heat heat
 
MOPAROFFICIAL said:
Unless you have over 170 cranking psi on un prep'd chambers ...Primary jetting is lean=surge at cruise.
The old mp .490 lift solid would be great for your combo, with 1.6 even better.
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Yes the chambers were just cleaned no real prep work other then a good valve job I'll get back to ya on the cranking pressure. Thanks
 
FWIW, I came up with the same numbers as AJ for DCR etc., ASSUMING a .039" thick head gasket. If you have the head gasket info, that would be helpful; with a .028" thick head gasket, DCR bumps up to around 8.2. Should be doable, but moving to 93 octane would help (if you are not using it already).

FYI, humidity will tend to LOWER the tendency to detonate. Some research work in the 80's concluded that going to your humidity levels approximated the same effect as 3 to 4 points increase in octane. So you are REALLY doing something special to get into detonation LOL
 
rumblefish360 said:
Jeff, thanks for accepting my sense if humor today.
Seriously, more cam would be my "Up the anti" choice.
A surge is lean & the distributor needs a tuning. Not coming in so fast.

RRR, is there a smiley that is giving out razzbeeries by chance?
Insert here ---->
LMAO

YR, you should have left a link to your post, "Help me choose a cam!"
And "I'm all over like a drunk out of a weekend lock up that just ran into the liquor store with a hundred bucks!"
(Funny thing is, my hot rod guzzled gas like that on a regular bassis! AKA W.O.T.! )
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Rumble fish 360.
Glad you enjoyed it.
This stuff has to be fun for everyone.
Too many keyboard alligators
You know the group
Alligator mouth canary behind.
I agree wt the surge just haven't identified which is causing it. I feel it's at the top of the transition circuit and the mains are just coming on line
The PV is not contributing fuel at this point Thanks keep em coming and as I get more info I'll post back.
 
nm9stheham said:
FWIW, I came up with the same numbers as AJ for DCR etc., ASSUMING a .039" thick head gasket. If you have the head gasket info, that would be helpful; with a .028" thick head gasket, DCR bumps up to around 8.2. Should be doable, but moving to 93 octane would help (if you are not using it already).
Click to expand...

I have it written down I'll look it up
Yes to 93 oct. of course it's 10% ethanol
I have been using Race Gas additive and using gas from just one vendor.
 
nm9stheham said:
FWIW, I came up with the same numbers as AJ for DCR etc., ASSUMING a .039" thick head gasket. If you have the head gasket info, that would be helpful; with a .028" thick head gasket, DCR bumps up to around 8.2. Should be doable, but moving to 93 octane would help (if you are not using it already).

FYI, humidity will tend to LOWER the tendency to detonate. Some research work in the 80's concluded that going to your humidity levels approximated the same effect as 3 to 4 points increase in octane. So you are REALLY doing something special to get into detonation LOL
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Sir I believe I have the fel pro # 8553pt. Head gasket and I think those are .039 thick. I was shooting for around a 9.5 to 9.7 car for this combo.
Thanks
 
IMHO you are shooting at a decent SCR for a street/torque cam. But with a 8553PT head gasket, you are likely around about 7.8-7.9 for DCR. It ought to work; I have put a bit higher on the street with iron heads and a bit smaller cam, but I could not get aggressive with total ignition advance.
 
48 cruise is perfect, up around 2200 or better.
Try not to blame detonation on the cooling system yet. My engine has far more compression and it has always run at 205* or better.Even with the Scr over 11.3 (aluminum heads), 205 was no problem. I would consider the minimum running temperature the last place to go. The hotter she runs without melting down, the more power you will find and the better the fuel mileage will be. So I run as hot as I can get away with. The trick is to have a rock-solid cooling system that you can depend on,that runs at exactly the same temperature all summer long,day and night,in traffic and out! So,IMO, kiss electric fans off. The temperature swing is just too great. It is my opinion that a simple clutch-fan with a temperature compensatory valve, on an adequate rad/pump/giant fan/combo gets the job done. And I was willing to sacrifice a few HP at redline to drive that monster fan,to get it.
Pick a temp. Make it rock-steady.Tune from there. If you just can't get rid of the Det, having tried everything else, then and only then would I consider backing down the running temp.
But that's how I roll.And its been over 16 years, and 125,000 miles and still going.

Ok so maybe this temp thing is unclear. The cooling system is just the straw thay breaks the camel's back. The difference from 180 to 160 is like 20* right? The difference between detonation and no detonation can be several hundred degrees in the chambers. You just cannot band-aid that with a 160 stat!
The first place to look is octane and cylinder pressure.
Then timing
Then fuel
Then load
Then the minimum running temp.
That is my opinion and has served me well. I just cannot tune 200psi on 87, no matter how hard I try. They don't make a carburetor small enough nor street gears low enough.But I can crank a ton of timing into a roto-tiller, crank up the governor, and bust me up some really hard earth and big clods.
 
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Jeff, for certain, keep the updates coming. I hope to get to my 6 pack build come spring. (Some how, I'm sure there will be a wrench in the works. :( )
 
AJ/FormS said:
Post #1 is full of info
but the most important info is missing. How much cylinder pressure is that engine running and at what altitude is it operating?

KB107s are flat-tops and in a 360 sit down in the hole. X-heads are open chamber items. The 262 has a very early ICA. But unless you have done a lot of machining, the engine should not be detonating. Well yeah your timing is all in a little early, but there is something you haven't told us,namely the cylinder pressure..

A little detective work,; with no machining, this is a 9.5 engine. the 262,in at 106 makes an ICA of 59*. This conspires to make a Dcr of 7.9 and cylinder pressure of 158 at sealevel;just about perfect,for iron heads.And should not require 93.
Soooooooooo, what's your pressure.
Three things lead to detonation; too much heat, and too much heat, and too much heat; for the fuel.The heat can come from excessive pressure,too-early timing, a hot-running cooling system,hot-air intake,hot spots in the chambers,restrictive exhaust, or lean AFRs.
Did I miss anything?
Oh yeah, too high a load.As in secondaries coming in too soon.

-If it detonates after 4000, you can probably rule out your timing. That combo should run full-timing ok at 180*engine temp.If you have a scoop, you can rule out hot-air. If you have headers and duals exhaust looks covered. That leaves just; pressure,hot-spots and AFR.
-But if it detonates right from the get-go, Perhaps the secondaries are coming in too early,or the exhaust is not getting out,or as you have already surmised, the timing is all-in too early.
-If it detonates between say 3000 and 4000, then cutting back the timing should help.But you tried that and even at 30* it is still detonating.
Soooooo, what's the pressure?
-If the pressure is below 160psi,and timing is under 36*,and it still detonates after 4000,then you have three choices,I think; Hot spots in the chambers,Lean AFRs, or hot inducted air.
It's all about too-much heat,or too much load.
Ok here's a wild card; the heat could be from something in the chamber that should not be in there,lol. Like exhaust,engine oil, something in the gas,or not in the gas that should be in, or a gasket overhanging the top of the bore,or plain old carbon. I would clean out the chambers and start over.
-If the pressure is over 160, you are gonna have to be sharp on the tune.
I like this combo;it should make a ton of torque, and be a pleasure to cruise around in. I also see lots of tire-smoke
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AJ/Forms.
Cylinder pressure is 182 psi. Cold.
Higher than I remembered
Thanks.
 
nm9stheham said:
BTW, you mention six pack. Are all the carbs the right ones in the right positions?
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Sir I've had them for about 20 yrs and have been fanatical about keeping them in position. Especially when setting mixture on rear carb. What a pain. Thinking of changing base plate in rear to one of the proform wt angled mix screws. Also may swap jet plate.
They are correct for small block app. Will tell you they are sensitive to the weather. With the cold starting down here they will be a touch lean but because it's seldom cool for long I have learned to just leave them alone.
On my prior combo which was just a 360 truck motor wt the six pack heads,exhaust and intake it would run 14.00 at a 102 mph. In the quarter I know it's not quick but it was built as a cruiser. Also it returned 18 mpg This new combo has some potential I feel but have to put in the time to tune. That's why I appreciate all of your help. Thanks
 
jeff1 said:
AJ/Forms.
Cylinder pressure is 182 psi. Cold.
Higher than I remembered
Thanks.
Click to expand...
Hmmm. That does not compute out with the info given for the build. (Assuming an XE-260 cam...) Is this a Magnum block? Or were the heads shaved a fair amount? Or is the cam advanced by a whole tooth?

I am coming up in the range of 155 psi. You would need an SCR of about 10.5:1 for that 182 psi pressure with a 260 range cam. Do you have access to another gauge?

BTW, the cam number given looks to be for a Chevy small block. Can you re-confirm that cam part number?
 
nm9stheham said:
Hmmm. That does not compute out with the info given for the build. (Assuming an XE-260 cam...) Is this a Magnum block? Or were the heads shaved a fair amount? Or is the cam advanced by a whole tooth?


I am coming up in the range of 155 psi. You would need an SCR of about 10.5:1 for that 182 psi pressure with a 260 range cam. Do you have access to another gauge?

BTW, the cam number given looks to be for a Chevy small block. Can you re-confirm that cam part number?
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Cam from card XE262H-10.
Checked wt two gauges because that number 182 was higher than I remembered
I was present during the block machining but not for the heads I had asked and was told they needed hardly any metal removed to confirm true.
But we are assuming they were stock uncut prior as I acquired them some 20 plus years ago and had them on my previous build.
The block is an old 360 truck block

IMG_1408.JPG
 
Got it... I just probably looked in the wrong place. The measured pressure just ain't workin' out.... so if this was confirmed with a 2nd gauge, I am at a loss as to why; something has to be different inside.

But that is surely too high for that cam; with you needing around 10.5 SCR to get to that cranking pressure, the DCR will be up near to 9. That may well 'splain the detonation.
 
BTW, for 10.5 SCR, the head chambers would have to be around 65 cc's (NHRA minimums) with the .028" head gasket, or around 60-61 cc's with a .048" head gasket.

Or maybe the block was decked down a fair amount. Were the KB107's truly flush to the deck? With a stock deck they would be about .012" in the hole.
 
nm9stheham said:
BTW, for 10.5 SCR, the head chambers would have to be around 65 cc's (NHRA minimums) with the .028" head gasket, or around 60-61 cc's with a .048" head gasket.

Or maybe the block was decked down a fair amount. Were the KB107's truly flush to the deck? With a stock deck they would be about .012" in the hole.
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They were down in the hole but just slightly. Interesting.
 
jeff1 said:
They were down in the hole but just slightly. Interesting.
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Well, .012" inch below deck is right for these KB107 pistons and the stock deck height and stock rods, and that seems like 'slightly' IMHO.

So perhaps the heads have been milled a bunch. Do you recall if the 'open' part of the chamber on the heads was very shallow? The stock area is around .090" deep; if the heads were milled about .060", then the chamber size would be down in the low 60 cc range.

And using nail head valves (straight across on the main surface in the chamber) would lose another few cc's. And then there is the head gaskets.....lotsa variables.

I think I would still try one more compression gauge....
 
AJ/FormS said:
182 is about perfect for aluminum heads. For iron, down around 165 will work.
I think you're gonna need to lose some cylinder pressure.
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Ok I'm gonna check wt another gauge and report
So what are our options ? And still keep the intended purpose of a cruiser. Alum heads, cam swap? Head gasket
I've got a call to my machinist hoping he still has his notes.
This would explain the detonation issues.
 
nm9stheham said:
Well, .012" inch below deck is right for these KB107 pistons and the stock deck height and stock rods, and that seems like 'slightly' IMHO.

So perhaps the heads have been milled a bunch. Do you recall if the 'open' part of the chamber on the heads was very shallow? The stock area is around .090" deep; if the heads were milled about .060", then the chamber size would be down in the low 60 cc range.

And using nail head valves (straight across on the main surface in the chamber) would lose another few cc's. And then there is the head gaskets.....lotsa variables.

I think I would still try one more compression gauge....
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I'll try another gauge but my confidence is high that these are accurate.
Hoping my machinist still has his notes
 
Roger on the gauges; I suspect you are spot on. It's just to avoid any teardowns if possible.

All the above ideas are on the table if the cranking pressure is still up there in the 180ish range. In order of effort and cost:
1. Thick head gasket: Think Cometic. If it were the case that you had 65 cc chambers with a .028" thick head gasket, you would have to go to around .065" or .070" thick to get the SCR to 9.5 or a bit less, and the DCR to 7.9-8.0. If the chambers are smaller, then the gasket needs to be thicker. I have no idea just how thick you can go, and if there is any risk in blowouts, but Cometic makes them well over .100" thick. You can always put in ARP heads studs and clamp the heads down harder. (Keep an eye on the rocker oiling path in the head bolt hole with ARP studs.)
2. Cam change for a later intake valve closing from some combination of :
- Wider duration
- Wider LSA
- Less advanced cam timing
This is gonna change the engines personality more than the compression drop, so if you picked the cam for a particular purpose, then perhaps this is the last thing to consider.
3. AL heads: Maybe look at the Edelbrock 63 cc ones (closed chamber) and Cometic head gaskets around .055", or the 65 cc 'open chamber' versions, with the 8553PT head gaskets. Either will put your SCR in the 10.0ish range, and DCR in the 8.4-8.5 range.

The AL heads are the costliest solution but also keep the SCR up higher to help maintain the crisp low RPM torque you have now. And the breathing will be great and will help performance across the board. Do you have the stock rockers right now?
 
nm9stheham said:
Roger on the gauges; I suspect you are spot on. It's just to avoid any teardowns if possible.

All the above ideas are on the table if the cranking pressure is still up there in the 180ish range. In order of effort and cost:
1. Thick head gasket: Think Cometic. If it were the case that you had 65 cc chambers with a .028" thick head gasket, you would have to go to around .065" or .070" thick to get the SCR to 9.5 or a bit less, and the DCR to 7.9-8.0. If the chambers are smaller, then the gasket needs to be thicker. I have no idea just how thick you can go, and if there is any risk in blowouts, but Cometic makes them well over .100" thick. You can always put in ARP heads studs and clamp the heads down harder. (Keep an eye on the rocker oiling path in the head bolt hole with ARP studs.)
2. Cam change for a later intake valve closing from some combination of :
- Wider duration
- Wider LSA
- Less advanced cam timing
This is gonna change the engines personality more than the compression drop, so if you picked the cam for a particular purpose, then perhaps this is the last thing to consider.
3. AL heads: Maybe look at the Edelbrock 63 cc ones (closed chamber) and Cometic head gaskets around .055", or the 65 cc 'open chamber' versions, with the 8553PT head gaskets. Either will put your SCR in the 10.0ish range, and DCR in the 8.4-8.5 range.

The AL heads are the costliest solution but also keep the SCR up higher to help maintain the crisp low RPM torque you have now. And the breathing will be great and will help performance across the board. Do you have the stock rockers right now?
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Stock rockers now
Considered 1.6 on the intake
I can mix 100 octane wt 93. But sometimes that's just not practical.
I can change advance curve
But in the end it just very well may be that I missed the proper combo.
So all options will have to be explored but the head swap is the only one that we aren't putting a bandaid on problem.
Wt power everything engine vacuum is important so cam selection has that restriction
An interesting dilemma.
 
Ok, I sharpened my pencil too. Your assembly is nearly n exactly like mine with the exceptiom that my combo runs aluminum heads.
I used the Wallace Calculator.
I used these inputs 4.03bore x 3.58 stroke, with the standard 6.123 rods and an ICA of 59 degrees for the 262 cam. The calculator spits out a Dcr of 8.88 and cylinder pressure of 183psi. To get the 183, I had to input a Scr of 10.7, exactly where mine is currently. To get a 10.7 Scr from the above specs requires a total chamber size of 77.14cc
Still working backwards, this requires some combination of parts and clearances to achieve and is all too easy. Mine was set up with a 4.04 bore, .003 pop up(-.6cc), 5cc eyebrows, 63cc Aluminum-heads and the standard .039 FellPro which I think is 8.9cc.
Doing the math, this totals 76.3cc. My swept is 752.03cc. So (752.03 + 76.3)/76.3 =10.856 Scr.
Now if your overbore is .030, the your swept is 748.3cc
So (748.3+ 77.14)/77.14=10.700Scr.
And to make the 77.14, with an 8.9 gasket and 5cc eyebrows, requires some combination of head and deck height to total, 77.14-(5+8.9) =63.24. If the KB107s are slightly down say .003, that would be .6cc. so that leaves 62.64cc in your heads.
The point of this exercise is that 182psi is easily possible with the parts that you have and that your Dcr is too high for iron heads and pump gas. I run my combo on 87 and full timing so I know it's not too high for aluminum. There are several guys on here that run quite a bit more Dcr on pumpgas.
But that doesn't help you cuz aluminum heads are not cheap, and for your intended useage really aren't justifiable.
So the way I see it, the money has already been spent on the heads so let's try and keep them. That means you are gonna have to manipulate the Dcr with the other parameters, namely ICA,gasket, and pistons. Since you really want to keep that little 262, that leaves gasket and pistons. Since the .039 FellPro is a tuff sob and it sets a nice tight squish on closed chamber heads, which yours kindof have to be to be down at around 63cc; That just leaves the pistons.
So your pistons either have to be modified or swapped out.
To mod your pistons will require a reverse D-dome, to maintain the squish. I don't know if the 107s have enough material in the crowns to achieve that, or even if it is permissible to cut them,or if it is cost effective to do that.. But I do know that KB makes pistons with pre-cast cups like that.They are the KB232s with 18cc cups. They also have a nice .050 quench pad that you can use, actually;have to use, to adjust your squish. So lets do the math with those installed; Your heads are around 62.64, the gasket 8.9, no eyebrows , and 18 cc in the cups plus about .64cc in the deck. That totals ; 62.64 + 8.9 +18 + .64 =90.18
And.....(748.3 + 90.18)/90.18 =9.298Scr plugging that into the Wallace calculator gets us a Dcr of 7.75/153psi. That is really good for your intended useage. But, firstly the Q-pad will need to be machined down to fit and if you ever want to upsize the cam, you have no place to go; so this engine is kindof written in stone,that is to say no cam-change allowed. But it will burn 87, and it will be a bit of a tractor as to torque.
Now on the off chance that the pistons were down a little more than "just a little", there is room to pre-plan for a future possible cam-swap. There is some room in the Dcr. So since the pistons are coming out, this would be a good time to maximize the Dcr, by a little decking.The above described combo at a Dcr of 7.75, could be bumped up to 8.00 and still run on pumpgas, probably still on 87. That means by re-decking to make the 8.0, you have room for a larger cam of 1 or maybe 2 sizes.
Keep it mind I made up all the number here for your perusal, the big picture being you are not sunk yet. Get the numbers; head CCs, Deck HT, and we can help you dial it in, and so should your builder be able to.
Now if you wanted to put a different cam in , um...new solution.......lol
But I gotta say a 7.75 Dcr in a 360, in your chassis and for your useage, will not be disappointing.153psi is a pretty decent number.
 
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