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Which brings up another question. I ended up with 9.92 CR. I will start this thing off with 93 octane, but was wondering if I could possibly run 89 with this combo? I really don't mind running 93, but 89 would be nice.
From what I've gathered, what octane you'll be able to run will depend on your Dynamic Compression Ratio.
Something that I read on the subject suggested that above 8.5 DCR with aluminum heads is where you'll start getting into detonation territory.
So it depends on the cam that you're using. Later IVC lowers the DCR, and vice versa.
I don't know what DCR range would allow you to use 89 octane.

Get the IVC @.050 from your cam card, and put that and the rest of your parameters into this calculator to get your DCR.

 

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Discussion Starter #162
From what I've gathered, what octane you'll be able to run will depend on your Dynamic Compression Ratio.
Something that I read on the subject suggested that above 8.5 DCR with aluminum heads is where you'll start getting into detonation territory.
So it depends on the cam that you're using. Later IVC lowers the DCR, and vice versa.
I don't know what DCR range would allow you to use 89 octane.

Get the IVC @.050 from your cam card, and put that and the rest of your parameters into this calculator to get your DCR.

I had previously used a different calculator to come up with 9.92 SCR and 8.68 DCR. I don't put much stock in DCR numbers. I know that a couple of major players in custom cams do not use DCR in designing custom cams. My 383 runs 11.03:1 CR and the DCR is over 9 as I recall. Way over the recommended numbers. No signs of detonation. I believe the widely accepted max DCR and SCR numbers are very conservatively stated.
 

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Yeah I'm in California, so I stuck with the conservative numbers, since we only have 91 octane at best, with whatever additives.
 

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I had previously used a different calculator to come up with 9.92 SCR and 8.68 DCR. I don't put much stock in DCR numbers. I know that a couple of major players in custom cams do not use DCR in designing custom cams. My 383 runs 11.03:1 CR and the DCR is over 9 as I recall. Way over the recommended numbers. No signs of detonation. I believe the widely accepted max DCR and SCR numbers are very conservatively stated.
I just ran mine, 10.9 static and 9.2 Dynamic. Aluminum Head 406 fresh build.
I have a fairly quiet exhaust, and a pretty good ear and no problems yet... But at WFO mine really barks, so hopefully I'm ok. Always 93 from Exxon, or other top tier stations. I wish we had E85 over here, I would play with that stuff. LOL!
 

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I had previously used a different calculator to come up with 9.92 SCR and 8.68 DCR. I don't put much stock in DCR numbers. I know that a couple of major players in custom cams do not use DCR in designing custom cams. My 383 runs 11.03:1 CR and the DCR is over 9 as I recall. Way over the recommended numbers. No signs of detonation. I believe the widely accepted max DCR and SCR numbers are very conservatively stated.
This depends on altitude, humidity and temperature; also vehicle weight and the topography the engine has to drag that through, overall gearing that being stiffer gearing is more forgiving as it gives the engine a better mechanical advantage against the load it has to move.

The race track is more forgiving than the street as generally the overall gear ratio’s are stiffer, vehicle weights are lower, and fuels are able to be of higher octane and have higher vapor pressures often working with cooler intake temperatures

Modern chamber heads are more tolerant whether the head is iron or aluminum. Certainly modern aluminum heads are way out in there innate ability to surprise detonation.

So yes under the right circumstances and with the right equipment and the right operator/driver situation management the compression ratios of the SCR and DCR can be pushed. I have built 400 horse 350’s that run just fine on 87 to 89 octane fuel. My daily driver runs an SCR of 10.7 with a DCR of 9.3 (D dish pistons, aluminum heads, HOT cam, 700R4 into a 3.08 axle, the vehicle wt empty is 2800 pounds. Most of the time it does just fine on 89 octane E10 corner station fuel. That’s in hilly country at sea level. In the cold of winter it’s fine on 87 E10. During the summer if going over the mountains to the desert I’ll fuel it with 91 E10 just to cover my butt in the hundred plus degree temps over there.

So yes there are conditions where the compression ratios can be shoved but you gotta understand what you’re doing.
 

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Discussion Starter #166
This depends on altitude, humidity and temperature; also vehicle weight and the topography the engine has to drag that through, overall gearing that being stiffer gearing is more forgiving as it gives the engine a better mechanical advantage against the load it has to move.

The race track is more forgiving than the street as generally the overall gear ratio’s are stiffer, vehicle weights are lower, and fuels are able to be of higher octane and have higher vapor pressures often working with cooler intake temperatures

Modern chamber heads are more tolerant whether the head is iron or aluminum. Certainly modern aluminum heads are way out in there innate ability to surprise detonation.

So yes under the right circumstances and with the right equipment and the right operator/driver situation management the compression ratios of the SCR and DCR can be pushed. I have built 400 horse 350’s that run just fine on 87 to 89 octane fuel. My daily driver runs an SCR of 10.7 with a DCR of 9.3 (D dish pistons, aluminum heads, HOT cam, 700R4 into a 3.08 axle, the vehicle wt empty is 2800 pounds. Most of the time it does just fine on 89 octane E10 corner station fuel. That’s in hilly country at sea level. In the cold of winter it’s fine on 87 E10. During the summer if going over the mountains to the desert I’ll fuel it with 91 E10 just to cover my butt in the hundred plus degree temps over there.

So yes there are conditions where the compression ratios can be shoved but you gotta understand what you’re doing.
Thanks Bogie! From your experience, I may be able to get away with 89. I will probably run a couple of tanks of premium through it, then go to about a half tank of 89 to see how it does. I have never used hypereutectic pistons before, always forged, and am a little nervous of detonation with them. I have a couple racing trophies (burnt pistons) on the shop wall that show the results of detonation.
I remember getting a new engine from my builder fresh from the dyno. Took it racing. It was a real slick track that night, and I won the feature running on 7 cylinders for the last 5 laps. Took it apart. Yep, burnt the lands off #5 piston. The carb had (3) 96 jets with a 69 in the secondary. Called the builder. He said he put them in there, but somebody handed them to him. Said he couldn't read those little numbers anyway. He fixed the engine for free.
 

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Discussion Starter #167
Aaaarrrrrrgh! I was just finishing up, putting the radiator and support rods in. The support rods run parallel from firewall to radiator, one each side of the radiator. They are 1/2" square tube and also provide the 4 hinge points for my forward hinging hood. They ran just across the top of the valve covers with just enough room to remove the covers. They just cannot be moved due to the hinge mechanism. They now have my valve cover trapped and would have to be removed to remove the valve covers. Which would be a total PITA!! A lot of disassembly. The culprit is the raised rail under the valve cover on the aluminum heads. I never gave that a thought. About a 1/2" of height got me. I told you it was tight in the engine bay. The valve covers I have are 3.5" tall and a stud girdle will fit under them, so there is enough spare room under them to allow shorter VCs. I don't have any stock height covers to see if they would work. I measured and it appears that 2-3/8" to 2-1/2" with a gasket should clear the roller rockers. I know roller rockers won't work on a stock head with stock covers, but I don't know if they will work with the raised oil rail on the aluminum heads. I'm going to have to buy a set of valve covers. I just don't want to buy something that won't work. Anybody have any experience with this? I wanted to fire it up in the morning, but I need to solve this first.
I do have a set of 60 year old Cal Custom covers and they are just tall enough, but they have no holes in them for the PCV or oil fill.
Thanks for sticking with me and for all your help guys!
 

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A guy over on Steve's Nova site just measured one of the typical die cast smooth aluminum valvecovers, short version, and they were 2.455" from gasket rail on the cover to underside of the top...he was facing the other situation, not sure if they would clear the roller rockers but had the raised valvecover rail on the ProMaxx heads working in his favor. He hasn't come back and posted it being a problem, so must be they cleared.
 

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Discussion Starter #169
A guy over on Steve's Nova site just measured one of the typical die cast smooth aluminum valvecovers, short version, and they were 2.455" from gasket rail on the cover to underside of the top...he was facing the other situation, not sure if they would clear the roller rockers but had the raised valvecover rail on the ProMaxx heads working in his favor. He hasn't come back and posted it being a problem, so must be they cleared.
That's pretty funny. After reading your reply, I was looking on Summit at VCs. One of the stock height covers had a review from a guy using the advertised stock height covers on his ProMaxx heads. He said they cleared his roller rockers. I'll bet it was the same guy. Mine will be here Tuesday. Another hold up. Out of the 27 days the car has been down, at least 12 days have been waiting on parts and probably 10 days waiting on an old man to get off his butt.
 

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Discussion Starter #170 (Edited)
Mine will be here Tuesday. Another hold up.
I'm telling you, Summit is on the ball. I ordered those valve covers at 1PM yesterday. They arrived this morning at 11:30 AM. 23-1/2 hours. They are usually 2-3 days. Summit's warehouse is 217 miles from me. I got a letter yesterday in the mail from a city 55 miles away. Took 8 days.
So today becomes fire-up day! I gotta get at it and make sure they clear the rockers.
Edit: My math isn't very good today. 22-1/2 hours.
 

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Discussion Starter #172
It's alive! Fought a little fuel leak was the only thing until I tried to use my new, one use only, timing light and no light. So I just timed it with the vacuum gauge until I can get the light replaced. I haven't driven it yet, but it really sounds good. I'll take it for a drive in the AM after I fix a leak in the trans lines to the cooler. It was never out, but I must have disturbed it somehow. Other than a couple little issues, I'm pretty happy with the way it went.
Thanks for all your help guys.
 

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Discussion Starter #174
Took it out for about a 25 mile drive this morning. It runs really good. Seat of the pants says I hit my 350 HP goal pretty close. Maybe just a little more. At this point it has only been timed by ear and vacuum. New timing light in the AM. There is a little off idle hesitation. Very slight, but there. I put the QFT 600-SL-VS straight off the stock 350 GoodWrench onto this engine. No changes. I had had an off idle hesitation on the stock engine and changed the 31 squirter to a 35. Then swapped it back and was able to get the off idle hesitation cured by opening the 4 corner idle screws about 1/8 of a turn. So right now there is a 31 squirter in it, but opening the idle screws doesn't seem to help this time. I may have to go back to the 35. I have a small cap ready to run chinese distributor in it. It is not your standard chevy design. I can't adjust the vacuum or mechanical advance. I can't even get to it. And both are too much. So tomorrow I should have a new Summit's version of the small cap RTR distributor (MSD copy). It is fully adjustable, so I can get my ignition curve how I like it. That's really first before I can decide what to do with the carb.
This is all caused by the dummy that built the car making the notch for the distributor a hair too small.:rolleyes: I wanted the least intrusion into the cab as possible. An HEI will not fit. A points distributor works but is really tight. It's not the base but getting the 4,3,6,5 plug wires on is tough. The small cap makes it a lot easier and it straightens the plug wires out.
The stock QFT jets worked well on the stock motor. I think they are 68/74. Would you expect that I would have to richen it up a little with this new combo? I figure I can do a high RPM chop plug check after it is broken in. I can do that on my country road and coast right into the shop!
I didn't quite make my time line, but close. I have it ready for the 4 day Duck Tail Run in Gas City, IN. Great show.
Thanks again guys.
 
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