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Old 02-13-2013, 05:34 PM
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I have a V-8 Chevy Vega with the early LT-1, 11.6:1 flat top forged pistons and a .010 quench (pistons stick out of the deck by .030, Felpro permatorque gasket .040 compressed). I run 91 octane (California) with timing set at 26 degrees (locked) and approximately 14 degrees vacuum advance. I shift at 8,000 rpm's with a Sig Erson Hi-Flow I hydraulic cam, ported and polished heads (2.02/1.60 iron heads right now), and it runs just fine. The tight quench makes the burn happen faster because of turbulence in the combustion chamber, so the mechanical timing cannot exceed 28 degrees. If you have any doubts about how this can work, check with Doug Roe (chief head design and intake manifold research engineer with Chevrolet for 17 years, now retired). This engine makes over 500 horsepower and gets 11 mpg with a 700R4, 3,000 rpm stall, and narrowed 12 bolt rear (3.08:1) with posi and Camaro suspension and brakes, 14 inch tires/rims (26 inch diameter). Line bore your engine first, then shot peen and resize rods, then buy, polish, and balance pistons (I used TRW forged flat tops), and then and only then deck the block for the quench. Pistons should stick out of the block between .020 and .030 with a .040 (compressed) head gasket. Any tighter and the rod stretch will let the pistons touch the heads. Any looser (less quench) and you lose torque. All quench benefits are lost if the piston to head clearance is greater than .030 inch. Gas mileage goes up, torque and horsepower almost double with the .010 inch piston to head clearance. Just don't make a mistake in machining. I use an HEI distributor with Pro-Comp's multiple spark discharge box. It does the same thing as a Digital MSD, but is way more reliable and 1/3 the cost.

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Old 02-13-2013, 05:45 PM
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8,k RPM & .010quench

Quote:
Originally Posted by barry425 View Post
I have a V-8 Chevy Vega with the early LT-1, 11.6:1 flat top forged pistons and a .010 quench (pistons stick out of the deck by .030, Felpro permatorque gasket .040 compressed). I run 91 octane (California) with timing set at 26 degrees (locked) and approximately 14 degrees vacuum advance. I shift at 8,000 rpm's with a Sig Erson Hi-Flow I hydraulic cam, ported and polished heads (2.02/1.60 iron heads right now), and it runs just fine. The tight quench makes the burn happen faster because of turbulence in the combustion chamber, so the mechanical timing cannot exceed 28 degrees. If you have any doubts about how this can work, check with Doug Roe (chief head design and intake manifold research engineer with Chevrolet for 17 years, now retired). This engine makes over 500 horsepower and gets 11 mpg with a 700R4, 3,000 rpm stall, and narrowed 12 bolt rear (3.08:1) with posi and Camaro suspension and brakes, 14 inch tires/rims (26 inch diameter). Line bore your engine first, then shot peen and resize rods, then buy, polish, and balance pistons (I used TRW forged flat tops), and then and only then deck the block for the quench. Pistons should stick out of the block between .020 and .030 with a .040 (compressed) head gasket. Any tighter and the rod stretch will let the pistons touch the heads. Any looser (less quench) and you lose torque. All quench benefits are lost if the piston to head clearance is greater than .030 inch. Gas mileage goes up, torque and horsepower almost double with the .010 inch piston to head clearance. Just don't make a mistake in machining. I use an HEI distributor with Pro-Comp's multiple spark discharge box. It does the same thing as a Digital MSD, but is way more reliable and 1/3 the cost.

Ive used the Sig Erson high flow II cam and it was done a 6500 rpm.

Do you have a video of your car.I would really like to learn these secrets
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Old 02-13-2013, 06:02 PM
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Hi Vinniekq2,
I've heard from several sources, one being Robbie at California High Performance, that the Sig High Flow II is junk and that the High Flow I outperforms it. I shift at 8,000 rpm because of fear! It shows no signs of shutting off even at that high rpm. I don't have a blanket and don't want to cut my feet off if something should let go.
Let me know where you are and I might be able to phone you and answer any questions you may have. I kept all the receipts for my engine and can help you build yours. In fact, if you are in southern California, I'll help you build it. I've been doing this for over 40 years (off and on) and have a lot of experience with high performance street engines and suspensions.
Barry
P.S. I have photos, but no videos.

Last edited by barry425; 02-13-2013 at 06:03 PM. Reason: add info
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Old 02-13-2013, 06:53 PM
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[QUOTE=F-BIRD'88;1644857]You'd be better served by getting a timing box that allows adjusting the timing a bit +/- as required, from the drivers seat. Rather than playing with the gasket. The fuel quality in the tank and the day-conditions will be the factors.

Just preset the dash timing dial in the middle of its range, and set the engine timing with a light.
Now you got convienient effective on the fly +/- spark timing adjustment.
Now you can adjust for different fuels, without lifting the hood.

X2 I Use that MSD Timing box and it works great.
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Old 02-13-2013, 07:02 PM
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barry425
I live directly north in Canada
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Old 02-13-2013, 09:49 PM
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Hi Barry 425,
I live WAY down south, in AUS.
I've always read that quench benefits are lost by .060" (OMG!... Der!) and are an avid fan of tight quench.
I run .035" in my 11.48:1 sbc 355 on 98octane RON (AUS ) which equates to roughly 92oct USA, with 34deg locked out.
I feel that a tight quench is extremely important for the reasons that you mentioned, but 10 thou! and 26deg, that's interesting, you got MY attention! Maybe I'll tighten mine up some! LOL!!
Is carbon build up a concern? I guess not if it sees 8000 regularly.

This should surely be 'food for thought' for the OP.

Btw Vinnie, your vette sounds ' great ' in the vid! , is that straight out of the collectors?


Duke
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Old 02-13-2013, 10:00 PM
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thinwhiteduke,that sound is out the mufflers,,,,Im using 3 inch short turbos.thanks,
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Old 02-14-2013, 01:49 AM
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Here in California, we only get 91 octane. 100 octane is available at maybe 3 or 4 stations in L.A. and Orange Counties combined, but it costs 9-10 dollars a gallon. I'm retired, so that is too rich for my budget. My compression ratio was calculated using a plexiglass plate and burette on each combustion chamber, piston eyebrow (valve relief), head gasket, and cylinder. It is a true 11.6:1 and the combustion chambers are polished so no carbon has a chance to build up. Also, because the quench is so tight, no burning takes place in the quench area and so no carbon would build up there even if the chambers were not polished.
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Old 02-14-2013, 09:41 AM
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Quote:
Originally Posted by Landshark928 View Post
I am running 11:1 with aluminium heads and a .043" quench on 91 Octane, 93 when I can get it. No issues. Cam is a little bigger at 253*@0.050" and 110LSA. I run 36*total timing in by 3000rpms. I use vac advance to add 8* more under cruise.

Read your plugs and add timing a little at a time.
When you say "read the plugs". If a guy is looking for signs of detonation what appearance will the plug have?
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Old 02-14-2013, 10:32 AM
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Quote:
Originally Posted by prostcelica View Post
When you say "read the plugs". If a guy is looking for signs of detonation what appearance will the plug have?
If you catch it early it looks like small specks of black or grey "pepper". If you see some, back off timing a bit.

When extreme or prolonged it can start to melt the strap and tip.

This one has gone too far too long.



You can also change the spark plug heat range to help fight off detonation. But it's a compromise at best.
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Old 02-14-2013, 12:51 PM
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Hi F-Bird'88,
You didn't read my blog, apparently. I'm running a negative deck (pistons stick out of the block) and my quench is not .033, but .010 piston to head clearance. Since you are not acquainted with Doug Roe's engineering, I would not expect you to understand.
The gas in California is regulated more than other states. We even have different blends mandated for summer and winter. The octane is calculated by: research+motor/2=octane
I've already tried 100 octane gas ($9 per gallon) with Moroso Octane Boost and advanced timing. No good. It pings like crazy because the tight quench makes the fuel burn faster in the combustion chamber.
By the way, when a flat top piston sticks out of the block, your factory calculations for compression ratio go out the window.
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Old 02-14-2013, 02:09 PM
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Generally speaking the lower the quench area the more forced lateral acceleration and turbulence of the charge gas. Leads to quicker more complete burns. Proximity of the piston to head also allows for a little more heat removal from the piston. Less is better up to the point of interference...

The reason most go .035 to .045 is to get a nice benefit with a nice safety margin. Also the increased gains are less measurable from .035 to .025... diminishing return.

At 0.010" quench most engines will leave piston marks on the heads. How much rock does your piston have? How many rpms are we turning? How strong are your connecting rods? Lots of variables. Recommended quench ratings keep things safe and easy while still getting a nice benefit. Even pro engine builders rarely go below .025" quench. In fact going to low can actually cause charge gas to be trapped in the ring land area instead of the squish area, leading to unburnt fuel, lost power and increased emissions. Chasing that last 5HP and 10FTLB is not worth it to most Hotrodders.

Doug Roe could afford to strip and rebuild his Vega after every race. A little piston kiss was not a concern like it would be a for a street car.
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Old 02-14-2013, 09:36 PM
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I am so glad that you opened the door to talk about Doug Roe's experience. When my Vega had the original 90 hp 4 cylinder in it, I purchased a Doug Roe head. When my engine was stock, it got 21.4 mpg on a measured course strictly on the freeway. I had the block decked for the tight quench and bolted on the Doug Roe head, which had a heart shaped combustion chamber (instead of the stock open chamber). I took the car on the exact same course, filled at the same pump in the same gas station and got 43.0 mpg.
I then took the car to a chassis dyno and the specialist started tapping his gauges. I asked if something was wrong. He asked if I had done something to the engine. I felt about 1 inch tall, thinking that I had ruined something. I told him that I had modified it and asked why. He said that it was making 58 horsepower at the rear wheels. I said that it was a 90 horsepower engine, thinking that I had ruined the engine. He said that a GT engine (110 horsepower) only makes 35 hp at the rear wheels! So, I had doubled the gas mileage, almost doubled the horsepower, and the icing on the cake was that it was smoother than a V-8. That engine lasted 94,000 miles, which if you recall, was some kind of a record for that engine design. Most became boat anchors at 40,000.
I did the same thing to the first V-8 that I put in the Vega. It was a small journal 327 with the .010 quench, quadrajet carb, modified (to fit) cast iron manifolds and a 400 turbo hydro. This engine took me to work and back for 20 years, logging 300,000 miles, and still passed smog when I took it out in favor of the reworked LT-1.
You can theorize and bench race all you want, but I made it work for, let's see, 37 years now. If you can't believe the truth when it is told to you, look me up in Diamond Bar, CA, and I'll take you for the ride of your life.
B.A. Murphy (in the book)
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Old 02-14-2013, 10:02 PM
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H.o.!

Quote:
Originally Posted by barry425 View Post
I am so glad that you opened the door to talk about Doug Roe's experience. When my Vega had the original 90 hp 4 cylinder in it, I purchased a Doug Roe head. When my engine was stock, it got 21.4 mpg on a measured course strictly on the freeway. I had the block decked for the tight quench and bolted on the Doug Roe head, which had a heart shaped combustion chamber (instead of the stock open chamber). I took the car on the exact same course, filled at the same pump in the same gas station and got 43.0 mpg.
I then took the car to a chassis dyno and the specialist started tapping his gauges. I asked if something was wrong. He asked if I had done something to the engine. I felt about 1 inch tall, thinking that I had ruined something. I told him that I had modified it and asked why. He said that it was making 58 horsepower at the rear wheels. I said that it was a 90 horsepower engine, thinking that I had ruined the engine. He said that a GT engine (110 horsepower) only makes 35 hp at the rear wheels! So, I had doubled the gas mileage, almost doubled the horsepower, and the icing on the cake was that it was smoother than a V-8. That engine lasted 94,000 miles, which if you recall, was some kind of a record for that engine design. Most became boat anchors at 40,000.
I did the same thing to the first V-8 that I put in the Vega. It was a small journal 327 with the .010 quench, quadrajet carb, modified (to fit) cast iron manifolds and a 400 turbo hydro. This engine took me to work and back for 20 years, logging 300,000 miles, and still passed smog when I took it out in favor of the reworked LT-1.
You can theorize and bench race all you want, but I made it work for, let's see, 37 years now. If you can't believe the truth when it is told to you, look me up in Diamond Bar, CA, and I'll take you for the ride of your life.
B.A. Murphy (in the book)
sounds spectacular,post a video for us to see! cant wait
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Old 02-14-2013, 10:07 PM
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When my daughter gets home next week, I'll try to have her video the car, engine, and a couple of burnouts. I don't want to race on the street and lose my car. I've been meaning to take it to the drags, just haven't had the time yet. I'll have her video that, too. Meanwhile, I'll see if I can find some still photos to post here or on Facebook.
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