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    Results 1 to 10 of 10
    1. #1
      Join Date
      Jun 2011
      Location
      St. George, Utah
      Posts
      1,629
      Country Flag: United States

      High Compression/ Boost on the street...

      Hey everyone-

      I’m preparing to install the 406 SBC engine from my old drag car into my wagon. This motor is 12.5:1 compression but I still plan on street driving it near daily. The cam has a ton of overlap, it’s 260/262 dur at .050 and is ground 4 deg advanced on a 110 centerline. I used to drive this engine daily in the Nova when it had flat tops and roughly 11:1. This engine has World Products iron heads on it. Guesstimated power is a little over flywheel 500 hp/ 500 ft lbs.

      I don’t have much experience with driving a pump gas higher compression motor so I’m looking for suggestions to keep it from rattling apart with detonation. I am at 3000 ft altitude in Southern Utah so that helps a little, but I’ll be driving down to Vegas and So Cal for events.

      • I can run 91 octane for daily use and something better for track days.
      • I’ll plan on retarding the timing for street driving
      • I was thinking to set up a methanol injection system for those occasional “freeway entrance ramp full throttle pulls”



      Anybody use the Crane or MSD timing retard dials for non boosted applications?
      Here’s a link to the Crane version- http://www.summitracing.com/parts/crn-6000-6425

      Those of you running the meth inj, is it something you run anytime you’re at full throttle or is it just occasionally to clean carbon build up out of the cylinders?

      Any other suggestions?

      Thanks!

      -Ben, Your friendly neighborhood Rendering dude

      SRD on Facebook

      79 Cutlass wagon build



    2. #2
      Join Date
      May 2015
      Posts
      249
      Country Flag: United States
      I think having 12.5:1 is a bit much for 91 octane, most likely it is going to ping as soon as you get on it lightly.

      I run methanol injection for my turbo truck, & have it turn on when the engine sees approx 6 psi of boost pressure.

      I think you are going to need to take out some of that compression, that cam is pretty wild for a nearly daily driver. Mileage is going to be bad.

      If you are going to run a methanol kit, it will have to & need to come on anytime you are @ near zero vacuum & will need to stay on until you let off. Not at W.O.T.

      It will basically increase your octane & reduce the chance of detonation.

      It's not just used for carbon clean -up on the pistons, though, that will be a side benefit.
      Those adjustable timing boxes work, so you can play around with what works best to prevent detonation.

    3. #3
      Join Date
      Jun 2011
      Location
      St. George, Utah
      Posts
      1,629
      Country Flag: United States
      When it had flat top pistons- 11-11.5:1, I drove this motor daily in my Nova with a 4500 stall and 4.56 gears. Nothing new to me, bad gas mileage is a sacrifice for power. I know there are more efficient ways to make this kind of power but the motor's free since I'm working out swapping a big block into the Nova.

      I put maybe 100 street miles on this motor in the Nova when I rebuilt it. I did plenty of hard first and second gear pulls and one really hard full 1/4 mile pull on 91 octane at 16 deg initial timing. No pinging at all. That was at 4500 ft altitude, so I'm assuming the high altitude's thin air and clean pistons helped. I'm more worried about what happens when carbon starts to build up on the pistons and that contributes to detonation issues.

      If I put my own kit together, sounds like a throttle activated switch is in order?

      Thanks again for your insight!
      -Ben, Your friendly neighborhood Rendering dude

      SRD on Facebook

      79 Cutlass wagon build


    4. #4
      Join Date
      May 2015
      Posts
      249
      Country Flag: United States
      You are still running 4:56 gears? If so, that will make for less chance of detonation. Still have a 4500 stall?

      What is your total timing set at?

      My friend built a 434 SBC approx 13:0.1 compression, big roller cam, that engine was so loud, you could not hear the detonation, but it was detonating on pump gas.
      Here was his car:
      https://www.youtube.com/watch?v=9e2UoXn5MNA

      https://www.youtube.com/watch?v=U23s7Ed-xMM

      What is the cranking compression? Maybe since your cam has so much overlap it's bleeding most of the cyl pressure?

      I daily drove my inline 6 250 engine with 12:1 compression & had 220-230 cranking pressure on 91 octane. 4:10 gears. The engine had a positive deck, pistons was above the deck, .002-.004"

    5. #5
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,971
      Country Flag: United States
      Is running E85 an option?

      Andrew
      1970 GTO Version 3.0
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      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    6. #6
      Join Date
      Jun 2011
      Location
      St. George, Utah
      Posts
      1,629
      Country Flag: United States
      No E85 in the area that I know of, we're a bit secluded in a valley, a big town in size but little town feel. Metropolitan areas in Utah have it but they're about 4 hours away, lol!

      The steep gears and converter are in the Nova. The wagon will have 3.50 gears and a 2600 stall, and is about 600lbs heavier. That will likely add to the load on the motor, at least from a stop, maybe not as bad from a roll?

      Someone's probably thinking to suggest it, at some point I'll look into aluminum heads with 74cc chambers to replace these iron 64cc heads, but that's not in the budget if I want travel to race at all this year. :/

      Honestly I've never checked cranking pressure. I'll check that when I swap things over.
      -Ben, Your friendly neighborhood Rendering dude

      SRD on Facebook

      79 Cutlass wagon build


    7. #7
      Join Date
      Sep 2006
      Location
      Southern Indiana
      Posts
      4,699
      Country Flag: United States
      To street drive engine your gonna be pushing every limit to try and maintain it and in doing so your gonna have a combo that's just a bitch to drive. If I had my preference swap/ sell cam and at least drop down to 230ish at .0.050 lift 108-110.
      Drop compression down to 10+ to one with flat tops. Use thicker head gaskets to drop it more.
      GM has 0.053 compressed head gasket that's good.
      Had a big cam in my Pontiac 400 idled at 1800 rpm.
      Even with water/methanol injection its gonna push every limit and probably destroy the engine anyway.
      Now if you had E85 or 93 or 94 octane , booster and a good water/methanol setup like Snow or another brand you would have running chance.
      OR 50/50 with race gas.
      To pull enough timing for that compression its gonna be a dog even with lower stall converter but its gonna buck ,surge and push at every light.
      Dig up a set of 487 castings, drill for steam holes slap in set of flat tops, planned gears and converter add in a 215-225 duration cam, 110ish centerline.
      I had 355 with PUNY cam, old 991 truck heads opened up to 194 intakes, old scorpion intake 600 Carter carb.
      That engine with TCI Saturday Nite Special converter 3.42 gears made a LETHAL take off it was a bullet at launch. All in my Monza with swingarm rear suspension hooked like a top fueler on a fast pass and never smoked a tire once, not even in rain.
      Before you try to nurse a hopeless case step back and replan or your ride won't be much fun.
      Lee Abel
      AFTERMARKET PERFORMANCE

      1977 Chevy Monza 2+2:Project "Cheap Trick"
      1978 C10 Long bed , On air and trailer puller
      2006 Buell Blast ,Just a bike to ride and for mileage
      1966 Caprice 4dr Sports Roof fact.327/now 350/SOON 454???? Project "II Old,,,ZERO BUDGET OR LESS CAPRICE!"

    8. #8
      Join Date
      Jun 2011
      Location
      St. George, Utah
      Posts
      1,629
      Country Flag: United States
      I see your point, but my current 8.5:1 small block 400 pushes this car to high 13s with 2.41 gears and a stock TH350 and converter with an air gap dual plane, Summit 600 cfm carb, Comp XE 268 cam and self ported factory 400 heads. It makes about 320 hp and 400+ ft lbs. By today's standards its a mild motor. I wouldn't want stock heads on my race motor, that's like backing up. I see where you;re headed, a good healthy torquey motor with total driveability, but the combo you described would probably produce results not much different to what I have now. My car weighs 3800 lbs with me in it, I need more power to play with the big boys. My drag motor is free and available so I figure why not use it. Your head gasket idea is a good one, I have been considering that too.

      As I mentioned with its prior build with flat tops this engine with it's 64 cc heads shaved .030 and a deck shaved .010 it made maybe 11-11.5:1. I used to drive this motor everyday as my only car and ran mid-high 11s all motor in a 3100 lb (with me) Nova. I enjoyed the cam shaking the mirrors loose at 1200 rpms. This cam is probably wrong for what I want to do, if I had the spare cash I'd go bigger with a roller and put the heads to good use to make 600+ ft lbs and hp. The whole concept is to have more torque and power for this heavier car. The ONLY issue I have with the engine is it's compression ratio, so I'm getting ideas on how to get around that. I think the retard dial switch for putting around town and hot starts would work well and adding race gas to the pump gas and bumping the timing back up would be fine for events.

      Not meaning to sound like a donkey, I just have a warped point of view of what "streetable" is, which might make some people cringe. If I could build a new motor for my my drag Nova with a 14:1 8000 rpm small block with .700" lift and get away with driving it to work everyday, I would.
      -Ben, Your friendly neighborhood Rendering dude

      SRD on Facebook

      79 Cutlass wagon build


    9. #9
      Join Date
      Nov 2011
      Location
      Livermore, CA
      Posts
      668
      Country Flag: United States
      Let's hope you are not a donkey when it comes to how bad 91 octane really is. At least the CA blend is pure donkey piss. You have no idea how bad it is until you try to tune boost with it, it's really bad. So bad that many folks will run over 75% meth to control the detonation and allow some timing to remain. I run 50% in my S4, but could easily handle 75% and my car would be happier.

      So don't excuse 91 octane as an issue, it's worse than you can imagine.. You need something to battle the detonation, so consider dropping your compression or loading up on meth as someone else has stated..

      Tory

      Livermore, CA
      American:
      1966 Chevelle SS "Tribute" Retro / Pro-Tour
      For Sale

    10. #10
      Join Date
      Jun 2011
      Location
      St. George, Utah
      Posts
      1,629
      Country Flag: United States
      Wow! I didn't realize it was that bad. Yep, the meth injection is in the "mix" lol! I've been looking at putting together a home made system, lots of info out there on that.
      -Ben, Your friendly neighborhood Rendering dude

      SRD on Facebook

      79 Cutlass wagon build






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