Horsepower estimates, please!

Discussion in 'Street/strip 400/430/455' started by ranger, Aug 13, 2019.

  1. ranger

    ranger Well-Known Member

    Hi folks,

    My '70 GS replica has not run since 2002. I am trying to get the motivation to finish it. "Life" got in the way of completion (wife's affair, divorce, bankruptcy, job loss--typical stuff) and now that I am unemployed I have the time to finish.

    I am hoping that your comments about the potential horsepower may be just what I need in terms of motivation. Here is what I have:

    1. 1975 Blue Block bored .038"

    2. Wiesco flat-top pistons, "020 in the hole. Piston skirts coated, as well as piston domes

    3. K-B coated headers w/ 3" exhaust. Dynomax muffs w/ H-pipe

    4. T/A 288-94 cam, installed at 8* advance--what it degreed in at.

    5. SP-1 intake massaged by Gessler

    6. 800 Q-Jet built and set-up by John Osborne

    7. Bulldog heads from the 2nd, and last (best) run. Ported by Gessler (his 1st set ever). Intake 310 at .500, Exhaust 185 (Exhaust same as he got w/ my iron heads back in 1991). One head milled by Gessler to equalize cc's. He didn't say how much he milled.

    8. Compression ratio is unknown as I don't know and, surprisingly, Gessler did not mention, combustion chamber volume. Chamber and valves are coated, so this will take up some space, but heads could be anywhere from 67cc to 85cc! Some guys I've asked, w/ Bulldogs, tend to favor the former/tighter volume. So, either way, I would guess compression ratio to be 11-1 to 11-.75 to one.

    Anyway, I appreciate your input and, hopefully, your motivation!

    Best,

    Ranger
    Aiken, SC
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    If your pistons are true flat tops with no valve reliefs, I'm thinking your SCR will be north of 12:1 with a 68cc chamber. In any case, the engine will not run on pump gas. The DCR will be at least 9.5.
     
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  3. ranger

    ranger Well-Known Member

    Larry, they were the Wiesco pistons that were sold back around 2002. They have valve reliefs and 7cc volume, as I recall. Yeah, I knew it prolly would need a boost of racing gas. Brian Earrick, who did my machining (actually, he farmed it out to a low-cost buddy of his), was building a similar set-up when I went to pick up my parts. He said that if pistons were flush w/ the deck that c.r. would be 12-1.

    In any case, what do you think about potential h.p.? 500? 550? I am guessing I am in this range?

    Best,

    Ranger
    Aiken, SC
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Yeah, 500-550is a good estimate.
     
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  5. Jim Rodgers

    Jim Rodgers Well-Known Member

    I would guess closer to 550. Its going to want more carb tho.
     
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  6. ranger

    ranger Well-Known Member

    Thanks, Jim! Yeah, I was suspecting a bigger Holley would add 10-20 numbers, but they seem to be gas hogs. I wish someone would repop the 1000 cfm Thermoquad!

    Best,

    Ranger
    Aiken, SC
     
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Do what I do, use a 1000DP at the track, QJ for the street. I can change carburetors in 15 minutes or less.
     
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  8. ranger

    ranger Well-Known Member

    My SP-1 is spread bore. I forgot how to do this. I guess there is an adapter? Might not have the hood clearance, tho. The Bulldogs sit up a bit higher than other heads.

    Thanks!

    Best,

    Ranger
    Aiken, SC
     
  9. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    No adapter, just a thin plate to square off the bore and 2 carburetor studs.

    https://www.edelbrock.com/square-bo...e-100-thick-for-edelbrock-manifolds-2732.html

    My fuel line is -6AN from the fuel pump to carburetor. I use this fitting to replace my stock Q-jet fitting,

    https://quadrajetparts.com/adapter-inlet-fitting-p-366.html

    My Holley has it's own male -6AN. The fuel line has an inline filter that sits under my distributor. I just move the line over to fit onto the Holley, the line has enough slack. Holley has it's own throttle bracket and return springs like this one,

    https://www.ebay.com/i/123417124466...MIkMX_le2A5AIVjgOGCh3-VwtVEAQYASABEgL5S_D_BwE
     
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  10. TrunkMonkey

    TrunkMonkey Well-Known Member

    Velcro. 3 minutes... :D
     
  11. Bens99gtp

    Bens99gtp Well-Known Member

    Big carbs dont have to be gas hogs, we have a customer 502 chevy is ss pickup, 3.73 gears, 1000cfm Holley 4150, th400 with gear vendors, gets about 14-15mpg on the highway
     
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  12. ranger

    ranger Well-Known Member

    Thanks! No doubt, the Gear Vendors helps 2-3 m.p.g, but good on him!

    Best,

    Ranger
    Aiken, SC
     
  13. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    You can make a big Holley more fuel efficient by calibrating them better. They usually aren't that way out of the box though.
     
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  14. Bens99gtp

    Bens99gtp Well-Known Member


    He has a 92 as as well it came from gm with the overdrive, its bone stk and get about 8-9mpg. So it's not all in the gv
     
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  15. Bens99gtp

    Bens99gtp Well-Known Member


    Yes they take some work, but all carbs do, in the end carbs are almost always a compromise, unless you want to tinker all the time
     
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