Classic Engine Tech 1967 - 1981 Engine Related

Why so slow?

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Old Oct 27, 2004 | 03:12 PM
  #1  
blueta's Avatar
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From: bethlehem pa
Unhappy Why so slow?

Ok, my dad just gave me his 69 firebird. This is the first "true" pontiac engine I've ever built so I need some info. First off the details: 68 gto 400 engine and heads. Block .030 over, forged trw pistons (told they were 11:1), R/A III cam, 1.5 roller tip comp rockers, heads decked and rebuilt, edelbrock RPM intake, holley 750 carb, HEI ignition. The tranny is a th350 with shift kit (don't know what kind of converter), stock rear with 3.55's and a posi. It has long tube headers (not sure of brand) and meinake dual exhaust lol. I've ran the car at the track and only could muster a 14.1@98-99. I cannot blast off the line cause of tire spin but it's really not too bad of an issue. One time I launched it as hard as it would go and got a 14.5 but MPH jumped to 105. I was shifting anywhere from 4500-5000. Initial timing is set at 9* BTDC and the best gas I can get my grubby hands on is sunoco 94. Can I bump the timing up at all? Or will it detonate to death? Is 94 even ok to run with that kind of compression with the iron heads? I don't hear any knock and when I pulled out a couple of spark plugs they didn't show any signs of it. Any help on how to dial this in will be appreciated.
Old Oct 27, 2004 | 03:30 PM
  #2  
81Z28355's Avatar
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From: Hemlock, Mich.
Re: Why so slow?

Well I can tell you that with that 105mph trap that car will go high 12's easy, We need your cam info and stall speed would be helpfull and also post your 60' time. Sounds like you need tires.
Old Oct 27, 2004 | 03:57 PM
  #3  
blueta's Avatar
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From: bethlehem pa
Re: Why so slow?

The 105 mph was a 1 time thing...every other time it ran in the 98-99 range with little spin (but had to baby it off the line). Cam specs are 224/236 .408/.408. The tach doesn't work anymore so I have to get a new one so I can try to foot brake a little against it to get an idea of what stall I have.
Old Oct 27, 2004 | 05:42 PM
  #4  
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Re: Why so slow?

Might want to look into a different cam, that one is kinda small.
Old Oct 27, 2004 | 08:43 PM
  #5  
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From: Calgary
Re: Why so slow?

I'd say thats about the best you can expect. That 105mph trap speed was good though. Got to repeat it otherwise you'll always wonder if it was an error.

Your gears are good but not great and your cams really small.
Pontiacs can take 1.65 rockers

Maybe you can whittle off a few more tenths. But really don't expect too much. I believe a Ram Air 4 Trans Am (69) could maybe do a 13.9 and that was it.
Old Oct 27, 2004 | 09:05 PM
  #6  
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From: Midwest
Re: Why so slow?

I kindda thought it was a good time too.
Old Oct 27, 2004 | 11:10 PM
  #7  
spinout's Avatar
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Re: Why so slow?

get the cam degreed about tree derees advanced and go to a 650 or 600 carb you will get better times
Old Oct 28, 2004 | 06:46 AM
  #8  
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From: Hemlock, Mich.
Re: Why so slow?

I run a constant 13.3 @ 99.7 mph with a 1.6 60' and a 8.4 1/4 mile. so you have the speed, whats you 60' time.
Old Oct 28, 2004 | 11:28 AM
  #9  
blueta's Avatar
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From: bethlehem pa
Re: Why so slow?

I was considering going with 1.65 rockers to help with that weak lift. That will at least bring me up to .449. Why go with the smaller carb? I think a 600 would be underkill wouldn't it? I have an extra 600 holley sitting here and maybe I'll give it a try. The 3.55's will have to stay for now as this is my daily driver and it's only a 3 speed. I wish the damn compression wasn't so high so I could slap on a blower I don't have the slips handy but the 60's were somewhere in the 2.1 and higher range indicating that traction wasn't good. Too bad I sold my et streets after I sold my t/a and took apart my t-type I didn't think I would be needing them anymore... Anyone got a suggestion on a cam?
Old Oct 29, 2004 | 10:06 PM
  #10  
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From: TX
Re: Why so slow?

Not only is that cam bad on lift, it is very lazy with the lifter movement. Just get any modern cam with about 218 to 224 duration @ .050. Only problem is that everybody offers cams for Chevy, but Pontiac is another story. I really like the Crane Energizer series of cams. Excellent bang for the buck. I run the 222 cam in my 400 sbc. See if they offer a Pontiac version. I also run the 750 vacuum secondary Holley. Perfect size for a 400 IMO. When I first installed the 400, I ran the 600 I had on the original 350. Much better with the 750.

Last edited by angel71rs; Oct 29, 2004 at 10:10 PM.
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