#121  
Old 11-12-2022, 11:30 AM
SD455DJ SD455DJ is offline
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You'll be fine with the 2.25" outlets. My stock 455HO did pretty good on the dyno (430 hp @ 4900 rpm/535 lb-ft @ 3500 rpm) with factory original RA manifolds with 2.0625"/2.125" outlets, so your larger outlet RA manifolds will work fine on your 400.

Dennis
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  #122  
Old 11-12-2022, 12:17 PM
KSZR KSZR is offline
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Originally Posted by SD455DJ View Post
You'll be fine with the 2.25" outlets. My stock 455HO did pretty good on the dyno (430 hp @ 4900 rpm/535 lb-ft @ 3500 rpm) with factory original RA manifolds with 2.0625"/2.125" outlets, so your larger outlet RA manifolds will work fine on your 400.

Dennis
Cool! I'll have to measure mine.

The Parts Place had a few sets on eBay. Next morning they were sold out. Not sure you can find 2.25" now either.

  #123  
Old 11-13-2022, 02:44 AM
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Dennis, your '70 looks good. Personally believe the pepper green steel wheels will give it a little contrast & really give a good look From the assembly plants, seldom did '70-72 Pontiac A-body's with poverty caps have same color wheels as body color, too many times the matching color steel wheels look contrived. Dave Hall has a 72 LeMans Coupe on eBay right now. Monarch Yellow with same color wheels & poverty caps...just does not look right.
My 71 had dark green wheels w/ poverty caps. Thought they were black until the first wash after driving up the Alaska Highway in April. Mostly gravel road. Really dirty. Noticed again when I put the slot mags on it.

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  #124  
Old 11-21-2022, 11:17 AM
KSZR KSZR is offline
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Quote:
Originally Posted by SD455DJ View Post
You'll be fine with the 2.25" outlets. My stock 455HO did pretty good on the dyno (430 hp @ 4900 rpm/535 lb-ft @ 3500 rpm) with factory original RA manifolds with 2.0625"/2.125" outlets, so your larger outlet RA manifolds will work fine on your 400.

Dennis
Did you have to grind down the lip of the head pipe that connects to the manifold? Mine is wider than the flange bolts.

My first exhaust job and want to do it correctly!

  #125  
Old 11-21-2022, 01:25 PM
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Did you have to grind down the lip of the head pipe that connects to the manifold? Mine is wider than the flange bolts.

My first exhaust job and want to do it correctly!
Yes, just at the studs when using the factory RA manifolds or the non-oversized repop RA manifolds when mating the Pypes 2-1/2" head pipe flared end. The 2-1/2" oversized RA manifolds must have the studs set a bit further out to fit the 2-1/2" flared end of the head pipe as we never needed to grind clearance with them like we do with the factory and other non-oversized repops. We just used a rat-tail file to do that.

Dennis

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  #126  
Old 12-02-2022, 09:18 AM
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RA manifolds on, tailpipes installed. Getting closer.

  #127  
Old 12-07-2022, 04:17 PM
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Definitely room for improvement! With your new RA manifolds and 2.5" Pypes 'X' system you'll likely need to richen the carb a bit to compensate for the improved flow. Your times should drop to very low 14's and mph jump to 100+ after this...before the engine rebuild that is.

Dennis
Picked up 3/10ths in a not so great test. Definitely making more power, spins the tires more on takeoff. I think there is more but need to have the time to drive it.

Sounds good with X and 18" Turbo Pros, no drone. RA manifolds do sound kinda like headers.

Bad weather/roads/salt coming so probably won't see the road for a while.

  #128  
Old 12-09-2022, 02:27 PM
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Originally Posted by KSZR View Post
Picked up 3/10ths in a not so great test. Definitely making more power, spins the tires more on takeoff. I think there is more but need to have the time to drive it.

Sounds good with X and 18" Turbo Pros, no drone. RA manifolds do sound kinda like headers.

Bad weather/roads/salt coming so probably won't see the road for a while.
Not a bad improvement...you may need to richen the secondaries with thinner metering rods and/or a lower alphabetical hanger due to the better exhaust flow.

Dennis

  #129  
Old 12-09-2022, 04:57 PM
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Not a bad improvement...you may need to richen the secondaries with thinner metering rods and/or a lower alphabetical hanger due to the better exhaust flow.

Dennis
Thanks, look at the plugs to determine? Roads a mess so no more tests.

Working to dial in the timing a little more, wasn't advanced quick enough. You like 36 degrees at 3200rpm?

I've just advanced it more, am at 12 initial now with maybe 33-34 around 3000. Didn't get to test this yesterday.

  #130  
Old 12-09-2022, 06:00 PM
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Thanks, look at the plugs to determine? Roads a mess so no more tests.

Working to dial in the timing a little more, wasn't advanced quick enough. You like 36 degrees at 3200rpm?

I've just advanced it more, am at 12 initial now with maybe 33-34 around 3000. Didn't get to test this yesterday.
We like to see a tan-light brown coloration on the plugs...very light tan & white is too lean, dark brown too rich. I think the timing all in at 36 degrees around 3200 rpm is a good starting point, but every engine has different octane toleration (93 assumed you're running), so you'll have to experiment next spring...but that is fun to do. You may have to modify your distributor to allow a bit more total advance by changing your advance bushing and trying to maintain 8-10 degrees initial with your compression (10+ to 1), so you have easier starting.

Dennis

  #131  
Old 12-09-2022, 06:20 PM
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Originally Posted by SD455DJ View Post
We like to see a tan-light brown coloration on the plugs...very light tan & white is too lean, dark brown too rich. I think the timing all in at 36 degrees around 3200 rpm is a good starting point, but every engine has different octane toleration (93 assumed you're running), so you'll have to experiment next spring...but that is fun to do. You may have to modify your distributor to allow a bit more total advance by changing your advance bushing and trying to maintain 8-10 degrees initial with your compression (10+ to 1), so you have easier starting.

Dennis
Cool!

Just checked it again. Hitting 36 degrees at 34-3500 rpm. I've got 91 non ethanol treated with 104 booster..

  #132  
Old 12-09-2022, 06:30 PM
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Cool!

Just checked it again. Hitting 36 degrees at 34-3500 rpm. I've got 91 non ethanol treated with 104 booster..
That's probably a pretty safe timing curve for that engine on that fuel blend. Keeping the water temp to 180 degrees in the summer will help a lot too.

Dennis

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  #133  
Old 12-12-2022, 11:37 AM
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I suspect my next focus should be my lousy 2.3-2.4 lousy 60ft time. Launching with my foot on the brake and revved up some.

With the upgraded exhaust the 0-60 improved quite a bit but 60ft stayed about the same.

I've got upgraded rear bushings(not rubber) I did in the 90s. Also added a rear sway bar but don't have boxed lower control arms.

And have rubber spacers under the springs to raise the rear an inch or so. Probably should ditch these?

  #134  
Old 12-12-2022, 12:44 PM
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here's my understanding with a quarter mile bent on them;

stock soft bushing = allows squat, and results in quicker weight transfer - you want as much weight over the drive tries as possible.

"upgraded bushings" = read: for autocross/handling; slows weight transfer because it resists movement better than rubber.

Rear Sway bar = read: for autocross/handling; prevents weight transfer; I have understood that often quarter mile guys will effectively disable the rear sway bar to permit movement

Rubber spacers under the springs = this is a "for looks" modification; this also shifts weight towards the front of the vehicle, and effectively raises ones "cool" quotient, because it makes it easier to do a burnout.

There's a reason why older race cars would have their noses in the air...


http://www.speedhunters.com/2013/05/...nce-and-style/
This might not be a perfect example, but hopefully you know what I'm getting at.

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  #135  
Old 12-18-2022, 06:52 PM
SD455DJ SD455DJ is offline
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KSZR, To add to what Jonny said, by keeping the rear end on a GM A-body lower, you improve the "instant center" geometry between the lower and upper control arms, where the imaginary lines drawn parallel to the upper/lower arms should intersect as close to the rear of the car as possible, ideally closer than the midpoint of the wheelbase. This helps to plant the rear end (causes lift) and control wheel hop more effectively. A rear sway bar doesn't hurt traction on lower hp cars, so keep it. The non-boxed lower arms are OK too if you added sleeves for the bolts to run through to prevent crushing the arms when tightening the nuts. I did the same thing to my '70 Tempest and just sleeved the control arms.

Dennis
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  #136  
Old 12-18-2022, 07:59 PM
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Thanks guys that is helpful. I'll ditch the spring spacers.

Car looks higher in the picture than stock. Even more than I thought.

I do have the sleeves inside the lower arms, can't see them in my picture.
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  #137  
Old 12-19-2022, 08:23 AM
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HWYSTR455 HWYSTR455 is offline
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Several places make the A-body lower mount that has multiple holes for adjustment of instant center, and the brackets are much beefier:

https://www.umiperformance.com/home/...ckets-bolt-in/

https://www.umiperformance.com/home/...ckets-weld-in/


EDIT: Some also make front mounts too for anti-squat.

.

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  #138  
Old 01-02-2023, 07:54 PM
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My front cover gasket is weeping antifreeze so I guess that is a sign to go for the cam swap!

Can I get away with the stock rocker nuts that torque to 20 lbs with the 2802 cam?

I'm 99% sure I've got HO racing valve springs cause I ran their HC-01 cam with these #16 heads on the original 350. Are the springs easy to ID?

I do remember when I took the 350 apart to swap these heads to the rebuilt 400 there was a bent pushrod.

  #139  
Old 01-02-2023, 08:15 PM
SD455DJ SD455DJ is offline
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Kent, You'll need to get 7/16" rocker studs and poly-locks for the 2802 cam.

Dennis

  #140  
Old 01-02-2023, 09:00 PM
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Kent,

Please start a new thread regarding whatever you’re doing with your car, this focus of this thread should be on what Dennis is doing with his car.

Thanks.

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