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 461 with nitrous oxide

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69TA Posted - 17 Jul 2017 : 9:10:02 PM
Hi everyone. I am new to this group, and have lots of questions.

I have a 1969 Pontiac Trans am (clone) I restored the car to be a show car, but now I race it every chance I get. I pulled the factory 400/ and 400TH and put away for safe keeping.

Acquired a 400 Block. casting 9790071, Had it 0 decked, Bored it .035 over, Eagle cast crank 4.25, Eagle I beam 6.8 rods, Mahle forged -22 cc pistons, KRE 74 cc d-port heads from SD performance (295 cfm) comes in at 10.1 compression ratio. Comp XR288HR cam 236/242 at 050, had it ground on a 112 LSA, .577/594 lift with PRW 1.65 roller rockers. Lunanti Hydraulic roller lifters. Cam is 4 deg advanced. Eddy Performer RPM. Holley 850 street HP. Pontiac HEI with 30 deg advanced, all in by 3000rpm. Ram air restoration 2.5 long branch factory headers. With there complete 2.5 exhaust. Changed out there spin tech mufflers for flow master 40 series. Trans is a TH400, shift kit and a 3500 stall. GM 8.5 limited slip 10 bolt, with 3.42 gears. Run 275/50/15 Hoosier drag radials. Have bolt in sub frame connectors. 90/10 Lakewood drag shocks up front and 50/50 out back. Removed front sway bar links. Do not have any other traction aid. Stock mulitileaf springs.
Last time at my tack ( 1/8 mile) ran a best of 7.501 and 1.66 60 foot at 92.7 MPH. Not bad for stock suspension. I lost in our street car shoot out final to a 73 Camaro with a Chevy small block that sprayed 150 shot of Nitrous.

I'm trying to see what else I can do to go faster. I am the only Pontiac that runs at my track. I want to show the guys at my track just how fast this almost 50 year old car can go.

I have a new Zex perimeter plate system in my garage just waiting to be installed. Along with the Zex kit I also purchased a bottle heater, window switch, WOT switch, pressure gauge, and purge system. The kit is adjustable from 100-300 HP, But I plan to only run 100 shot first and then maybe up it to 150 HP max.

Trouble is I have never used Nitrous or been in a car with it. I have been doing a lot of research online, but cant seem to find anything about using Nitrous with a build similar to mine.

I read that the stock Pontiac block is only good for 600HP. I think my combo now should be between 525-550 HP?So If I add a 150 shot, do I really stand a chance of major engine failure?
(I had the engine dynoed before with a smaller cam 230/236, 112LSA, 561/572 and came in at 485HP/564 Torque.) No dyno since new cam.

Before attempting to install the nitrous, I installed a fuel pressure guage that I could read inside the car and went for some runs to see what fuel pressure I had a WOT. It came in at only 4 psi using the cater 140 GPH mechanical high performance pump. I then removed the mechanical pump and installed a Mallory 110 electric pump back close to the fuel tank. I have yet to do any testing to see if my WOT pressure has improved. Kit states I need 6 psi constant for the nitrous. I know I need to ensure my fuel system is up to the task before continuing to add the kit.

My question is concerning spark plugs in the KRE heads for nitrious. I currently have Autolite 3924 in my heads. They were suggested by Dave from SD performance and gaped at 035. There perfect now, but what should I use with the juice? Anyone have experience with nitrous and the KRE heads with 10.1 compression ratio.? I know that with nitrous I should not use a projected type plug, and these are. So I need something different. I read you should go 1-2 colder plug also. I see Autolite has a Racing plug AR3935 or AR3934. I can not find any info on there web site that shows its heat range. I also plan to pull 6 degrees of timing, but I will then only be at 24 total. Too low?

Besides the things mentioned above. What else should I consider before I spray the 461? Or is this just a bad idea?




12   L A T E S T    R E P L I E S    (Newest First)
69TA Posted - 22 Oct 2017 : 1:25:25 PM
Update: After adding a set of Caltracs, and relocating the battery to the trunk, on the last pass of the season i ran a personnel best!!!
7.344 in the 1/8. with 1.530 sixty foot @ 90.87 MPH. I did not play around with the Caltracs to much. Just made the basic adjustment. Either i got real lucky with the first setup, or theirs more in it with some playing of the adjustments.
69TA Posted - 24 Jul 2017 : 3:40:28 PM
Has anyone had a eagle crank failure?
cortcomp Posted - 20 Jul 2017 : 09:55:26 AM
Honestly, i don't see as much nitrous or even blowers or turbos on pontiacs as i do LS groups or generic SBC groups. Part of it seems to be that you can buy such crazy aftermarket NA parts that they're not needed. I saw one of the builders with their RAV heads, RAV intake, one carb, NA, tame for a RAV motor, throw up like 1100 on the dyno. That's ridiculous, and no computer, fuel mapping, custom fab or whatever. So, i think there's a bit more power to be had with a pontiac NA vs an LS, SBC, SBF, whatever. I think that has less guys doing nitrous unless they're at the track most of the time, and investing in some of the better heads, intake, whatever NA parts.
69TA Posted - 20 Jul 2017 : 07:43:43 AM
Anyone else with experience running nitrous in a pontiac??
69TA Posted - 18 Jul 2017 : 12:54:07 PM
500-550 hp with the eagle stroker crank? I thought eagles suggested horsepower limit was 700?
js292 Posted - 18 Jul 2017 : 12:00:17 PM
As far as the weak link in your combo, I'd be more concerned about the cast crank than the block.I've heard they are only good to 500-550hp, and the pic's I've seen of the broken ones did major damage.
69TA Posted - 18 Jul 2017 : 11:26:22 AM
Well it seems my 1.66 60 foot are not to bad then? What do I have to gain by adding Caltracs? More consistency? I have to admit, that the 60 foot can range from 1.8-1.66. When I launch at 2800RPM or so the left front tire comes off the ground 3-4 inch (From what I see from people pics from the track) Is this slowing me down because I have loaded up the suspension? Would it be better to leave off idle? As the car goes down the track the nose of the car is pointing up in the air and the rear is down for the entire run. I assume this is a good thing, with good weight transfer?
Steve C. Posted - 18 Jul 2017 : 10:18:48 AM
We had slapper bars on my car at first then later upgraded to Caltracs. With the previous pump gas 462 it was not uncommon to have 1.59-1.6 60-ft times at its best running into the 10's. In the heat it might be a 1.62 60-ft running low 11's. All this said, consistency is the the key to winning. Example at the last Pontiac Southern Nationals with my car and the four time trail runs.... 11.099, 11.098, 11.081, 11.084
The right convertor can make or break your combination, many use too tight of a convertor with a Pontiac making peak torque at 4400-4600 rpm.

Prior to that with a 4.125" stroke 450 cid engine was the only time we played a bit with a nitrous using a plate system, probably a 200 hp shot if memory serves me right. Ran a best of 9.59 at 140 mph, 1.43 60 ft. on 10.5 D.O.T tires. Keep in mind the nitrous is going to push your converter to a higher rpm.


.


69TA Posted - 18 Jul 2017 : 08:38:28 AM
The Camaro had 3.73 gears, and uses Caltracs.

There are a few cars that run at my track regular, and we are are close when running naturally aspirated. A 1970 Nova with a small block chev running NA 7.4, The Camaro mentioned before, runs 7.5-7.6 NA, 1980 Camaro running a LS conversion runs 7.4 NA, 1970 Dodge dart running 7.35-7.45 NA. I have only been to the track once since I installed my new cam. Best run 7.501 and slowest was 7.65. Before the new cam 7.6(Best)-7.75

I think you my be right about my own combo. I think theirs more in it yet. Converter for one thing. My converter was purchased from a Chevy guy used. I was thinking of going with a custom converter from Cliff. I read Pontiac's need a different approach for converters then a Chevy.

I am very curious how my combo will react to nitrous. I had always felt natural aspirated was the way to go, But watching these other guys using it and leaving me in there rear view mirror is p#%%ing me off.
Bill Boyle Posted - 18 Jul 2017 : 07:31:50 AM
I can offer no first hand advice with automatic transmission cars--I'm a stick guy only. However, there are many others with exceptional racing experience with auto transmissions that are likely to post advice on launching. Pontiac guys don't like to lose, and they really don't like to lose to a Chevy.

Traction is always an issue. I've seen F-body cars run with Caltracs that didn't do well, while others have dialed in their hardware and performed very well.

I'll bet there's more in your engine that has yet to be tapped without resorting to nitrous.

Any idea what the Camaro used for rear gearing? Did the Camaro have any traction bars etc?

Check this FB out-- http://www.pontiacstreetperformance.com/psp/rebuild461DS.html

This Bird used Caltracs and did very well at the strip. Dan sold the car a few years ago, but info is on point.
69TA Posted - 17 Jul 2017 : 10:04:49 PM
The Camaro ran a 7.00 flat 1.45, 60. He fell asleep at the light .999. I had a .570 light. It was real close at the end. But natural aspirated he usually runs a 7.5-7.6. This was a small tire street car shoot out, run what you bring type of thing.

1.66 is pretty good? I have since ordered a set of caltracs. Do you think it will improve my 60? I was trying to keep the car stock looking with out traction bars, but I thought I may be leaving a little on the table with out a traction aid. What are your thoughts?

Since I installed a 3500 stall. I had been bringing the RPM up until its just about to push through the lights,(2900 RPM) then on the third yellow I drop the gas. Speaking to Calvert racing they said its better to flash the converter? Never tried this approach, but have tried lower RPMs. Example 2400 RPM, then my reaction time really suffers. Converter too loose? I am no track expert so looking for any help you can give.
Bill Boyle Posted - 17 Jul 2017 : 9:51:07 PM
How badly did you lose to the Camaro? What was his ET/MPH? What was your reaction time compared to his?

1.66 60' is pretty darn good.

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