Racingartist

I am getting my 83 RX7 ready to race next weekend at Thunderhill raceway. This is and all out race car and was raced under Pro7 in SCCA. I have built a stainless header and exhaust pipe. The header is 2 inch tubes into one 3 inch. I ran the engine for about 3 or 4 minutes from 2500rpm to 6500 rpm mostly around 3000 to 5000 then rev to 6500 maybe 3 times. The water temp got up to 160 and exhaust temp 1000. With it sitting still is it normal for the header to glow red?

jgrewe

iTrader: (1)

Yes. I would double check your timing though, timing advanced too much can make one glow at pretty low power levels. If you haven't changed anything else you are probably fine.

Racingartist

Thanks I changed the exhaust to a tubing header and 3 inch pipe I have a mufler I made with 5 Perpetrated baffles. I welded up the intake manifold filling in all the divits and vacuum ports so that I now have smooth runners with enough grinding marks in the runners to keep the fuel/air mixed. The engine is stock other than that no porting. Do you know what the timing should be? On the radiator there is a tag that gives color coding with the degrees of timing. I have to keep the engine rpms up around 1800 revs to keep it running. What plug wire do I clamp the timing light to. I have be racing sprintcars for years and stockers so I have worked on Chevy and Ford engines and making them go fast.

jgrewe

iTrader: (1)

A stock port engine should idle below 1K with no problem. Stock carb? or something else?

As for timing, for the marks on the front pully, hook up your timing light to the bottom, front plug(that is your "leading plug"on the front rotor). The top ones are the trailing plugs. Set the leading ignition by turning the distributor, set the trailing by moving the vacuum pot on the side of the dist. You'll see the screws with slots.

Timing on a stock port is 19 degrees BTDC for leading and 0 BTDC for trailing. We slot the trailing adjustments to be able to push them within a couple degrees or even firing at the same time. Advance the timing to around 24BTDC and look for the best power, I don't think you'll need to go as far as 28BTDC but give it a try if you have any time on the dyno. 24 is pretty safe. Timing as just like any engine when it comes to tweaking the last few HP, set it without vac hooked up around 4000 rpm. You don't need the vac pots, there is mechanical advance built in the stock dist that will give you good enough numbers for it to still start and have full advance at high rpm.

Racingartist

Thanks you rock. Like I said before I have be racing car with pistons for many years started back in the early 60s till late 80s then I retired from racing but got the bug again in 2009 when a co-worker wanted me to help build a car for Chump car race at Infineon in 2010. I was a crew chief for a SCCA F Modified now B sportsracing team 64 to 68 SF region been crew chief on some dirt cars built two supers that we ran at San Jose speedway 1980 till 1988 we were one of the top two teams for most of that time so I am not new to this. I am a little rusty but its coming back but as far as rotorys I am in the dark. I traded my 89 Corvette for this RX7 that is a full on race car with a 24 ft enclosed trailer. I don't think its ported but it maybe. I ran the car one time last year and will run again next weekend at Thunderhill raceway its a 3.1 mile roadcourse. This year I have been working on making more power I think its going to be faster this year. So I will work on trying to tune it so it runs better Thanks so much for your help thats what I like about racers you can get pointers from the good ones. Good luck on your racing this year.

Racingartist

Today I tuned the engine to the modification I made to it. They were I built a stainless steel header and a 3” exhaust pipe and I reworked the stock intake by removing the butterfly valve welding up all the vacuum port holes and building up all the divots and making the runners even so the flow is much smoother. I also made the secondaries manual instead of vacuum operated. I set the timing and adjusted the Nikki carburetor and WOW the engine came alive you hit the throttle and it revs now on hesitation. I was hoping for 10 to 15 HP but this thing sounds like over 50 HP. It is way more than I was hoping for. I am not saying I got 50 extra HP it just sounds like way more power. Before it sounded like a load stock engine and now it sounds like a racing engine. I will be racing it this weekend at Thunderhill road course so I will see how it pulls out of the corners now.

jrx13

iTrader: (3)

Just saw this post. Did you run with NCRC? I was there in my 2nd Gen (1987) running Time Trials. My stainless header glows red as well - see dyno video here:


RX7Club.com - View Single Post - Karack Group Dyno Tune Session

Kentetsu

The 2 main causes I've seen for glowing headers:

1. Loss of leading ignition. Only secondary ignites the mixture, and continues burning as it enters the exhaust.

2. Running lean.

Sounds like you've got your situations sorted out, just thought I'd add this bit for others who may come along later.



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Racingartist

Yes I did run the car and I needed to jet the car richer but i had to remove the header and pipe because I was at 108 DBs (to loud). The first race I ran was the second race of the open group and I got black flaged for being to loud. I am recovering from knee surgery so I move slow so it took me the next two races to change the exhaust system. I ran the last race of my group and had a blast. I ran Sunday first race of open group I had been having trouble getting the car to start I was getting use to the track layout so I could pay more attention to how the car was running so before the next race I adjusted the timing a little and started playing with tire pressures that made a BIG differents and my times started coming down every lap by .01 to .02 so I was realy have a great time now. My car is old the engine is getting tired and so it may have 100 hp to 110 hp at the wheels and that maybe more than it has. So I was able to keep up in the corners with a lot of the cars but as soon as they can get back on it their gone. I would be on the straights foot to the floor and most of the car would blow by me. But I was still having a blast going as fast as the car would go. How did you do? I was pitted next to a guy the had the yellow RX7 he is a great guy and teaches automotive and has alot of experience with rotary’s. All my experience is with Sprintcars and stockcars with pistons so he gave me alot of help.