RacePak EGT's Q's

Hi.
Just running the motor up (part throttle) after fitting a V300 and there's a variance of 200 degrees between hottest and coldest on the EGT's.
IF this the case on full power runs, is it worth chasing the jetting to equalize them ? Anyone have any experience ? Did you pick up HP staggering the jetting ? How much does changing one jet effect its neighboring cylinders ?
580 wedge, heavily ported 572-13 heads, Indy T/R and 2x1150 T/R Dominators.
A little bit more info: square jetted (98?) 1:1 throttle linkage.
TIA.

I wouldn't sweat it until you run it hard, the intake manifold isn't going to function right unless you are operating in its range.

I have read some people say that timing will influence EGTs more than mixture, but I don't have any experience there. Unless you are coil on plug per cylinder timing changes aren't easy anyways.

Hmmm...Food for thought, I have a grid but no cam sync....I also only monitor O2, per bank, in each collector. In hind sight I maybe should have got 8 O2's Thanks

Edit: I found out you just need this to individually time cylinders with a grid
https://www.holley.com/products/ign..._grid_modules_and_accessories/parts/7555

BEFORE the days of one O2 per pipe per cylinder. I used to dyno for a pro NASCAR team. YOU CAN tune an engine WELL with cylinder egt data. YES it is worth power and worth to understand HOW to adjust and WHY it needs it. Probably most intakes including 2x4 tunnel rams can respond to either modifications AND/or jetting changes. We used to balance all 8 egt's within around 10 degrees F and it ALWAYS was worth power. Based on my O2 data, which was bank to bank only, my right bank was about .5 point LEANER than the left on my INDY T/R with 2 4150's

You have two carbs, 8 jets so IMO yes its worth the effort as it will respond to changes more readily. Question is whats the target tat makes the most power. I personally don't use EGTs but prefer O2's.

Screen shot: Difference is way more here at a fast idle. Note the O2 readings

PS> Ignore Cylinder 8 as it wasn't connected properly, It went to a -ve reading later on when Investigating the wires weren't in the terminals correctly

Good point, my plan was to read the plugs and go off the best cylinder(s) as a reference.

Excellent! many things can guide you. I didn't speak to you noticing an 'issue' during part throttle and idle because distribution can be biased due to throttle blades IAB/carb tuning in general too. One thing i'll mention in addition is the INDY plenum IS SMALL. adding a spacer will help distribution as well.

I plan to get a buddy to machine a 1" spacer for me (I was thinking of a phenolic one but the dust is an issue). Talking to Indy, they didn't see an improvement on a 572 (1/2" spacer) until over 7200 rpm. Pretty sure the 580 we have starts tailing off there anyway (Best shift seems to be around 6800). I do think it will help on the 655 though. I might just go ahead and try it my self in phenolic to see what occurs.
I didn't want to, but also I think I'm gonna strip down the induction, give everything a clean and set it all up on the bench before it goes back on the engine just to eliminate any possible issues as it's been standing over a year. We're house hunting at the moment so racing is taking a bit of a back seat but we should out at the start of Sept for a day of testing, then 4 days of racing. Should get plenty of passes if the weathers good so plenty of data and tuning

PS out of interest what was the issue you spotted ?

There are also a couple versions of that Indy intake, one with a smallish plenum and one with almost no plenum and a peak in the "tent" protruding into it. The open version is clearly the better option and yes it will need a spacer...How much of one can vary but if it were me I would have a couple made up. We use high temp teflon stuff

As far as whats an ideal EGT I would pay way more attention to the timeslip than a plug. I have seen way to many people chase an ideal number in a racepak and ignore the timeslip, rather than giving the car what it wants/needs and then referring to the data for benchmarks. You woudl be surprised what you might find. But you have to start somewhere and reading a plug is a good start I suppose. But we run what many would consider an ugle plug to achieve the best ET's in the heads up car

We've got the tent one......

Ya know I might be getting the choices confused. I just sold one not long ago to a buddy in Canada and seem to recall it being open, but maybe that was the Predator version?!? I cant seem to find the pictures but for some reason I thought they had both depending on how old they were...I cant see the "tent" being any help, I suppose the thinking behind it was to help direct flow to the 4 cylinders on each end?!? Seems like a bad way in my mind to build a tunnel ram but maybe I'm wrong.

There is definitely a more "open" version, pretty sure it's the earlier one. It has about double the amount of bolts fastening the top plate. I don't know why Indy redesigned it ?
Indy had a picture of a 572 (or a 588) going out to a customer, I noticed the T/R it had was fitted with a 1" spacer and asked if it was worth anything. The reply was "yes, a small gain between 7200 and 7500 rpm"

The one I sold which I am pretty sure was open was on a 655" deal we had tat i bought used. We freshened it up and made some big changes to since it is going in a bracket car we went with a single 4. I was pretty sure it was open but so many engines of our own around here and getting older aint helping. I thought/ assumed the tent version was the older one. The 655 we bought was not that old but who knows..I know I sold it to my buddy in Canada to replace hos tent version which he as had for long time, at least a 15 years I have known him. He crashed his car and intake got hurt when it was sliding on its roof and the old BG Demons got destroyed(thats how old this was). Sold him the tunnel ram and a pair of Book carbs I had for it so he could fix his 655.

Have any pictures of the EGT's on the engine? What part # did you buy, from RacePak, for a Mopar?

Racepak EGT's can be bought in singl and 4 sensor packs so 8 EGT's are getting close to $2000and take up some channels espcially if you have a Sportsman logger. Less money than the 8 O2's for sure.

The pic of the Indy RB wedge T/R definitely is a tent version in their current on-line catalogue, but it may be an old picture ? There was a thread on here a while back where someone had modified a tent version to be an open one. I assumed the tent version was the older one also back then but I now have it in my head it's the newer one.




Only this one below: They are Racepak ones though you can buy probes elsewhere (K Type) that are compatible. They are universal, come in BB Chevy or Hemi spacing and lengths from racepak but they fit a wedge OK with a little juggling. I was informed you can cut them to length but the ends are sealed with the glue type heat shrink sleeves so it could get a bit messy if you only need to remove an inch or so.
You can just make out the probes at the bottom of the valve covers, they are about a 1 1/4" from the header flange, the amplifier is on the inner wing marked 2 4 6 8
HTH's

Ya know I am not sure on the intake thing clearly I have had four or five of them over the years but never run one. Just stuff bought and sold over the years. I tend to spend to much time and money buying lots of parts.

I prefer the O2 method but it is fair bit more expensive for sure than EGT's, not that either is "cheap" The fuel we use also seems easier to deal with using O2's than EGT's. Although if it gets to rich it can sometimes read lean on the sensor..Oh the joy of racecar tuning.

I have all 8 Racepak EGT and both Racepak O2's on my car. Yes, it gets costly..... Zoom in. I have all engine mounted sensors on my snout bars.

I hear ya, all part of the fun, I've been watching you tube where they picked up 60 hp by staggering the jetting as below....but they were using O2 sensors rather than EGT sensors, there was a surprisingly big swing in the jetting !! (We got our tent T/R in 2014 BTW if that's any help ).
https://www.youtube.com/watch?v=EP1Rh829rVk&t=1291s



Neat, I can see a row of V-net Tees but cant find the EGT amp boxes Snout bars are on the other side on the inner fender on mine We used a USM for our engine monitoring but I'm looking at more (as ya do )

Have not seen a tunnel ram yet that did not benefit from staggering the jetting, and even the bleeds. They are much more tunable than a single 4 in that respect for sure. I have run a number of tunnel ram deals just have not used a cast intake for it in years. We struggle trying to make all 8 happy with a single 4 deal on the heads up car but there are ways there as well. Knowing how to use those 3,4,5 circuit carbs to bias mixtures in those set ups help a lot. We also have different boosters in each hole to help with mixture issues. Its a process for sure

I have been thinking of going away from the racepak stuff and going to Holley systems to monitor all logging. I particularly like their dashes better than racepak. I Have not made the jump yet but thinking on it pretty hard. As for racepak expense it can be pretty stiff. But Low Dollar Motorsports sells alot of those pieces(sensors)for less money.

When you jump ship Al, keep me in mind. I would be interested in some stuff.

I researched this a lot before I purchased my 8 O2 sensors. 2 AF/4 Controllers.
I was told by numerous engine builders who had dynos and all said don't waste your money on EGTs.

Will do. Have three cars full of racepak stuff so it is going tobe an expensive venture. Especially since we just rewired two of them....Ugh no one ever said I was smart or liked money though

The EGT boxes are down lower by the frame rails. There are 8 V Nets on one snout bar and 9 V Nets on the other snout bar hidden down under the master cylinder. 6 more V Nets are mounted in side up under the dash. Monitoring 23 systems altogether. Not sure why I needed all of this on a street car. Lol.

A friend of mine has an old Pro Stock Pontiac w/a Nitrous Fulton 648 BB Chevy with 2 cast 1150's which I actually made slightly smaller by skirting down the banjos and before I went through em the afr's were all over the place like 3-4 numbers different from leanest to richest. He went a 1.06 60 ft 4.36 1/8 at 167 mph with it like that then after stagger jetting and bleed changes the afr's were within1-1/2 on all 8 cylinders and he went a 1.01 60 ft 4.30 1/8 at 170 mph so not exactly sure on the actual hp power gains but even distribution is the key to good clean power......