Carb heat insulator plastic thingy

[Guest_benracin_*]

Still trying to track down my intake leak which I think to be the cause of crazy high exhaust temps. Yesturday I started messing with the carb insulator. First it had a gasket on the top and bottom of it, still leaked. So I pulled the top gasket off, still leaked. By using carb cleaner and running the engine and spraying around till the idle goes up I think I tracked it down to the bottom gasket. In a moment of pure tiredness I pulled that gasket and put on a thin film of gasket maker. I'll know if it worked tonight when I run it.

So question for ya. Do you guys run gaskets on this thing? When I got the car the PO had just put the carb directly on the intake which I think was giving me pre-ignition issues due to the heat. Are these plastic spacers known to be a leak fest? Is gasket maker a bad idea there?

Oh, and what have you guys done to plug off that area on the lower intake. It's the large opening that has 3 bolts on it. There was a crappy metal panel with a home made gasket on it. I hit that with the gasket maker as well.

Website is looking good!

Ben
ITA RX7

[dickita15]

Originally posted by Guest_benracin_*@Aug 8 2005, 09:45 AM

So question for ya. Do you guys run gaskets on this thing? Ben

Never used any other gasket just the heat shiel and I never had any problems on our cars.

[ddewhurst]

Ben, I have had two different carbs on my motor & neither carb had a leak issue. No gaskets required. Is the bottom of your carb or the top of the intake manifold screwed up with a crack or marks or ? My plastic insulator was as smooth as glass on both sides. No carb impression marks or anything. Of course the thing got busted when I toasted the car.

EDIT: Do you have all the holes from the vaccum tubes PLUGED ?

[Marcus Miller]

No gaskets and no leaks on mine, and Mazdatrix.com sells a block off plate for what you are looking for.

Marcus

[benracin]

These high EGT temps are making me nuts. I think I'll bring a couple spare insulators and a couple other intakes with me when I go to the track. I can't really even tell if I fixed anything with my garage testing. I have GIANT jets in the carb right now so if I'm hearing people right it should be running to cool right? Lean is hot, rich is cool, or can you get so rich that it gets hot?

[Marcus Miller]

Originally posted by benracin@Aug 9 2005, 05:50 AM
These high EGT temps are making me nuts. I think I'll bring a couple spare insulators and a couple other intakes with me when I go to the track. I can't really even tell if I fixed anything with my garage testing. I have GIANT jets in the carb right now so if I'm hearing people right it should be running to cool right? Lean is hot, rich is cool, or can you get so rich that it gets hot?

[snapback]58060[/snapback]

What temps are you seeing?
What size is "giant" ?
Have you checkeed your timing?
Sure your header have no cracks?
Sure your probe(s) and guage(s) are in good working order?

Marcus

[ddewhurst]

Ben, just because IMHJ you are a neat young man with some principles I'll come on up to Road America early in the morning & see if I have any knowledge to help sort out your hi temp/carb leak issues.

Are you doing a Friday open session if there is an open track day ?

What day/time is your first track session ?

After an on track session what do your plugs look like ?

What is are your EGT's ?

What is your water temp ?

What is our oil temp ?

Who is your carb builder ?

Have you talked to your carb builder about the jet size in the carb ?

EDIT: What float level did your carb builder spec ?

EDIT: What fuel pressure did your carb builder spec ?

If you have the hose clamp type EGT gauges I'll bring mine along so that if required we can side rig up my gauges for test purposes.

[benracin]

No Friday session. Last time I raced with the possible intake leak my temps were over 1700 with the gauge pegged. It's as far as my guage goes! And I know that was after I increased the jets 3 times making large changes without affecting the temps one bit. Also later in that session I got a crack in my header, wonder why? That could of been a result of a little off tracking though. Plugs have actually looked good this whole time strangly enough. I'm pretty sure I got the timing correct but this was back before I made all my latest changes. Other than the exhaust temps and the poor poor performance HP wise the engine seems to run just fine with water temps right around 180. Don't have an oil temp guage I'm afraid.

I believe the carb was made by Petit racing way back before I owned the car. Don't know if there is a Petit racing anymore. It was set up to run with out the insulator and with no return line. I've since put the insulator back on after getting possible pre-ignition issues although a jet size up could of cured that. I was told the insulator is probably a good idea so I'd like to make it work with one to keep the heat away. I've also hooked up the return line again because it just seems to make more sense.

Fuel level in the bowls is right in the middle of the glass.

Probes have been used for 2 race weekends and seem to be working great. They are the hose clamp style.

Never had a spec fuel pressure and never had a fuel pressure regulator, till now! Since I've heard numbers from 2.5 to 3 I thought I would go with 2.75 for a trial.

Although this isn't a Yaw carb I've been trying to set it up like one using all the cool advice on his website. I'll take a look at my books tonight and see what jets I last put in there. I'll take a random guess and go with 195 and 70 something but I'll really need to look to be sure.

Thanks for the assistance guys! I think the first run at RA is around 11:30 on saturday David.

[joeracerx95]

Originally posted by benracin@Aug 9 2005, 12:50 PM
These high EGT temps are making me nuts. I think I'll bring a couple spare insulators and a couple other intakes with me when I go to the track. I can't really even tell if I fixed anything with my garage testing. I have GIANT jets in the carb right now so if I'm hearing people right it should be running to cool right? Lean is hot, rich is cool, or can you get so rich that it gets hot?

[snapback]58060[/snapback]

Ben, I've been told by Dave Lemon (owner of Mazdatrix) that if you get your jets big enough that you'll start dumping raw fuel into your exhaust and that your exhaust temperature will go extremely high. This is because the fuel starts burning inside the exhaust manifold. If everything else is right, that may be your current issue. On the other hand, if you drop your jets down to a "normal" size and melt the inside of your engine, you didn't hear this from me.

[ddewhurst]

Ben & folks, if the header temp is over 1700* with the heat coming out of the motor (not burning excess gas in the header) is it normal for the water temp to be at only 180* ?

How far are the thermocouples from the header face ?

Ben, my Westech temp gauge goes to 1950*.

Shall I bring my Yaw carb (still thinking about getting another one from another place) which I know is a worker ? Do you have a good pressure regulator & a good pressure gauge ?

Do you have an extra crew space ? I like cheep & I work for free. Do you get two practice & qualifying sessions on Saturday along with an Emergency session before the race ?

[benracin]

That's a good question David, and I have no idea what the answer is. My only guess is that maybe the engine is actually happy up there but then I don't understand why 3 seconday jet changes (160,165,170 I think) plus a change on the primaries haven't made a dent in those temps.

I forgot to mention that I have a spankin' new ISC header and exhaust, so no header cracks.

Thermocouples are approx 14"-16" from the engine.

Jets are 95 and 170. Anyone know what "normal racing carb" is?

And thanks a ton for the offer of the carb and crew David but I'd really love to make my carb work and I'm all full of crew at around nine at the last count. Feel free to stop by though! The weekend goes practice - race Saturday, then practice - race Sunday.

I've been working on my jet changing speed so I'm considering changing jets during a pit stop with the help of my awesome crew. Just an idea though.

Pressure guage is a Holley 1-4 psi I think and the gauge is a very nice one (thanks again for the advice David).

I've only been able to garage test the temps so far so here's a good question. In the racing environment where the secondaries will be open much more often then in my garage, will that extra shot of fuel help cool things down, or does the extra does of air as well as the fuel keep everything about the same?

Help you magic carb wizards! Oh, and thanks.

[Marcus Miller]

Here are my thoughts, in no particular order, based on my experience in pro7. (no header)

Your primary jets are way smaller (depending on temp, between 25-30 numbers) than mine, and your secondaries are way larger (again 25-30). I've heard both sides of the argument, based on which side to run larger/smaller. not sure it ultimately matters.

EGT over 1700 is starting to get bad. I would get a digital gauge that reads higher (I love the sigtronic sold by aircraft spruce). Each car combo is different, but I'd be looking more for ~1675 ish, depending on a dyno run to verify where your car with its engine/header/carb/ignition/gauge combo show.

I have run egts from 1550 to 1725 with no change in water temp.

Petit racing is around, doing mostly 3rd gen stuff.
Yaw no longer does carbs, not sure who is the hot ticket these days...

just random thoughts...
Marcus

[joeracerx95]

Originally posted by benracin@Aug 10 2005, 04:02 AM

Jets are 95 and 170. Anyone know what "normal racing carb" is?

[snapback]58137[/snapback]

FWIW, in Pro7 a reasonable starting point is 125P 155S. My carb ended up closer to 135 145.

[benracin]

Time to hear from someone with headers me thinks. Those are interesting numbers. I wonder how much they differ than the rest of the crowd.

[Marcus Miller]

Originally posted by benracin@Aug 10 2005, 11:21 AM
Time to hear from someone with headers me thinks. Those are interesting numbers. I wonder how much they differ than the rest of the crowd.

[snapback]58187[/snapback]

Agreed completely! My ITA car is 330 miles away, and I 've never had the carb off it...

I would think with a header, you would be looking at even more fuel....

Marcus

[ddewhurst]

Ben, ya don't think this is called the Secret Car Club of America for nothing do ya.

I offered you my carb so that you could learn if your issue is with your carb, jets, what ever. I am not a brain surgen while at the same time I do have some thoughts on what makes a motor get it done. That don't mean I was going to let you take the carb apart & play peek :119: & see . Ya might have put my carb on your motor & still had issues. Also, had I brought my 1950* EGT readout ya might have found your EGT is 1725* & not an issue. But as someone else stated if ya do some Dyno runs than ya have some know facts & a base line to work from. Those two items would have gained you positive info for sorting out your issues. In my mind $400 for a new carb is cheap as compared to event fees & not eliminating the issues. But then, priority one with me is driving the race car & I only work on the race car because I can't afford to pay someone to do the work.

All I was trying to do is support your effort so that you might get closer to the plastic car.

[benracin]

Not a problem David. Maybe you should bring the whole engine, carb included, and we'll put that in my car for a trial run. Now that would be a comparison! Maybe I'll see you around this weekend for some RAIN FREE racin'. Actually, you can leave the engine at home. Some rain tires would be really nice. It's the one piece I really don't have! :119:

[lateapex911]

Ben, some good points there. You don't know how far above 1700 you are, so it might not be a huge issue.

I spent the better part of a day chasing issues with my motor (brand new, with ignition changes, attributing the problems to the ignition, and finally eliminating those, I went into the carb...deep! To no avail. I slapped a buddies carb on and bam! problem solved.)
....so, it takes 5 minutes to flip carbs...take Mr. Dewherst up on his fine offer and you will have eliminated a variable on your logic tree.

If the problem remains, you know it's not jetting.

Also, measure the distance vs other cars of your EGTs. Closer is hotter.

Check and double check all the gaskets, carb, intake, and exhaust. I run the gasket on both sides of the phenolic spacer. Use Epoxy or JB Weld on all the holes there.

Ideally, the dyno is your best tuning tool.

Remeber to check total advance, make sure you aren't too aggresive with timing.

Finally, I know that DD doesn't want to give up any trade secrets, but I am sure he will steer you into the right ballpark by giving you at least one part of the puzzle when it comes to jet sizes.

[ddewhurst]

Ben, the motor & trans is hanging on the motor hoist just waiting for the new chassis to be shoved under it. The whole assembly has a :angry: . The new rust free car should be here in a week or two.

Jake, you are correct. I enjoy passing on some of what I know to others to support their race deal. Not everything. <_< Now what I need is for a guy like you to pass on some of what you have learned to me & I&#39;ll filter it to Ben. The trickle effect........... It&#39;s been interesting lately on the Production site. A production guy brought up a thread about the 1st gen RX-7 12A being classed in another class other that E as a non-ported car. In the BS that follows a great friend of yours whose brother you know very well has stated that the Southeast ITA/7 cars are so fast that the non-ported 1st gen RX-7 should be in F Production. A different Southeast guy came along & suggested that just maybe the fast 1st gen&#39;s in the Southeast were not legal. INTERESTING stuff....

[lateapex911]

DD...I wish I was the grand poobah of knowledge and had something worth passing on! LOL

So, do you have a link on this thread??

sounds like interesting reading.

the question of what a legal IT rotary can actually make comes up often, and the answers are surprising.

I will say this, I would love to have whatever juice the SE guys seem to have in a straight line. I&#39;m working on it, but they are stout down the straihgt, for sure. That said, Mr Dobson, and mr Lukas have their cars moving thru the corners well too.