I have a question that I wanted to pose to you all. I have a 340 six pack setup that idles very well at about 850-900 with a Comp 305/.525 cam in it. The question is that she refuses to idle well until at 170-180 degrees of warmth...anything under that and it idles too low to run. Once she's up to temp, it'll idle all day long. When I assembled the engine, I did put in the heat crossover blockoff style head gaskets, so the manifold is "cold." I'm running a Mr. Gasket 180 High flow thermostat with an aluminum radiator, so it takes a little bit to get some heat into it. Once the car sits for as little as 20 minutes, it wont idle correctly until it gets back up to 180...frustrating at cruise ins and local car shows.

My question is what can I do to either speed up the warming up after not running or how can I get her to idle with lower engine temps?

Thanks everyone.

How much initial timing do you have?

22 degrees if I remember correctly. I'm not runnign a vac. advance and have my total at 34 or 35.

Bump...

The Mr Gasket high flow stats - when they work - seem to crack open at lower than rated temp. This can slow warmup and cause extra cooling which shows up at low load/idle. That's what mine does anyhow and I've seen other posters with similar results.

One change that could help is a better Stat to help keep temps at or above 180. Premium NAPA and Milodon are supposed to be good. That's what I'll do when it comes time to replace the Mr Gasket. You might even consider a 195 stat.

Beyond that, I suspect there are some tuning opportunities with the carb and possibly timing. Over 20 deg is a lot of initial advance. It might be worth trying 18 or 20 and re-set idle speed.

PS. it sounds like you have a great cooling system. To much cooling is a lot easier to solve than too little.

Nature of the beast. Small engine+ big cam+ blocked heat crossover= poor/no idle when cold. Try raising the idle speed some. 900 rpm seems low to me for a 305 magnum in a 340. And unblock the crossover. You might be better off with a smaller cam anyway. I don't care for hyd cams that radical in such a small engine. You will be reaching the upper limits rpm wise of what a hyd is capable of. That cam profile is asking for 7000 rpm but the hyd lifters may not give it to you. My point is: not only would your idle improve with a smaller cam, but your car might be faster too.

Thanks guys. I was suspecting the thermostat wasn't helping my situation. I may switch to the Napa soon.

Yea, I knew the cam was too big, but the price was too good to pass up, FREE and NEW, so I thought it might be worth a try. I know it also greatly complicated the tune of the six pack setup, but I'm glutton for punishment I guess. Thanks for the input, I was hoping that wasn't the case...I was hoping for the heat crossovers being the reason, but the combo is probably mostly to blame.

Thanks again.

hi
when the engine is cold and choke actavated you have to set the small arm on the fast idle cam by sticking a small scerwdriver in the slot and bending it slightly to get the proper rpm when cold !
look up the adjustment in any FACTORY service manuel that covers the six pack setup!

A set of "Rhoades" lifters might help your cam / idle problem.

You are asking us?

If your car sits for 20 minutes and you need time to warm it up, what's your secret?

Ok seriously, with no choke I think it's perfectly normal for a car not to idle properly until the intake is warmed up.

Thanks guys, I guess I just needed confirmation. The reason it has thrown for a loop is two fold...This is my first six pack setup and my Hemi doesn't have a choke either and that old that ol' girl will gladdly idle with just a minimum of warm up, really. My hemi is a 472 with a solid roller and stock AFBs and she'll happily idle with just a few minutes of warmup, long before the temp gauge nears normal op temp.

Yea, this 340 six pack, for whatever reason, shedds heat VERY quickly when parked. The gauges are AutoMeter Sport Comps and were new for the engine last year. I can park her for an icecream with my son and 20-30 minutes later I'm 30 degrees cooler already. I agree, if you're going to have cooling problems, its better to have my situation instead of the normal heat creap that usually accompanies short stops.

Thanks everyone. I plan on doing a cam swap this winter as I am in total agreement with the size being too large...but somewhat fun when I let the six pack sing around 7000! It's like angels singing

maybe back off the timing to 15 or so and turn the idle up to around 900 rpm, sounds more like a tuning thing. My sb with a solid cam idles fine and its heat crossover is blocked.

Admon, is your small block running a six pack too? I'll admit, mine is a little fat at idle. I'll tinker with the timing some and see what I come up with. Thanks for the input.

no just a 4 bbl, holley 750 dp or this T-quad, depends on my mood but maybe your throttle plates should be opened more, on a holley the sec are cracked a bit with the primary,

FWIW, my 440 with a mighty demon annular carb (no choke) doesn't idle decent until the temp hits 130. It gets there within 1.5 minutes or so, then goes up to 180/195 area when driving.

I'd adjust the choke myself.

Been running with blocked crossovers for years and a choke is vital. When I had my 300 up north I put in a manual choke setup, worked fine. Otherwise I had the same issues you mentioned.