I have a set of dorman 2.5 vette style exhaust manifolds on my tub right now, and I think they maybe to restrictive and making it run to hot. I'm thinking about swapping out to a set of block hugger style headers for better flow, and wondering if anyone knows of a brand that will directly swap in and out. It's tight on the drivers side and I hope to find some brand that will allow me to unbolt the exhaust manifold and bolt the block hugger in without redoing everything. Anyone just swap in a set of block huggers that were a direct bolt in?
What pug man says X2. I have a set of cast iron Ram Horn exhaust m,anifolds on my 350 powered wagon and no running hot issues. If I were you I'd look else where for your problem. Its not your exhaust manifolds. Check your timing.
I wasn't going to get into all the specifics, but this is what i'm trying to cool... all the rest of the cooling system is doing what it is supposed to do, i've been all over the cooling, and this is the last thing i can think of. Here's how the exhaust manifold looks today yah, the pic sucks but the dichromate on the 2 inner bolts is actually coming off meaning it's getting to hot, and i believe where the exhaust meets and has to get to the center maybe too restrictive giving me the weird issues i'm having. Dyers has this in there trouble shooting section... 3. Increase size of exhaust system - We recommend using 1-7/8 or larger headers with a minimum 2-1/2 pipes out with high flow Flowmaster mufflers. That's why i want to swap out the manifolds, but looking for something that will not require changing everything as the drives side is very tight. Timing is set @ 32 total, same thing we dynoed the motor at, so that should be right on
I don't think you are gonna find an 1 7/8" block hugger. I don't think I've even seen a 1 3/4. Speedway makes block huggers (1 5/8) and sells 2 1/2" leadoffs for them, but I still don't think they will help your overheating problem.
If it was the air cleaners being restrictive, then it wouls be rich. But exessive rich wil get the manifolds hot if all of the fuel is not burned in the combustion chamber, correct??? The speedway reproduction ram horns are claimed to flow very well, similar flow to a header
Lean = hot. Have you put an Oxygen sensor in the tailpipe and checked the output? I won't tune without one these days, especially not on a forced induction car. Did you point a non-contact pyrometer (infra-red thermometer) at that spot and verify that it is a "hot-spot" and not just the coating happening to fail, by coincidence? Cheap, thin plating on the studs/bolts is not evidence enough. My stock 305 and my OT/DD does that to bolts too. Holding back combustion gasses in the chamber is effectively like having EGR, only not all-the-way to the intake manifold: "EGR puts a portion of the exhaust gas back into the intake manifold, so it mixes with the fuel and air. (Note that the exhaust adds to the fuel and air; it doesn’t replace any of it). The added mass in the cylinder is harder to heat up, so the combustion events have lower peak temperatures. The lower temperatures prevent the O2 and N2 from splitting and combining. Even though the exhaust is hot, about 600°C (or 1112°F), it's much cooler than the 1300°C required to make NOx." Your problem lies elsewhere. What do your spark plugs look like?
That is what i've been looking at. But looking for something that will not require changing everything. The motor is only 608hp, so i'm don't need the 1 7/8. The dyno was 1 3/4 with no problems so the 1 5/8 should do as this is a street motor, not a race motor. I probably will never put that kinda load on the motor that the dyno did.. as it sits now, just tapping the go pedal and the tires are breaking loose. The air cleaners in the pic were only there for a pic. The plugs are clean, no black smoke, no rich smell so that is not a problem. It is a tad rich, but that isn't a problem as a blown motor should be to prevent leaning out on boost.
Any car carb I've seen has the bowl vents positioned inside the air cleaner. The general result is a restrictive air cleaner lowers pressure in the float bowl too, keeping the A/F ratio pretty constant, especially at cruising speed. Unlike a zillion motorcycles whose bowl vents are external. http://www.mikunipower.com/VM01.htm The air cleaner restriction will limit airflow, and reduce max power at higher rpms. There are fairly reliable reports that some air cleaners cause sharply non-uniform airflow entering the carb, and the resulting local high velocity air streams whooshing over the vent can mess with the pressure in the bowl with resulting mixture changes.
I can think of about 20 things I'd want to check on a blown engine before a restrictive exhaust if it's running hot.
Typical Overheat problems "I've" dealt with throughout the years: >Small or clogged radiator >Water pump impeller slipping >No thermostat...circulates back to the engine too fast >Air bound in water jacket (Put a small hole in Thermostat) >High temp thermostat...to hot >Kinked lower Rad hose (Or collapsed at higher RPM) >Crap in rear water jackets (However your engine is fresh) >Lean condition (You checked) >Valve timing wrong >Ign timing or advance wrong (Checked?) > Head gasket (Small Leak) >Back pressure Crush pipe(s), Defective muffler baffle blockage >And......Brake drag. Good luck...Let us know what you find!
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