Carb spacer plates: Do they make a difference

[fasterthanu]

I am running dual quads on my car. Believe it or not, I blew my rubber gasket out of the back of the intake manifold. Go figure, I have never heard of that happening before. I've been checking my intake manifold bolts every couple weeks. So, now I have to rip the intake manifold off, and change the gaskets. Since the carbs will be off, I was thinking about putting on 1.5" spacer plates on both carbs. I have always been told, and read that they add more power and torque. Noticable difference? Anyone out there running them?

 

[Stallion]

Yes they do make a difference. They do add more power, but they also make the peak of power at a higher RPM. Technically, I'm pretty sure the idea behind it is air volume. With the spacer, more air volume is allowed into the intake, therefore resulting in a performance gain.

But like I said, it also raises the peak of power to a higher RPM.

Good luck!

TR

 

[MaineShark]

Believe it or not, I blew my rubber gasket out of the back of the intake manifold. Go figure, I have never heard of that happening before. I've been checking my intake manifold bolts every couple weeks. So, now I have to rip the intake manifold off, and change the gaskets.

Hmmm... are your PCV and vent(s) in proper operating condition? That sounds like crankcase over-pressure, which is a bad thing, both from a performance and a reliability standpoint. The crankcase should be at vacuum. It certainly shouldn't have enough pressure in it to blow out a gasket...

Joe

 

[fasterthanu]

I agree, there shouldn't be enough pressure to blow it out. I DO have 104,000 miles on it. I do have typically 70-80lbs of oil pressure. I do have a high pressure and high volume oil pump. I was stupid, and did all my mods at about 95,000 miles on the motor. My theory, I guess goes with my age of 22 when I did the stuff, is when, not if, when I blow my engine, I will rebuild it to be a power house. I did the dual quads, full race cam, high reving hydraulic lifters, roller rockers, the racing heads, a piece here, and a piece there. I knew that when I did blow it, the whole top half of the engine is basically new, and will be used on the new engine. Anyways, my luck seemed to take a turn for the worse. Started my car, with full oil, sounds like a bad rod knock now =( Dad is coming over tomorrow to look at it. Nice.. Great... In college, no money to rebuild... But... Grants and loan money for school is coming in... hmm.. hehe. With about 9000 miles on the top half of the motor, it is basically brand new, and will save me a couple thousand on the new motor. I mean realistically, we can get machine work on the block out here for I think $700. Expensive parts are the heads, they are still new =) Just need a crank, and maybe 10.5 : 1 pistons, and the car should fly. should be able to do it for under $1k. The car ran 13.5 with what I have in it now, and I could have got a lot more out of the timing, but I drive it on the street, and don't have a high torque starter. I have it set to where she just starts on hot days. I once turned the timing down 1/8 of a turn, and had to lose 2seconds on 1/4mile. RPMS went no where. From my current setting, I can't turn it up more, the vacume advance *which isn't used, it was strobed and set up* hits the intake manifold. I need to take it out and swing it back so i can get more advance out of it. If 1/8 of a turn can slow me down that much... 1/8 forward.. hmm... And to think, I only have 8.5:1 compression now. You KNOW damn well, that cam is not even near it's potential with 8.5:1 compression. The heads can breath now, but with my current compression, not seeing anywhere near their potential either. I really believe, and have been told by a couple machine shops I know, that my current setup with 10.5:1 compression should easily see 11's =) Oh, FYI. I have dual quads, full race cam, Pro Line Heads *open chambered*, hooker header/sidepipes with JCL inserts, 4.11 rear end, 3000 stall speed, and a 700R4 trans. The car should fly with 10.5:1 compression!

 

[AKRAY4PLAY]

the back gasket is easy to blow with high oil pressures. the stock distributor does not have o-ring seals and as a result pressurized oil blows into the lifter valley. when turning up the pump pressure and engine rpm, the oil jets past the distributor and directly hits the intake gasket. after time it will give up the ghost. i would clean the area very good with starting fluid when you get it apart. them use a RTV Ultra Black to fill the gap during reassembly and forget about the rubber gasket. this is the new preferred method recomemded by GM. Brian

 

[Stallion]

How can oil pressure blow out an intake gasket? What's the idea behind that?

 

[MaineShark]

fasterthanu: Sounds like you have some trouble. I'd agree with Brian, but that knock you describe sounds like more than simply having too much oil pressure. If I were in your position, I'd do a compression test, pretty soon, to make sure I didn't have a damaged piston or ring. Because that would certainly be a way to get a lot of extra pressure into the crankcase...

How can oil pressure blow out an intake gasket? What's the idea behind that?

The lower portion of the intake manifold also serves as the cover for the cam/lifter valley, as well as covering the top of the distributor port and containing some water passages. This dates back to the origins of the small-block, as a way to simplify things and reduce cost, compared to the typical engines of the era, which had separate intake manifolds and valley covers, and sometimes even separate oil and/or water passages.

It's a nice way to simplify things, but it does have drawbacks (heating of the manifold by the oil and water, for one).

As Brian says, the distributor passage is right next to the back of the intake manifold gasket, so oil hits that gasket. If the pressure is too high...

Joe

 

[fasterthanu]

My baby is out of comission. Blown engine. IT sounds like a cam journal bearing cam loose I think my dad said. grrr. Looking forward to finally rebuilding it the way I should have to started. 383 stroker, with my dual quads, open chambered race heads, full race cam, here I come. =)

 

[JohnZ]

Notes for your rebuild - 10.5:1 will get you some more power, but it will also blow any plan you may have for running straight pump gas, and if you don't have a proper crankcase ventilation setup, it will continue to blow the weakest seals or gaskets.

 

[Stallion]

John, what does the crank ventilation have to do with blowing seals and gaskets? If the PCV is clogged, would it cause more pressure and build up? And what gaskets and seals would be affected?

Thanks!

TR

 

[JohnZ]

The PCV system continuously ventilates the crankcase by bringing in outside air, flowing it through the crankcase, and extracting it through the PCV valve (which meters the flow, and only allows flow in one direction) into the base of the carb, where the vapors are taken into the intake manifold and burned with the incoming fresh fuel/air mixture. If the PCV system is absent or blocked, pressure will build in the crankcase and will exit through the weakest seal or gasket it can find - intake gaskets, timing cover seal, oil pan gaskets, or the rear main seal.

 

[Stallion]

Okay, I see now, John. Is the PCV valve something you should change annually, so this doesn't happen?

 

[JohnZ]

PCV valves are pretty simple - just a spring-loaded check valve; if you remove it and shake it and it rattles, chances are it's OK; if it doesn't rattle, it's sludged up and should be replaced; they only cost a couple of bucks.