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Filling or getting exhaust crossovers filled??

sled_dog

sled_dog

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I've seen places that offered this on Pontiac heads before. While porting me heads I really started thinking, there is no reason other than maybe cost that I shouldn't fill my exhaust crossover passages. Can only increase my exhaust side flow(and we all know thats a good thing on a Chevy especially a 383).

Can I do this myself? Maybe buy block filler from Summit and fill them up after sandblasting out the carbon? I know block filler is really for waterjackets so not sure that would workout.

If I pay to get it done, about how much will it run me?
 
I did this on my Olds455, should be identical to the Pontiac. You can actually buy plugs, I got mine from Jegs, think they are made by Moroso, cheap and not too hard to do, requires some grinding to get them to fit right. Definitely glad I did it, although now that I have the torquer manifold it doesn't matter, but with the stock manifold that had the crossover the benefit was huge, no more cooked carb and cooler intake charge = more power = faster = :D
 
well the intake I am going to use doesn't have the crossover or EGR so its really pointless. Basically they would be big flow restrictors that let the center 2 cylinders mix gases.

wow, thanks. Any idea if those will work on my chevy heads?
 
gasket block off plates??

You probably already know about the "restrictors" fel-pro puts in some intake manifold gasket sets--there are "block off" plates available as well...not sure if thats what youre looking for--I dont think its nessasary to fill the whole passage with something... :crazy:
 
exhaust port flow

I think it would be more cost effective to buy some good heads like a pair of 23 degree AFR's or Dart Pro 1's.
I've been down that road trying to improve on a poor design and you can really waste a lot of money doing that.
You would benefit with a 190-200 cc intake runner on that 383 so just stop where you're at and look at the big picture. :crazy:
 
huh? These aren't stock TBI heads. They are the heads GM put on their 300HP crate motors in the 90s. Sure I'd do better with a set of AFRs but the idea that they would be more cost effective is ludicrous. Free heads that all I need is a set of valve springs and the exhaust crossover filled, or $1200 for heads????
 
Block filler is made to withstand the 200 some degrees the lower block runs, not the 1200 degrees an exhaust port runs. When it comes apart, hope it is in small pieces and that it flows out the exhaust port instead of hanging a valve. Having to do your motor over would negate any savings on the heads. Poor idea imho.
 
that why I asked instead of just doing it. Says block filler is temp resistant but no spec.
 
block fill is designed to replace the coolant in a drag race engine.....
It adds rigidity to the block but it is not a coolant and can only be used on engines that are run for a few minutes during a burn-out and high-speed pass then shut down and cooled off.
I'm assuming (very dangerous) that you want to weld up the crossover so you can open up the exhaust ports on 1,2,7 and 8 to some ungodly size that will have no velocity whatsoever.....what about 3,4,5 and 6 ?
i guess you could weld up the push-rod guide tubes....never mind.
Cast Iron welding is a very expensive, time consuming and not very reliable operation.
Port match the intakes, polish the exhaust ports and you're done...
 
uhh no, I want to fill the 3,4,5, and 6 ports so they are THE SAME as the others. As of right now they have a big chamber in there that the exhaust gases flow into before they find their way out the header. Sounds like a big time flow restrictor to me. I completely understand the proper methods of porting and polishing, I've barely messed with the other side other than to smooth all the rough edges and reshape the valve guide. But it really almost seems pointless when I look in there and see this big hole where I know my gases are going to go. Exhaust follows the roof of the port and the hole is located on the roof of the port.
 
I have heard of guys using the filler with good results, the plugs are just easier IMO. If those plugs don't fit you could always grind em down. I run the plugs plus the gasket that covers the port. I think plugging the crossover was actually a requirment for my intake manifold because it does not completely cover the crossover if I rememeber correctly.
 
Ahhhhh.i'm with ya now......i totally agree with you on eliminating the crossover/egr port that is located in the top of these runners.
that wiil definately smooth out the flow, i can't recommend anything other than welding to close up those ports as i have never used any of the metal patching/liquid steel compounds......but if you block the crossover on the intake side and rotate the head until the port bowl is level then pour some compound in, let it dry then smooth it out....it may work in this application
(2 hail mary's and a shot of whiskey).
If it does fail and come apart then it will just fly out the exhaust port and you'll go back to drawing board with no harm done.....good luck my friend
 
thanks, I am going to hit some local speed shops and see what they say. I know I have seen this service offered before but I really don't know if they weld them up or what.
 
If you are after better flow in those ports then melt down some old pistons or a bunch of aluminum cans and fill the x-over ports with that. You'll have to do some port work to get the contour back though.
 
I think I will stick with just paying 1200-1500 for new heads. Less B/S this way.
Thanks
Adam
 
I thought about that. According to online sites aluminum melts at 1220*F. I guess as long as the temperature at that area doesn't exceed that temperature for a prolonged time, it would be fine.

I just don't know enough about aluminum to know if heads and pistons are specially alloyed to increase the melting point of the material, and if exhaust temps typically reach anywhere near 1220*F (I find 14-1500*F quoted online for exhaust gas temps?) I might be somewhat apprehensive about using aluminum in an application like that...it would "see" the exhaust stream twice as often as say, a piston does (less cooling, more heat) and it also will likely not dissipate heat nearly as well, since that area of the head IIRC doesn't really have cooling jackets.

Apparently silicon (used in pistons for one thing) actually reduces the melting point of aluminum, but again with the cooling characteristics in a single cylinder, unless something is wrong, that brief "over temperature" is not an issue.

Maybe I'm wrong, but if AL was a viable material for those filler plugs, I'd think it would be easier to make those, (as a manufacturer) than out of cast iron. (which is what the Oldsmobile fill plugs I have are made of) Material cost could be higher I'm sure, but it would only take a few of cans to make a couple of plugs, and since they melt so easily, and could be worked more easily...

I can tell you from experience though, a chunk of ANYTHING getting between the valve and seat is not a good thing.
 
The engine shop I do some fab work for uses this technique to fill heat riser ports. Never heard of one failing. I've got to think that the piston sees higher temps than the exhaust port, and the exhaust port has coolant directly surrounding it.
 
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