Thanks for all the suggestions guys! I don't know what I'd do without you.

Cardo:
Wupps. Somehow I missed you saying that C3s had the ram's head exhaust too.

Mtwoolford:
Yeah, I currently have stock cast iron manifolds. Are you referring to the same ram's head manifolds that cardo mentioned? Sorry, I just haven't been a 'car guy' long enough to know much about other cars' engines.

Churchkey:
Wow, I'm kinda glad I had this spark plug problem actually because I didn't even consider that the exhaust ports might be difference. AFR recommended the Fel-Pro 1404 gasket for it which looks like it's for a standard square port.

John:
Only the outer half is all of the way off (like you said I can't get the inner half off with the manifold bolted on) but I was able to get the inner half enough out of the way to tell that, even with it totally off, the plug boot would be touching/dangerously close to the manifold itself.
Mine has cast iron manifolds, not the tubular steel kind.

Everyone:
How would all those different manifolds work with EGR? Would the exhaust manifold fitting be in the same place as on my manifolds? In the picture of the '84 manifolds on Ebay that Churchkey posted, I can't even see the EGR pipe whatsoever.

 

4th gen F-body the EGR is on the pass side rear manifold. The C3 ram horns dont have EGR fitting as the intake mounted EGR get exh gas from the head exh cross over - sorry that wont help your car much.

I can see u will soon be the forum expert on sbc exh manifolds.

Good luck.

 

Well, looks like I'll be picking up a 4th gen Camaro manifold set from a junkyard. I sure hope the EGR tube is in the same location as on my manifolds: otherwise getting new valve covers to avoid having to modify the EGR pipe was pointless.

Edit: Just to be sure, the fourth gen Camaro has exhaust ports like my new heads, not the raised D port, right?

 

I think u should slow down and sort things before spending any more $$. Its not going to be any fun to buy used parts then find u cant use them. But it is a lot more fun to relax and keep looking until u find a working part or substitute - thas hot rodding itself. I found a pic of an '88 C4 with the L98 motor and stock EGR - looks pretty tight in there. Make sure u can return any exh manifold u buy used at the boneyard or at least get credit for it against other manifolds/parts.

Well im a little confused here. I have to ask, arent the exh manifolds u have the same as the '90 ebay manifolds that Churchkey posted? The '90 ebay manifolds look like tube steel to me but i guess pix can lie and could be cast. Do u have the correct ech manifolds for your '90? Or PO swapp'm out? Im think'n if u can find tube steel exh manifolds more than likely u can find an exh shop that can modify'm like mtwooly and churchkey mentioned. Ive had best luck with mom and pop owned specialty exh shops than the franchise (midas) shops but just dont get pushy and expect something for free. That '90 ebay manifold had the correct EGR piping BTW.

Im guessing as long as u have any kind of stock exh manifold with the shielding tin and EGR, AIR fittings on them not many CA smog technicians would know the difference. Chances of a smog tech that knows the difference is pretty low considering none of us here know the difference. But beware any tube header (aftermarket) will need a CARB number plate welded on tube #1.

Oh and im not sure what u have for D ports or what u need - im sure u can sort that one now so u dont waste your $$$ on the wrong part. 4th gen exh manifolds are cast and pretty thin at that but have EGR and AIR fitting - dont buy'm w/o the tin shieling on them.

 

Thanks for the advice.

You got me there. I had been told they were cast so I assumed that was the case, but they very well could be steel. As far as I know they're the original manifolds, and they look just like the '90 manifolds in that Ebay listing.

Assuming they're steel, how would an exhaust shop modify them? Seems to me they'd have to completely re-route the tubes going to the 1 and 7 and 2 and 8 cylinders.

My new heads have regular square ports. I did a bunch of research, but I couldn't figure out for the life of me if 4th gen Camaro heads had square or D-shaped ports.

 

they would probably cut away a portion of the tube and weld in a patch that "dimples" into the tube to provide the necessary clearance; of course this may restrict the tube somewhat, but sometimes sacrifices have to be made when you start mixing and attempting to match different parts.

 

How do I tell if they're steel? I know how to tell stainless from cast iron, but I have no idea what the visual differences between regular carbon steel and cast iron are.


I just checked, and my heads have D-shaped exhaust ports, which is good if I can use my current manifolds, but bad if I can't since it looks like most manifolds I see are for square ports. I didn't unbolt it from the Y-pipe though, so I couldn't see the ports super well to see if the ports are centered or offset from the bolt holes. Are all D-ports raised, or are there some that have the ports centered on the bolt-holes?

 

Your stock headers are no doubt tube steel. Look @ the pic in post 240, focus on an end tube going into the mounting flange. See the joint line? The tube is welded to the mount flange on the side of the flange that mates to the head.
Cast iron manifolds are one piece = no welding except for a repair.

Stock 90 manifolds are restrictive, you need to port match the exhaust especially since your engine is 33 cubes bigger + bolting the l98 manifolds to your current heads has raised them up 3/8" no doubt blocking your ports to some degree & creating the clearance issue with the plugs.

Suggest the 84-85 Vette manifolds, everything should bolt up & be smog compliant. Have a muffler shop or street rod shop connect the EGR tube after the car drives.
Cap the EGR @ the intake until the tube is installed.
You will get a CEL code 32 when the manifold is capped @ the EGR port. No way around it other than burn a new chip without the EGR function.

Other options: Long tubes or block huggers that are CARB certified then deal with the EGR tube issue + a custom connection to the Y pipe.

Good luck.

 

I just checked, and my heads have D-shaped exhaust ports, which is good if I can use my current manifolds, but bad if I can't since it looks like most manifolds I see are for square ports.

Dont worry if round or square ports on exh manifold to your D-port heads. U just dont want large exh port of head covered by tighter header exh port. But dont even worry 'bout that now. U are treading water for now and any size life preserver is good enough. U can optimized the exh 10 years from now if u want to - no rush. Same goes for the EGR pipe and even the AIR plumbing.

Let us know what u find out for your exh manifold. Curious myself, tube steel pipes or cast? I expect tube steel. And take your time to get the manifold that fits or even need to mod it. Im guessing that will be cheaper than shorty spark plugs.

 

Finally found an answer! From superchevy.com:
(Edit: Oh. I guess Churchkey already figured out they're steel.)

So modifying my current manifolds is an option. Some good news for a change! Is dimpling them something I could do myself?

Also, is getting other manifolds still possibly worth it? I'll be the first to admit I'm no expert on exhaust, but it seems to me that manifolds designed for a 250hp engine would limit a (guestimated) 325hp engine significantly if they were dimpled ~3/8" in several locations.

Know any manifolds/headers with a CARB EO and EGR hookups? Could I get new manifolds that would clear the plugs (e.g. these), then have a muffler shop transfer the EGR equipment from my old manifolds to the new ones? I get the feeling that wouldn't fly...

Churchkey:
I pulled a manifold off and my new heads are D-port too, so the '90 manifold should match up properly, right?

Unfortunately, LT headers aren't CA legal.

 

Suggestion:
Find a gasket that fits your current head ports properly then match that gasket to your current exhaust manifold lining up the mounting holes. This procedure should give you a visual of what/where the problem area is & what will be required for a fit up.

 

I'll have to take the manifold completely out to be sure, but I believe my manifolds match the head ports. I know for certain that they are both D ports, but I'm not positive if the head has raised ports.

 

Post a pic of the head ports + a pic of the manifold with the gasket on it. Try to get pix at 90* to each surface.

There will be a way to sort this issue.

 

Okay, I pulled the driver's side manifold.




Gasket alignment on manifold





Gasket alignment on new head





Gasket alignment on the old head



After checking gasket alignment, I installed the plugs and fit the manifold back in. I found that it was about 1/8" from being able to bolt in (vertically: the manifold was too low), hitting solely on the #3 plug. Numbers 1 and 7 cleared by a mile (well, about an inch) and the #5 plug had about 1/2" of clearance, meaning it would have 3/8" if the manifold was fully bolted on.




Fitment of manifold





#5 spark plug


Given that the spark plug boot requires clearance of about 3/8" and I'd need an extra 1/8" - 1/4" to fit header wrap, I'm looking at having to ding the manifolds 1/2" - 5/8" on the #2 and #3 tubes and about 1/8" - 1/4" on the #4 and #5 tubes. Because of the angle of the plugs, shorty plugs might help a bit, but I wouldn't think by much. By the way, how much shorter are shorty plugs?

Dimpling the manifold 1/3 of the tube's total diameter (about 1.5") seems pretty substantial to me. Do you guys ever dent headers that much without serious adverse affects?

But really, what options do I have? I can't find any manifolds that have the necessary smog equipment and a vertical collector in the center (most have horizontal collector in back), and installing headers seems cost-prohibitive, and from what I've heard very likely could introduce other clearance problems to work around. The way I understand it, I'd need to buy the headers, a new Y-pipe to go with them, possibly bullet cats to replace the precats (not really sure how that works), and pay a muffler shop to fab it. I'm guestimating that would be in the ballpark of $1000.

It's so frustrating to encounter all these problems, finally see the light at the end of the tunnel, but then encounter a setback like this on literally the last thing I had to do to the engine. It seems like such a lose-lose: either I take a performance hit by restricting the manifolds, or I totally blow my budget for this project.

 

Young Jedi, your perseverance & dedication has reminded me of myself as a young man.
I would like to help you with the manifold/plug clearance issue. I have a lot of experience building custom tube headers for street rods & oval track cars..
If you want I will lower all 4 end tubes for plug clearance. I have found my old set of Brownfield heads (pre AFR) that I can use as a jig to hold your manifolds in place when the end tubes are cut out & repositioned/changed.
Let me know if this option works for you if so I will pm my shipping addy.
No charge for labor, I have a supply of tubing on hand. Just pay shipping both ways, figure 48 hours turn around time.

 

Reid,

Churchkey is offering you the best deal. He would just cut the tube and separate the manifold by 3/4 to 7/8 of an inch and weld in a new section of tube into each which would then lower the bottom of the manifold and give you the clearance you need.

The only thing about these manifolds (but your stuck because of California CARB) is that the collector is so small. Just look and you will see that each tube is forced to about 2/3rds or less of their diameter into the collector. I ran these on my 85 and was still running 13.2 in the quarter with low compression heads. So they work, but short tube or long tube headers would be much better......if you could every find a CARB legal set.

I might suggest that you use the gasket on the bottom half of the manifold as a pattern and grind the manifold to match the gasket. You will be pretty close to the bottom of the "D" ports on the heads (looking at your picture) when you grind the manifold. You will probably have to do a little welding to build up the area your going to grind.

I also took a grinder to the tubes that enter the manifold from the top and ground them down so they were no longer sticking out into the manifold.

Churchkey's alteration would push your "Y" pipe down the same distance that he would add to lower the manifold. This would probably not be an issue. Or if it is, we can cut a section out of your "Y" and weld it back together.

-John

 

Wow, thanks for the generous offer, Churchkey! I'll definitely take you up on that. Knowing that I won't have dented manifolds makes my day, and my dad and I are so relieved to actually have a good solution to this. I really appreciate your help.

John,
Thanks for the advice. I'll definitely grind off the tubes that stick through into the manifolds. When I took them off I wondered about those. Not sure if I'll have time to port the manifolds this time around though--I'm leaving the state for college in just over a month and I'd like to drive it with the new engine before I leave.

 

I got my exhaust manifolds back from Churchkey a few days ago, and they fit like a charm. The heat shields fit on them, and all the plugs went in no problem. Thanks a ton, Churchkey!


Well, it's all back together, and I'm now working on the finishing touches: filling it with coolant, filling the transmission with fluid, and installing my Ostrich 2.0 for tuning. I was hoping to start it tonight but a few coolant leaks have set me back.

Also, I'm not sure about installation of the Ostrich. The ribbon cable needs to come out of the ECM enclosure, which prevents the memcal cover from fitting back on well (it sharply bends the ribbon cable if I put it on). I'm guessing leaving the cover off is out of the question, since dust and dirt would get into my ECM? Here are a couple pictures:




ECM (upside down) with cover off





ECM with cover on

 

Wow thats too cool how Churchkey helped u out of an difficult problem. I have to say this forum is all the better with Churkey in it. That fix would be difficult for any seasoned owner let alone a young'n starting to learn. Cant say enough good for how he helped u out and did some hard work fast to.

Ok be careful with that ribbon cable as tight bends will break wires and u will get intermittent opens that will drive u crazy. I believe that cable for the "Ostrich" is only temporary? I would try and protect the ribbon cable from sharp bends and seal the box - just plane old cellophane/saran wrap can do a good job temporarily. If u need something more permanent u will have to cut out the memcal cover and fab/install some soft seals.

Hope u havent pinched that ribbon already and thx for the update.

 

Yeah, I couldn't believe he did that for me as a favor and got them back to me so quickly, especially since I'm sure his day job keeps him busy.

Unfortunately, that ribbon connects the chip emulator to the memcal socket, and as such needs to stay attached. I considered using plastic wrap, but I don't think that would hold up long-term. Sounds like modifying the cover is gonna be the way to go. I think I can just grind the ridge off the inside of the cover for the width of the cable. Pinching the cable between that green rubber seal and a flat surface on the metal cover shouldn't damage it, right?

Edit: My dad figured out an easy solution. We peeled up the rubber seal a bit and ran the cable underneath it, which gets it out of the way of the ridges on the cover that would pinch it. The seal isn't perfect around it though, so once I'm sure it's working I'll put a bit of silicone on it.