Hi Olli, you should consider to upgrade your old worn bolts to ARP bolts. I understood that you have more going on than just exh. manifold. ARP has also complete engine and accessory kit. Check from: arp-bolts.com
Maybe somebody can also tell me the actual thread length of the bolts. As it appears the thread length is the same for all bolts, which, thus, only differ by the shaft length. I checked the holes on the LH exhaust manifold to cylinder head again and it could be that the bolts are only missing, since I’m able to stick something deeply into both holes. If they are actually only missing I could screw new ones in and replace only the RH exhaust manifold, which is cracked, with the engine in place. Addressing the leaking engine could then be done in a follow-up task.
Firebirdcentral’s customer service replied with this link after I had sent an email explicitly stating my engine and carb combination. From having a look at pictures showing long branch manifolds the thickness of the bolt hole spots look very similar to my ones. So the layouts of standard and long branch manifolds appear similar where they are mounted to the heads, diverging more and more towards the exhaust. If you wonder why I not only remove the bolts, measure them and order afterwards, shipping to Germany takes 2 weeks - of course, returning wrong parts is rather not feasible. Thus, I prefer to order in advance, which requires a bit more verification upfront.
Do yourself a favor and just go to the hardware store and buy the bolts that you need. Just make sure they don't bottom out in the holes before they get tight. Don't overthink it. Be sure to "never sieze " the threads.
@Firebob - since we have the metric system almost everywhere, local hardware stores don’t have imperial system bolts .. if at all only a very restricted selection. Of course, I can order somewhere in Germany via eBay getting them faster compared to ordering in the USA but the quality is unknown.
Google a good quality parts supplier. Try Ames Performance. They do only Pontiac and they know exactly what you need. Talk to a real person and they will get you exactly what you need. There are others too.
Ive ordered some stuff from them over the years. Had no issues. It just depends on your needs. Sometime you need a real person who understands exactly what you are talking about. You can't beat Ames for that. Best of luck.
I checked several other parts companies and the only one explicitly listing a suitable bolt kit is this one https://www.amkproducts.com/i-kits/pontiac/?year_=1968&model=Firebird&category=499 However I was surprised that it contains only 12 pieces - 8 bolts and 4 spacers. After asking them they replied that originally only 8 bolts were used and the outer most holes were left unused on my engine configuration. Can anybody comment on this? I tried to verify this information - without success.
@cme469 - on the driver side the two outer bolts are indeed missing. First I thought - based on the remark by my mechanic - they sheared off. Then I checked the holes (with the manifolds in place) only to see that there are, apparently, no remnants of them in the head (holes considerably deeper than the thickness of the exhaust manifold at this spot). Preliminarily, I came to the conclusion that they were not installed after a previous fix. However, the spacers are there on the second outer most bolts. This would corroborate the statement that the outer ones weren’t installed by the factory at all. The passenger side one has got 6 bolts installed. But this was obviously removed once since weld seams of former cracks are visible. Amk also mentioned that I could buy a second set or 4 individual bolts in case I want to have a bolt for every hole.
I checked the service manual and textually no references regarding number of bolts are to be found. However, scrutinizing the pics revealed pertinent information - see the attached ones - supporting AMK’s statement that only 8 bolts were installed.
4 bolts @ $??.?? times XX,XXXX Firebirds = savings
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
One of the great things about Pontiacs is that all the parts from different years basically interchange. But it isn't perfect either and doesn't always work. Different years had different "this and that" bolt holes and add ons etc for different options. Some might be there on yours but not used. Curious what number heads do you have? They should be #17 on 1968 350 2bbl. (best 350 head by the way!) Possibly even #47 in a late run. But often they were swapped out when they got tired. Could be anything?
Interesting, I have a box of miss matched Pontiac exhaust manifolds. Most are drilled for 6 holes, and all my heads are tapped for 6. Though I have seen heads that were not. I assumed they went to 4 holes in later years but Jim’s 68 only used 4? I’m sure the manifolds are rigid enough to seal ether way. Have also noted that service manuals do not always reflect exactly what the assembly plant did, and that things sometimes could be different at different plants. Go figure. Another mystery?
The missing exhaust manifold bolts on my car have interested me for a long time. Your thread got me thinking about it again so I started searching. This Hot Rod - Reader Tech Q&A from 2009 The Rocky Rotella response was interesting.
I went to my "Nut and Bolt wholesaler and got the best they had for pennies! To get the correct size just put the exhaust manifold in a vise on it's side. Put a bolt in the hole and note the distance the threaded end comes out of the manifold. Do this for each hole. You will be able to discern which bolts go into which holes based on the how far they come out the head. It will be either "Bolt is too long", "Bolt is too short" or "Bolt is correct length". I believe there are 2 or 3 different size bolts
#16 350 HO heads rock!.
Engine Test Stand Playlist: https://www.youtube.com/playlist?list=PLwoxyUwptUcdqEb-o2ArqyiUaHW0G_C88 restoring my 1968 Firebird 400 HO convertible (Firedawg) 1965 Pontiac Catalina Safari Wagon 389 TriPower (Catwagon) 1999 JD LX Lawn tractor 17hp (my daily driver) 2006 Tundra (another driver) 2017 Murano (wife's car) 202? Electric car 203? 68 Firebird /w electric engine _______________________________________________________