454 intake gaskets?

[cadunkle]

I want to replace the intake gaskets on the 454 in my '89 Saltare. I suspect a slight vacuum leak and it's definitely not carb related. When I go on Summit I see listings for 454... I believe it's Gen IV, but there's also several port styles. Does anyone know what port style and how to easily identify them without disassembly?

[Sdc77]

I remove the carb last weekend. Seems to be this set that you need : http://www.summitracing.com/parts/HLY-20-124/

[OUI]

Have you tried spaying carb cleaner, starting fluid or some other combustible around the intake manifold? Try that before taking things apart. If there is a leak, the motor will speed up when sprayed.

[cadunkle]

Sdc77, thanks but that is a carb base gasket. I am talking about the intake gasket.

OUI, I have done the spray thing with no results. I'm thinking it may be pulling air from the bottom of the ports. As first I thought it was carb related. I rebuilt the 800 CFM double pumper, replacing the very worn base plate with a new billet base plate. Still would idle high sometimes (but much better), replaced carb to spacer and spacer to intake gasket... again, and used my line sander on the spacer to ensure it was flat with a good sealing surface. Still had the occasional high idle problem. Since I couldn't find any leaks anywhere, out of frustration I bought a brand new 800 CFM double pumper (and cleaned/checked/changed carb base gaskets again). Does the same exact thing. Also when it idles high (comes up maybe 200-300 RPM) it will stumble when you hit the throttle quick, as if it's lean from not enough accelerator pump shot... Leading me to believe it's a vacuum leak. Spraying carb cleaner all around the carb, throttle shafts, vacuum ports, carb base plate, spacer, and intake ports gives no change in idle.

So basically at this point I'm grasping at straws. Boat runs great aside from this. It's more of a nuisance, but I'd like to get it solved this spring. One thought that occurred to me that I had not tried, is changing the PCV. Maybe I'll try that, but I'd still like to get the intake gaskets to be ready. If I don't use them now I'm sure I will eventually.

[Moose]

Does sound like a vacuum leak. But probably a pretty good sized one to do what your describing. I don't see the bottom of the intake manifold ports developing a large leak like that unless something broke or maybe a good overheat cooked the gasket. I'm not real familar with boats or chevy engines but I know in older vehicles disconnecting the large vacuum line from the vacuum brake booster will create very simular results. Thats a big leak. Does yours have a vacuum advanced distributor? A mechanical advanced with weak or broken springs may cause simular issues. Maybe start pulling vacuum lines one at a time while running. If you pull one and the engine doesn't change it may show where your issue is. Maybe your mechanical fuel pump is getting ready to fail. Again I'm not a boat or chevy expert. If you do need intake gaskets check http://www.skidim.com/prodinfo.asp?number=RM0200 or http://www.hardin-marine.com/c-1278-intake-manifold-gaskets.aspx they both carry marine duty intake gaskets. I also have the 89 saltare with the 330 hp 454 and mine has the oval ports. Hope this helps.

[Moose]

The more I think about your issue the more I wonder about your distributor. Mainly the timing advance and where your timing is set.

[cadunkle]

Timing is at 10* initial, it advances smoothly... To what I'm not certain since my dial back light went missing after loaning to a friend... But it looks about right by the eyeball test. It does return to 10* as it should.


I've seen problems sealing the lower flange of the intake mainly when blocks and heads are cut too much and the intake face of the heads aren't cut to give a flat level surface. This motor was rebuilt before I got the boat so I have no idea what I'm working with. To top it off I'm not a Chevy guy, I build Ford motors. No vacuum advance, all parts are marine. The only vacuum line is to the PCV, which should be fine unless the spring is messed up and it only functions intermittently.

Float level is always where I put it whenever I check, so I doubt fuel pump problems but it's possible. I may have a closer look at pump and pressure since I'm running out of things it could be.

I need to order some other things from Summit, so I'll likely get the gaskets there to save on shipping. I'm not hardcore on "marine" everything. For things like gaskets, using good quality non metallic gaskets is plenty good and I've never had a problem. Thanks for the input, always good to have some additional thoughts on a problem.