cougla

Does anybody have experience with an after market low profile aluminum intake manifold that eliminates the exhaust crossover to help with carb issues namely heat warpage and hard starting because of heat?

Here is a picture of one used on a GMC Motorhome

Olds64

I didn't know Olds developed an intake manifold without the heat cross-over. I do know that the 455 was used in a number of motor homes in the 70s.

You can always block the heat crossover port in the head. The most permanent way is by melting aluminum to fill and shape it. Others have tried it with epoxy; however, I don't think that was very successful. You can also cut a soda/beer can and use the aluminum to cover the intake manifold gasket at the cross port.

2blu442

I've never seen an aftermarket low profile intake before. Do you know who the manufacturer is? John

joe_padavano

Frankly, neither of those are real problems. "Hard starting" will be due to improperly adjusted carb or choke. I've certainly never heard of "heat warpage" of a carb. Literally tens of millions of cars have been built with heat riser passages under the carb. This is NOT a problem.

Now, if you are looking for an excuse to drop $600 on that aftermarket intake, find a different one.

They didn't. It's aftermarket.

Gary Rockwell

There are an amazing number of aftermarket parts for the GMC motorhomes, including things like limited slip differentials for the Toro final drive. None of that stuff is cheap.

joe_padavano

I should add that this guy Gary Rockwell did a heck of a job on this intake. Apparently he scanned an original, 3D printed a plastic master, used that to make a mold, and cast aluminum manifolds. Very cool! See the photos here.

cougla

New Aluminum Intake Manifold 455
$850.00
[info] [order]
By Mondello Performance Products . There are two levels of acceptance on this item. The first is acceptance level from Mondello. The second is acceptance level from Applied GMC where the the bolt holes are deburred and surfaced. No need to raise the floor. Built-in exhaust bypass. Identical fit to original.GM08-006-27D It is highly recommended to use the intake manifold gasket kit with the sealant. You will need to use electric choke and special pigtail connector.

joe_padavano

It's apparently only $600 if you're not paying Lynn's markup...

cougla

INTAKE MANIFOLD GASKET with exhaust block off plates
Price: $49.98
With Stainless Steel Exhaust Block Plate

GM08-030-SSGAKTPLT Not sure why they would sell this if they weren't trying to overcome an issue?

oldcutlass

The biggest reason people like to block the crossovers is because the paint on the manifolds discolors and burns. The other reason is to keep the carb a bit cooler.

joe_padavano

So by your logic, the fact that companies sell these is proof that unmagnetized gasoline is an issue to be overcome???




The reality is that cooler inlet air is more dense, meaning that you can pack more air mass into the same cylinder volume if the heat riser is blocked. This ASSUMES you also rejet the carb to optimize performance. On a drag car where a tenth of a second ET can mean the difference between winning and losing (and you don't care about rough running on a cold start), blocking the heat riser makes some sense. On a street driven, nearly stock car, even the most highly calibrated butt dyno won't feel the difference. There are a LOT of parts designed for racing that are unnecessary and even undesirable for a street driven car. Unfortunately, there are a lot of car owners who are too uninformed to know this and simply buy whatever the latest magazine article says they should.

oldcutlass

Are batteries included with that?

cougla

Thanks for clearing that up Joe....I won't go down that road, however I still got the hard staring issue. I can drive all day (and it runs very well now) but as soon as I shut her down for any longer than say 20 minutes I need pedal to the metal to start it. same thing in the morning. I thought the wells were leaking, but pulled the carb as suggested here and sat on paper overnight and.....nothing leaking. Could it be as simple as the float level is set too high?

oldcutlass

When the car sits for about 20 mins, pop off the air cleaner and look down into the carb to see if there is fuel dribbling. A float to high will cause this. Also a poorly tuned engine will cause your hard start issue.

joe_padavano

Also an incorrectly adjusted choke.

cougla

Okay, Thanks Eric I'll try that Tomorrow

cougla

I'll make an adjustment on the choke also Joe, Thanks.

I feel I'm very close to getting this Toro to run correctly, hope it's just a little more fiddling.

Jerry

Olds64

Who sells that? I couldn't find it on RockAuto, Amazon or Summit. Seems pretty pricey too. Especially when you can buy an intake manifold gasket from Summit for about $15. You could probably get it cheaper from Amazon or RockAuto.

https://www.summitracing.com/parts/s...ake/oldsmobile