merim123

Just looked at a set of heads and they had epoxy on the floor of the ports. I'd never heard/seen that before so I'm curious if anyone else has?

Also, looking at the roof of the intake ports, there were spots where the porting got really thin and got opened into the rocker area (very small holes).

I'm going to call the shop that did the work tomorrow, but I'd like to hear any thoughts.

Thanks,
Merim

Dr.Mudge

Sounds like quite a set of worked heads. The roof is generally the most active area of the head, the floor has laggy, slow air. So not only do you not port the floor, it often will be filled in, if you can achieve the runner volume you want by raising the roof you will do so.

Mindgame

Epoxy to fill in the ports of a "street" engine?

I'd make a pass on that. First off the guy's really gotta have experience working with the stuff to do it right.... it needs to get a sealer also. Either way... any kind of oil contamination in the intake will likely allow the stuff to lift. If you can imagine, dropping a piece of epoxy into a cylinder is not gonna be pretty and I've seen that more than once from guys who've tried to use the stuff in a street engine.

If you want to do it right, then you weld. But you have to have it done by a pro. No seats, no guides..... bare to the bone, then welded.... then normalized, then machined. That kind of work runs into the $$$.

-Mindgame

Dr.Mudge

You certainly know better than I do, I didn't know it was so brittle, I suppose flexing from temperature changes could probably be bad over a period of months/years.

As far as getting stuff in the engine, I know someone that got some RTV inside a cylinder and that wore down one of the walls badly.

Mindgame

I don't doubt that you could find some guys who've been running an epoxied head on the street without problems Doc. But time is against them.
Of course, there are guys round here running aluminum rods in their street motors too. How big a "risk factor" do you like to take? I guess thats the question but I prefer the "safe" approach for a daily driver.
The ports in my heads are welded up along the floors, as they were originally some 270 ccs.... now ~220. I don't have to worry about the longevity of the head though cause it was done right.... no epoxy.

-Mindgame

limige

this might sound dumb but why would you want to fill the floors and decease volume? i thought you wanted as much flow as possible, less turbulence and best burn? please explain.

Dr.Mudge

I already mentioned, the bottom of the floor is "wasted" because it is laggy/slow air, so the roof is raised to obtain the desired volume. Also, the runner is not the be all end all of head flow, in fact on stock ported heads its not going to get you as much flow as a good bowl port.

In the old days people used to hog out the ports big time, which is almost acceptable for a full on race car, but for street it'll kill low end and is a bit more sophisticated than just gutting things.

Witherspoon

With the top of your runners having small openings into the bores for your intake studs, you may want to put high temp silicone on the stud threads. I had a problem with oil getting pulled past the studs - about a quart every 350 miles and smoke on start up like bad seals. The silcone took care of it.

NightTrain66

If you could shape the port any way that you want, filling in the floor would be what most people do. I am not sure about using EPOXY though. It would work great on the flow bench and when the port is shaped like you want t, than you can have the head welded to match that. That is not prctical on an LT1 casting unless you are running in a class that says that you MUST use LT1 castings. If you are wanting to make an LT1 go fast, it would be better off (and less expensive) to convert a NON-LT1 racing head into an LT1 head.

If the epoxy is gonna hold it would have to be VERY clean when installed and probably some holes drilled in the floor on the intake port to help it hold a little. It is probably just a matter of time before it falls out. I am sure that there are some people that know some tricks and have had no problems but for the most part, it is an accident waiting to happen.

Filling in the floor will make the runner volume smaller and cross sectional area of the port in that area a little smaller. It "might" lose a few CFM or gain a few CFM by doing this if the flow can stick to the floor and it was not before but the main reason would be to keep velocity up. It also keeps the roof and floor closer to the same length. That will help with turbulence. If you have a low floor and a high roof, the flow can stick to both and by the time it reaches the valve the flow on the roof could be moving faster and cause it to have turbulence. these are all MY theories and I am sure that others can add ALOT more with the PRO's and CONS and why the floors are filled.

There "might" be alot of research and development in these heads, they "might" never have a problem with the epoxy falling out, they "might" make killer power and last forever. They "might" be a nightmare and destriy an engine.

If you can get 1 head and take it to a reputable shop and have them flow it and inspect everything else you might find out that they flow VERY well and they might assure you of the epoxy being safe. If the flow #'s are not very good and they are not "hip" on the epoxy and question the placement and what they were trying to do than ya might stear clear of them.

NightTrain66

OldSStroker

Epoxy in intake manifolds, yes. But when you get to the head, I would be concerned with operating temperatures.

About the best epoxy I've seen has a continuous operating temp of about 350F. There may be some higher. Intake manifolds shouldn't get that hot, and neither should the area right near the manifold flange on the head, but closer to the valve I expect you'd see higher temps.

In any application, the bond to the parent metal is important.
Proper preparation both in cleaning and mechanical configuration means a lot. It's a little like filling a tooth.

I would pass on these heads also.