reducting port sizes

**The Real Roadrunner** · 04-02-2008, 04:37 PM

Originally Posted by abently

You do understand that some rules stipulate using only certain cylinder heads cough *holden 308 red/black/ blue etc* cough........

WTF what real sprintcars run a 308 head? most are 372 or bigger and run alloy everything. unless you are talking about some poverty pack sprintcar lookalike then you may be right but then its not really a sprintcar now is it?

**Sam_Q** · 04-02-2008, 07:09 PM

so basicly the verdict is that the epoxies available are great and last for a while but no-one knows exactly how long it would last and no-one has used them long term.

roadrunner: I only have a radius I want to build up between the port and the low flow side of the valve bowl, other than that the head is good (me thinks)

**The Real Roadrunner** · 05-02-2008, 02:31 AM

how far do you want to build it up? is it going to need 3mm or more? or just a couple of mm to make the short turn flow a bit nicer.

have you got a pic of a cut down head? how close are the galleries and such?

cheers
linden

**Sam_Q** · 05-02-2008, 09:25 AM

just a couple of mm to make a nice radius and thats it. I have a diagram which I will post when i can

**jeffro ra28** · 05-02-2008, 09:26 AM

Originally Posted by abently

You do understand that some rules stipulate using only certain cylinder heads cough *holden 308 red/black/ blue etc* cough........

I've used loctite 3805 personally. The only thing I noted different with it from other epoxies was that the loctite was definitely more tackier. The shelf life of it was only a month max once opened so be prepared to use most of it that day if you can.

Anyhow I think we've gone through all the for and against arguments so I'll just leave it here. The poster can make their own mind up on what to do.

Yeah but the totall difference dude is that 308 blue/black/red all have cast iron heads, which sorta makes it totally irrelivant to the topic at hand anyway...... with your co-efficient of expansion theory anyhow....

Ok so now these old skewl shitter cast iron headed 308 sprint cars are seeing "Sprint car engines see very high cylinder pressures and vibrations"???? Thats fine, if these old 308 "sprint cars" are making in excess of 700hp.....

Sam, some of us have used this epoxy in the ports.

I personally have used it 3 or more injected alcohol sprint car syle motors used in boat racing. These engines were 366-372 cubes and were making around the 500-550 ft/lbs of torque and around 750hp.

I followed basically the same procedure as abently has descrived above but used a stud for the epoxy to form around on most places. These engines get an internal inspection very regularly (every 2-3 race meetings). The location of the epoxy in these ports was used because of the low-mid torque the boat motors required, and the heads(made in house at my old work) where originally designed more so for high revving drag racing applications. The only time we ever used it was in the manifold and start of the runner in the head. no where near the short turn. Now, after engine dyno time it has fallen out, after race time it has fallen out and numerous times after inspection it was starting to fall out. Remember this was probaly after no more then 10 hours work from that motor.

So you tell me if you would use it on an even more difficult section of the port exposed to more severe conditions for 100 000km's? Even if the product was totally different bla bla bla, Would it be that much different and better to allow it to withstand more severe conditions and for 99 percent more time?

**Sam_Q** · 05-02-2008, 04:31 PM

I would think that the iron heads would still have some sort of thermal stresses as they expand and contract just not as much as aluminium. Anyway your report sounds interesting Jeffro, it bizzare, what you did failed regually and some people get away with it indefinately. Either way it confuses the hell out of me.

Now how about something different along the lines of what oldeskewltoy is talking about, what about some silver solder or something like that? is there something available thats a braze on job?