exhaust backfire

[rficalora]

Would it make sense for the cooling system to be pressurized after just a few minutes of running the engine?  I ran it long enough to get the temp up to about 175 or 180 before draining the oil and drained the radiator at the same time.  I was surprised that the radiator was under pressure - nothing excessive, but noticed it when I took the radiator drain plug out.

[DiDueColpi]

Absolutely normal Rob. Pressure builds up as your engine heats up. Your engine is near it's running temp and should be very close to your rad cap rating. The stuff in your coolant is also pretty normal. Rust from the block, corrosion from the heads and oils from assembly all accumulate to contaminate the coolant some.
Have you changed out the plugs yet?
Your timing light will still fire whether your plug is good or not, it just confirms that voltage is present. So don't count on that to confirm a good plug. I'm with Curtis I think your problem is going to be something simple.
If you are using one of the more popular stainless steel band clamps for your exhaust. Position it so that the aluminum block is on the short radius of your oval pipe. Lube the nuts and crank them down tight. Somewhere around 40ftlbs. You should see the stainless band deform to take on the shape of the joint. The aluminum block will do the same. If this is a butt joint it will be hard to seal perfectly but it can be done. A slip joint is much easier.
Good luck
Fred

[rficalora]

Sounds like concensus is nothing wrong with the radiator water which means nothing is pointing to a bad intake or head gasket.  That's good.  I hadn't refilled the fluids because I was assuming the next step was going to be to pull the intake & heads.  I'd read several posts on the mustang & factory five boards where apparently the Fel-Pro printo seal gaskets - especially intake gaskets - were failing & there's a replacement out that's been redesigned (steel core gasket) that supposedly holds up better.  A few members of this board have had the intake gaskets fail & had luck with the updated gaskets.  Also several posts talk about using RTV on both sides around the water passage openings on the gaskets which I didn't do.  

I'll probably pull the intake & replace the gaskets for peace of mind - but, since I'll have to order them, I'm going to proceed with with trying to isolate the #5 problem assuming the gaskets are ok - at least till the new ones come in.

I did already turn the band clamps so the aluminum blocks are on the short radius & they are sealing better.  I didn't do a smoke test or anything but I don't feel the exhaust at the clamps any more.

So, seems like the next step is reflill the fluids, replace #5 plug & retest.

[DiDueColpi]

Rob,
Re the RTV silicone. Don't do it!
Silicone is grossly overused and generally for the wrong purpose.
Gaskets these days are pretty high tech, and don't require any "help" in sealing. Proper prep and assembly is all that's needed.
Most gaskets have some form of sealant built into them and adding another product usually defeats that sealants ability to work.
I use the Felpro gaskets all the time. As in several times every day. And haven't run into sealing problems yet.
If the surfaces are clean and flat and the proper torque procedure is used they will work well for you.
If you need silicone to make it work then something is wrong and you should fix that problem first.
Cheers
Fred

[BlownMGB-V8]

X2

[flyinlow]

X3
I have been a mechanic for 30+ years(yes I am old) and you can usually tell how good a mechanic is as an inverse proportion to the amount of silicone he uses

[mgb260]

Rob, Just try retorqueing  the intake first and try your new plugs.

[rficalora]

Actually, Jim, that idea hit me today.  I re-torqued the intake and checked the heads after the first heat cycle but haven't touched them since.  It also occurred to me that my torque wrench is at least 30yrs old & while it was a good brand (Snap On) and hasn't been used much in the past 20 or so, it's hasn't been calibrated in that time.  So, I picked up a rental one today (my AutoZone says they send them out to have them re-calibrated on a regular schedule).  I'm going to check both as well as replace just #5.  My kids have scouts tomorrow night so it'll probably be Wednesday before I can do that.

As for the silicone, what do you guys make of these intake & head gasket instructions for Ford 302's from AFR's web site?  http://www.airflowresearch.com/sbf_install.php

[DiDueColpi]

I would call that a blatantly irresponsible comment by AFR.
#1 why would you ever not torque a bolt when you have the opportunity? Torque specs are provided by the manufacturer for good reason. In particular this instance where the load is spread over such a large area. Doesn't it just make sense to have all the clamping forces the same over all the sealing surfaces? In this day and age of precision fasteners "just tighten it up by hand" doesn't cut it anymore. Pick up any engine assembly manual. Every bolt and nut has a torque spec.
#2 Read the instructions for any gasket installation. They all say tighten to manufactures recommendation. No manufacturer says tighten it up until it feels good. As well they all say do not use any coatings or sealants on the gasket and apply to a clean properly prepared surface. I would be inclined to follow the guy who makes millions of gaskets rather than the guy who makes a few heads. Possibly the tighten by hand recommendation leads to the need for the silicone use.
Cheers
Fred

[ex-tyke]

Rob, just for reference sake, Ford Racing recommends intake gasket M-9439-A50 for use with GT40 alum heads - the cheaper alternative is Felpro #1262S3 - both are steel backed Print-O-Seal gaskets.
If you decide on gasket replacement, do not use supplemental silicone on the head faces but certainly use at the front and back seal to gasket joints (as per Felpro instructions).
You should also instal 4 threaded rods to guide the intake manifold as it is lowered onto the cyl heads - this prevents distortion of the print-o-seal. If you don't use the guide rods, you'll risk seal damage and potential leakage.

[DiDueColpi]

Sorry Rob,
I should have mentioned that a little dab of silicone at the interface of the intake gasket and the valley seals is proper procedure.
I guess I was too busy frothing at the mouth to notice.
Also please note that all RTV silicone's are not the same.
They have grown from a one size fits all into very specialized applications.
Make sure that you are using the correct product.
Cheers
Fred

[roverman]

I like the "new and improved Kryptonite Fortified". This stuff would break Superman's ba$#@^'S ! Previous owner of my "Huff" car used enough on intake manifold to create "stallagmites" in the inlet ports. This was beneficial in helping the car get , off the turns, by not slipping the rear tires soo easy. More is always better. Cheers, roverman.

[rficalora]

Thanks again guys.  New gaskets are on the way; haven't come in yet.  Did re-torque the intake bolts in the meantime, they were all loose.  Also swapped out my header bolts for locking ones - guess I should say started to.  Right side had burned through the front most portion of #1 sealing surface (remember header bolts had worked loose) so will pick up new exhaust gaskets tomorrow & retest once back together.

[ex-tyke]

My experience with header bolts is that they require periodic tightening for a few weeks until the gasket 'settles in' - after that, bolts retain their torque.

[MGB-FV8]

If you run EFI with oxygen sensors or have a A/F ratio meter, be very careful about using silicone around the induction system as it could ruin your expensive sensors; food for though........

[rficalora]

Pulled the intake; no sign of a gasket problem.  Ran out of time between church & the Superbowl and flying out in the morning so won't get to reassemble till Friday.  Had planned to do it Saturday afternoon, but of 14 people who signed up to help replace soffit and facia wood on a deserving lady's house, only two of us showed up.  What was supposed to be a few hrs was an all day job & I was worn out by the time I got home!  

Anyway, before I pulled the intake I re-torqued the intake and exhaust & ran the engine for a while.  Runs the same but noticed 2 things this time...
1.  Pops every now & then thru exhaust when turning btwn about 2k and about 3.5k (didn't rev it more than that).
2.  Checked temps on header primaries and they weren't as consistent as I remembered from before.  No's 5 & 6 down in the 150 - 180 range.  7 up around 300 and #8 a bit over 400.  #1 was also down around 170.  Don't recall 2-4 but pattern was same in that forward cylinders were cooler than rear ones.  I'm wondering if the ceramic coating might not be even thickness?

[mgb260]

Rob, Another idea. Valve adjustment (rocker arms actually). If adjusted too tight and valve barely seating could cause a miss. I adjust mine in the normal manor initially but ,after breakin put the little clips on the rockers to prevent oil spraying everywhere,with the engine warmed up and running. Loosen until slight clatter,tighten slowly until no more clatter and tighten another 1/2 turn.

[ex-tyke]

...Loosen until slight clatter,tighten slowly until no more clatter and tighten another 1/2 turn.

That method works great for a Chevy, but the std Ford 302 valvetrain is not adjustable. It relies on achieving a lifter preload range while the rocker nut is torqued to value (18-20 ft.lb). If the preload falls out of range either longer pushrods or pedestal shims are required.
It's unfortunate that Ford hasn't caught up to GM with their adjustable rocker assemblies - they sure make life easy!

[302GT]

I am using an aluminum exhaust gasket. It stays soft and will reseal even if reused many times. It solved my exhaust leak problems.

[mgb260]

Graham, I had assumed Rob had upgraded to adjustable rockers. I always do,same adjustment as with Chevy.

[rficalora]

Replacing the intake gasket today & noticed something I hadn't when I first put it on...   Don't think it has anything to do with the #5 fouling issue, but this center port is a water port, right?  My old gasket had the cut-out for it so it never occurred to me to compare it to the intake.  The new gaskets (Fel-Pro 1262S3) don't have a cut-out for it so I looked @ my intake and sure enough, there's no port there.  What's the implication of having it on the heads but not on the intake?

[BlownMGB-V8]

That might be an exhaust crossover port.

Jim

[rficalora]

Turns out it's an EGR port.  Still not sure if I should cut the gasket there.  May not matter but seems like it might seal better with the exhaust gasses hitting the edge of the gasket vs that whole area?

[flyinlow]

that is an exhaust crossover and the gasket you have is correct dont cut it

[ex-tyke]

As usual, there are arguments both ways to retain or eliminate the exhaust crossover...keep in mind that this feature was designed to improve the driveability of carburetted engines operating in colder climates .
PRO:  Cooler intake manifold allowing a denser intake charge and more power
Mitigates vapor lock in Summer

CON: Less fuel vaporization resulting in poorer distribution to cylinders
Increased air density changes A/F ratio, possibly requiring a jet/rod change

Since Rob is domociled in Houston, blocking the exhaust ports shouldn't create a problem (mine are blocked off, BTW)