I was just wondering if anybody else has noticed the huge variance/tollerances in the bolt holes for some intake bases? I was looking at a TPI base I have and there are huge variances in the size and location of the bolt holes, and obviously the bolt doesn't exactly center in all of these.

So some of you gasket matchers out there, does anybody ever do anything to correct this so that they know their runners line up and the gasket stays where its supposed to when you install your intakes?

 

Glue the gaskets to the heads first, then install intake.

 

haha


Yea i use gasket adhesive

The qustion is the intake though, with oversized and mislocated holes... it could bolt up in any number of ways around the port, could be sitting high, low, to either side... Just because the gaskets perfect on the face of the head doesn't mean the intake is perfectly located to that...

Thus my question, or does nobody else feel that its that much of a concern having a dead block (the head) in the way of the intake path? (assuming your intake mislocated)

 

There is only one way to know that every thing is lined up - pin the gaskets to the intake manifold (use dowel pins, or plastic pins as are used on the runner gaskets). Apply layout blue dye to the intake manifold gasket surface, and mark the intake manifold ports using a scribe to trace the gasket ports, and match port the intake to the gaskets, or vice verca, if necessary. My TPIS Big Mouth was matched fairly well to a Felpro 1204, however, I had to widen a few of the gasket ports to make them match up perfectly. Then apply layout blue dye on the head gasket surface - makes scribed lines stand out - and install the intake on the motor & install all of the bolts & leave them a bit loose. The intake will have some play fore to aft - measure the "endplay" and push it to one extreme - fore or aft. Scribe a line along the top of the intake gasket on the cylinder head. Remove the intake, and gaskets from the intake, and place the gaskets on the cylinder heads, lining them up with the scribed lines, to see how the ports line up. You have the end play that was measured to move the gasket for or aft, to optimally line up the ports. Use a dial indicator to position the intake manifold fore to aft, if necessary. Stock head ports have a chunk of iron in the corneer adjacent to each push rod, which will need to be removed in order to have a truly matched port to the Big Mouth intake.

 

Yea I've always loved those corner cast chunks, I figured they were some extra meat for the threaded valve cover holes (if we're talking about the same chunk)


I think i get what you're saying about pushing the manifold around to extremes, if i do follow that means that after gasket matching the head runner will be slightly larger than the intake runner port or did i miss it?


Here's the scenerio, I drilled the bolt pattern into my LT1 intake by lining up the gasket tabs to the bottom of the gasket surface (as they were on a mocked tpi intake) and centering the middle bar of the gasket between the two runners at either end of the gasket with the lt1 intake, at that point I marked my holes and drilled them. It now appears that I need to maybe drill the holes a bit taller by maybe a 32nd of an inch, such a minor detail its nothing but an annoyance, and I'm concerned after having an ovalized bolt hole (no play from front to back of the block) that the intake could rise up or lower down misaligning where the injector sprays into the head, maybe blocking the flow, or blocking air flow at the bottom of the passage.

To properly gasket match Id need to know that the intakes going to bolt to the same spot everytime i bolt it down. I dont think i can have that security with slighly ovalized bolt holes


but then i started thinking about the stock TPI intake, and literally the holes look cast into the manifold, not drilled, the sizes are all different, the locations seem to be off so slightly, there's no consistancy.


I want perfect runners

 

By the way thanks tim

 

You should just get a blower, then you don't have to worry about porting and all that.

Under pressure is under pressure.. -

-- Joe

 

I'd have to disagree with you there - fluid dynamics still apply when using forced induction - normally aspirated engines operate under pressure, as well - atmospheric pressure - forced induction simply increases the pressure differential across the intake valve, while mismatched ports reduce mass flow rate, regardless of the pressure differential, or type of flow - laminar or turbulent.

 

I understand your theory, but do you think it makes that much of a difference, assuming the holes aren't grossly oversized or egg shaped ?

 

1/32-1/16th of an inch overlap


thats enough to annoy me


I was kinda stoked beause being that i was the one drilling the holes I made sure they were all small enough that there was very little to no play, but now i need to slightly elongate them upwad and so I dont even know where the intake will sit on the heads after its clamped down.

 

Attention to detail pays off. Many details of assembling a motor can be very time consuming, if you choose to be meticulous - or you could just slap it together - you may be fortunate in doing so, but most of the time the only way things go together for optimum efficiency is when they are forced to do so by the assembler. For example, it's not too shabby to run in the 11 second range with a 305 - I've spent countless hours making sure that every port from the throttle body to the headers are perfectly matched with gaskets pinned in place - and it seems to have paid off.

 

Believe me i know the virtues of a well matched and flowing intake system, thats why im being so persistant about getting this to line up. Looking at the intake again last night it appears i only need to raise the holes about .050", only worst possible case scenerio would cause the full .050" to overlap so I think I'll be ok on this one.

 

I've talked to people who have been doing port work on heads, and intakes for many, many years.

On N/A applications, porting helps usually. For instance, a fellow racer spent almost 2,000.00 on a porting job, matched and all. He ended up gaining a little more than a tenth in the 1/4 mile.

For blown applications, i've NEVER seen any increase after INTAKE porting was performed. Boost is boost.

I mean, obviously physics prooves thats not 100% entirely accurate, there will be some minimal resistance, but I guess the point I'm trying to get accross is - the amount of money spent on intake porting is _NOT_ worth the output.

Exhaust porting however, can be worth up to 100HP.

-- Joe

 

Ok.....


and that helps my gaskets line up?