Checking Intake Manifold Fit After Resurfacing Heads

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1970 TA

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Working on my 1970 340. I have open chamber "O" heads (3418915B), 2.02 / 1.60's with tulip valves.
Just got the heads back from the machine shop after a cleanup on the seats and valves.
The combustion chambers are measuring an average of 78cc's, so they're going back to the shop to remove 0.020 from the deck surface. Approximately 4cc chamber volume reduction will give me the SCR / DCR I'm looking for. I want to avoid any machining on the aluminum 6-Pack manifold if possible.
The machine shop says what they like to do is machine the deck surfaces and give me the heads to do a trial fit on the block / intake and see if any further adjustments are required. If adjustments are needed, they can machine the intake sides of the heads.
What techniques do you builders use to check for proper fit of the intake manifold?
I've read of a method using plumbers solder taped to the intake gasket in several places and measuring the crush on the solder. Might try this.
What about using Dykem / bluing on the intake gaskets to check port alignment?
Since vertical position is affected, is the mesh of the distributor gear to the cam gear a concern?
Do I need to shim the distributor for clearance?
What about pushrod length?
When I checked piston to head clearance (flat tops with chamfered OD), at max travel the piston hits the edge of the open chamber. Am I correct in thinking that the piston to head clearance will not change since the piston will hit the edge of the chamber in the same place, but the piston to valve clearance will be reduced?
Any other things to check?
 
Might it not be cheaper, easier, better, to just change the cam's ICA to adjust the Dcr?
By the time you add up all the machining costs, the port-matching, new pushrods, possible adjustments to the eyebrows, and possible changes to header clearances ....... I mean 4ccs cannot be compensated for by retarding the cam, but a different cam, or a custom cam, or a different type of cam...... might. As would different pistons with a larger cd.
>I say this because I have not had the greatest luck with multiple machinings. I swore I'd get the proper pistons next time, and not machine anything, beyond what HAD to be done.
>As to the pushrod length, in all fairness a hydraulic lifter should be able to compensate for a .020 cut..... BUT Should it have too? If you have adjustable arms , then,maybe no problem. But what will that do to your geometry? And then there is the small matter of lifter pump up. The plunger has about .090 or even .100 inch of compensation but when/if pump-up occurs, pow, those valves are into the pistons ....... unless you have built in an overly generous safety clearance. Nobody does that because that causes a compression loss that you just worked hard to overcome. Typically guys run about .020 lifter preload or a bit more, cuz that is probably a little less than the valve to piston clearance. So then if you overspeed the engine and the lifters pump up, then nothing ..... hopefully.... touches. So pushrods always get measured, ordered, and installed, last.
>But again, delaying the ICA has the unloved side effect of reducing your low-rpm performance. Here is a 340 similar to yours.
With a 10/1 Scr and an ICA of 62* ( a cam of 268/276/110 in at 108.) The Dcr comes in at 8.09 and 162psi with a VP of 130. The pressure shows that this is about the max for pumpgas. If this is your target, it requires a total chamber volume of 77.37 at stock bore and stroke. But if you had 4cc more, or 81.37 total chamber volume, then the numbers would come in at 9.56Scr/7.74Dcr/153psi@123VP. Notice the loss of VP. To get the low-rpm performance back without changing the compression, the ICa would have to be reduced to 56*. The numbers then come in at 9.56Scr/8.08Dcr/162psi@137VP. Notice that the Dcr is back up, as is the pressure. But look at the VP; it has jumped 7 points from the original 130 .... even at the Scr loss.
So that's kindof cool.
But wait-up. If these are both hydros,and from the same manufacturer, then the second cam is one size smaller at .050, so that might be 15 or 20 hp loss at the top. ... But if the first was a hydro, with typical 46* ramps, then the .050 of that cam would be 222*. and if the second was a fastrate SOLID with a 222@050; it might have ramps of 40*, and so it would be a 262 advertised. This could be cut on a 108LSA to yield a 262/268/108 and in at 108 would yield a 59* ICA, which after lashing might be 56*, exactly what is needed.This cam is practically identical to the first now, except it makes more torque, better fuel economy, but with quite a bit less overlap;perhaps as much a 8* less, will likely make a lil less power.
So this second cam is a pretty good deal, if you don't mind the occasional lash adjustment......... And no machining was required.
BTW his is just an exercise in what-ifs. The best solution, IMO, is reverse-dome pistons.And that would give you a little more flexibility in cam selection
 
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Since vertical position is affected, is the mesh of the distributor gear to the cam gear a concern?
Do I need to shim the distributor for clearance?

Oh, boy. I"m really gonna show my ignorance here.... but, how is distributor gear/cam gear going to be affected?

As for checking fit, could you place the intake into position on the new gaskets and lay down some Plastigage?
 
The distributor and cam gear wont be affected. Its a mopar not a chevy.
 
Agree that distributor and drive gear will not be affected...
 
Working on my 1970 340. I have open chamber "O" heads (3418915B), 2.02 / 1.60's with tulip valves.
Just got the heads back from the machine shop after a cleanup on the seats and valves.
The combustion chambers are measuring an average of 78cc's, so they're going back to the shop to remove 0.020 from the deck surface. Approximately 4cc chamber volume reduction will give me the SCR / DCR I'm looking for. I want to avoid any machining on the aluminum 6-Pack manifold if possible.
The machine shop says what they like to do is machine the deck surfaces and give me the heads to do a trial fit on the block / intake and see if any further adjustments are required. If adjustments are needed, they can machine the intake sides of the heads.
What techniques do you builders use to check for proper fit of the intake manifold?
I've read of a method using plumbers solder taped to the intake gasket in several places and measuring the crush on the solder. Might try this.
What about using Dykem / bluing on the intake gaskets to check port alignment?
Since vertical position is affected, is the mesh of the distributor gear to the cam gear a concern?
Do I need to shim the distributor for clearance?
What about pushrod length?
When I checked piston to head clearance (flat tops with chamfered OD), at max travel the piston hits the edge of the open chamber. Am I correct in thinking that the piston to head clearance will not change since the piston will hit the edge of the chamber in the same place, but the piston to valve clearance will be reduced?
Any other things to check?

78 cc seems a little high for what I've seen...

Most heads like those run 72 cc - 74 cc....
 
78 cc seems a little high for what I've seen...

Most heads like those run 72 cc - 74 cc....


It's a possibility the additional volume came from valves sinking into the chamber after valve job......a lot to gain, but it is a possibility

To the OP......for every .010 cut off the chamber side of the head, cut the intake face .0095.........from "How to Hot Rod Small Block Mopar Engines" by Larry Sheppard
 
What techniques do you builders use to check for proper fit of the intake manifold?
I've read of a method using plumbers solder taped to the intake gasket in several places and measuring the crush on the solder. Might try this.
What about using Dykem / bluing on the intake gaskets to check port alignment?
I am trying to visualize the crush of just solder strips without gaskets in a vee interface and am thinking this might be inaccurate if you don't very carefully put equal torque on each bolt; it seems too easy to push the intake off one side or the other. Witht he gaskets, I think I would get some very thin electronics solder; plumbers solder seems to thick.
I set the intake on the gaskets, look at how well the holes align without being torqued, the head holes should be near the bottom edges of the intake's holes. Then I use a feeler gauge to see how evenly the gaps are front to back on each side, and then poked into the upper and lower edges at each end to see how even the gap is top to bottom. A good eye will pick up some variations too. Not sure that this is the best way to do it.


When I checked piston to head clearance (flat tops with chamfered OD), at max travel the piston hits the edge of the open chamber. Am I correct in thinking that the piston to head clearance will not change since the piston will hit the edge of the chamber in the same place, but the piston to valve clearance will be reduced?
This is odd sounding.... sounds like you have pistons like the Speed Pro L2316's... what pistons DO you have? Is this without a head gasket in-between head and block? Even then, this sounds odd... How much has the deck been cut so far, if any? Standard early 340 pistons stick around .018" above the deck and the open chambers should clear around them.

Any other things to check?
Not sure how to answer this....
 
This is odd sounding.... sounds like you have pistons like the Speed Pro L2316's... what pistons DO you have? Is this without a head gasket in-between head and block? Even then, this sounds odd... How much has the deck been cut so far, if any? Standard early 340 pistons stick around .018" above the deck and the open chambers should clear around them.

Not sure how to answer this....[/QUOTE]

Specs on the pistons below.
They are Race Tec forged customs. I had the compression height made to 1.840 to match the TRW 11.5:1's that they replaced. They were originally made flat with no chamfer around the OD like the TRW's. On the first mockup of the engine, the piston to head travel was about 0.020 to 0.030 using an 0.054 gasket. The pistons were hitting at the edge of the diameter of the open chamber around the valve pocket side of the piston. I had the pistons machined to add a 37 degree chamfer to the edge to match the TRW profile. Now my piston to head is measuring 0.060 to 0.070 using the 0.039 gasket.
The deck surface of the block has never been cut.

Thanks for everyone’s responses.
I agree that the distributor / cam gear is not an issue.
Here’s the situation I’m dealing with.
Street driven car for cruise nights. 3:55 gears with 727 Torqueflite. Turbo Action converter, 11 inch, 2500 rpm stall. I’m trying to maintain decent low rpm torque.
I rebuilt this 340 over the winter, it’s +0.030 (4.070).
New forged Race Tec pistons, flat tops, compression height = 1.840, so pistons are above deck 0.020.
Valve pockets are 7.6cc, 0.295 deep.
Top ring down = 0.250
Reusing the Mopar Purple Cam, P4452761, adv dur = 268/272, installed at 107* ICL. Intake close at 61*.
Heads are open chamber “O” castings with tulip 2.02’s, stock, no mods. I thought they were 72cc (I remember measuring one of the chambers before taking them into the machine shop and it was 72cc.). Maybe I misread the burette, because now they all measure 77 to 78cc.
The problem: With my original parts combo (Felpro 0.039, cam @ 107 ICL, pistons +0.020 above deck, 72cc chambers), the calculated SCR = 9.4, DCR = 7.67 (using the Pat Kelly DCR Calculator). I get similar numbers using the Wallace Calculator. Substituting 78cc for chamber volume, SCR = 8.83, DCR = 7.22.
If the heads are shaved 0.020, reducing the chamber volume to 74cc, yields a SCR = 9.2, DCR = 7.5. Cranking psi predicted to be about 147 psi
I’m thinking at these specs, I may be able to run mid-grade / 89 pump gas.
The heads are going into the shop tomorrow. I’ll have them cc a chamber to see if my numbers are correct. Depending on their results, we’ll make a decision on taking some material off the deck surface

Might it not be cheaper, easier, better, to just change the cam's ICA to adjust the Dcr?
I've installed the cam 1* advanced @ 107*.

It's a possibility the additional volume came from valves sinking into the chamber after valve job......a lot to gain, but it is a possibility
I'm having a hard time believing that the volume increased by 6cc. I'll have the machine shop recheck a few.

To the OP......for every .010 cut off the chamber side of the head, cut the intake face .0095.........from "How to Hot Rod Small Block Mopar Engines" by Larry Sheppard
The shop I'm using knows these numbers, but they don't always work out due to block deck variation / other factors. That's why they resurface the deck side and do a test fit before adjusting the intake face.

New piston vs TRW before chamfer addition
piston_5.JPG

piston_11 (2).JPG

Impression in clay from interference prior to adding 37 degree chamfer
piston_7a.JPG

340 short_a.JPG

340 short_b.JPG
 
New piston vs TRW prior to chamfer addition
piston_5.JPG

piston_11 (2).JPG

Impression in clay from interference
piston_7a.JPG

Short block completed
340 short_a.JPG
 
OK.... The piston top .020" above deck makes sense. Still can't see how a piston edge that is .020" above the block could hit the head with a .054" head gasket.....I am either missing something, or the head was sticking down through the head gasket...can't think how that is possible. New piston rocking would be maybe .005" or so, so that would not do it. Sounds like perhaps the larger intake valve is the culprit....based on the description of the contact location, that makes sense.

If this is the case, what material you take off of the heads will reduce that clearance as you said. Any chance that the checks were done with the lifters all pumped full of oil and the valves not closing and being held open too far? Or pushrods wrong (too long)? Or something amiss in the rockers? That cam is not that high a lift. (Or the Race Tec valve pockets are off of the proper locations.)

Did the heads have flat (nail head) valves in them originally? Tulips are gonna add 2 cc's or maybe a bit more. The 72-73 cc's sounds normal; but putting in the larger valves could easily take out some material around them.. I am with you on where you want to go for a stout street cruiser.
 
He has tulip valves- a few cc's there
you need to cc both ends of both heads in case they are slanted- not uncommon even on virgin teardowns
nm I do not think piston rock is going to give .005 vertical
I have a BBM with FT pistons (D dished- 915 wedge heads) that far out with .051 gasket- no problems
 
nm I do not think piston rock is going to give .005 vertical
Yeah that was just a worst case thought....OP, if this is possibly valve to piston clearance, is you cam timed right for sure? Again, that is not a big lift cam; it would have to be jumped off a tooth or more to get the valve clearance out of whack. But stranger things have happened.... just trying to figure this out...
 
Yeah that was just a worst case thought....OP, if this is possibly valve to piston clearance, is you cam timed right for sure? Again, that is not a big lift cam; it would have to be jumped off a tooth or more to get the valve clearance out of whack. But stranger things have happened.... just trying to figure this out...
I have a lot of clearance piston-to-valves.
The interference I referred to was piston-to-head.
I'll post more info when I return from the machine shop today.
 
Yeah that was just a worst case thought....OP, if this is possibly valve to piston clearance, is you cam timed right for sure? Again, that is not a big lift cam; it would have to be jumped off a tooth or more to get the valve clearance out of whack. But stranger things have happened.... just trying to figure this out...
Some clarification on the interference problem I discovered.
My first mockup of the shortblock used the new Race Tecs before the chamfer was added around the OD. The first cylinder I measured was #8, which had the largest above deck height, approximately 0.025. I brought the piston up to TDC using a bridge / indicator, then layed the 8553PT / 0.054 gasket and head on the block. I pulled the rod cap off and using a magnetic base on the pan rail, placed the indicator tip on the bottom of a connecting rod bolt, pushed the piston up until it stopped and recorded the indicator reading. The reading was 0.029. (Note that this matches (gasket thickness - deck height).
I repeated this test on cylinder #7, using the domed piston and the 0.039 gasket which resulted in piston-to-head clearance of 0.060.
At this point, I realized the chamferred edge on the piston was critical.
The machine shop added the chamferred edge to match the TRW piston. My piston-to-head measurements now, using the 0.039 gasket:
Cylinder # /piston-to-head Cylinder # /piston-to-head
1 / 0.070 2 / 0.070
3 / 0.060 4 / 0.070
5 / 0.060 6 / 0.060
7 / 0.070 8 / 0.050​
Note that the open chamber head is not round. The 4.067 piston will not fit into the chamber.
piston interference.jpg
I brought the heads back to the machine shop to see if my 78cc measurements are correct. No results yet. Note that as material is removed by resurfacing, the 3.978 dia will be reduced due to the sloped surface above the spark plug.
If they are really at 78cc, which puts my DCR @ 7.22, maybe I should leave the heads alone and just change the cam. Several of the Comp profiles (252H, IVC@52*; XE250H, IVC@51*; XE256H, IVC@54) would boost my low rpm torque compared to the Mopar "761" IVC@61*. The XE250H would yield a DCR = 7.70.
I've sent my specs to Jim at Racer Brown to see what he recommends.

 
Grind the #8 chamber a little. I ground all of mine to 4.06". Buy some flat face valves. Those cams are too small
 
I am not sure why one would worry too much over the original clearance results. Folks run piston to head clearances down in the .035-.040" range all the time, to get the quench effect with closed chambered heads. So that range is safe.

.029" IS a bit tight for regular street driving; the local circle track guys will run just under .030". But .060-.070" is not necessary. That is what had me 'scratchin' ma haid'....But hey, you are paying attention!

I personally would mill the heads. I agree with the goal to get the torque up if this is mainly a street driver/cruiser, but 78 cc's is getting pretty large. With milling to get smaller chambers, you're gonna be able to keep that torque with a larger cam so it'll have wider overall torque and HP curves.
 
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