XR274HR-10 in 318

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Instead of milling the intake, your machinist should be milling the intake side of your cylinder heads, but the end rails of the intake will probably need milled too. I got to checking and the .050 comes closer to reducing the chamber volume closer to 53 cc's, so plan ahead on your compression before having them milled.
 
Garrett Ellison said:
Instead of milling the intake, your machinist should be milling the intake side of your cylinder heads, but the end rails of the intake will probably need milled too. I got to checking and the .050 comes closer to reducing the chamber volume closer to 53 cc's, so plan ahead on your compression before having them milled.
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Best idea. I had the heads milled and I bolted them on and the stock intake wouldn't fit. Instead of pulling the heads again I just machined the intake. Now the heads and intake will have to be used together. No worries though. I don't plan on any changes and some time in the engines history one head was replaced.
 
Garrett Ellison said:
Instead of milling the intake, your machinist should be milling the intake side of your cylinder heads, but the end rails of the intake will probably need milled too. I got to checking and the .050 comes closer to reducing the chamber volume closer to 53 cc's, so plan ahead on your compression before having them milled.
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That’s another reason I say just mill the intake manifold. If you are going to mill the head, then you really need to mill the China wall on the block. That’s the correct way to do it.
 
yellow rose said:
That’s another reason I say just mill the intake manifold. If you are going to mill the head, then you really need to mill the China wall on the block. That’s the correct way to do it.
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While we are on the subject, If you deck the block is there a head/intake mismatch? I would think so but I haven't heard any comments about it.
 
toolmanmike said:
While we are on the subject, If you deck the block is there a head/intake mismatch? I would think so but I haven't heard any comments about it.
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Depends on what you start with and where you end up.
That’s why I say “Check first!”
 
JoJo said:
The purpose of this setup is for street cruising... Daily driven occasionally and riding out-of-town on the weekends. I Love the lower RPM torque, but it seems to fall on its face in the mid-high RPM range.
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Thanks very much. That is quite helpful.


Garrett Ellison said:
Those heads usually cc in at around 60 cc. I know someone who uses them for budget truck builds but gets them milled about .050 (around 56-58 cc's) along with .028 MP head gaskets for a bump in compression. He also bowl ports them and opens the intakes up to 340/360 gasket size. 1.88/1.60s are good, some of our people in the know here like a 1.94 intake in a 318 head. If your going to use a hydraulic roller but confined to a shelf grind, I like this one fairly well.
Howards Cams Retrofit Hydraulic Roller Camshafts 713175-10
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This was this cam like I was thinking would be a bit better; it looks like it is from the Howards aggressive ramp hydraulic rollers lobes. So it will have something like 10 more duration at .200" lift. Put it in advanced at 106 or 104 ICL. It is listed in the catalog as 272 advertised and 219 at .050" lift and .525" valve lift at 1.5 ratio rockers. I wish there was one step smaller but there is not.

Lunati has one step smaller for a VooDoo HR cam, which is 262 advertised and 211 at .050" and .507: intake lift. That might be a better fit. This is probably where I would head.

I agree with the idea of using the thinner head gaskets.... if this has been rebuilt, then it likely has the standard Felpro kit gaskets and that lowers static CR by about .3-.4 points. I'd have the head milled down a bit (even just .020" will help) to get good flat gasket surface and use the Mr Gasket 1121G's in there.

And I see no reason to step up the rear gear higher for cruising.
 
I believe the Magnums were a bit closer to their advertised compression ratios. Don't forget, the Magnum blocks have a shorter deck height, plus the Magnum heads have a smaller chamber. Both help get compression up.
 
Thanks nm9stheham! I was on the fence between those two grinds. I correlated the extra .050 & .200 of the Howards grind to be somewhat similar to the old Comp 268H/220 .454 on a 110 grind. That cam works pretty well across the board with a Performer RPM.
 
toolmanmike said:
While we are on the subject, If you deck the block is there a head/intake mismatch? I would think so but I haven't heard any comments about it.
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Yes there is. Any time you lower the block or the head or both, you need to verify intake manifold fitment and correct it accordingly.
 
IIRC a member here did the math on his LA roller 318 and it came out 9.17:1
 
JoJo said:
I haven't done anything to the heads yet. I plan on having them ported and adding 1.88/1.60 valves. As far as the compression ratio, I think these engines are rated at 9:1 if I'm not mistaken.

I'm a little skeptical on the converter... I was browsing around trying to collect information and some say it would be fine and that a quality converter would be the best route. Even though my combination is mild, I don't want to hurt the performance in any way.
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I have a 3400-3600 FTI 9.5" converter and it is terrific for street driving. You will be fine with your choice.
 
OK if you are going to port do it and get head flows for input into your cam choice
also get true compression with aftermarket head gasket
Someone got a Howard for $150 with a changed exhaust lobe- must have been a HFT I forget but not much of an extra charge
I'm not saying 26- or 264 is the right number for you
I was just saying you could get the larger cam performance with the small cams driveablilty/ torque
 
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