I was wondering what’s the hp benefits to go with stock 318 heads (+stock valve train) and kb167 pistons + thin gasket compared to everything stock. With xe262 or xe274 cam, eddy intake & 500cfm, 3,55’, dual exhaust. Goal: dart fun street build. What would be the expected rwhp?
Stock 318 heads question
- Thread starter KirtDart
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ChargedDart75
Well-Known Member
Welcome! With your combo, the stock 318 heads are a limiting factor. I think the 302 heads were some of the best stock 318 heads, and I'm not sure that they'll support much more than 300 horsepower. If you want to go this route, I'd say it'll still be a fun car to drive. I don't know those cam specs, but I would be trying the smaller 262 with a stock headed 318.
200-230 at the real wheels. Maybe.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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The KB 167s have a cd 1.810, and are about the tallest pistons you can find. Adding the rod length and half the stroke comes to 9.5905..
Off an assumed to be 9.600 deck height, leaves the 167s about .0095 short of the deck, which is a pretty good number. But your decks may not be 9.600, you will have to measure.
Assuming you get them there, this represents 1.9cc
the thin gasket is about 6.8cc
the heads are estimated to be 70cc
so this all adds up to 78.7cc
At .020 o/s your swept area becomes 658.96, and
your compression ratio becomes 9.37.
But your design has no quench to speak of so your cranking cylinder pressure is limited to in the range of 155 to 160 for your local gas... at sealevel.
Wiki says ;
"Looks like greater Dublin varies from sea level to around 200 meters." or 660ft, so lets say 400ft and target a pressure of 157psi.
The Wallace calculator predicts that an ICA of 58* will get you 158 psi@ 400ft with a VP of 123, about the same as a stock 5.2Magnum. This is your MINIMUM ICA. So not great but pretty good and all around fun. while still burning pumpgas.
Read about V/P here; V/P Index Calculation
Going from memory
( cuz I can't navigate the crappy Comp webpage)
the XE262 is; 262/270/110+4 and work out to have an Ica of 57* in at 106. Close enough. This will work very well with the 3.55s
So you done good
IMO, the 274 is too big, your bottom end will get too weak at 9.37 Scr. But you could go up one size, say 266/268ish ( at same .006 tappet rise). But you might like a lil more stall to go with that.
IDK what your gas in Dublin is like, so I base my calcs on what I get in Manitoba Canada., which may be borderline for you. If you run into detonation with the 262, you can retard it a few degrees to get rid of some pressure. But if your pistons are a little lower in the holes, then your Scr will also come in a lil lower. And if still too much. just run the .039 gaskets. This will bring you Scr down to 9.17, and pressure to 153psi. So all in all, from 158 to 153 is a pretty tuneable combo.
Having said that, go back to the top of the page and see where I assigned to the heads 70cc. I could be wrong. If yours are 65cc then the 262 cam is not big enough.
So ; here is a link to the Wallace CAlculator,
Wallace Racing: Dynamic Compression Ratio Calculator
Measure your stuff and play with the calculator, or come back here and post your measurements. There are lots of guys here that can help you dial it in.
If you get to thinking about buying heads, you can run a lotta lotta pressure with alloys. Think 180psi. That will let you run a 340 type cam, with buckets and buckets of low rpm torque.
Off an assumed to be 9.600 deck height, leaves the 167s about .0095 short of the deck, which is a pretty good number. But your decks may not be 9.600, you will have to measure.
Assuming you get them there, this represents 1.9cc
the thin gasket is about 6.8cc
the heads are estimated to be 70cc
so this all adds up to 78.7cc
At .020 o/s your swept area becomes 658.96, and
your compression ratio becomes 9.37.
But your design has no quench to speak of so your cranking cylinder pressure is limited to in the range of 155 to 160 for your local gas... at sealevel.
Wiki says ;
"Looks like greater Dublin varies from sea level to around 200 meters." or 660ft, so lets say 400ft and target a pressure of 157psi.
The Wallace calculator predicts that an ICA of 58* will get you 158 psi@ 400ft with a VP of 123, about the same as a stock 5.2Magnum. This is your MINIMUM ICA. So not great but pretty good and all around fun. while still burning pumpgas.
Read about V/P here; V/P Index Calculation
Going from memory
( cuz I can't navigate the crappy Comp webpage)
the XE262 is; 262/270/110+4 and work out to have an Ica of 57* in at 106. Close enough. This will work very well with the 3.55s
So you done good
IMO, the 274 is too big, your bottom end will get too weak at 9.37 Scr. But you could go up one size, say 266/268ish ( at same .006 tappet rise). But you might like a lil more stall to go with that.
IDK what your gas in Dublin is like, so I base my calcs on what I get in Manitoba Canada., which may be borderline for you. If you run into detonation with the 262, you can retard it a few degrees to get rid of some pressure. But if your pistons are a little lower in the holes, then your Scr will also come in a lil lower. And if still too much. just run the .039 gaskets. This will bring you Scr down to 9.17, and pressure to 153psi. So all in all, from 158 to 153 is a pretty tuneable combo.
Having said that, go back to the top of the page and see where I assigned to the heads 70cc. I could be wrong. If yours are 65cc then the 262 cam is not big enough.
So ; here is a link to the Wallace CAlculator,
Wallace Racing: Dynamic Compression Ratio Calculator
Measure your stuff and play with the calculator, or come back here and post your measurements. There are lots of guys here that can help you dial it in.
If you get to thinking about buying heads, you can run a lotta lotta pressure with alloys. Think 180psi. That will let you run a 340 type cam, with buckets and buckets of low rpm torque.
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Id be happy with that considering that stock rating for my 78 is about 1/2 of that
Thanks!
It’s a 4bbl intake.
yes 70cc heads.
I was thinking about heads, but importation taxes and shipping fees made them out of budget. Stock 302 heads are more affordable, maybe the best to have on budget better compression and maybe run a bigger cam...
It’s a 4bbl intake.
yes 70cc heads.
I was thinking about heads, but importation taxes and shipping fees made them out of budget. Stock 302 heads are more affordable, maybe the best to have on budget better compression and maybe run a bigger cam...
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