273ci thoughts?
- Thread starter papabear
- Start date
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Early 70's I just remember looking at it once. I was ordering a new Commando cam and valve springs. No way I could afford any of those engines. In school and working part time at Esso or Mr Tire.
Talk to Hughs to coordinate cam and piston choice. Are you going to balance the engine? If so Magnum pistons might be a good choice, higher compression ratio and narrower rings? What octane gas are you willing to buy and what is available where you will be driving?
Bighead440
Well-Known Member
I'm not big on the Whiplash cams. If you go with a KB flat-top (valve reiefs and close-to if not zero deck), you can stand some camshaft. Some of the Street Force Howards cams look good, the 265DEH Comp Dual Energy is a possibility and the old Cam Dynamics Energizer (available white box generic for cheap) 272/.454"/110* is a default for this kind of build. The 272 sounds great in a 318 and is snappy. Open the Performer intake to slightly under 360 size (it comes 318) and gasket match the 318 heads to the 360 gasket. Put 360 valves in and bowl-hog (70* cut)/blend the cuts to the runners, use drop in 901 Comp springs or even NEW 340 red replacements. You can use the Mr.Gasket .028" head gaskets if you end up negative a bit on deck clearance. I use a 625 Street Demon with the TQ-like plastic bowl on my hyped-up .060" over 318 (270s Comp cam), and it works flawlessly out of the box. I use a Flowmaster 2.5+2.5>3" merge collector and use one 3" muffler behing 318s for torque production and packaging. Plenty of flow!
Bighead440
Well-Known Member
Every Magnum 5.2L piston I've ever seen had 5/64" rings with no valve reliefs, basically a smogger LA piston. The 360/5.9s did get the narrow ring pack and that soap-dish recess. I always wondered why, when even the 4.0L Jeeps went to the narrow rings in 1996....
Interesting, evidently a bad assumption on my part. I have not checked the only 318 magnum I have yet.
pishta
I know I'm right....
Petty motors claiming same HP levels sounds like the slant: same head, same power but at different RPM's. 170 will make 225's HP but much higher in RPM's. Torque isn't as easy. Wonder if the Petty motors all ran the same 340 head? 273 would need a notch for the larger valves.
Bighead440
Well-Known Member
I thought the same thing!! I had a Magnum 318 that I bought already used in a carb'd application from a kid who put the oil pump on crooked (not in the pilot register in the cap) and was breaking in the cam and the oil pump shaft broke. He was away from the truck with it wailing, and heard it change tune, and by then the crank was smoked (especially the thrust, wtf?). He had it torn down and gave up when he found a 340 cheap. I assumed he had swapped pistons with LA units, until later when I tore down an unmolested late '90s truck for a customer and it had the same antique '80s pistons. Go figure!!
Plus I would think of upgrading to 1.88 valved 360 heads or even Magnums since your buying pistons anyways, easy 50 hp over stock 318 heads.
66fs what pistons do you run with 360 heads on a 273 ?
pishta
I know I'm right....
Magnum pistons wont fit an LA rod. The magnum rods had a .100 ish narrower little end as did the pistons. I bought a set of magnum stroker pistons and had to clearance the pistons to fit the LA rod little ends. It was a small difference but they didnt fit OOTB.
@66fs & @273 As well as everyone else who were waiting in this..... SORRY FOR MY DELAY.
These are my W5 heads ported by Brett Miller. Brett tested them on a 4.125 bore plate. This engine will have a 4.03 bore size. These are the difference between the flow plates (4.125 & 4.03) and not the tester or the bench. The second tester of my heads has been building race winning engines about as long as I’m alive and his son was a just a few years younger than me, has always been working in the family owned shop. Years back he was schooled by none other than “Joe Mondello.”
Enough said....
........... 4.125………............................4.03...........
Lift —-— In ——exh ——--In —-——Exh————
.100 —-. NA ——————- 60 ——— 57
.200 —-.121 —- .110 —— 115 —- 120.4
.300 —-.180 —- .151 —— 172.4 - 141.8
.400 —- 228 —- 184 —— 230 —-176.9
.500 —- 278 —- 206 —— 275.7 — 188.1
.600 —- 308 —- 218 ——- 294 —- 212
.650 —- 312 —- NA ——— not tested —
.700 —- NA —— 235 ——— 298.6 —- 222
NA = Not Available/Not Tested
I asked Brett about the .650 & .700 oddity.
I’m not remembering 100% correctly here but it was something along the lines that the port went noisy and turbulent. So it was backed down the .050, read, recorded and reported as quite.
My guy said the port got loud at .700. And recorded the number. He also included swirl numbers if anyone is interested.
As talked about before, bore size has an impact on power production despite what anyone says. There nutz to think otherwise.
While there is only a few scant cfm number differences, at a lay mans calculations @ 2 cfm per HP on a honesty nice street machine build, not race territory, which can be much greater, there is a 28 HP difference just in the head flow alone. All due to bore size allowing more cylinder head flow for more air and fuel.
It’s a dam shame 1 of the W5 cylinder heads gave up the ghost and revealed a thin walled port halting anymore porting. It should still make for a good power producing engine though. It fell short for me. A little bit of a disappointment, but not entirely unexpected though fully hoping for better.
These are my W5 heads ported by Brett Miller. Brett tested them on a 4.125 bore plate. This engine will have a 4.03 bore size. These are the difference between the flow plates (4.125 & 4.03) and not the tester or the bench. The second tester of my heads has been building race winning engines about as long as I’m alive and his son was a just a few years younger than me, has always been working in the family owned shop. Years back he was schooled by none other than “Joe Mondello.”
Enough said....
........... 4.125………............................4.03...........
Lift —-— In ——exh ——--In —-——Exh————
.100 —-. NA ——————- 60 ——— 57
.200 —-.121 —- .110 —— 115 —- 120.4
.300 —-.180 —- .151 —— 172.4 - 141.8
.400 —- 228 —- 184 —— 230 —-176.9
.500 —- 278 —- 206 —— 275.7 — 188.1
.600 —- 308 —- 218 ——- 294 —- 212
.650 —- 312 —- NA ——— not tested —
.700 —- NA —— 235 ——— 298.6 —- 222
NA = Not Available/Not Tested
I asked Brett about the .650 & .700 oddity.
I’m not remembering 100% correctly here but it was something along the lines that the port went noisy and turbulent. So it was backed down the .050, read, recorded and reported as quite.
My guy said the port got loud at .700. And recorded the number. He also included swirl numbers if anyone is interested.
As talked about before, bore size has an impact on power production despite what anyone says. There nutz to think otherwise.
While there is only a few scant cfm number differences, at a lay mans calculations @ 2 cfm per HP on a honesty nice street machine build, not race territory, which can be much greater, there is a 28 HP difference just in the head flow alone. All due to bore size allowing more cylinder head flow for more air and fuel.
It’s a dam shame 1 of the W5 cylinder heads gave up the ghost and revealed a thin walled port halting anymore porting. It should still make for a good power producing engine though. It fell short for me. A little bit of a disappointment, but not entirely unexpected though fully hoping for better.
I would assume so, that was a long time ago...
I ran a set of +.040 TRW forged 10.5:1 pistons, honed with torque plates, and mains torqued to spec, to a plateau finish for Speed Pro file to fit Moly rings. The heads were milled .040 and .038 on the intake side to get down to NHRA min spec. Chambers were equalized at 64.8 cc. And the chambers were centered over the bores with offset dowels. Bowl cleanup, and intake port gasket matched on top and sides. Same for the exhaust ports. Always thought you had to know what you were doing to port heads. That was not me.
Wow, all kinds of unexpected land mines...
Nice, I remember seeing your post before. Shame about your heads. You never got to run them? I will never be in that league. I was already too fast for a street car for me with the J head 273. You know you are crazy when you shift from 3rd to 4th at 100 mph in a 64 Barracuda. Nice to figure some things out though. I can now concentrate on enjoying the Barracuda.
I have a Early A Body with a 4 speed, an 8 3/4 rear and a stash of pumpkins from 4.86 to 2.76 all with sure grips except the 2.76. I could have a blast, even with a 170 /6.
I have been side tracked. Heads are ready to rock with just a little bit of epoxy in 1 runner. I have a few (actual important) things in front of me so the toy will wait... again... I just need to get gaskets, pistons and rings for the short block. Everything else I have. I was going to do a 430+ engine, but with the current virus and retirement date fast approaching, I’m better off holding off. The soon to be worked on (I hope! LOL!) will be a 340-372.
Good luck and stay safe, Still hoping to go to Carlisle this year. Sounds like you will have to spin your motor up high to take advantage of those heads.
pishta
I know I'm right....
What Epoxy are you using? I need less than a peanuts worth and don't want to buy 6 oz as Ill never use it all. Intake roof has a <BB sized break into the head bolt boss area. Gonna fix the window with epoxy and the head bolt seat with a hardened washer and some epoxy under it and then torque it down so it hardens under the bolt stress. The bolt torque keeps compromising the repair.
Now that's decided, You should get an adapter for the 318 crank to index the 67 904 smaller converter hub. I always use Fel-Pro head gaskets. I can't recommend a certain header, but the headers will have to seal to the 318's smaller exhaust port. Some headers are made for the larger 340/360 exhaust port. I also like a Thermo-Quad so I'd also look at the Street Demon carb. My 2 cents.
Spin it high? Maybe so. The thought is not a street machine build. It will drive the street in a limited fashion and distance. Solid roller cam, 4.88’s, a manual shifting 904, spartan interior... etc...
Brett Miller did the work. I don’t know the brand name of the epoxy. Though I’m in the same boat and (not quit yet) looking for epoxy for iron and aluminum metals that play nice with gasoline for a long time.
Pictured below is the only port and the very small portion that needed epoxy. I’m hoping to get to these one day soon since life had other plans for me.
Back to the 273 thread.
papabear
Mopar Noob
No tags on the rear end, appears to be a 9 bolt 7 1/4...someone's been in there, maybe they changed to a better gear at some point. Guess I'll have to pull it apart and see what's in there.
Always nice to know what you have. Just costs a rear cover gasket and some fresh lube. If you are lucky you will find a Sure Grip and 3.23 gears.
Wyrmrider
Well-Known Member
I'm not a fan of the b & d cams either
street farce howards and those chevy ms? you can do better
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