Little cam selection question.

Topic: Little cam selection question. (Read 1454 times) previous topic - next topic

Little cam selection question.

February 21, 2006, 06:40:44 PM

88 SO shortblock
89 E7 heads

would a B303 cam go in there with no PTV issues?

I was informed by a mustang guy that his flat top piston 5.0 has E7's, stock cam, and 1.73 roller rockers, that came out to being close to .02" less lift than a B cam, if thats the case, id think it would fit, but id like a few opinions

Little cam selection question.

Reply #1 – February 21, 2006, 07:14:06 PM

If it's a Mustang with the stock pistons that this Mustang person had, they were not true flat tops. Either way a b-303 has .480 lift on both sides with 1.6 rockers......286* duration and 224* duration at .050" lift on intake and exhaust. It SHOULD work with your combo.

Little cam selection question.

Reply #2 – February 21, 2006, 07:36:01 PM

Unless it was an 86.

Little cam selection question.

Reply #3 – February 21, 2006, 07:50:28 PM

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Unless it was an 86.

I always forget that!

Little cam selection question.

Reply #4 – February 21, 2006, 09:23:08 PM

Since were on subject. Is there any cam that would fit an 84 SO 5.0 motor with out clearance issues?

Little cam selection question.

Reply #5 – February 21, 2006, 10:46:14 PM

All 1984 302's left the factory with a cam that is the same lift and duration as the later SO 5.0 in the roller block birds and cats. Only difference is they were not roller cams, just have the same lobe profile (incidently they put the same cam in the evil 255 in '84 as well).
As far as performance cams go you have a lot of options due to the fact that you DON't have a roller motor AND the old style 302 firing order. Basically anything that says early 302 and your good to go.
On yet another side note also in 1984 the Police Interceptor vesion of the 351W had the same lobe profile as the first roller cams in the 5.0 HO's (up to mid '87). After mid 87 the 5.0 HO cam got an ever so slight reduction in lift on the exhaust side.

Little cam selection question.

Reply #6 – February 22, 2006, 01:31:05 AM

Interesting...I didn't know that. So as far as engine mods go I can use most parts for early 302's? What kind of things would be best to do for performance, is this motor even worth modding? or would a HO 5.0 be something to invest in instead?

Little cam selection question.

Reply #7 – February 22, 2006, 09:15:47 AM

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is this motor even worth modding? or would a HO 5.0 be something to invest in instead?

What year is your engine block?

Little cam selection question.

Reply #8 – February 22, 2006, 05:36:58 PM

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would a B303 cam go in there with no PTV issues?

Unfortunately there's only one way to know for sure and that is to mock it up and clay a piston... that is unless you're a gamblin man, heheh... Also, it's the duration of a cam that has more affect on piston/valve clearance and that B cam hangs the valves open pretty long @ 224 duration. I would definitely check to be sure assuming the SO pistons have no valve reliefs.

Little cam selection question.

Reply #9 – February 22, 2006, 06:54:50 PM

The engine block is 84 from my t-bird. At the moment I have no idea what kind of mods I can do to my engine. I thought it was an SO block so I was under the impression i was restricted with flat top pistons. What would be the best things to do to gain some power? Its only 140 stock hp so its really lacking in the power department, where would be the best place to look for parts?

Little cam selection question.

Reply #10 – February 22, 2006, 07:14:13 PM

Quote from: Dogcharmer

Unfortunately there's only one way to know for sure and that is to mock it up and clay a piston... that is unless you're a gamblin man, heheh... Also, it's the duration of a cam that has more affect on piston/valve clearance and that B cam hangs the valves open pretty long @ 224 duration. I would definitely check to be sure assuming the SO pistons have no valve reliefs.

Regadless of how long its open, the clearance is only an issue at or close to TDC. The valve could be open for 20 minutes, as long as it clears for TDC, its good.

id just like more definate answers before i spend the money on a cam, never run it, and lose half the money i spent because its second hand.

Little cam selection question.

Reply #11 – February 23, 2006, 09:51:32 AM

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Regadless of how long its open, the clearance is only an issue at or close to TDC.

Exactly, and the longer the valve stays open the closer it will come to meeting the piston when it is on its way back up to TDC at least on the exhaust side. If the exh valve is closed when the piston is half way into the exh stroke it doesn't matter how much lift there is because the short duration has already got the exh valve closed long before TDC. Or if you're talking about the intake side if the valve opens early and fast enough it could contact the piston on its way back down from TDC on the intake stroke. The way I understand it is that when P/V interferance occurs the valve is not at max lift anyway. It's either on its way open or closed. I.e. the valve is in transit and somewhere in its mid lift range. That's why I've come to the conclusion that duration, valve timing events and ramp rates have more to do with P/V interferance than anything else.

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The valve could be open for 20 minutes, as long as it clears for TDC, its good.

If the valve hangs open that long and doesn't touch anything you've got bigger problems than P/V clearance;)

Sorry, I couldn't resist that. The bottom line is that with flat top pistons like ours clearance should be checked when an aftermarket cam or heads are used. Unfortunately this does nothing to help in your decision to buy the cam. I'd check the corral message boards. Someone there has probably run that combo.

Little cam selection question.

Reply #12 – February 23, 2006, 08:01:38 PM

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The bottom line is that with flat top pistons like ours clearance should be checked when an aftermarket cam or heads are used. Unfortunately this does nothing to help in your decision to buy the cam. I'd check the corral message boards. Someone there has probably run that combo.

Like I said above, I believe it will work, BUT Dogcharmer is dead on correct. Have it checked.