need help with 1.7 R R

STRIZZY

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Dec 25, 2003
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I Have A Stock 90 Lx With A 302 In It. I Been Talking To Difrent Cam Companys And Some Telling Me That I Can Use Them Some Say I Cant Any Help??? The Guy Told Me That With A 1.7 R R Will Ad .30thosand And Will Cause Vavle To Piston Issue
 
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Nope, don't worry what so ever with P/V clearance using stock heads and cam. I've got 1.7's, with .030 cut off of my stock heads and still have tons of room. At the same time though, without other breathing upgrades, don't expect huge power from them either.
 
I've seen dyno tests in car magazines that showed a LOSS of 1 HP on a lightly modded engine too -- each combo is different. I wouldn't count on more than 5HP; if you get more, be grateful. Are your stock valve springs up to the task of managing the increased lift? Tired springs are known to float early with the stock cam and stock rockers. THe 1.7's are gonna really put them to work; if your springs are already tired, the 1.7's could lose you power due to valve float. Not always as simple as just bolting stuff on.

The 1.7's will increase your peak valve lift from .444 to about .472. However, they will only reduce your p to v clearance by about 3 THOUSANDTHS. At peak lift the piston is well down the cylinder - there's no clearance issue then. Clearance is tight during overlap when valve is only open about .050" -- swapping the 1.7's makes that about .053" -- not enough to worry about especially with stock components. I don't think I'd give my money to companies that are giving you that unsound advice on the clearances.
 
Heres a dyno I have from a mostly stock (had 80mm MAF) 91 5spd Mustang:
...........RWHP...........
RPM......1.6's......1.7's
2300.....102........109
2500.....114........119
2800.....131........139
3000.....144........153
3300.....160........168
3500.....171........180
3800.....184........191
4000.....189........197
4300.....194........203
4500.....194........204
4800.....195........205
5000.....195........203
5300.....188........195
5500.....175........185
---------------------
...........RWTQ...........
RPM......1.6's......1.7's
2300.....233........248
2500.....239........249
2800.....246........262
3000.....253........267
3300.....255........267
3500.....257........270
3800.....254........264
4000.....248........258
4300.....237........248
4500.....227........239
4800.....214........224
5000.....205........214
5300.....186........193
5500.....167........176