[Sagacious]

i've decided to take some further technical measures with my machine shop who did my heads. he claimed it was due to "overrevving" i run a th-350 and 2.73 gears. being that its an automatic and i dont manually shift, i find it kind of hard to overrev the engine. i run 14'' rims all around with P23560r14's, i believe the wheel diameter is 25.2''. the cars 2-3 shift is at 80mph,

with 2.73 gears, wheel diameter of 25.2'' and @ 80mph. what should my rpm be? the heads were made to go to 5,800rpm+.

need help, thanks.

 

[Black Sheep]

Assuming no converter slippage, with your combo of gears and tire size it works out to be 82 mph at 3000 rpms. If you have enough horsepower to overcome the wind resistance, 5800 rpms works out to 159 mph (with a 1:1 final drive ratio in the trans) It would be pretty hard to over rev it in top gear. It would be possible to over rev on the 1-2 or 2-3 shifts. TH 350 gear ratios are 2.52, 1.52 and 1.0...

If I'm figuring it right (trans ratio x gear ratio) the 1-2 shift @5800 rpm is around 63 mph, the 2-3 shift @5800 would be around 105.

What happened to your motor?

 

[MRGM]

this sounds lnteresting, i also would like to know about this little situation.....


500 5 9 14
600 7 11 16
700 8 13 19
800 9 14 22
900 10 16 25
1000 11 18 27
1100 12 20 30
1200 13 22 33
1300 14 23 36
1400 15 25 38
1500 16 27 41
1600 17 29 44
1700 18 31 46
1800 20 32 49
1900 21 34 52
2000 22 36 55
2100 23 38 57
2200 24 40 60
2300 25 41 63
2400 26 43 66
2500 27 45 68
2600 28 47 71
2700 29 49 74
2800 30 50 77
2900 31 52 79
3000 33 54 82
3100 34 56 85
3200 35 58 88
3300 36 59 90
3400 37 61 93
3500 38 63 96
3600 39 65 98
3700 40 67 101
3800 41 68 104
3900 42 70 107
4000 43 72 109
4100 45 74 112
4200 46 76 115
4300 47 77 118
4400 48 79 120
4500 49 81 123
4600 50 83 126
4700 51 85 129
4800 52 86 131
4900 53 88 134
5000 54 90 137
5100 55 92 139
5200 56 94 142
5300 58 95 145
5400 59 97 148
5500 60 99 150
5600 61 101 153
5700 62 103 156
5800 63 104 159

 

[Sagacious]

the exhaust valve retainer springs fell apart. all the pieces that drifted into the motor went into the oil. none were in the pistons. machine shop is saying its due to overrevving.

 

[Simo]

the exhaust valve retainer springs fell apart. all the pieces that drifted into the motor went into the oil. none were in the pistons. machine shop is saying its due to overrevving.

Iff they did your heads for you and you havent changed any other
driving and rev habbits amd your spitting collets theve stuffed up,,

Iff you could valve bounce the eng before without it droppin one
then they may have done ya heads wrong.

 

[Black Sheep]

Even if you float the valves they should stay in place, unless they were installed wrong. I buzz my 440 to 6 grand on occasion and never had a problem. It sounds like the keepers weren't seated properly...

 

[Sagacious]

what do the keepers have to do with it if the valve springs didnt fly off? the inner springs on the exhaust just broke...

 

[Lonestar]

What are the cam specs and what heads?

 

[Black Sheep]

Sorry, I misunderstood what you mean by "the exhaust valve retainer springs fell apart". I interpreted that as meaning some valve spring retainers came off. Overreving, bad springs or the wrong springs for your cam. Are you using the manufacturers recommended springs?

 

[Sagacious]

no idea, about the springs. other than what the machine shop tells me. they say they're .525 max. which suits my application. so that leaves overrevving or the wrong springs. and given the gear ratio (2.73 and th-350 trans. it doesnt really make overreving possible unless i manually shifted the trans. and i dont drive like that. i guess they're just convering their ***** and saying i dont know what im talking about.

 

[Simo]

what do the keepers have to do with it if the valve springs didnt fly off? the inner springs on the exhaust just broke...

I musta miiss understood your Question.
I call valve retainers the things that hold the valve stem in place.
Iff your breaking inner valve springs ya might wanna get the correct ones for your high lift cam,,
Simo,,..

Wrong grade of springs are not good,, buy better Quality springs,,(not so brittle and will take the extra load).

 

[MRGM]

sounds like the shops problem to deal with.wrong springs.