Thread: LT1 or...

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Hello,
I just discovered you all today. I am back in hot rod building after 30 years away. No I have not lost my mind. The mistake I made was keeping my son away from my first love - small block chevy's. I need some assistance I think I have a couple of good four bolt 350 blocks both with the number 39700010 on the flange back by the bell housing area. Both have threaded holes in the lifter valley. Are these roller blocks? If so have any of you used stock GM roller lifters in a performance application? I have a lot to catch up on as you can see.
Thanks, Twolane

Yes if you have threaded bosses in the lifter valley they are roller blocks.The stock hydro lifter retainers do have a limited RPM range and Comp Cams offers a solution somewhat for that.

Welcome to CHR Twolane -

I think you’ve got one too many zeros in your number. My guess is that you have a 3970010. This casting was used for 1968 327 and 1969-79 350 (2 and 4 bolt). Four bolts were used in trucks, Camaros, and ‘vettes during those years with HP up to 370. Good builder – but not a roller.

The numbers on the front pad (passenger side – lip on the front of the block example would be "V0722TXD") are the key if you want the specific application these engines were originally used in. Get those numbers and we can give you some more info.

Regards,
Glenn

A roller-ready block would have the tops of the lifter bores machined flat to accept dogbones. If the tops of the lifter bores are still as-cast, then it is a flat tappet block.

There are fellows building Gen I flat tappet motors every day, but it is not the hot tip any longer. We have seen failure after failure and now pretty much try to suggest a Gen I roller block to anyone who asks. Specifically, the 350 Vortec 5700 RPO L31 motor which came in '96 to '00 Chevy trucks and vans. Those motors would have the much sought after Vortec heads, so you could have roller cam and good heads in the same package. Although the wrecking yards are onto this scheme, many times you can find the motors on craigslist or other advertising medium for a reasonable amount of money. I would still pay up to about $400 for one, less the intake but otherwise complete pan to valve covers and with spider, dogbones and roller lifters. The heads will need some work for a performance application as the valve lift is limited to about 0.430" with the stock arrangement. The bottom of the valve retainer hits the top of the valve guide seal with lifts beyond stock. Do some searching and you will find the alterations necessary to hot rod these heads.

Now, if you are the hard-headed type and just have to build a flat tappet motor, then here is a list of failures to fix....
http://www.crankshaftcoalition.com/w...ips_and_tricks

There are roller 305 motors out there also, so check the head casting numbers before you lay down the long green for a motor. Cylinder head numbers 12558062 and 10239906 are the only two numbers used on L31 Vortec 350 heads.

You'll have to talk with some of the other fellows on this board about the Gen II LT1 motors. I have not built one. If I were going to build anything more radical than a late Gen I Vortec motor, it would be an LS motor.

welcome to chr twolane.

other than cam type---Something tp remember is that LT engines are reverse cooling

Originally Posted by techinspector1

A roller-ready block would have the tops of the lifter bores machined flat to accept dogbones. If the tops of the lifter bores are still as-cast, then it is a flat tappet block.

There are fellows building Gen I flat tappet motors every day, but it is not the hot tip any longer. We have seen failure after failure and now pretty much try to suggest a Gen I roller block to anyone who asks. Specifically, the 350 Vortec 5700 RPO L31 motor which came in '96 to '00 Chevy trucks and vans. Those motors would have the much sought after Vortec heads, so you could have roller cam and good heads in the same package. Although the wrecking yards are onto this scheme, many times you can find the motors on craigslist or other advertising medium for a reasonable amount of money. I would still pay up to about $400 for one, less the intake but otherwise complete pan to valve covers and with spider, dogbones and roller lifters. The heads will need some work for a performance application as the valve lift is limited to about 0.430" with the stock arrangement. The bottom of the valve retainer hits the top of the valve guide seal with lifts beyond stock. Do some searching and you will find the alterations necessary to hot rod these heads.

Now, if you are the hard-headed type and just have to build a flat tappet motor, then here is a list of failures to fix....
http://www.crankshaftcoalition.com/w...ips_and_tricks

There are roller 305 motors out there also, so check the head casting numbers before you lay down the long green for a motor. Cylinder head numbers 12558062 and 10239906 are the only two numbers used on L31 Vortec 350 heads.

You'll have to talk with some of the other fellows on this board about the Gen II LT1 motors. I have not built one. If I were going to build anything more radical than a late Gen I Vortec motor, it would be an LS motor.

Richard.Just to clear up some confusion on my part.1995 was one of those weird GM transitional yrs.From what I think I know,some came threw with flat lifters and some came threw as hydro roller lifters.So if you have a block(mine is at the machine shop so I can't look)with the threaded bosses,did all of those also have the machined flat lifter bores too??.

Thank You in advance,

Gary

Sorry Gary, can't answer the question, don't know what Chevy did back then. As you said, transition year. Call up the machine shop and ask 'em if the lifter bores on your block are spot faced.

late 89to 90s are when the block were spot face for rollers but truck s still used a solid hyd cams gm did not have a roller cam that work with throttle body with out mass air in truck use .the block will have hold downs in the valley .tops of lifter bores will be machined . the front of the block will have cam retaner plate holes if you have all this then you can use gm roller lifters dog bones and spiders .roller chain set . cam retaner plat. push rods .and cam with a step nose. and the right cam gear. i done some