convert 328/TR engine to non-int and add turbo

ndnguyen · #1 03-03-2006, 01:23 PM

If you have to rebuild a 328/TR (particularly TR) engine or planning to turbo charge it, how difficult/expensive would it be to convert the engine to non interference (valves-pistons won't collide even if t-belt breaks) via one or combination of the following:

- reduce valve lift
- deeper cut in valve cut-out areas on the pistons
- raise the head via thicker gasket. Does anyone happen to know by how much?

I think the lost (due to lower compression/flow) in power would be more than make up for by the turbo. I think the added cost would be more than make up for by not having to do the t-belt/idler pulley out of fear. One can also drive the tar out of the car without worrying about t-belt break.

Thanks for your thought.

- Nguyen

pma1010 · #2 03-03-2006, 02:02 PM

Contact James at Norwood's. He'll know. Builds them.
Philip

ROLOcr · #3 03-03-2006, 02:07 PM

if you turbocharge it you have to lower the compretion ratio of the engine, yo can dig depper into the valve cut-out areas on the pistons and use a smaller head gasket so you loose a lot of compretion ratio due to the cut out area increase but you gain more from the thinner gasket
you will end up with less compresion anyways that you need for the forced induction

ROLO

Fred2 · #4 03-03-2006, 04:36 PM

I don't think this would be possible on a twin cam motor.
While you should be able to eliminate valve to piston interference, you may not be able to eliminate valve to valve interference with out major re-design work.

If you have a set of heads off of the car, it should be easy to spin the cams and see if the valves will crash if the belt breaks

pma1010 · #5 03-03-2006, 06:28 PM

I think this might be more trouble than it's worth. Stock TR is what, 8.8:1 or similar CR. Pretty modest for turbo.

Again, recommend you talk to James at Norwood Performance. I'd expect he's done more TR turbo conversions and can guide you well without guess work.

I'd be surprised on valve to valve contact given cam characteristics of K-Jet.

BTW, on the Brian Hart "big valve" (Lotus) twin cam engine, you could (just) slide a cigarette paper between the valves when timed properly given size, lobe centers and cam duration...
Philip

**Mark 328** · #6 03-04-2006, 12:24 AM

If someone had a head off and apart it is real easy to tell if there is interference. Did it on my BB Chevy when it was Iskyised (recammed); here is an abbreviated procedure.
The valve springs are removed. Springs are replaced with springs of the same size that can be compressed with light hand pressure (hardware store). The piston is set at TDC. Head is mounted over head gasket on the block. Valve is pushed until it contacts the head and a measurement is taken. If the measurement is less than the cam lift you have interference. On the BB Chevy, if there is less than .100" you "may" have interference.

I would be curious to see the results of a test.

Mark

**CliffBeer** · #7 03-04-2006, 01:19 AM

While it certainly would be easy to physcially fly cut the valve pocket in the piston crown to a greater depth, this poses the question of whether there is enough thickness to the crown to either a) not cut completely through, or, b) not create a hot spot if there is only marginally enough thickness. It's probably going to be very close. Just one more issue to consider in the analysis here.

Racer98 · #8 03-04-2006, 01:23 AM

Better to work with the people mentioned on the thread, but if your going to turbo a N/A car you need to do all of the following

1) Drop the engine compression
2) Head gaskets
3) Aftermarekt engine mangement - Fuel injection
4) oil cooling and taping the block
5) Manifolds
6) Choice of turbo and what type of responce you want and at what RPM
7) Choice of clutch
8) internals overhall and upgrades
9) upgrade of ignition system.
10) Intercooler set up.

once you get it all together, dyno time for calibrating everything together.
also depending on the state your in, this might be or not be allowed.

Racer98 · #9 03-04-2006, 01:26 AM

Quote:

Originally Posted by CliffBeer

While it certainly would be easy to physcially fly cut the valve pocket in the piston crown to a greater depth, this poses the question of whether there is enough thickness to the crown to either a) not cut completely through, or, b) not create a hot spot if there is only marginally enough thickness. It's probably going to be very close. Just one more issue to consider in the analysis here.

but will this cause the motor to be off balance ?

**DGS** · #10 03-04-2006, 03:31 AM

Everything old is new again? RCV Ltd and a few others are re-exploring the Knight sleeve valve as seen on the Willys-Knight, some older Daimler, and pre-war aircraft engines.

I haven't been able to find the link, but a company was experimenting with replacing the poppet valves with rotating ball valves, aligned on a common shaft. As the "cam" shaft rotated a hole through the ball would align with the intake or exhaust channel, opening or closing the flow path. 90 degree ball valves (or "air locks") are pretty common in industrial applications, and even common plumbing fixtures. This would be a derivation of that principle.

I'd have thought that, for an inline cylinder bank, a rotating cylinder would be easier to seal, and would permit larger openings. But maybe the company was worried about time warps.

**CliffBeer** · #11 03-04-2006, 03:44 AM

Quote:

Originally Posted by Racer98

but will this cause the motor to be off balance ?

After fly cutting the shop should weigh each individual piston and then balance if out of tolerance.

**Artvonne** · #12 03-04-2006, 11:26 AM

It would be far easier to avoid valve to valve interference on a four valve engine, as the chamber is flatter. But on a two valve, you cant have very much lift and not colide. You want good lift and valve timing, even on a turbo car to have good low boost throttle response. If your worried about the belt breaking, consider Scotts new belt drive using the modern HDL belt tooth design.