Is my engine a flat or roller cam?

[JohnSaints]

Here's the description from the Haynes manual:

Quote:
The engine is of four-cylinder, in-line, single overhead camshaft type, mounted transversely at the front of the vehicle. The crankshaft is supported in five shell-type main bearings. Thrustwashers are fitted to control crankshaft endfloat. The connecting rods are attached to the crankshaft by horizontally-split shell-type big-end bearings, and to the pistons by gudgeon pins. The gudgeon pins are a press fit in the connecting rods.The aluminium alloy pistons are of the slipper type, and are fitted with three piston rings - two compression rings and a scrapper-type oil control ring. The single overhead camshaft is mounted directly in the cylinder head, and is driven by the crankshaft via a toothed timing belt. The camshaft operates the valves via inverted bucket type followers, which operate in bores machined directly in the cylinder head.


Does this mean it is a flat, roller or none of the two? Will I need specific oil or normal spec oil (API SN, ACEA A3/B4)?

 

[Clevy]

What car and engine size.
Not
That it matters. Ohc engines actuate the valve directly. No you don't need any special oil.

 

[JohnSaints]

Originally Posted By: Clevy
What car and engine size.
Not
That it matters. Ohc engines actuate the valve directly. No you don't need any special oil.


It's a Renault Laguna mk1. 1.8 liter engine.

 

[Hokiefyd]

Originally Posted By: Johnyjj1212
Here's the description from the Haynes manual:

Quote:
The camshaft operates the valves via inverted bucket type followers, which operate in bores machined directly in the cylinder head.


Does this mean it is a flat, roller or none of the two? Will I need specific oil or normal spec oil (API SN, ACEA A3/B4)?


The underlined passage means that the lobes on the camshaft slide directly against the valve "lifter", which is really just an inverted cup sitting over the top of the valve and spring. While this is probably a flat tappet arrangement, I would defer to the owner's manual on the type of oil required. Renault may or may not call for a special type of oil. I would wager a guess that they likely call for an ACEA A3 or A5, such as a 5w30 or 5W-40 perhaps.

 

[Hokiefyd]

Originally Posted By: Clevy
Ohc engines actuate the valve directly.


The cam lobes in some OHC engines actuate the valve directly and in some OHC engines do not. I own an OHC engine and a DOHC engine, and the cam lubes do not actuate the valve directly in either one. Both of the engines I own use roller-tipped rocker arms for valve actuation.

 

[Trav]

Technically its a flat tappet cam but its a non issue with buckets. As Clevy pointed out the cam lobes sit directly over the valves so there is very little stress on them only the actual valve spring pressure.

Valve travel is equal to the cam lobe height 1/1. Old school OHV with cam in block and rocker arms use the rocker arms as a multiplier which is the crux of the flat (non roller) tappet issue.
Cam lobe stresses can be very high depending on the multiplication factor of the rocker arm.
Any good ACEA A3/B4 oil will be fine in the Renault 1.8 engine.

Edit: This pertains to your engine type not every OHC on the street which is irrelevant as far as your engine is concerned.

 

[Garak]

Originally Posted By: Johnyjj1212
Will I need specific oil or normal spec oil (API SN, ACEA A3/B4)?

The A3/B3 A3/B4 oils we discussed in the other thread should be more than sufficient. If ZDDP were an issue, such oils have elevated levels compared to the SN/GF-5 North American lubes, anyhow. Aside from that, the API SN 40 grades can also have higher amounts, so, again, you'll be okay.

Plenty of ACEA A3/B4 lubes can also be SN because most of them fall within the 40 grade (German Castrol being an exception). Don't worry much about the API spec for your purposes.

 

[A_Harman]

Yes, it's a flat tappet cam with a sliding wear interface. Use an A3/B4 oil in the viscosity specified in your owner's manual.