Did a compression test on my stroked Olds 215, not good. #4 cylinder at 50 lbs.

Started by Gswest236, April 24, 2025, 09:43:55 PM

Previous topic - Next topic
Print
Go Down Pages 1 ... 3 4 5 6 7 ... 29
User actions

Gswest236

#100
May 14, 2025, 06:01:54 PM
Here's a shot of the heads with gasket. Am i correct that the gasket shows scorched areas where it shouldn't?



IMG_1430.png

Gswest236

#101
May 14, 2025, 06:06:56 PM
Drivers side head with dark area on the right.


IMG_1429.png

Gswest236

#102
May 14, 2025, 06:24:38 PM
The valley has areas where the casting looks like it's been modified or open up. This may be what they all look like. You guys would know. I'm curious what the consensus is on the Olds vs Buick heads? The head gasket looks like the picture posted by Carl.

IMG_1895.png

Gswest236

#103
May 14, 2025, 06:27:58 PM
Which hole  would have been drill and tapped?

mgb260

#104
May 14, 2025, 07:10:42 PM
Scott, The ones closest to the valley with the bosses where the rocker shaft hold down bolts were. The Buick heads have their own rocker hold downs and the Buick gasket would cover the holes. With your high compression pistons, the Olds heads you have or the Buick 300 heads (which only have 4 bolts per cylinder and don't use the lower bolts) are the only ones that will work unless you change to a dished piston. The one you call #4 is #7 actually if you look at the firing order image I posted. Head gasket may have leaked combustion there into water jacket. Does that piston looks a little cleaner? I'd have the deck and head surfaced and use a composition gasket.

mgb260

#105
May 14, 2025, 07:33:50 PM
Also, if you were to use the Buick heads, you would have to use early Buick head gaskets and valve covers and the pushrods are different lengths too.

Gswest236

#106
May 14, 2025, 08:30:50 PM
The cylinder that was low compression was #4. Passenger side 2nd piston from the front.

mgb260

#107
May 14, 2025, 08:39:10 PM
Scott, maybe a small head gasket leak on #7 too. EDIT: after looking closer #1. I'd look close at #4 top and second ring and the land between. Here is an image of a Buick 215 showing the upper head bolt holes not drilled and absence of the four small steam holes. Note the dished pistons because of the smaller cc chamber in the Buick heads.
MikeAlexander-MG-MGB-32-808422837.jpg

Gswest236

#108
May 14, 2025, 08:47:18 PM
So, why is it said that the olds head has 6 head bolts and the Buick head only has 5 when the olds head has 4 extra bolts per head??  The scoring i saw with the scope turns out not to be that bad, so honing should be all that's necessary. Unless there's something I haven't uncovered yet. I used my digital mic and the cylinders all measure 3.5, so its not been over-bored to this point.

mgb260

#109
May 14, 2025, 10:02:24 PM
Scott, 6 per cylinder for Olds vs 5 for Buick 215 and 4 for Rover and Buick 300. You will have to visually inspect the piston and rings. Broken rings cause vertical scratches and if not too deep maybe honing will be fine that's what we did on Jon's motor which had 3 pistons with broken rings. I thought the build in BritishV8 said they were .020 over. The top of the piston will be stamped if oversize. The back of the rod and main bearings are stamped if undersize. It's a good idea to replace rings and bearings, seals etc.

Gswest236

#110
May 15, 2025, 11:15:04 AM
It says 3.524, so I'll remeasure. I hope it only needs rings and honing. But of course new seals and gaskets. Any ideas on a better head gasket?

mgb260

#111
May 15, 2025, 12:07:09 PM
We are using a Best Gasket overhaul set for an Olds 215. You have to order a Felpro intake valley pan as it is not included. Also Best Gasket and TA have the rubber rear seal for the 300 crank. The pistons you have are probably for another engine that has that bore size. I tried looking up the TRW # and came up empty. I'll look for an application with that bore size. you will need to know that for the ring size. Our pistons meant for 80's Camaro 2.8 V6 are .040 over, actually .039 and are stamped on top 1.0 metric oversize. Some stroker builds use other pistons from a Ford 3.0 Vulcan V6 or GM 4 cylinder. When you get the pistons out measure the compression height from center of piston to top of piston.

mgb260

#113
May 15, 2025, 01:10:16 PM
If it is a GM 173/2.8 V6 piston that is .020 over it will have a .5 stamped on the top. If that is the case you need to measure the ring thickness on the top 2 and oil ring gap to verify. They used 3 different ring packages over the years.

Gswest236

#114
May 15, 2025, 01:19:39 PM
On a positive note the engine isn't stuck; the flywheel is contacting 2 bolts on the engine stand. I need to add some more spacers to give clearance.
I'm afraid I'll be over my head reassembling the motor internals as I've never attempted a complete engine rebuild. Ive taken heads off and had valve jobs done and reinstalled them. Thats the extent of my mechanic on the job training. I can take it apart, but complete reassembly is  not something I'm comfortable with. With that in mind should i disassemble  it if i don't intend to be the one putting it back together.?  This site (you guys) offers all the expertise as guidance, but with the cost involved and the possibility of having to remove the engine and start over; I'm very hesitant. The question is at what point should I turn it over to a real expert and who.

mgb260

#115
May 15, 2025, 01:30:05 PM
I would at least pull #4 piston to see what is going on there. Call the machine shop and ask if they would prefer it left together or you disassemble. I think you'd be fine and we could talk you through it. Keep the lifters in the same holes and keep the rod caps with the rods. The main caps are numbered 1 through 5. Did you look on top the piston for a .5 stamp?

mgb260

#116
May 15, 2025, 01:42:36 PM
If you do decide to assemble here is a simple ring gap diagram:
ring gaps.jpg

Gswest236

#117
May 15, 2025, 02:40:46 PM
I appreciate the tips!! And I agree on pulling #4 at a minimum.

IMG_1909.png

mgb260

#118
May 15, 2025, 02:48:59 PM
Probably similar to what we used only .020 over.

mgb260

#119
May 15, 2025, 03:11:07 PM
I think that is a discontinued Sealed Power #. That is the brand Jon had with broken rings in his motor. The top ring is supposed to be 1.5 and they installed 1.2. Probably unaware there were 3 different size ring packages over the years. He has Silvolite now.

mgb260

#122
May 15, 2025, 04:21:32 PM
I found your pistons on Ebay. The # is a TRW #. Lists the application so if you need a replacement for # 4 it would be helpful.

https://www.ebay.com/itm/195785420902

Now they are Speed Pro:

https://www.campbellenterprises.com/trw_pistons_speed_pro_pistons.htm
Print
Go Up Pages 1 ... 3 4 5 6 7 ... 29
User actions