I am currently rebuilding my 455 for my 71 Cutlass. Will be using stock block with oil restrictors, oversized oil return and polished valley. Using eagle cast crank, diamond 40 over flat top pistons 11.5/1 comp. using ported procomp heads with comp cam springs and retainers. Edelbrock performer intake, with holly 750 double pumper. The cam I currently have is comp cam ol-255 deh-10. Very mild cam since I’m still gonna run vacuum assisted brakes. Will be using Muncie 4 speed M21 close ratio with 3.08 rear gears. Has anyone already had a similar build and found a bigger cam that will still retain enough vacuum to run the brakes? Any advice and help is greatly appreciated. Still want to run flat tappet cam due to trying to reduce cost since I’m already at almost 10k in the engine and driveline.

 

Comp 280H
or
JM 25-28

 

I don't think you'll like the 3.08 gears with the M21. Maybe an M20 would be better with 3.08 but strength wise no. I've use oil restrictors in the pass (Mondello) old school, Travado says no to oil restrictors. I like a bigger oil pan. Jmo

 

Very much a mismatched combination. Ditch the regular Edelbrock performer, use the RPM with an 850.
3.08 gear is wrong as well as stated. Oil restrictors are a waste of time and money.
What fuel do you plan to run? Will it be dynode at some point? Vacuum shouldn’t really be an issue for you because of the manual transmission.

 

Thank you very much for the input. So with a manual the cam won’t be much of a problem? I’ve heard nothing but good things from mondello so figured the oil flow and return fixes were the right way to go. I’m not looking for a show or drag queen. Just a good respectable fun car for the family and something to pass down. Hoping for 450hp range. I think my cam is the weak point

 

I agree with the others that the 3.08 gear is going to be a killer even though the 455 will make a ton of torque. I would definitely go with an M20 if you can. I dont think there is any difference in strength between the 20 and the 21, I raced my Chevelle for many years with the M-20 and never had an issue.

I also have to wonder about the 11.5 to 1 compression ??? Way too much for today's fuels. I would stick with no more than 10.5 to 1 450 HP should be a no brainer with even less compression and be a lot more streetable.

 

Which Mondello are you talking about? The one in Paso Robles has a bad reputation since Lynn took over.

 

I called them and talked to the engine builder he tried telling me that for the hp number I was looking for that I’d need to use them for the machine work. I always ran premium gas before with stock top end. From what I’ve read the 11.5/1 will work well on premium pump gas. I already have the M21 close ratio and if it doesn’t perform like I want will go up to 3.42 gear set. I do think buying the dual energy cam was a mistake though. Anyone want to buy it? Cam, springs and lifters? 😂

 

X 2

I'm with Bill, 10.5 actual compression ratio should be more than enough.

........Just my two cents worth.

 

Dougsupra, you need to go back over this thread post by post and answer the questions you've been asked if you expect to get any useful help. Right now, you're all over the map and you need to settle down and take a more methodical approach. Start with cutlassfi's post. Answer all his questions and see what he comes back with. He can be very helpful if you don't **** him off.

And if the Mondello shop you're dealing with is the one in Paso Robles, Ca. you can pretty much disregard everything they've told you.

 

In case you have doubts about the sources of Mondello's complaints...here's some reading material

https://classicoldsmobile.com/forums...ondello-51417/

https://classicoldsmobile.com/forums...rmance-117422/

https://classicoldsmobile.com/forums...ormance-26088/

https://classicoldsmobile.com/forums...ondello-35417/

https://classicoldsmobile.com/forums...ndello-112103/

https://www.oldsmobilecentral.com/fo...ngine-had-.php

https://www.hotrodders.com/forum/do-...lo-163873.html

https://www.jalopyjournal.com/forum/...ervice.821072/

 

thank you for the feedback.

 

As some have already said for 450hp you don’t need half that stuff, but I’d still change the rear gear.
Here what you’ll need to make 450;
800+ carb
Performer intake
Decent Heads, whether they’re aluminums or a set of warmed over irons
10:1 compression
A cam in the high 220 to low 230@.050 range.
A good tune and you’re there for sure.
Note: the quality of machine work is important but there are competent shops around. I have the luxury of a top notch shop not far from me, and I purchased additional tooling to raise it to the next level.
But 450hp is not a lofty goal by any stretch. You’ll hit it with the above recipe.

 

Jmo, be happy near or at 450 hp. After that you'll just be breaking things finding your weakest link. Put some slicks/drag radials on it and you'll find it very soon. You should upgrade your drive shaft and pull a safety loop. It's a can of worms. I don't see 10K in your drivetrain yet, maybe $6,500. A lot of mismatch or weak parts there. You should have looked for a Super T-10, or an M-22 Muncie, Auto Gear is a good option but for sure the gear ratio (3:08) blows. Figure out your combination, then sell anything that doesn't work and replace will correct. Jmo.